Date: 11/06/11 17:51
Dear Colleagues:
92nd day!
I. Three months since the earthquake.
On this occasion, most news media issued a series of special feature of the consequence of the Higashi-Nihon (Eastern Japan) Great Earthquake series. All pointed out that the recovery activities are very slow. Most of them pointed out that delay in disposal of tsunami debris is one of the biggest obstacle for recovery operation. In addition, 91,000 people are still in refuges. Although 28,700 temporary housings have been completed, only 17,000 of them are occupied. For evacuated people, some of the temporary housings are located in inconvenient places, nor necessary social infrastructure has not been recovered yet. For example, as many as 57, 900 houses are not provided with the city water service yet. More serious issue is nearly a half of the evacuated people became pessimistic for returning to where they have been living.
From this point of view, there is no prospect in sight in the planning for recovery and resettlement of the evacuated zones.
In the “emergency preparedness” zone, there are 153 industrial facilities, in which no one has prospect for re-opening. Everything depends on when the damaged plants became under control. From this point of view, increased number of workers are getting out of condition due to working in air tight radiation protection suits in hot weather, such as due to dehydration. The improvement of working environment is becoming an urgent issue and some rest areas have been constructed. They are now provided with a pack of refrigerant. During the hot season, there will be a rest hours in the hottest afternoon hours.
The total volume of the highly contaminated water continues to be increasing. The pre-functional test of the new water purification system has not been started yet, due to miniscule leakages at the zeolite sorption stage. The leaky valves and flanges have been ameliorated by putting sealing compounds around the joints. This can be seen in the updated set of photos uploaded by TEPCO: http://www.tepco.co.jp/en/news/110311/index-e.html please visit “Coupling Parts of Inlet and Outlet of Cesium Adsorption Tower (pictured on June 9, 2011)”
http://www.tepco.co.jp/en/news/110311/images/110611_03.jpg
http://www.tepco.co.jp/en/news/110311/images/110611_02.jpg shows a side view of this facility.
II. Recapping on removing contamination from 1F2 reactor building
In 1F2, the moisture level is as high as 99.9%. Combined with the high dose rate, the worker entry is greatly restricted. In view of this, TEPCO has started to decontaminate the room air by employing the heated filtering system used in entering into 1F1 by improving to add heaters. For that the double doors from the turbine building has been opened at 12:39 on June 11. After a few days of operation, they plan to open the truck entrance door, facilitating the natural draft ventilation. By opening the door, some contamination may also leak out to the environment. By exchanging the room air by natural ventilation, TEPCO hopes to allow the worker entrance.
TEPCO uploaded a series of photos in their website: http://www.tepco.co.jp/en/news/110311/index-e.html
This is the first time that a set of relatively clear photos became available inside of this building. The photos were shown in *pictured through vinyl which covers the camera on June 11, 2011”.
http://www.tepco.co.jp/en/news/110311/images/110611_08.jpg shows the temporary intake air duct for filtering air.
http://www.tepco.co.jp/en/news/110311/images/110611_09.jpg shows the air cleaning units installed inside of the turbine building.
http://www.tepco.co.jp/en/news/110311/images/110611_10.jpg shows temporary air duct laid down
http://www.tepco.co.jp/en/news/110311/images/110611_11.jpg shows the air cleaning units installed inside of the turbine building
In Unit 2, the air cooler has been installed and working for the spent fuel pool.
III. Recapping on inspection of 1F3 reactor building.
Also, http://www.tepco.co.jp/en/news/110311/images/110611_001e.pdf is showing a map of radiation level data taken along the route of the inspection, http://www.tepco.co.jp/en/news/110311/images/110611_06.jpg is showing that the dose rate was higher near the large machine hatch. http://www.tepco.co.jp/en/news/110311/images/110611_07.jpg shows that the water treatment skid may not be accessible for workers for piping.
IV. Recapping on inspection of 1F4 reactor building.
A set of photos taken by entering into the 1F4 is also uploaded in the TEPCO website. The “4th Floor of Unit 4 Reactor Building (pictured on June 10, 2011) Pictured at South Side on 4th floor of Unit 4 Reactor Building”
http://www.tepco.co.jp/en/news/110311/images/110611_04.jpg is showing that a part of the piping of Spent Fuel Cooling and Cleaning System is bent, perhaps may not be usable for installation of the air cooling system.
http://www.tepco.co.jp/en/news/110311/images/110611_05.jpg, “4th Floor of Unit 4 Reactor Building (pictured on June 10, 2011) Pictured at South Side on 4th floor of Unit 4 Reactor Building” is showing severity of the hydrogen explosion in this building.
Well let me stop here.
Genn Saji
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(Previous e-mail sent at 0:22 AM on June 11 as Earthquake (91))
Dear Colleagues:
91st day!
I. Disposal of the contaminated tsunami debris
Yesterday, I touched on the anticipated difficulties for ultimate disposal of highly radioactive wastes to be released from the new water purification system. In parallel with this, a huge amount of tsunami debris is left in the shore line of the Fukushima Prefecture. Currently the contaminated debris have been moved to 117 temporary depositories, where radiation levels are being monitored. So far two of them with minor contamination were allowed to be disposed by using ordinary incineration facilities. The Ministry of Environment (ENV) is investigating possible radiation effect of disposing these by constructing a special waste incineration facility, where exhaust filters will collect flying asses. Through this process radioactive ashes will be generated, for which an ultimate disposal facility will become necessary. ENV sounded to the Fukushima Prefecture Government, however, the Governor responded with a flat rejection, by saying that nuclear energy policy should need more in-depth thought. Now it is increasingly becoming a political issue how to dispose the Fukushima Daiichi waste in the near future as well as those left within the 30 and 20 km zones. The debris within these zones have been left untouched, preventing recovery from the tsunami damages. The approach made by ENV was also poor. The way they explained to the Fukushima Prefecture does not convey that the Government is thinking of true welfare of the affected people. The most critical issues should be how to ameliorate land, for future resettlement, within the “scheduled (and organized)” evacuation zone, “emergency preparedness” zone as well as the 20 km “vigilance (off limit)” zone. Where such studies are being made in the Government is not visible for the affected people.
II. Recapping on two TEPCO operators found received excessive internal radiation exposure
On this issue, I introduced in Earthquke (80) . (81) and (84). Further detailed inspection now concluded the accumulated doses as below.
identification approximated age accumulated doses (mSv)
MaleA >30 678
MaleB >40 643
Approximately 80% of their doses are reported to be due to internal exposure through inhalation pathway. If we assume a tissue weighing factor of 0.05, an estimated thyroid absorption dose should be around 12 Gy, since the external doses were 74/89 mSv. In the UNSCEAR 2000, there is no risk factor estimated for adults from the data obtained through the Chernobyl accident. If we use the risk for children 0-18 years old, the excess absolute risk for the thyroid dose group of >2 Gy was 2.4/(10000 PY Gy). Since this risk factor is obtained by the epidemiological study and may not be appropriate to apply to this situation. Although it is reported that there will be no health effect, I think they need to be kept under medical monitoring, since 12 Gy of thyroid dose is at a high level, although no thyroid cancer was reported among adults at the time of the Chernobyl accident. It is reported one additional worker may have received high internal doses.
III. Recovery of the off-site environmental monitoring station.
Before the accident, the environmental monitoring around the Fukushima Daiichi and Daiini has been surrounded by 23 monitoring stations. Because of the tsunami, all of them went down except for just one. Fukushima prefecture successfully restored 8 of them, by entering into Nuclear Energy Center, which is located within the “emergency preparedness” region. All of the monitoring data have been processed by a computer system located in this center. They crew will try to recover remaining 11, although last 4 have been devastated by the tsunami.
IV. Recapping on water purification system completed
TEPCO announced today that the pre-commissioning test is being delayed since they discovered small water leaks from valves and joints from as many as 10 locations. The test was conducted by using sea water. These troubles will be repaired tomorrow and may be able to go into the test very soon.
Well, let me stop here. Today I went out to pickup my 29 months old grand daughter from her day nursery and a bit exhausted since she insisted to play tag for more than an hour at a park near by. I cannot cope with her vitality.
Genn Saji
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(Previous e-mail sent at 10:53 PM on June 10 as Earthquake (90))
Dear Colleagues:
90th day!
I. Water purification system completed
TEPCO announced today that installation of the highly waited water purification systm was completed and ready for pre-service test. The system is constructed at the Centarized Waste Processing Facility. TEPCO plana to test the system for a week, for the targeted commissioning date of June 15. Although the most recent photos has not been released yet, an outline of the system has been posted in the TEPCO’s website as attached. http://www.tepco.co.jp/en/news/110311/images/110604_outline.pdf
The system has a capacity of 1200 tons a day hoping to achieve a DF of 1000 to 10000. As can be seen from the attached outline, the first stage is for removing oily inclusion, followed with a zeolite sorption stage for cesium and iodine and the third stage is co-precipitation for removal of cesium and strontium and then comes a reverse osmosis stage to finally distillation stage. The sorption material will be supplied by the US Clion Co. Many people are crossing their hands that the system works as intended. However, there are many unresolved questions whether the system works as intended. The first issue is in the high salt concentration came from the sea water injection, as well as sea water left behind the tsunami. In March, many chemists in Japan looked for zeolite which may show high DF in the salt water, only to confirm the DF of 10 at most. Also a group of Russian scientists tested layered hydrazinium titanate (LHT-9), which also showed no much better than zeolite in sea water, even though it showed sorption capabilities in wider nuclear species. As a matter of fact, TEPCO is going to use a zeolite water purification system to reduce the activation of the sea water by 60 to 80 % for Cs-137.
Also it has not been reported that the AREVA’s co-precipitation process works in the salt water. Professor Ohta of Kanazawa University has also developed a much better chemical, although it is not reported whether it works in the sea water. ( http://jp.wsj.com/japanrealtime/ )
The situation of accumulation of contaminated water continues to be urgent in all of the Fukushima. TEPCO is requesting for a permission of releasing 3000 m3 of sea water left behind by the tsunami from Fukushima Daini. They plan to release slightly contaminated water, after decontaminating it to the level specified by the nuclear safety criteria. They plan to used a temporary decontamination facility with a capacity of 30 tons?an hour. ?However, Mr. Tsutsui, Vice Minister of Agriculture, Forestry and Fishery (MAFF), flatly refused to accept by saying it will induce hearsay damage.
Even when everything turned out to be successful, the waste disposal should also a problem, Currently as much as 105,000 m3 of the highly contaminated water is estimated and the total volume of the contaminated water may reach 200 thousands tons. As much as 500 tons of water is injected into the reactors. In the beaker tests, the liquor to the sorption material ratio was around 100. This indicates that as much as a few thousand tons of contaminated sorption materials can be generated. The resultant waste disposal issues must be investigated from now on. Since cesium is a volatile species, the waste gas generated from the ceramic process may not be feasible. Perhaps one of the most practical solution is just bury into a layer of bentonite (cray), after putting the sorption materials in metallic containers, in the medium depth of soil. It is anticipated to be a big political problem to find a waste disposal site. I envision to request to Fukushima prefecture to accept construction of such a disposal site in the already highly contaminated zone in Fukushima to dispose all other surface soils in that area eventually needs to be disposed.
II. Inspection of 1F3 reactor building.
After completing removal of debris around 1F3, 11 TEPCO team went inside of the reactor building first time after the hydrogen detonation for about 20 minutes. They measured doses as well as inspected the status of piping which they plan to use for injection of nitrogen gas into the containment vessel. TEPCO plans to install air cooler to cool down the reactor vessel.
III. Detection of strontium beyond 30 km region.
NEXT announced that a small amount of strontium was found at 11 sampling points 60 km from the Fukushima Daiichi, although strontium has been detected within the 30 km region. The surface contamination level is approximately 1/1000 of Cs-137. The release fraction of strontium is much less than the case of Chernobyl accident, where approximately 80 PBq of Sr-89 was released together with 74-85 PBq of Cs-137, according to UNSCEAR 2000, Annex J: Exposure and effects of the Chernobyl accident. Apparently, this large difference comes from the difference in release mechanism between these two accidents. The strontium release from the Fukushima Daiichi is due to the release of the contaminated steam from the containment vessel, after being decontaminated by the suppression pool water. Whereas in the Chernobyl accident, a significant portion of the reactor materials were discharged directly through steam explosion. I do not think this observation support the early melt through scenario as being concluded by TEPCO in their recent analyses.
Let me add one episode. When studying the land contamination sampling data containing strontium, I noticed a local hot spot of Ag-110m (half time is 250 days). It appears that some fuel particles may exist in these sample, since strontium as well as silver is the “intermediate” species, some very small amount of fuel materials may have been released together with the contaminated steam.
Well, let me stop here,
Genn Saji
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(Previous e-mail sent at 00:13 AM on June 9 as Earthquake (89))
Dear Colleagues:
89th day!
I. IAEA Ministerial Conference
On June 7, NISA posted the following report for the IAEA Ministerial Conference to be held on their website
Report of Japanese Government to the IAEA Ministerial Conference on Nuclear Safety - The Accident at TEPCO's Fukushima Nuclear Power Stations - http://www.kantei.go.jp/foreign/kan/topics/2 01106/iaea_houkokusho_e.html
This document is an English translation of the Japanese version. Unfortunate4ly, the translation seems to have not been completed as of this morning. Therefore, some of the later additions, such as the section of “meltdown” analyses, contained only a summary section in the English version. By quickly glancing through the document, this document is for the ministerial meeting and is not for specialists. It is written by the bureaucrats of the relevant ministries, headed by Mr. HOSONO, Gowashi, Assistant to the Prime Minister. It is reported that he requested the ministries to rewrite many times, to reflect the direction provided by the Prime Minister. It also contains 28 lessons learned, which has been immediately used to order, by MEXT, to all of the power companies to report how they will try to implement by June 14. Although most of the lessons learned are reasonable, however, many of them are not easy to implement in the current nuclear reactors in Japan. For example, independence of layout for reactors are requested, however, this may imply that the half of the current fleets should not be able to be operational. Although the Prime Minister has been saying that, except for the Hamaoka NPPs, all other fleets should be kept in operation, the local residence is reacting “not to allow unsafe NPPs”, making local government in a difficult situation in permitting them to restart. Currently many NPPs are in the scheduled shutdown to be prepared for summer peak electric power demands. However, they have not been able to restart in the wake of the anxiety of the local residents.
In view of the nature of this report, the contents may not be satisfactory for specialist people, nor it contains detailed engineering data necessary for independent verification. Perhaps your should wait for the Prime Minister proposed international nuclear safety specialists meeting to be held later next year.
Let me stop here.
Genn Saji
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(Previous e-mail sent at 11:28 PM on June 7 as Earthquake (88))
Dear Colleagues:
88th day!
I. Comments on recapping on the 1F4 water radiolysis studies by Prof. Bartels
Professor David Bartels, Notre Dame Radiation Lab and is one of the authors of the data for radiation chemical studies (AECL 153-127160-450-001), commented by saying “Your calculation of H2 produced by radiolysis is just wrong, if you are assuming pure water with ca. 1e-4M dissolved O2 as the starting point. Something is very wrong with your solution of the steady state concentration. It makes no sense that there would be a sudden jump at 40-50C....We do need to account for H2O2 decomposition on the surfaces. The dissolved O2 is probably too high, once the pool gets close to boiling. We have omitted dissolved CO2 which could change things a bit, as well as other impurities. And there is certainly a gradient of the radiation field. But I think the most important thing is the boiling. Once boiling is possible, probably on the surface of the fuel rods, there is a mechanism for the H2 (and O2) to separate into the gas phase bubbles, which destroys the steady-state as calculated above. This was nicely demonstrated by the recent experiment of Katsumura-san.
He provided me a set of calculation results, by solving with a Gear integrator. I have been checking my computer tool to benchmark with his results. There are some difference in the temperature dependence between these two and I am investigating the cause of the difference. However, his comments are useful to explain the difficulties in applying the radiation chemical methodologies for the spent fuel situation. That is the extremely long time scale necessary for computation by incorporating the natural convection. In the infamous NC model I have used, the ‘residence time,” a duration of the water entered from the bottom of the fuel assembly to the top, ranges from 1000 second to 10000 seconds. During that time the water is keep being irradiated. The initial dissolved oxygen, for example, can be burn out before reaching to the exit of the fuel assemblies. When such a situation occurs, the reverse reaction so far preventing hydrogen generation can be lost, resulting in an high hydrogen release rate. Considering the burn up, I think the QSSA (quasi steady state approximation) should also be a feasible approach, since the time dependency can be expressed by the resident time. However, disadvantage is in the need of more rigorous material balances.
The computer code solved a set of reaction kinetics system with a wide variety of characteristic times varying as large as ten orders of magnitude, with the concentration variation often 20 orders of magnitude difference.
II. Update of the hydrogen generation by NISA.
NISA people seem to be occupied in preparing presentations for the coming IAEA Ministerial-level meeting soon to be held during June 20-24. For last several weeks, many of the previous NISA releases are being updated. This include the amount of hydrogen generation along their melt down scenario.
Unit Hydrogen Generation (kg)
1F1 1000
1F2 800
1F3 750 + 100
Also, a few days ago, it was reported that the severe explosion in 1F3 was due to hydrogen detonation, whereas deflagration for 1F1 and uncertain whether it was a hydrogen explosion in 1F2.
III. Special Committee for investigation of nuclear disaster
The first meeting was held today by the Special Committee for investigation of nuclear disaster, which was convened by the prime minister. They will investigate the Fukushima Daiichi accident digging deep into the causes of this accident not only from a technical point of view, but also the societal background. The chairman of this committee is Youtaro Hatakemura, Professor Emeritus of Tokyo University. He is a famous person by proposing “sippaigaku” (failure-cology) in his data base of lessons learned from failure experiences. In their first meeting, they decided to consider the Fukushima Daiichi as an “organizational accident” as proposed by James Reason, 1997. Managing the Risks of Organizational Accident, Ashgate Publishing Limited. They plan to complete an intermediate report by the end of this year, to be followed with the final report after controlling this accident. The prime minister himself will be the subject of their inquiry. They also investigate the Japanese regulatory system from the time it was formulated. The committee members consist of specialists of diverse arena, including former supreme court justice, IAEA ambassador, writer, radiation safety specialists, etc.
Well, let me stop here tonight.
Genn Saji
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(Previous e-mail sent at 2:27 AM on June 7 as Earthquake (87))
Dear Colleagues:
87th day!
I. Recapping on the 1F4 water radiolysis studies
The trial calculation (III) attached two days ago seems to have attracted an interest and I received a few questions and comments. In order to respond to these, attached please find an update. The largest point in update is to restrict the dissolved hydrogen concentration not to exceed the solubility limit. This is equivalent to increase concentration of DO as well as oxidative radicals that enhance reverse reaction for hydrogen generation. As anticipated, it resulted in a significant reduction of hydrogen generation. At this stage, effect of boiling is not clear. It should be a higher priority issue.
II. NISA released their meltdown calculation
Today, NISA released their calculation to estimate the initiating time of melt down. The results are summarized below.
Unit Approximate time of RPV failure
1F1 8 PM of March 11
1F2 10:50 PM of March 14
1F3 10:10 PM of March 14
It is reported that these results will be presented at the coming IAEA ministerial level meeting.
Their results are certainly conservative, by totally ignoring the effect of “feed and bleed” operation, for that purpose ECCS is integrated into the plant, including Pressure Release and Safety Valves, Isolation Cooling System and High/Low Pressure Injection System. Even under the “station blackout”, most of them worked as designed, using the battery power, although heat removal was not possible due to the “loss of ultimate heat sink.”
III. Planning to remove moisture from 1F2 reactor building
In 1F2, the moisture level is as high as 99.9%. Combined with the high dose rate, the worker entry is greatly restricted. The air sampling has shown the following activity concentrations (Bq/cm3): I-131=4.2E-02; Cs-134=5.8E-02, and Cs-137=5.6E-02. In view of this, TEPCO plans to remove moisture by employing the filtering system used in entering into 1F1. Honestly speaking, I do not understand whether the filters are any good for removing moistures. If we assume the total volume of the building as large as 2E+05 m3, the total amount of moisture need to be removed is as large as 10 tons. What they need will be huge dehumidifiers. However, I suspect that the moisture should be coming from cracks in the primary pressure boundary or containment vessel. Without stopping the leak source, it should be very difficult to improve the working environment.
IV. Removal of debris around 1F3
TEPCO has been removing the highly contaminated debris scattered around 1F3. So far they removed debris to fill 250 containers, employing remote controlled power shovels. However, there still remain some hot debris with a dose rate of around 1 Sv/h. Removal of hot spots are still necessary to improve the working environment.
V. Off-site center did not function
The off-site center was supposed to become a control tower of global accident management, however, it failed to function due to the earthquake damage, loss of power, in sufficient air cleaning capability, failure of communication network, etc.
Well, let me stop here.
Genn Saji
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(Previous e-mail sent at 9:02 PM on June 5 as Earthquake (86))
Dear Colleagues:
86th day!
I. Recapping on installation of a new pressure gauge
I introduced this issue in Earthquake (83). One of the most troublesome issues is that, due to the “station blackout”, the central control panels went out when battery power was exhausted around the midnight of March 11. Although the control room operators struggled to make some of the essential instrumentation and control channels recovered by calling for dispatching auto batteries, however, many of the instrumentation showed questionable readings, especially those using Burdon pressure elements, such as pressure gauges, differential pressure level gauges as well as differential pressure flow gauges. Many of these gauges are using three-fold redundant common instrumentation pipes. In particular the top level pipes provide the reference pressure of the reactor vessel. In all of 1F1-3, there occurred events where the reactor pressure readings suddenly dropped and after that all of the readings started to show strange results. Since these event induced these events simultaneously in each unit, I have been suspecting that “internal hydrogen explosions” occurred as preceded by the Hamaoka Unit 1 hydrogen explosion/pipe rupture accident as introduced in Earthquake (69) by an one page summary in English. Without this failure, sufficient amount of water injection could have been possible, resulting in a cold shutdown state much earlier, I believe.
Early today, TEPCO announced that the correct pressure reading was 1.26 atom at 11 AM on June 4, after installing a new reactor pressure gauge in 1F1. This reading is obviously showing that there should be cracks somewhere in the primary pressure boundary of the reactor vessel, however, it should not be a pipe break since the damaged reactor vessel is still maintains a residual pressure retaining capabilities, In addition, there should be a damage in the reactor containment vessel, since much more than the volume of containment vessel is needed to keep its pressure above atmospheric pressure to prevent buckling due to cool down inducing vacuum.
II. Plutonium first detected offsite
It was reported today that a trace amount of plutonium was detected at Ookuma-cho, 1.7 km from the Fukushima Daiichi, detected the first time off-site. The amount detected was 0.78 Bq/kg of soil for Pu-239+240. Although the concentration is at the same level as being detected in the Japanese territory due to the fallout from nuclear weapon tests performed in the past by other countries, it was concluded to be released from the Fukushima accident, since the isotopic composition was different.
III. Recapping on the continued threat of leakage of rain water into the buildings
I introduce this issue repeatedly, the last one in Earthquake (81). Due to the continued water injection, as much as 500 tons of water volume is continue to increase, not including the rainwater nor the underground water. The TEPCO was predicting that the trench water may overflow as early as in June 20. In view of this urgency, TEPCO decided to increase the storage capacity of the water-proofed Centralized Waste Processing Facility by 1500 tons. Since June 4, TEPCO re-started to pump the highly contaminated water at a rate of 24 tons an hour. This operation is reported to be successful in preventing further increase of the 1F2 water level in the basement as well as its trench.
Well, let me stop here today.
Genn Saji
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(Previous e-mail sent at 10:27 PM on June 4 as Earthquake (85))
Dear Colleagues:
85th day!
I. Recapping on the 1F4 water radiolysis studies
Being motivated by the Prof. Y. Katsumura’s rapid experimental test (as introduced in Earthquake (80)), I could complete a detailed water radiolysis assessment to find the root cause of hydrogen generation as attached. The assessment was performed by integrating a simple natural circulation flow through the spent fuels in the 1F4 SFP water. The estimation of the flow rates through the spent fuels became necessary to compute a residence time of irradiation of the pool water when going through the fuel assemblies. Since the residence time of the reactor water during the full power is in a order of one second or so, this flow rate should be much lower, proportion to the decay heat ratio which is only P/Po = 3.4E-04 at the time of the 1F4 accident. As a matter of fact, the flow velocity calculated from this model is around this value.
The results are shocking for me. There exists a “quasi equilibrium state” below 50 degreeC, where the dissolved hydrogen (DH) is less than the solubility limit of the hydrogen gas in the water. Above this, the DH concentration becomes higher than the solubility limit and should start hydrogen gas release from the spent fuel. When this information is converted to the hydrogen release rate, as much as several thousand STD-m3/day of hydrogen gas can be easily generated when the pool temperature is over 80 degreeC.
The lessons learned through this exercise can be summarized as below:
Due to the “station blackout”, the circulation of the SFP water was terminated. The resultant long residence time of water inside the spent fuels, through natural circulation, induced a rapid removal of oxidative radicals, resulting in termination of the reverse reactions so far restricting the hydrogen generation.
When the DH concentration exceeded the solubility limit, a substantial hydrogen stared to be released.
The increase in the pool water temperature induced higher natural circulation flow, resulting in higher rate of hydrogen gas transfer from the irradiated region.
With a rise in the temperature of SFP water, the DH is released to the Fuel Exchange Room with steam bubbles. The steam was condensed in the wall of the room, separating the hydrogen gas.
According to this modeling study, it is essential to keep the SFP temperature below 50 degreeC, under which a “quasi equilibrium condition” can be maintained to prevent extraneous hydrogen gas generation. This threshold value may change depending on the decay heat level. The plant operator should have this kind of results to be prepared for severe accidents.
This calculation should be benchmarked by other institutions independently, since errors are easy to slip in, due to complexity of the chemical kinetics equations and rate constants. I believe this is a pretty good topic for an international benchmark exercise, in view of the safety implication of the SFP in an event of “station blackout.” Also, some test should be performed to confirm this mechanism, including the flow velocity of water in the spent fuels.
It should be fare to add that the current TEPCO position is that the 1F4 hydrogen explosion is due to in-flow of hydrogen transported through a common ventilation duct due to venting. One of the biggest difficulties of this hypothesis is in the fact that there is no way to estimate an amount of hydrogen gas generation as well as transport of the gas through the common ventilation duct. However, TEPCO withdrew this claim today, since one of the double valves should have been fail closed upon loss of DC power.
II. High dose rate steams found by “PackBot” inspection
A video taken by “PackBot” is posted in Confirmation of steam situation at a reactor building of Fukushima Daiichi Nuclear Power Plant Unit 1 (ZIP 5.55MB) of http://www.tepco.co.jp/en/news/110311/index-e.html . The steam is leaking from a penetration of piping through the floor level. It is reported that the dose rate around this penetration is as high as 3000-4000 mSv/h. By consulting with the PSAR, the location is where pipes from the suppression pool are led to ECCS. I further intensified my suspicion that there should be a pipe damage in this pipe, due probably to the “internal hydrogen explosion,” although TEPCO is relating this to their meltdown scenario.
III. Outline of contaminated water processing facility
Please visit http://www.tepco.co.jp/en/news/110311/index-e.html to download Fukushima Daiichi Nuclear Power Station Outline of water processing facilities (PDF 70.1KB)
Also today, transportation started for additional tanks for storage of contaminated water. The “Tamada” Industries manufactured 170 tanks of 120 m3 capacity and 200 with 100 m3 capacity, totaling to 40,000 m3. The basic sizes for 120/100 tons tanks are: height 3.7/3.4 m, length 15.1/13.5 m and weight 15/13 tons. They are steel tanks with the wall thickness of 9 mm, covered with re-enforced plastic linings of 1 mm inside, 1.8 mm outside.
Well, let me stop here today.
Genn Saji
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(Previous e-mail sent at 00:06 AM on June 4 as Earthquake (84) (Earthquake (83) should have been (84))
Dear Colleagues:
84th day!
I. Strategy for storage of the contaminated water
According to the TEPCO’s recent estimation, the overview of the highly contaminated water is as summarized below.
1F1 16,200 tons
1F2 24,600
1F3 28,100
1F4 22,900
Centralized Waste Treatment Facility 13,3300 (transferred mainly from 1F2)
13,3300
------------------------------------------
Total 105.100 (with a total activation of 7.2 PBq)
Currently the new onsite water treatment facility is scheduled to become partially available on June 15. Without this, the water may overflow as early as in June 20. With this facility, TEPCO plans to decontaminate the water to a mid to low level waste water and store them in the tank yard being constructed. (Although definition of the waste management levels is not disclosed,according to the reprocessing practice, MA/LA correspond to 10/0.18 TBq per m3, indicating that TEPCO seems to be anticipating a modest DF.) In addition, TEPCO plans to construct an underground emergency tank for HA water storage, targeted to be completed in August. They are working hard to increase a margin urgently needed. One action was to transfer the water in the basement of 1F3 turbine hall to its condenser well of the turbine.
II. Recapping on Two TEPCO operators found received excessive internal radiation exposure
On this issue, I introduced in Earthquke (80) and (81). Further detailed assessment revealed that the their 50 year life span accumulated thyroid doses may reach 210-580 mSv for the worker at the age in 30th, 200-510 mSv for the worker at the age in 40th. These internal doses should be added on top of the external exposure of 74/89 mSv. Although their thyroid doses are high, however, considering their age, the health effect should be very small, comparing with the case of the Chernobyl accident, where much higher thyroid doses were accumulated through pasture -> cow -> milk -> infants food chain. In addition, the thyroid of the Japanese people are generally saturated with stable iodine, through our habit of taking a lot of sea food. There are practically no iodine deficiency case in Japan.
However, there is an increased concern that internal exposure measurements have not been performed for thousands of workers, due to the limited availability of whole body counters. Only 1400 workers have gone through this examination.
Well, let me stop here today.
Genn Saji
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(Previous e-mail sent at 11:43 PM on June 2 as Earthquake (83))
Dear Colleagues:
83rd day!
I. Recapping on the continued threat of leakage of rain water into the buildings
With arrival of the rainy season, the effect of rain water as well as underground water is becoming continued threat to all units. Today TEPCO introduced the tank yards for 1F5 and 6. Please visit Fukushima Daiichi Nuclear Power Station Temporary storage tank (for the purpose of low level radioactive materials in Unit 5 and 6) installation status
Place: Storage Area (North Side) http://www.tepco.co.jp/en/news/110311/index-e.html
In 1F3, TEPCO is trying to pump the highly contaminated water to its steam condenser well, which can store as much as 2000 tons of water.
II. Installation of new pressure measurement instrument
Recognizing the insufficient reliability of 1F1 pressure gauges, a set of new pressure gauge is being installed. I believe this is a prudent operation, since most of the pressure gauges are showing strange readings, including differential pressure level gauges as well as the different pressure flow meters. I am suspecting an occurrence of the “internal hydrogen explosion”, since there are 8 cases in TEPCO that gauges are broken by sudden high pressure and temperature during normal operation. In the cause of the accident, since there were no water circulation, there could have been more chances for hydrogen accumulation and separation from water, leading to the hydrogen explosion. In all of the reactor pressure vessels, there were events when the pressure suddenly drops followed with strange readings after. These incidents have been known inside TEPCO and reported in Japanese in the following addresses:
http://www.tepco.co.jp/cc/press/betu03_j/images/030821b.pdf
http://www.tepco.co.jp/cc/press/betu03_j/images/030821c.pdf
http://www.tepco.co.jp/cc/press/betu03_j/images/030821d.pdf
These investigations were reported in the light of the Hamaoka Unit 1 hydrogen explosion/pipe rupture accident, which occurred at a part of ECCS piping, as introduced in Earthquake (70). I am suspecting that similar events have occurred one after another during March 11-16, resulting in the“spontaneous venting.”
Also in 1F1 turbine hall, the water level of the highly contaminated water slightly decreased, probably leaking into other area of the turbine hall. Currently no sign of leakage into the underground water has been suspected.
III. Prevention of leakage of highly contaminated water into the sea
Today TEPCO reported to NISA that they have investigated whether there can be another contaminated water leakages such as occurred from 1F2 in April and 1F3 in May. According to their study, the most vulnerable leakage passes are through “trenches” which lead cable to the pumps and screen facilities from the basement of turbine halls. There are total of five of them as well as 39 “pits.” They are currently pouring concrete in the pits one by one. They are also trying to fill cracks in the concrete walls facing the sea. These operations should be completed by the end of this month.
IV. Recapping on water supply lines recovered for all of 1F1-4 spent fuel pools
After start operation of the air cooled decay heat removal system in 1F2, the temperature dropped down to 39 degrees, 10 degreeC lower in a day, achieving the one month goal of cooling down in just two days. Similar operations are being planned in other plants and should be ready by early next month.
Well, let me stop here today.
Genn Saji
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(Previous e-mail sent at 10:21 PM on June 1 as Earthquake (82))
Dear Colleagues:
82nd day!
I. Recapping on the 1F4 water radiolysis studies
Being motivated by the Professor Yousuke Katsumura’s rapid experimental test, I also tried to provide a trial detailed radiation chemistry calculation as attached. Through my study, I could extract the following accident scenario.
(i) Due to the “station blackout”, the circulation of the SFP water was terminated.
(ii) This resulted in a rapid removal of oxidative radicals through water radiolysis, resulting in termination of
the reverse reaction for reducing hydrogen generation.
(iii) This resulted in a substantial increase in the radiolytic hydrogen generation rate.
(iv) With the rise of the temperature of SFP water, th DH is released to the Fuel Exchange Room with steam bubbles.
(v) The steam was condensed in the wall of the room, separating the hydrogen gas.
(vi) When the hydrogen concentration reached to the flammability limit, the hydrogen explosion occurred.
This mechanism should be different from that of 1F1-3, where much more amount of hydrogen gas was released
through venting, both manually and spontaneously.
II. Recapping on water supply lines recovered for all of 1F1-4 spent fuel pools
After start operation of the air cooled decay heat removal system in 1F2, the temperature dropped down to 49 degrees, 20 degreeC lower in a day, indicating that the system is working as intended. This is going to help greatly, since the successful operation should prevent diverting recovery efforts to more urgently needed areas.
III. More effective water injection through feed water lines
TEPCO changed the water injection line now through the feed water lines from the previous fire fighting line routes, resulting in some decrease in the necessary water injection rate than before.
unit thru feed water line thru fire fighting line temperature at lower portion of RPV (June 1)
1F1 5 m3/h 6 m/h 108.4 degreesC
1F2 4.9 7 110.2
1F3 11.5 6 + 12 (feed water l.) 136.4
I believe this is an indication that a significant portion of the injected water has been leaking before reaching to the RPV.
IV. Zeolite sea water decontamination facility installed near the sea water intake port for 1F2/3
Please visit http://www.tepco.co.jp/en/news/110311/index-e.html to see
Circulating Seawater Purification Equipment at the Fukushima Daiichi Nuclear Power Station (pictured on June 1, 2011).
The unit is expected to start operation tomorrow, after replacing the faulty cable. It has a capacity of 30 tons per hour.
V. Total cost of decommissioning Fukushima Daiichi
The Japan Economic Research Center, a private institution, reported to Atomic Energy Commission that the cost of decommissioning of the Fukushima Daiichi as well as paying compensation to the evacuees, may reach 70 to 250 billion dollars in the coming 10 years. The cost estimation was made by referring to the case of the Chernobyl accident.
Well, let me stop here today.
Genn Saji
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(Previous e-mail sent at 0:0? AM on June 1 as Earthquake (81))
Dear Colleagues:
81st day!
I. Recapping on Two TEPCO operators found received excessive internal radiation exposure
TEPCO investigated why the two operators received nearly 10 times more of internal doses compared with other operators. It began to reveal some clues.
(1) They neglected to wear masks when they were struggling at the control room on March 11.
It appears that masks can reduce the aerosol inhalation by a DF of 10.
(2) They only took the iodine pill on March 13, distributed by TEPCO.
If that is the case, it is too late. The iodine pill is to saturate thyroid with stable iodine. It is not so effective unless
taken at the very early stage of iodine exposure.
TEPCO continues to investigate into this issue.
II. Recapping on water supply lines recovered for all of 1F1-4 spent fuel pools
Today, TEPCO has started operation of an air cooling system in 1F2 spent fuel pool. It is hoped to bring the temperature down to 40 degreeC from the current temperature of 70 in a month or so. With the reactor building is covering the damaged spent fuel pool, the hot water releasing a lot of moisture inside of the reactor building, resulting in nearly 100% in relative humidity. Similar air coolers are being prepared to be ready early next month in 1F1 and 3, followed with another one in 1F4 in July.
III. Recapping on the “scheduled (and organized) evacuation” status
At the time limit of one month came today, 1800 people (18% of population) have not been evacuated yet. Especially at Iidate-mura, 1427 people (23%) of the total population of 6177 have evacuated. Those families with small children or living in the highly contaminated zones are mostly evacuated. However, those who have not found a good way to dispose of their cattle or those small business factories unable to do business at another relocated site are still remaining there. However, the government has relaxed their guidelines for these factories allowing them to stay there to keep their business going. In those places, the first thing the workers do in the morning is to put down the dosimetory readings at the entrance of the factories, where some measures for dose reduction, such as closing the openings to a minimum and taping the gaps around the windows are provided. Many of the ranch owners have to close their business, mainly because they are unable to provide pastures in their farm lands. They are all crying since it took years for them to build up their ranches and raised their cattle. They are all feeling that they lost their reason for living. The monetary compensation cannot recover their salt of life.
IV. Recapping on the continued threat of leakage of rain water
Due to the heavy tropical low pressure, the heavy rainfall into the damaged reactor buildings increased the volume of the highly contaminated water in the buildings. For example, the water level increased 38 cm a day in 1F1, 6 cm in the basement of 1F3 turbine halls. The most critical situations are in the water accumulated in the 1F2 and 1F3 trenches, now rose to 39 cm below the ground level in 1F2 and 29 cm in 1F3. Since the new water purification system is not anticipated to be ready until July, TEPCO is looking for some other storage facilities. With its very high activation, it cannot be stored in the open tank yard, now being constructed on the site.
Well, let me stop here.
Gen Saji
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((Previous e-mail sent at 10:21 PM on May ?0 as Earthquake (80))
Dear Colleagues:
80th day!
I. Recapping on 1F4 spent fuel pool situation
Through this accident, the mother nature left us many mysterious issues, indicating that our understanding of the nature is much limited. One of the mysteries is the hydrogen explosion in the 1F4 pool, where all the fuel assemblies were moved into the spent fuel pool at the time of the accident. Many distinguished scientists and engineers insisted that the hydrogen must have generated through the zirconium steam reaction at a high temperature.
In order to find a clue to this issue, Professor Yousuke Katsumura and his colleagues performed an urgent radiolysis test using hot water. He was kind enough to provide me his draft paper, unpublished. With his permission, I made an urgent condensed translation as attached. They tried to confirm their hypothesis that the hydrogen produced through radiolysis of the boiling water is released with steam and condensed in the room by separating the hydrogen gas.
I am also suspecting that the hydrogen is produced through water radiolysis, however in my opinion, the dissolved hydrogen containing up to the solubility limit at the operational temperature in the pool water was released to the room atmosphere by heating up near to the boiling temperature. It is more of well known Henry’s law.
Also, one of my audience informed me the picture of 1F4 pool released on March 31with annotated explanation by
http://www.tepco.co.jp/en/news/110311/ )
The fuel rack appears to be the one with a size of approximately 1.2x1.7 meters with 4.2 meter tall for storage of 60 spent fuels.
Today TEPCO also released a set of photos taken inside of the 1F4 reactor building showing a very clean situation inside. It is very different from what we have been seeing in 1F1-3, with full of debris and often with water leakages.
( http://www.tepco.co.jp/en/news/110311/index-e.html#header “Inside the Reactor Building, Unit 4, Fukushima Daiichi Nuclear Power Station)”. It appears that the mechanism of hydrogen explosions in 1F4 should be different from those in 1F1-3.
II. Two TEPCO operators were found received excessive internal radiation exposure
A whole body exposure measurement performed at JAEA to account for internal exposure identified two control room operators who have accumulated the thyroid exposure from I-131 at 9760 Bq and 7690. Combined with the external radiation, the converted total doses may exceed the 250 mSv limit, the limit specified for recovery activities for nuclear accidents.
III. Continued threat of leakage of rain water
With a heavy rainfall induced by the typhoon, the volume of the highly contaminated waters are increasing rapidly, now threatening for overflow from the trenches. In the 1F1/1F3 turbine hall basements, the level increased by 19.8/4.2 cm a day, respectively. At the trench of 1F2, the water level has increased by 6.2 cm. TEPCO quickly put sandbags to be prepared for possible overflow. Fortunately, the typhoon now is heading toward the NE direction and has already diminished into a tropical depression. However a heavy rain is still predicted in the Fukushima region tonight.
Well, let me stop here tonight.
Genn Saji
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(Previous e-mail sent at 0:0? AM on May ?0 as Earthquake (79))
Dear Colleagues:
79th day!
I. Water supply lines recovered for all of 1F1-4 spent fuel pools
The water supply to the spent fuel pools was provided through a piping from the Condensate tank before the accident. Since this function was destroyed by the tsunami, the pool water has been injected by using concrete pumps. TEPCO announced yesterday that these feed water routs are now recovered and can supply water by using the normal Fuel Pool Cooling and Water Purification System, although the cooling function is still not available due to the “loss of ultimate heat sink”. External air cooling system will be installed soon to recover this cooling capabilities.
II. Near emergency in the loss of the 1F5 sea water pump
On Saturday night, the temporary sea water pump was found not working. The temperatures both at the reactor vessel as well as at the spent fuel pool were started to increase as high as 93.7 degreeC in the reactor vessel last night. Fortunately, TEPCO was able to replace the pump by the noon today and another emergency was avoided. Since the temporary pumps are vulnerable without sufficient monitoring from the control room, the trouble seems to have been unidentified. It is necessary to provide a temporary I&C system so that its function can be monitored from the control room. TEPCO staffs seem to be taking that this issue as a minor trouble, however, the sea water pump is now in a safety grade for decay heat removal, even it is temporary.
III. Cs-137 found in the sediments of the sea water
MEXT collected 12 samples of sedimentation from bottom of the sea of 300 km square during May 9 to 14. Their analyses indicated as much as 110 Bq/kg of Cs-137 from a sample takes 30 km off shore, 45 meters deep, 50 Bq/kg off Mito, 45 meter below the tidal surface. Specialists are speculating that the contamination was first picked up by plankton and deposited at the sea bottom. No data are shown yet about the strontium contamination, however, the real threat is in Sr-89 and 90 in the marine food chain, I believe.
IV. Recapping on more detailed environmental monitoring data released today
For last two days, I have been spending a significant amount of my time to investigate the environmental monitoring data released on May 27 from TEPCO. Currently I could only plot the results in a form of Monitoring-Events graph as attached. On this issue, I have introduced several time in the past, but this in the newest one. My general observations are:
(1) With more detailed environmental monitoring data released from TEPCO, including the raw data of every 2 minutes, the overall picture of large release events became visible more clearly, although they are limited to only a few locations around the damaged plants. Depending on the wind direction, some of the important events may have been overlooked.
(2) Nevertheless, the reported 1F1 events and the environmental monitoring records are now relatively well correlated. However, it appears that there was a subsequent large release event from 1F1 after the hydrogen explosion. I have been suspecting this through my assessment of the land contamination maps released from DOE/NNEA ( http://energy.gov/news/10194.htm ). For more detailed explanation, please refer to the attachment.
(3) Further destruction of the plants seem to have occurred spontaneously even after the hydrogen explosions, continue releasing large amounts of radioactive effluents. The mechanism of these releases are not known yet.
(4) The large releases occurred between March 12 to 16. Previously, I though it was limited uppp to March 15. However, TEPCO’s new environmental monitoring data are showing another large release event occurred on March 16.
I do not think these releases are due to core melt though, since after releasing the contaminated steam, the events terminate by themselves spontaneously. I will study these results more in detail by referring to TEPCO released “Plant Data” to identify possible correlation of the operator actions with the environmental monitoring data.
Through my quick study, I noticed that TEPCO seems to be not releasing the raw data for March 15 and 16. Since there are several uncharacterized large release events identified as attached. The raw data are highly requested, if available. The environmental monitoring data, although they were taken by monitoring cars and survey meters, the data are one of the few robust data available for this accident due to the station blackout which induced blackout of the control panels.
Well, let me stop here today on Sunday.
Genn Saji
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(Previous e-mail sent at 0:00 AM on May 29 as Earthquake (78))
Dear Colleagues:
78th day!
I. Improvement of medical assistance to radiation workers at Fukushima Daiichi
On May 14, a worker passed away, at the age of 60, by a cardiac infarction during the time when on site industrial health care doctor was absent. Unfortunately it took two hours to send the patient to the hospital by an ambulance. The doctor was staying at the site every other day, only during day time. In the light of this, the Ministry of Health, Labor and Welfare made an arrangement to have a industrial or roentgenology doctor to stay 24 hours at the site in rotation. The doctors are all worried about deterioration of the working environment in the coming summer while wearing air-tight radiation protection suits.
II. Recap on the MEXT’s plan to construct a detailed land contamination map.
A question was raised from one of the audience of this daily updates, by saying “How did MEXT pick the top 5 cm of soil? Why not the top 1 cm? What percentage of fallout is trapped by the first cm, the second? Aren't people exposed to mostly the fines in the surface layer? Does the bottom 4 cm just dilute the top 1 cm?” The attached one page memo should explain to this question.
In the projected soil sampling in Fukushima by academia for construction of a detailed land contamination map, they plan to collect soil samples up to 5 cm from the surface and the total activity of each nuclear species will be shown per sample. By knowing the area of the sampler used, the results will be converted to Bq/m2, the unit used at the time of Chernobyl accident.
III. More detailed environmental monitoring data released today
Currently I am checking the new data. It is nice to find more data on March 11.
Well, let me stop here today!
Genn Saj
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(Previous e-mail sent at 9:27 PM on May 27 as Earthquake (77))
Dear Colleagues:
77th day!
I. Recapping on remediation of school grounds
On this issue, I have recapped in Earthquake (51), (58) and (71) in the past. Today I learned from media reports that the MEXT showed a new guideline for ALARA to 1 mSv a year for school exposure. The Government will support 98% of necessary costs for remediation when the surface contamination level exceed 1 microSv/hr at school. The government is going to re-measure the contamination level and identify school ground for remediation, working closely with the Fukushima municipal government. This issue is likely to be resolved in an appropriate direction, I believe. However, I am concerned that general public do not seem to understand there is no threshold between a safe and non-safe limit in the current LNT hypothesis. This seems to be making people suspicious that the government is hiding something grave.
II, Distribution of dosimeters for every school children.
In Kawamata-cho, Fukushima, the municipal government decided to distribute a personal dosimeter to each school children of day nurseries, Kindergarten and grade schools, in the total of 1500 school children. These will be collected once a month and checked by a private monitoring company. The dosimeters were supplied by Kinki University who offered to measure doses of the school grounds there. I can foresee this will spread more widely in the highly contaminated areas in Fukushima.
III. Health monitoring in Fukushima
MEXT also distributed dosimeter to all of the 1200 plus schools in Fukushima. The schools include day nurseries, Kindergarten, grade schools and high schools. The ministry is requesting the principals to report the readings once a month. The results are free for each school to release locally.
In addition, Fukushima Prefecture government decided to screen all of their residents of 202 million people to estimate radiation exposure since March 11 asking them to respond to a questionnaire. The total accumulated doses are estimated to select a cohort whose radiation health effects will be monitored for several tens of years. For high dose group, continuous blood and urine tests, as well as whole body monitoring will be performed. The procedure is similar to what was done to select the LSS (Life Span Study) cohort for Hiroshima-Nagasaki atomic bombing survivors.
IV. Recapping on a leakage from the contaminated water storage facility
I introduced this story yesterday. TEPCO converted the basement of Miscellaneous Solid Waste Compacting Facility for temporary storage of the highly contaminated water for 1F3, however, the water level inside started to get lower even without pumping. A worker found that the underground corridor is being flooded with water. The corridor connects this facility to the Process Room in the Centralized Waste Treatment Facility. The contact dose rate was 70 mSv/h, not very high compared with the dose rate of the 1F3 basement water of the turbine hall. This dose rate appears to be that of the trench of 1F3.
The increase of the volume of the contaminated water coming from the underground water is becoming an increasingly troublesome issue, since Fukushima will soon go into a rainy season. As a matter of fact, here in Yokohama, where I live, entered into the rainy season today. On top of that a large typhoon is heading toward Japan threatening Japan. The underground water level can substantially increase during the rainy season.
V. Cost of processing the highly contaminated water
TEPCO explained today that a cost of the contaminated water processing is estimated to be approximately $2.60 per litter.
VI. More detailed environmental monitoring data will be released soon
Today TEPCO reported that there are still un-incorporated data from the environmental monitoring station waiting to be released. Upon hearing this news, Mr. Edano, the Chief Secretary of State, was furious, after the fuzzy issue as to the initiation of the seawater injection. I can guess what the data is all about. Due to the station blackout, all of the environment monitoring posts went dead. TEPCO quickly set up a portable dosimeter in place of the the monitoring stations, as well as put a monitoring car dispatched from Tohoku Electric Power Company. The software system of this monitoring car seems to be different from the one used by TEPCO and could not have been able to incorporate these data yet. I can tell this since I have already used a part of this data and introduced in Earthquake (62). Certainly, I have been waiting this set of data be released soon, because there are several release events which are not well correlated with the currently available monitoring data. I do not think TEPCO is intentionally hiding the data or anything. Just due to a possible technical difficulty.
Well, let me stop here today!
Genn Saji
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(Previous e-mail sent at 10:43 PM on May 26 as Earthquake (76))
Dear Colleagues:
76th day!
I. Initiation of the sea water injection to 1F1
For last several days, at the current Diet session, there has been a big political argument whether the Prime Minister ordered to suspend the sea water injection, which was started at 7:04 PM of March 12, due to his concern about re-criticality through the sea water injection, reported to be advised from the Chairman of the Nuclear Safety Commission. Each people involved changed their explanations each time and induced a lot of confusion among the Japanese people. So far, TEPCO was reporting that the sea water injection was suspended at 7:25 until 8:20 PM for 55 minutes. TEPCO made a correction today that the sea water injection has never been suspended, due to a judgment of the Fukushima Daiichi Director, Mr. Yosida. Since no record nor process computer records are not available in support of this operation, he public entertained doubts about the Government as well as TEPCO.
In addition, those people who are still evacuated because of this accident were dismayed at these political scenes, by saying this is not the time to argue who said what, rather wanted to see the politician discussing how to stop that nuclear accident.
II. MEXT decided to construct a detailed land contamination map.
The Ministry of Education, Culture, Sports, Science and Technology (MEXT) decided to construct a detailed soil contamination map of the entire district of Fukushima. The soil samplings will be made every 4 km2 within 80 km, every 100 km2 beyond, from 2200 locations. Each sample will take 5 cm deep soil, by mobilizing 25 universities and research institutions.
With already detailed land contamination map released by DOE/NNEA, I do not see why they can make a better planning of resources such as by distributing more measuring points at the heavily contaminated regions located at the NW direction of the Fukushima Daiichi. This region has a width of 20 km and a length of 50 km, which should call for more detailed measurements. For the land of habitation in the Iidate-mura, for example, a detailed soil contamination map is highly waited, I believe. At the same time, I worry about possible exposure of students by entering this region for sampling, since the dose rate is high as 100 microSv/hr. In addition, most of this highly contaminated region is located across the Abukuma mountain chains and a mountain climbing is going to be necessary, with much difficulties in collecting soil samples. It is a kind of radiation work. Considering these difficulties, I do not think the MEXT’s plan is feasible, I am afraid.
III. A leakage from the contaminated water storage facility
TEPCO converted the basement of Miscellaneous Solid Waste Compacting Facility for temporary storage of the highly contaminated water, after waterproofing, with a capacity of 4000 tons. After pumping 3700 tons from 1F3, the water level started to decrease by 4.8 cm in 20 hours. The leaked water is likely went into another areas of this facility. Currently TEPCO intensified monitoring.
Well, let me stop here today!
Genn Saji
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(Previous e-mail sent at 10:55 PM on May 25 as Earthquake (75))
Dear Colleagues:
75th day!
I. TEPCO uploaded the accident scenario of 1F1 and results of core melt analysis for 1F2 and 1F3
As I introduced in earthquake (74), TEPCO made the following Press Release (May 24,2011),
Submission of a report on the operation of the plant based on the plant data etc. of Fukushima Daiichi Nuclear Power Station at the time of the earthquake to NISA.
Please visit the website to look into their results.
http://www.tepco.co.jp/en/press/corp-com/release/11052412-e.html
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110524e13.pdf
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110524e14.pdf
Attached please find an update of my “back of an envelope” calculation performed to include the “feed and bleed” function for 1F2 and 1F3, which releases the reactor vessel pressure through automatic release and safety valves. The “release” function requires a battery power, however, the “safety” function actuates even in an event of the station blackout. It will take about a day for the reactor level to be down to the bottom of the fuels in the 1F2 case and about half a day for 1F3 case. The case for 1F1 has been shown previously in Earthquake (70). This update is attached just for completeness and I do not intend to challenge the results by TEPCO. I think this kind of issue should be assessed in the future more carefully when everything settle down. I do not believe the we have to make a hasty conclusion that a gross core melt has occurred in 1F1 to 1F3.
II. Glowing evidences for pipe failure accidents during the first few days.
TEPCO disclosed that there could have been a pipe failure accident soon after the earthquake, resulting in a leakage of the reactor water. Their analyses show that a 7 to 10 cm diameter equivalent holes in 1F1 and 1F2. At the night of March 11, a very high radiation was detected in the 1F1 Reactor Building, and operators suspected a pipe failure. For 1F2, a postulated failure as large as 10 cm diameter hole assumed to have occurred at 21 hours after the seismic trip yields a good agreement, according to TEPCO. For 1F3, the High Pressure Coolant Injection System was started around 12:30, however, both the reactor pressure vessel and containment vessel pressure suddenly dropped. By performing an analysis by assuming a pipe break in HPCI, the results of the pressure transient agrees well.
I also found that TEPCO has experienced eight hydrogen explosion damage cases to the instrumentation systems in normal operation ( http://www.tepco.co.jp/cc/press/betu03_j/images/030821b.pdf and http://www.tepco.co.jp/cc/press/betu03_j/images/030821d.pdf, in Japanese ) between 1994 and 2001. These events have a common feature that the damaged portion appeared to have exposed to a high temperature and pressure. In pressure transducer cases, a sudden pressure peak is detected, followed with no indication or abnormal indication. Post accident examination revealed that the sensor was broken by overpressure and high temperature.
I am increasingly confident that an “internal hydrogen explosions” have occurred in all of these cases. I introduced this possibility in Earthquake (69) by attaching an one page summary of the Hamaoka Unit 1 pipe rupture accident.
III. Additional storage capacity of the highly contaminated water
TEPCO disclosed that the Centralized Waste Processing Facility can accommodate additional 5000 m3 of the highly contaminated water on top of the almost full situation so far disclosed. I remember that they wanted to make a further check to use it in full.
IV. A memo for lessons learned from the tsunami-induced nuclear disaster (continued)
For memory sake, let me add lessons learned.
(56) “Internal hydrogen explosion” and instrumentation
In following plant data released from TEPCO during this accident, very often the indication of pressure and level gauges have been showing unreasonable reading. In view of this, TEPCO had an instrumentation engineer to go inside to the reactor containment vessel to re-calibrate the level gauges. Through this reading, TEPCO changed their view that the entire 1F1 reactor core has now lost its submerged status, resulting in the core melt scenario.
However, the current plant data indicate that the fuels are reasonably cooled inside of the reactor pressure vessel. The image of molten core at the bottom of the cold reactor vessel are not compatible for me. While looking for evidence of a possible occurrence of the “internal hydrogen explosion” as occurred in the pipe rupture accident at the Hamaoka Unit 1, induced by a hydrogen explosion, I noticed that there are several precedents experienced between 1996 to 2001inside TEPCO, who has been charged by an anonymous accusation. TEPCO made a response in Japanese in the following document. http://www.tepco.co.jp/cc/press/betu03_j/images/030821b.pdf
Since the troubles resulted in minuscule damages to small diameter instrumentation piping only, with no environmental effects, they were fixed internally. TEPCO also had been performing R&D studies before the accusation. According to the report, it tends to occur in horizontal instrumentation piping, damaging the pressure transducers. Sometimes a pressure surge is observed, followed with sudden loss of the reading.
Although the radioactive release might have been disregarded, the loss of instrumentation function can be of a safety concern. As a matter of fact, unreliable indications of level and pressure gauges confused accident management. In particular, many pressure transducers are connected to horizontal instrumentation pipes, which should have been vulnerable for hydrogen accumulation.
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(Previous e-mail sent at 1:12 AM on May 25 as Earthquake (74))
Dear Colleagues:
7?th day!
I. Activity data of the highly contaminated water at turbine halls
On May 22, TEPCO disclosed a set of activity data taken from the basements of 1F1-4 turbine halls. These data
have been sampled on March 24 and 27. The early information was first released on March 25, however some errors had slipped in and TEPCO was admonished by NISA to improve quality of data. After that, they released only the
data of I-131, Cs-134 and Cs-137, to be followed with more detailed data, confirmed by the third party, after going through a reviewing process by a group of specialists. After going through these procedures, TEPCO released detailed data two days ago.
These are very precious data, I believe, since they are a few of the robust data hiding “foot prints” of the accident procession. For estimation of the extent of core damages, for example, these data should become a starting point. Recognizing the importance of the data well, I compiled the data as attached. The original is posted in the following website. http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110522_04-j.pdf (in Japanese)
I made a scoping study by using this data to estimate the fuel damage fractions as attached. It is very strange to find somewhat different footprint left by 1F2 with an order of magnitude larger sampling data compared with both 1F1 and 3. For more detail, please read the remarks in the attachment.
II. The “melt-through” analyses released for 1F2 and 1F3.
Following the melt-through scenario as most recently explained in Earthquake (70), TEPCO released their assessment of the severe accident assessment of 1F2 and 1F3, mostly through extending the assessment of 1F1. For 1F2, around 1:00 PM on March 14, three days after the earthquake, the total loss of the cooling capability occurred, followed with a start of core melt at around 8:00 PM. By this time, most of the fuel meted down to the bottom of the reactor vessel. A similar results are also provided for 1F3. I have not performed a follow on “back of an envelope” calculation yet, but form their illustration, they ignored the effect of “bleed” cooling. Since the decay heat is further down as compared with the 1F1case, I believe we should have much longer time allowance that what is being predicted by TEPCO’s pessimistic scenario.
One of the new points of the TEPCO’s analysis is that they provided hydrogen generation rate, through zirconium water reaction. According to their estimation, 800 kg for 1F1, 300 kg for 1F2 and 600 kg for 1F3, In another interview, they explained that a portion of the hydrogen flowed through a common ventilation duct to 1F4, hydrogen gas discharged through venting, inducing the hydrogen explosion there. I forgot to introduce this scenario. Some of the difficulties in this is that the ventilation ducts are severely damaged through a series of preceeding hydrogen explosion nor ventilation fans to the common stack were working due to the station blackout.
Anyway, I do not think this kind of argument is helpful in finding an urgent way to mitigate the consequence of the accident. For me, the most important issues are (1) find an effective way of the damaged core cooling, (2) without substantial increase in generating the highly contaminated water. Since a large fraction of injected water seems to be leaking before reaching to the reactor vessel, finding a better cooling water passage is urgently needed. TEPCO appears to be injecting a few times more water than necessary to remove the decay heat according to heat balance studies performed by many people. The water injection through the ECCS may not be effective, in referring to the Hamaoka Unit 1 hydrogen explosion experience. A better route should be through the feed water line, which is located at a lower level.
III. Root cause of the “loss of off-site power”
The Fukushima Daiichi and Daini are hooked up with six transmission routes to the TEPCO grid. TEPCO reported to NISA to answer to the question of why external power source was all lost by the earthquake. Four transmission routes went out, due to shorts induced by the earthquake. The remaining two went down due to damages at switchyard. Due to these troubles, the circuit breakers tripped. One of their nearby transmission tower tumbled down due to a land slide from a hill, although the tower itself was designed against earthquakes. The earthquake again demonstrated the common cause nature. TEPCO has been boasting that loss of off-site power is not likely at Fukushima thanks to the sufficient redundancy.
IV, TEPCO continues to find the operation of the Isolation Cooling System
According to their investigation of the plant data, the turbine driven Isolation Cooling System automatically started at 14:52 but manually stopped at 15:03, 11 minutes after. At 18:18 and again at 19:30, operators attempted to start up again, however, the actual operation has not been confirmed yet. If so, it is strange since the battery power was thought to be still available until 10 PM. They continue to investigate this issue.
V, International investigations
Stating today, on May 24th, a team of IAEA dispatched an expert fact-finding mission to Japan to make a preliminary assessment of nuclear safety issues at the Fukushima Daiichi nuclear power plant following the March 11th earthquake and Tsunami. The Japanese government assured that any necessary data will be open to them. Mr. Weightman from England will present the mission's report at the Ministerial Conference on Nuclear Safety organized by the IAEA in Vienna from 20 to 24 June 2011.
The UNCEAR also decided to investigate the radiological consequences of the Fukushima accident. They plan to spend two years for their investigation, to complete their preliminary report in May, 2012, Professor Wolfgang Weiss from Germany spoke at an press interview.
Well, let me stop here!
Genn Saji
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(Previous e-mail sent at 9:44 PM on May 23 as Earthquake (73))
Dear Colleagues:
73rd day!
I began to notice that, although the Fukushima Daiichi plants are not completely under control, the reports from TEPCO as well as the Government are becoming less frequent, since the ‘time constants’ of the accident became much longer. I plant to follow the daily progress best I can, however, if you started to feel annoying, please drop me a line so that I can stop sending you my daily updates. I can now spend more time on my assessment of the accident. Currently, my high priority is to make further progress in confirming the root cause of the 1F4 hydrogen explosion from a radiation chemistry point of view.
I. Gamma camera view of 1F1
I have been waiting for the TEPCO to upload the gamma camera view in English. Here it is.
http://www.tepco.co.jp/en/news/110311/index-e.html
When you first crick the optical view image, followed with another crick to see the gamma camera image, you will find that the very high dose region is from a piping, located near the ventilation duct. Although the gamma camera does not tell the actual dose rates, it should be a very powerful tool to identify hot spots. For general explanation of gamma camera, see
http://en.wikipedia.org/wiki/Gamma_camera
II. No significant earthquake damage in Fukushima Daiichi, but it was tsunami that devastated the plants.
Following the release of the plant data on May 16, TEPCO confirmed that the plants responded to the seismic trip signal as designed, all the reactors went into sub-critical states, followed with the planned decay heat removal operation sequence without any serious problem. After the arrival of the tsunami, Fukushima Daiichi went into a “station blackout” combined with a “loss of ultimate heat sink” situation. After the tsunami, the available plant data are much limited, only the data obtained by dispatching auto batteries to the control room. Therefore, TEPCO collected information by interviewing the operators through fact-finding on the spot. This indicates also indicate that the plants went into the “(feed) and bleed” operation as designed, by releasing the reactor water into the suppression pool by “bleeding” from the automatic release and safety valves, while sacrificing the water inventory. The TEPCO continues the fact- finding of the operation of the turbine-driven Isolation Cooling System (a part of ECCS) of 1F1. The ECCS was said to be manually terminated before arrival of the tsunami. On this issue, I made a “back of an envelope” calculation in Earthquake (71) to assess the effect of early termination. My study indicated that the recovery/maintaining the reactor water level by subsequent recovery of the ECCS should have been more critical. Unfortunately, no clear data are available to confirm this point yet.
III. Continued critical situation in the storage of the highly contaminated water
It was disclosed today that the Centralized Waste Processing Facility, which is being used for the water storage after making the building water proof, has been approaching to a full level in a matter of 4 days. TEPCO plan to keep the water at the basement of turbine halls, while intensifying inspection for possible leakage. They have to wait for the availability of temporary water purification facility in mid June. So far, 8700 tons of water was pumped from 1F2, and 2700 tons from 1F3.
The aerosol monitoring sample of the 1F2 revealed 0.024 Bq/cm3. It is reported that the sampling was questionable, being 1/10 – 1/100 of the value obtained by the “PackBot” on April 18. TEPCO plans to re-sample the air again. I stopped to convert this to a dose rate.
Well, let me stop here today!
Genn Saji
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(Previous e-mail sent at 8:36 PM on May 22 as Earthquake (72))
Dear Colleagues:
72nd day!
For last few weeks, I was so busy in doing my assessment of the Fukushima Daiichi accident and I did not have a time to introduce a hart warming story. That is, in spite of the tsunami death toll over 15,000, there were not a single death from the 315 day nurseries caring babies and pre-school children in the earthquake stricken districts. At the time of the earthquake, infants at these nurseries were at the time of afternoon nap. The nurses quickly woke them up, hump babies up to the nearby heights, pushing toddlers in big baby carriers (called evacuation carriers, commonly used in these facilities for taking kids to nearby parks), followed by small children on foot. Many of the nurses made best judges while observing the magnitude of the tsunami, moved up and up trying to escape from the tsunami. These facilities have been exercising drills for tsunami, earthquake, and fire once a month. For example, at Noda-mura day nursery in Iwate Prefecture, the tsunami washed away its building, leaving behind only the front gate. Twenty eight villagers were dead among the population of 4700, 450 houses were destroyed. In the drill, they were supposed to evacuate to a “hill top house”, 500 meters away, however, the chief nurse Ms. Yuko Hironai (53) judged it may not be safe enough this time and quickly decided to run another 500 meters to “Genpei Hill”. When glancing back they observed many autos were being washed away from the country road below. Their 90 babies and kids, with 14 staffs all survived. There are many miracle stories like this. The nurses are really professionals, knowing well their vulnerabilities with babies and kids.
I. Recapping on remediation of the school ground
(Earthquake (51)) Professor Kosako appeared at a press interview and strongly criticized the government’s decision, especially related with allowing the accumulated dose to 20 mS/y for children, from the previous 1 mSv. He also criticized sharply the Prime Minister’s accident management policy by saying that the decisions were made in a haphazard way. In addition, he has been insisting on dissemination of the results of atmospheric dispersion code, SPEEDI, during the early phase of the accident.
(Earthquake (58)) Following the surface soil removal method performed by Koriyama-shi to reduce the dose rate of some of the school grounds, Fukushima-shi tested a method to put the contaminated surface soil at the bottom of the soil whose surface was temporary put aside. By digging up to 50 cm, the dose rate decreased by a factor if ten. Before this treatment, the dose rate at the surface was 2.3 - 2.1microSv/h. After the treatment, the dose rate went down to 0.2 microSv/h. Another test showed that this method can be equally effective, when the depth is around 20 cm.
By taking these messages very seriously, parents of school children of the schools with contaminated school grounds applied pressure to the local government to reduce the dose rate as low as reasonably achievable (ALALA). Currently as many as 217 school grounds are being in remediation or scheduled to be decontaminated. The method is now converging to remove the 3-5 cm of surface soil and put it into a deep pit and cover the contaminated soil with about 1 meter thick clean soil. The estimated cost is in an order of 7.5 million dollars. Although the local governments are requesting to MEXT for support this operation, the government is not prepared for such a budget, since their official position is 20 mSv/y. The government has not decided what to do with the expenditures.
Even after the remediation, or with grounds less contaminated, most of the schools are refraining form using the school grounds, replacing them with gyms, having their sports day indoor.
Well, this kind of news made me feel happy, since there are a lot of unknowns in the effect of low level radiation to youngsters. Even among the Hiroshima-Nagasaki LSS cohort, the real radiation risk may not become clear until most of them passed away, another a few tens of years. However, the LSS cohort tends to live longer, perhaps because they pay more attention to their health and they are under better health examinations, although their quality of life is a different issue. A kind of selection effect. However, they also tend to suffer from non-cancer malignant diseases more than unexposed comparison group. Not only that, the LSS cohort have received significant doses just once in their life. The effects of the continued irradiation of 20 mSv for a long time is not completely known although ICRP’s principle is to limit the life time accumulated dose to less than 1 Sv for human being.
Not also that the amelioration of the school grounds are limited to only the least contaminated areas, Zone I as introduced in Earthquake (61). These schools are distributed in the “Naka-dori” district of Fukushima Prefecture, the wide and flat valley districts between the Abukuma Mountain Chains to the east and the Ohu mountain Chains to the west, with the contamination area of 956 km2 in the following grouping
Zone Cs-total (Bq/m2) area (km2)
V 6E+06 – 3E+ 07 151
IV 3E+06 – 6E+06 116
III 1E+06 - 3E+06 483
II 6E+05 - 1E+06 379
I 3E+05 - 6E+05 965
Total 2094
The real issues will be how to decontaminate higher contamination zones, Zone II-V. These areas include Iidate-mura and Namie-machi. However, fortunate issue is that the most severely contaminated areas, Zone IV and V, are mostly located in the Abukuma Mountain Chains and the habitable areas were only a portion of these. There are 9 schools in Iidate-mura, 11 in Namie-cho and 4 in Futaba-machi and 7 Ookuma-cho. A part of these towns and districts are heavily contaminated as high as Zone IV and V, For these schools, school by school planning should become necessary.
It is interesting to see a decontamination experiment being performed by a volunteer group for a farm house. According to their experience, cleaning the roofs and gutters seems to be effective in reducing the dose rates.
Also, some people are interested in using biotechnology for remediation of the contaminated farm lands. I do not know how the soil bacteria can reduce the dose level. It appears to strip cesium out of the soil taking into the cells of bacteria, and can be mixed more evenly by cultivation. http://tidt.jp/pdf/110513/fukugo-en.pdf
Well, let me stop here today, Sunday, to be refreshed for better tomorrow!
Genn Saji
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(Previous e-mail sent at9:18 PM on May 21 as Earthquake (71) with corrections to (Corrected) H2andO2 Accumulation.pdf.)
Dear Colleagues:
71st day!
CORRECTION
In trying to confirm my H2 and O2 calculation by solving the detailed chemical thermodynamics equations, I found an embarrassing error in converting the g-values expressed in molecules per 100eV into SI unit. Attached please find a corrected version. The results are not that hazardous as I contemplated but still not completely free from a concern. If the suspected “internal hydrogen explosion” had actually taken place, the important question is a separation of hydrogen gas from the reactor coolant and accumulation of the gas in the pipe line located at the upper portion of the reactor vessel.
I. A memo for lessons learned from the tsunami-induced nuclear disaster (continued)
For memory sake, let me add lessons learned.
(54) Radiation chemical studies in the accidental situation
From the day of Manhattan Project, the field of radiation chemistry has been studied deeply through 1960th. This provided scientific foundation of this field necessary to address water radiolysis behavior during normal operational conditions, although there are many unresolved issues for engineering application, such as CHC (critical hydrogen concentration) necessary to suppress radiolytic decomposition of water as well as the role of water radiolysis as a driving force of “macro-cell! corrosion is structures. This field of science is also closely connected with high temperature electro-chemisry. In spite of the brilliant progress in these field of science, its application to nuclear engineering arena has not been performed well compared with the computational fluid dynamics, for example.
The Fukushima Daiichi accident has revealed significant roles played by hydrogen produced through water radiolysis. Unfortunately, there are very few scientists and engineers who are prepared to cope with the accident management from this point of view. I believe these two field of science should have been a part of basic education in nuclear engineering courses just as the reactor physics.
(55) Environmental monitoring stations in the sea
In trying to assess Fukushima Daiichi accident consequences, it was disappointing to find no radiation monitoring data from the eastern direction from the plant, when the large lease occurred through hydrogen explosion but when the wind direction was towards the ocean. Due to the increased environmental consciousness, the ocean should not be considered as a sink of radiation release. Therefore the monitoring station in the ocean. However, the Eastern Great Earthquake experience imposed serious damage to the lighthouses either constructed on the shore line as well as in the ocean. Among the 251 lighthouses located in the coast line of eastern Japan, 121 of them were destroyed by the tsunami. Therefore, it is not anticipated to be easy. A practical solution should be investigated. On this issue, I have proposed to install a radiation monitoring station on above the reactors. However, it may not be able to detect ground level, low temperature releases. A feasibility of detection from a remote radiation source was discussed also in Earthquake (63).
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(Previous e-mail sent at8:46 PM on May 20 as Earthquake (70) with Summary-Hamaoka Unit 1 Pipe Rupture.pdf and H2andO2 Accumulation.pdf)
Dear Colleagues:
70th day!
I. Continued recapping on the status of 1F1 core
Now the TEPCO as well as the Japanese news media are taking the melt down scenario as granted for 1F1. This scenario is now being expanded to 1F2 and 3 as well, and people tend to explain all the difficulties are rooted on this scenario. I am not trying to challenge this notion, although I do not believe we have robust scientific evidence that the gross meltdown occurred as early as on March 11 in 1F1.
I made a quick “back of an envelope” calculation, on top of my recent assessment on reactor water level vs. decay heat curve, to address the issue of accumulation of hydrogen gas in the reactor pressure vessel as well as in the containment vessel. This should help to understand the mechanism of early hydrogen explosion of reactor pressure vessel as well as containment vessel, as well as verify continued needs for hydrogen gas management to prevent another hydrogen explosion. I summarized my results in the attachment, together with the data I assumed for this assessment. In a matter of 10 hours after the reactor trip, as much of 24 m3-STP of hydrogen can accumulate in the reactor containment vessel, 1.2 m3-STP in the reactor vessel. These values correspond to 72 and 4 kg of TNR-equivalent, respectively. With this much of hydrogen gas accumulated inside of the containment vessel, the continued nitrogen gas charging operation into the 1F1 containment vessel is justified, I believe. As a matter of fact, TEPCO is urgently looking into a route to charge hydrogen into the 1F2 and 1F3, followed with the previous operation in 1F1. At the same time, due to the “internal hydrogen explosion” as occurred in the Hamaoka Unit 1 in 2001, there is a high possibility that the hydrogen gas accumulated inside of the reactor vessels has also be released. Still it is prudent to charge nitrogen also into the reactor vessel to prevent another hydrogen explosion.
II. Tsunami photos
I forgot to introduce a set of photos at the time the tsunami attack released yesterday. It is amazing to see buckling of the huge surge tank by the force of tsunami. I believe such a buckling may have taken place by a large horizontal force induced by the tsunami.
(1) Pictures of Tsunami that hit the Fukushima Daiichi Nuclear Power Station
(pictured on March 11, 2011)-11 photos.
Place: North side of Radiation Waste Treatment Facility taken from 4th floor
(2) Pictures of Tsunami that hit the Fukushima Daiichi Nuclear Power Station
(pictured on March 11, 2011)
Place: The slope at the eastern side of Radioactive Solid Waste Storage Facility (The east side of Unit5 taken from the southern side of the unit) Taken by: TEPCO's affiliate company-6 photos
Well, let me stop here!
Genn Saji
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(All of the previous e-mail sent at11:29 PM on May 19 as Earthquake (69) with Summary-Hamaoka Unit 1 Pipe Rupture.pdf) were removed to reduce the mail size.)
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(All of the previous e-mail sent before May 10 as Earthquake (60) were removed to reduce the mail size)
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(All of the previous e-mail sent before April 30 as Earthquake (50) are removed to reduce the mail size.)
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(All of the previous e-mail sent before April 16 as Earthquake (36) are removed to reduce the mail size.)
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(All of the previous e-mails sent before April 6 as Earthquake (26) are removed to reduce the mail size.)
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(All of the previous e-mails sent in March are removed to reduce the mail size.)
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