Fukushima (167, Nov 25-Dec 2)

This mail bounced back from several recipients, due to exceeding the fixed mail size. Let me re-send by removing the bulky attachment as introduced in Chapter VI. A comprehensive set of viewgraphs of Fukushima Daiichi disaster (5.9 MB). Dear Colleagues: 259th - 266th day! Apology for delay in completing this mail. In the last few days, two very important reports were released from TEPCO as briefly introduced below. The reports are comprehensive, calling for detailed review in the coming several days for me. I intend to revisit these two reports in my next updates. I. Assessment of the damaged core status of 1F1 - 1F3 On November 30, TEPCO released a comprehensive report and viewgraph summaries of assessment of the damaged core status of 1F1 - 1F3 (only in Japanese. The reports of this kind have never been translated into English by TEPCO, I am afraid.). Previously, on May 15/23, TEPCO release their results of MAAP (Modular Accident Analysis Program) analyses, concluding that the in-vessel retention of core debris have been achieved, in spite of the severe accident induced by the tsunami. TEPCO revisited this issue,since many new information became available through amelioration activities after that. Their new results conclude the following: 1F1: Most of the molten core debris has moved down to the bottom of the reactor vessel. Reactor Pressure Vessel (RPV) has likely be destroyed with the corium 1F2/3: The damaged core debris has likely been moved to the bottom of the RPV in their conservative assumption, or, the damaged core debris is still retained in the reactor core region, If the actual indication of level gauge is trusted. TEPCO's view of the core status of 1F1has been substantially updated. Although the assessment of the core state was made from multiple viewpoints, including the MAAP assessment, a heat balance approach, the new level gauge data and nuclide assessment, I got an impression that the biggest impact came from the new level gauge data. In their previous assessment as introduced in Earthquake (138,July 28-30), the water gauges of 1F1 RPV was indicating approximately 0.53/1.30 m for Narrow range gauges A/B above the TAF (Tope of Active Fuel level) at 02:30 of March 12, the time of starting the water injection. If the water level was actually as high as the indication, the melt-through should not be the case. However, on May 11, TEPCO re-calibrated the level gauges and concluded that the water level should be -500 cm below the TAF after calibration. In view of this new information, TEPCO appears to have made a very conservative new assumption, that the reactor cooling was lost at the time of the earthquake, even before the "station blackout" induced by the tsunami. Although TEPCO tried to support this new core-melt scenario by other approaches, they are too weak in my view. II. TEPCO's Internal investigation committee report on Fukushima Disaster On December 2, TEPCO released an interim report (140 pages) of their Internal investigation Committee on Fukushima Daiich committee. (Currently, the Government has also launched Investigation Committee on the Accident at the Fukushima Nuclear Power Stations (http://icanps.go.jp/eng/) Their interim report is also expected soon, reportedly by the end of this year.) Media's evaluations are generally with harsh criticism, such as saying that now new facts have been disclose, full of excuses and insisting on responsibilities of the nuclear regulation. However, since TEPCO has an overwhelming information of the accident, it is highly expected to see a good final report, reported to be completed in June next year. III. Fukushima land contamination maps and effect of local topography I introduce this issue several time, the most recently in Earthquake (164, Nov 11-18). MEXT (Ministry of Education, Culture and Sports) released, on November 25, the soil contamination maps of wider regions of the Japan mainland, extended as far as 450 km from the Fukushima Daiichi, through http://radioactivity.mext.go.jp/ja/1910/2011/11/1910_1125_2.pdf in Japanese. This survey is the last of this series this year, since some of the districts are now covered with snow, reducing the dose rate significantly for remote (airplane) survey. MEXT plans to resume this activity next year to cover the entire Japan, since some contamination was identified even at Okinawa, which is located as far as 2,000 km from Fukushima Daiichi. In the recent report, MEXT included an interesting map, in which a contamination map is shown on top of the topology (terrain) of the contaminated areas. It is instructive to understand how the drifting of the plume occurred first towards NW then to the SW direction. Let me attach an English translation of this map. The map shows a projection taken from a hypothetical spot of 150 km NE from the coast at an altitude of 250km. In this map, please note that the Fukushima Dai-ichi is surrounded by mountains, Oou Mountain Chains and Echigo Mountain Cahins at the west. Abukuma Highland is located at the NW direction of the site. There mountains are gently slopping, eroded by tens of thousands years of erosion. There is a large river flowing down the "Naka-dori" flats from south to west direction. The elevation of "Naka-dori" is sloping from an elevation of 250 m to 60 m. Further south, the elevation is as high as 400 m. The Fukushima site is located in the "Hama-dori" flats near the shore line. Around the time of the accident, which occurred on March 11, the meteorological condition of the eastern Japan was unstable, sometimes in a pattern of three cold days and four warm days, marking the end of winter and the beginning of spring. This phenomena is not so clear in Japan as in the case of coastal regions of China or Korea. It is often induced by a migratory anticyclone produced in the coastal region of China. Without the occasional passage of the anticyclone, the wind direction was generally from the west to east, due to the prevailing westerlies. During the active phase of the accident, this general wind direction (towards the sea) greatly helped in reducing the in-land radiation contamination. During the active phase of the accident during ten days, March 11 to 21, as many as ten times of large releases occurred with largest three occurred between March 15 to 16. Even eight months after accident, exactly which release event correspond to which unit or event has not been identified. Although it is not known when and what event produced the in-land contamination, the land contamination density distribution is showing that the wind direction should have been toward NW direction until the plume run up onto the Abukuma Highland, finally reaching to the "Naka-dori" Flats. The plume was blown towards SW direction along the Oou Mountain Chains as well as other mountain walls located in the west edge of "Naka-dori"Flats, contaminating this region. When the plume arrived at the Abukuma Highland, due to reduced atmospheric pressure, the volume of the plume increased forcing he thermal energy contained in the plume in a form of steam condensing into a local rainfall along the plume passage through a mechanism of "black rain", producing the distinct strip mark of the plume passage with heavy contamination along the Abukuma Highland. When the plume reached to "Naka-dori" Flats, the plume contained only mist, still highly contaminated but should have been in higher altitude from the flats. The fallout from the remaining plume contaminated the flats widely along the "Naka-dori" Flats, perhaps due to mist rain or fog. The initial core diameter of the semi-sperical plume, with highest concentration of radioactive cesium should have been 2 km, surrounded with 1-2 km thick mist region of a lower concentration volume, which can be estimated from the Cs-137 contamination map near the plant. The diameter of the plume further increased while traveling further NW, likely as large as several kilometers due to atmospheric dispersion. However, the estimated initial plume diameter of 2 km corresponds to a thermal energy release of 15 GJ, when the methodology as explained in my previous paper is applied. (G. Saji, 2005. A Scoping Study on the Environmental Releases from the Chernobyl Accident (Part I): Fuel Particles. In: Conference CD of International Topical Meeting on Probabilistic Safety Analysis, PSA’05, 11-15 September 2005 Sir Francis Drake Hotel, San Francisco, California, USA. Let me attach the pre-print of this paper). This methodology has been successfully applied for characterizing the highly contamination strip observed in the Chernobyl accident as well as the Hiroshima atomic bombing. This energy can be compared with the energy released by the hydrogen explosion. Assume that the total volume of the room is 30,000 m3. Approximately 1200 m3 of hydrogen is necessary to reach a concentration of 4%. Since the standard enthalpy of hydrogen gas combustion is ΔH2(g)=285.83 kJ/mol, the total energy released by hydrogen combustion is 1.5E+10 J=15GJ. Although these two results agree very well, it can be just a coincidence, since the released energy is proportional to the third power of the diameter of plume and its accurate estimation soon after the release is indispensable. However, the highly contaminated corridor near the Fukushima Dai-ichi has not been inspected, since it is within 5 km region where air plane flight is prohibited. Although this approach leads to a conclusion that the highly contaminated corridor stretching NW direction from the Fukushima-Daiichi results from a hydrogen explosion, the temporary radiation monitoring data performed by using the monitoring cars did not show good correlation except in the case of the hydrogen explosion from 1F1 occurred on March 12, although the observed dose level was much lower among the 11 giant releases recorded with this temporary environmental monitoring method. This is likely due to the fact that the dose rate of the plume high in the sky should have been substantially reduced with distance from the detectors through shielding effect of atmosphere, according to my "back of an envelope" calculation reported in Earthquake (63) distributed on May 5. Let me quote the relevant parameters below. "(2) Radiation source – dose calculation Assumed the following: - Equivalents of one Sv of X- or Gamma radiation = 6.77E+02 MeV absorbed per cm3 of air. - Energy absorption coefficient mu = 3.35E-5 cm-1 - distance form the plume to the detector: Z meter - Dose rate: D(sphere) = Sa/2x(25-Z)/(25+z)x(exp(-mu x (Z-25)) - exp(- mu x (Z+25))) - Source density Sa=147.5MeV-PBq*0.000000335/677*3600 (3) Results: Z(meters) 100 200 300 400 500 600 700 800 900 1000 D(mSv/h) 315 31.3 6.9 2.12 0.79 0.33 0.15 0.07 0.004 0.002 This means that I should have looked for the dose rate data as low as several to 100 microSv/h region for the detector located in 700-800 meter region. I revisited the dose rate data on March 12, to correlate with the hydrogen explosion from 1F1. Although I could barely identify a bip of a few microSv around the time of explosion, however, it does not positively support a significant increase in the dose rate due to hydrogen explosion. Unfortunately, the wind direction was towards NW and increased the distance from the nearest monitor, making the measurement more difficult. "　However, the atmospheric shielding effect suggests that the ground level release, traveling near the monitoring station, appear to be the cause of "giant releases. The ground level releases do not accompany significant energy releases." The highly contaminated corridor stretching toward NW direction from the plant cannot be reproduced by the atmospheric dispersion methodology since the fundamental physical mechanism is different. In the dispersion calculation, the fallout of aerosol is through either the dry or wet (washed out by rain) deposition mechanism. It applies only in a flat terrain, such as covered with prairie, bushes or housings in some dispersion sets, and does not consider atmospheric pressure difference in height, which can induce condensation of steam into droplets, which transport the radioactive aerosols down to the ground. IV. Update of radiation release to the marine environment I covered this issue most recently in Earthquake (164, Nov 11-18). Due to the station blackout, which wiped out all of the on-site radiation monitoring stations, it is difficult to estimate the total amount of radionuclides introduced to the environment from data obtained from the in-site instrumentation. Following explosions and steam venting of the reactor containments, an atmospheric plume of contaminated aerosols was transported mainly to the sea between March 12 and March 23. Contamination of the marine environment following the Fukushima Dai-ichi accident results firstly from dry and wet deposition processes, from an atmospheric contaminated plume directed mainly toward the sea between March 12 and March 23 during the active phase of the accident; secondly from direct releases of highly contaminated waters into the sea; and thirdly of the transport of radioactive pollution by leaching through contaminated subsurface water. After some of the recent studies were introduced, an interesting observation was released by Asahi Shinbunn (http://www.asahi.com/english/). (I looked for the original paper, however, I have not been able to get it yet.) A team of scientists, from Kyoto University, Tsukuba University and Meteorological Research Institute, has been measuring the radiation contamination of runoff of the Abukuma River and its tributaries, flowing through the "Naka-dori" Flats. These rivers collect rain water from a major portion of the contaminated water with is wide watershed (5400 km2). The monitoring was performed between June to August. They found that an estimated runoff of the radioactive cesium reaches approximately 23.4 GBq of Cs-134 and 29.1 GBq a day in an average. More than 90% of cesium was found absorbed on fine particles of clay and other suspensions at the river mouth. The remainders were found dissolved in water. Whereas at Iidate-shi, near mid portion of the river, the radioactive cesium run-off was 83.9 GBq and 925 GBq, individually. This is showing some of the suspensions were deposited at submerged weirs, before reaching the river mouth. This runoff rate is much larger than the direct discharge of vey low waste water performed in April, dischagring 40 GBq. This operation was performed to empty the storage tanks to provide capacity for storing the highly contaminated water. Since September, the concentration of cesium in the several locations of the rivers indicated below detection limit. V. Estimation of the current effluent release rate from the Fukushima Daiichi The Japanese Government is targeting to achieve the "cold shutdown" status by the end of this year. Since the Fukushima Daiichi is damaged, it is necessary to define a technical definition of "cold shutdown". TEPCO's definition is to achieve (1) reactor temperature is sufficiently below 100℃ and (2) an environmental release should be benign. In addition, it is indispensable that the damaged plant will not return back to another active state, such as through hydrogen explosion. TEPCO has been trying to improve an accuracy in estimating the radioactive effluent releases from the damaged plants for last several months. Because of the hydrogen explosions, the secondary containment (reactor building) was severely damaged. The heating and ventilation system, which has been keeping a negative pressure, is no longer available, resulting in releasing radioactivities from several openings not well accounted for. On November 26, TEPCO released an interesting overview report: "Fukushima Daiichi Nuclear Power Station Unit 1-3 Evaluation method of the present amount of radioactive material released from the Reactor Building" through http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111126_02-e.pdf. Their methods consists of both atmospheric release from the plant to the land and to the marine environment as well as the underground liquid leakage into the ocean. The effluent leakage from the reactor building is being performed by "Extract and measure dust above the reactor building, near the ventilation system of the reactor building cover and the gas controlling system of the Primary Containment Vessel". How these sampling and measurement are being performed is illustrated in the handout. The current estimation of the results are summarized below: 1F1 : approx. 10 MBq/h 1F2 : approx. 10 MBq/h 1F3 : approx. 40 MBq/h Total : approx. 60 MBq/h The total amount is reported to be equivalent to approximately 0.1 mSv/y at the site boundary. The reason why the effluent release from 1F3 is four times larger as compared with the other two is likely from the fact that filtered venting system for 1F3 Reactor Containment System has not been installled yet. TEPCO appears to be facing much difficulties for human access near the RCV due to high dose rate, even after removal of debris by employing robots. http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111105_02-e.pdf VI. A comprehensive set of viewgraphs of Fukushima Daiichi disaster In June, the Japanese Government has released a comprehensive report of the Fukushima Daiichi disaster: Report of Japanese Government to the IAEA Ministerial Conference on Nuclear Safety - The Accident at TEPCO's Fukushima Nuclear Power Stations - through http://www.kantei.go.jp/foreign/kan/topics/201106/iaea_houkokusho_e.html Many of the information was supplied by TEPCO, which appears to be integrated into the Government report. Recently, I found the attached presentation compiled around this time. This set of viewgraphs is provided by TEPCO, although it appears to be not released, perhaps due to political confusion. Let me attach this document, titled: "Effects of the Earthquake and Tsunami on the Fukushima Daiichi and Daini Nuclear Power Stations, July 26, 2011, Tokyo Electric Power Company for convenience of many of my international colleagues who have to speak about the disaster to the wider audiences. VII. Concern of aged plants in the wake of Fukushima disaster There exists a general concern of aging effects in the Fukushima Dai-ich, worrying about a possibility of worsened the accident progression. In order to clarify this possibility, NISA (Nuclear and Industrial Safety Agency) held the first meeting on November 29 to hear opinions of the designated professors knowledgeable for material degradation issues. According to the meeting announcement, the objectives of the meeting is (1) two plants will reach the 30 years mark, and one plant will reach the 40 years mark, the time stamps necessary to have detailed aging assessment, (2) an unexpected rapid increase in ductile/brittle transition temperature was recently identified in a plant (3) to hear specialists opinion to cope with these backgrounds to help decision making, (4) such discussion should be made open. (However, NISA is also saying that the handouts may not be made open. There is not technical document posted in their webpage as of today. ) I got an impression that NISA is asking for an endorsement that there was no substantial aging effect, leading them to conclude that an ordinary regulatory procedures can be followed for life extension. It is true that no apparent aging effect has been identified so far during the accident. For example, the Mark I RCV (Reactor Containment Vessel) of 1F1 to 1F3 appear to have withstood nearly twice the design pressure before venting, although the temperature may have exceeded the design temperature of 171℃ at some parts of dry well. The overheating may have damaged some of the elastomer gaskets. The Reactor Pressure Vessel (RPV) appears to be retaining the damaged core debris. Some engineers worried about a dislodging of the control rod housing, however, no apparent symptom has been reported supporting this phenomena. Nevertheless, there is a high possibility that leak-tightness of both RPV and RCV were seriously damaged. This is clearly shown by the series of radioactive releases, not correlated with venting events, and hydrogen explosions. In particular, in 1F1, a high dose rate was observed at the personnel hatch of the PCV as early as around midnight of March 11. There are several possibilities of such failures during the accident. (1) "Internal hydrogen explosion" such as occurred at Hamaoka Unit 1 in 2001. The hydrogen explosion/pipe rupture occurred during the normal operation at a ECCS pipe as explained in Earthquake (70). Minor incidents of such explosion have been disclosed experienced eight times inside TEPCO, occurred in small instrumentation piping. (2) SCC (Stress Corrosion Cracking) (3) The preceding seismic event, occurred one hour before arrival of the tsunami. The NISA appears to be interested in a structural assessment by combining Point (1) and (2). However, by some unknown reason, TEPCO seems to be indifferent to Point (1), which I believe is most likely when the RPV is isolated superimposed by the station blackout. This will make removal of water- radiolysis induced hydrogen gas impossible. (4) Met-through of corium For last several years, I have been mainly researching on the root cause of unthinkable severe corrosion degradation phenomena widely being experienced in water-cooled reactors. I am insisting that it is due to a "macro-cell" (I am using the word "long-cell" in honor of R. Pope, then Chair of NACE), where a gigantic batteries are short circuited through piping in LWRs. The batteries can be induced easily by radiation, temperature differences, flow, etc. The battery induces rapid electrolytic corrosion at its anodes. Some of my recent publications are as follows: G. Saji, Degradation of aged plants by corrosion: ’Long cell action’ in unresolved corrosion issues. Nuclear Engineering and Design 239 (2009) 1591–1613 G. Saji and B. Timofeev, Scientific paradigms of structural safety of aged plants—lessons learned from Russian activities, Nuc. Eng. and Des. 239 (2009) 1614–1627 G. Saji, Radiation induced ‘long cell’ (macrocell) corrosion in light water reactors, Nuc. Eng. Des. 240, 1340–1354 Although NISA seems to be more interested in material issues, the real issues are in obsolete safety design of aged plants, I believe. These vulnerabilities should be clarified through the Step 2 of the "stress test" currently underway in Japanese utilities. VIII. Update of radiation monitoring methods used at the Fukushima Dai-ichi I introduced this issue on Earthquake (166, Nov 18-25). Drs. Joyce Sloof and Joost Woittiez of Isotopics in Netherlands kindly responded to my request to comment on the analytical techniques that Tepco has published for the use of the determination of Pu and Sr and on the application of Gamma-Ray spectrometry. Their comments include: "Any information on pre-sampling considerations, sampling strategies and actual sampling procedures is absent. ...For example, there is no use in analyzing a 5x5x5 cm soil sample and report a result in Bq/kg, which is basically a volumetric assay, when one deals with a surface contamination issue, as is the case in Japan. Also, the analyst has to define a representative sample, i.e. he has to know the distribution of the contaminant in the sample population." "Pu analysis-The major issue of concern here, is that the use of a spike is not mentioned. A spike of some Pu isotope is absolutely essential to determine the yield of the chemical separation procedure." I made some research on this subject. I found that TEPCO seems to have been contracting a few laboratories, including Japan Chemical Analysis Center (http://www.jcac.or.jp/index2.html). This laboratory is perhaps one of the most highly evaluated organizations in Japan. I contacted them and found that their methodology of analysis closely follow guidelines established by MEXT (Ministry of Education, Culture, Science and Sport) through http://www.kankyo-hoshano.go.jp/en/index.html. For analysis of Sr, the procedure is compiled in Radiation Measurement Procedure Series 2 and, for Pu, in Series 12. Unfortunately, these guideline are all in Japanese. They also told me that the methodology of Sr analysis published by TEPCO is completely different from the one used by JCAC, indicating that TEPCO may have used other results. In the Series 12, for analysis of soil sample, the following procedure is specified. (1) Fifty gram sample should be baked at 500℃ in an electric furnace for 4 hours. (2) After natural cooling, the baked sample should be put into one liter beaker and add 2 ml of a standard solution of Pu-242 or Pu-236 (0.02Bq/ml). (3) Slowly add 250 ml of nitric acid (3+2) . In case of extensive bubbling, ad a few drops of octyl alcohol (4) Boil the hot liquor in a watch grass for two hours on a hot plate or in a sand bath (5) Filter with a fiberglass filter (GA-100) and washout the residues with a small amount of nitric acid (3+2) (6) Boil the liquor until condensed like sirupus (7) Add 100 ml of nitric acid and 100 ml of hydrogen peroxide. Decompose the hydrogen peroxide (8) After cooling, filter with fiberglass filter, collecting the filtration in a 500 ml beaker. Rinse with a small amount of nitric acid (3+2) Plutonium separation of the prepared solution is performed either by using nitric acid compatible negative ion exchange resin column (Dowex 1-X8) or by using TOA-xylen extraction method to make electro-deposition specimen for alpha counting. I think this chemical method of separation of plutonium be a practical way, however, the physical configuration of hot particles are lost by baking and extraction by nitric acid. It is well established, through the Chernobyl accident, that plutonium is released as hot particles in the reactor accident. The physical separation method as performed at the time of Chernobyl accident should retain the morphology of the hot particles, which may be more resourceful for further study, I believe. In addition, for radiation safety assessment, number of inhaled hot particles should provide more direct information in estimating exposures by using a lung dynamic models such as ICRA Pub. 30. Well. let me stop here, this evening! Genn Saji ________________________________________________________________________________________________ (Previous e-mail sent on Nov 25 as Earthquake (166, Nov 18-25) Dear Colleagues: 252nd - 259th day I. Update of effects of low level radiation exposure (Part 2) I have covered this issue several times in this series, the last one on Nov 11 as Earthquake (164, Nov 4 -11). So far, I have been covering mostly the internationally well-known approaches, however, I intend to introduce some of the recent Japanese publications. Some of the Japanese public seem to trust these books much more than the Government explanation based on the ICRP: (1) Akira Sugenoya, 2011. "Diary of Diagnosis and Treatment at Chernobyl - with Apocalipsis of Fukushima Accident. ("cherunobuiri sinnryouki"), shintyoubunnko. ISBN978-4-10-134641-0 (2) Shuntaro Hida and Hitomi Kamonaka, 2011. "Threat of Internal Exposure: from Atomic bomb to Depleted Uranium Bullets". ("naibu-hibaku-no-kyoui") Tchikuma Shinsyo. ISBN978-4-480-06241-3 C0236 (3) Ryuichi Hirokawa, 2011. "Nuclear Reactors Running Away." ("bousou-suru-gennpatsu"), Shougakkan. ISBN978-4-09-388190-6 Although these NPO authors are all strongly insist on abolishing the nuclear energy, however, these books contain many valuable scientific information as well. Since very little is known about the effects of low level exposure, let me extract some of the useful information from these books. Dr. A. Sugenoya, MD, is a surgeon, specializing in thyroid. He volunteered to work in National Thyroid Cancer Hospital of Belarus for 5 and a half years. He is now the Mayor of Matsumoto-shi, Nagano Prefecture. His book helped me to understand the real life of the cancer-affected Chernobyl children. By working closely with NPOs, he assisted to modernize the thyroid cancer diagnostics and treatment in Belarus. He is reporting how actual thyroid cancer diagnostics and treatment were being performed in Belarus during his stay of 1996 to 2001. When he first visited the hospital, there was no ultrasonography (USG). He arranged to present it working with a NGO. In the book, I also found that the thyroid tumor is removed by surgery, without further distinguishing whether it is malignant or not, considering a possibility of eventual development into cancer. These explanations alarms us to be careful in using the epidemiological data. A part of the recent rapid increase in thyroid cancer patients may be due to a selection effect of introducing USG. A majority of thyroid tumor is non-marignant. Due to their economic difficulties in Belarus, the hospital does not have a luxury of keeping the thyroid patients under periodical medical checking before surgery considering QOL of patients. Dr. S. Hida was an Imperial Army Doctor at Hiroshima, at the time of the Atomic bombing. He himself survived from the disaster after blown off by the blast, while he was making a house call to a child in suburbs of the city. He treated many dyeing sufferers by returning to Hiroshima. Although he did not received fatal dosage, he believes he suffered from internal exposure, which motivated him to look into this mode of exposure. However, while I was reading his book, I got an impression that he may have been more highly exposed externally, by radioactive fallout deposited on the ground through the "black rain." The internal exposure should have been through inhalation (including skin respiration) or ingestion. The radioactive species suspended in air should have been blown away quickly by wind or with rising current of wind, which later fell back on the ground with the "black rain." Anyway, in the book he mentioned about the "genbaku bura-bura" (atomic bombing induced inactive state of life) syndrome. The sufferers are generally weak in health, complaining "easy to get tired," or "lacking patience", although no outstanding causes of the difficulties were detected by ordinary diagnosis. The syndrome suggests some kind of low radiation induced troubles in the neuron-synaps signal transfer mechanism in cerebral nerve system, I think. I also read a similar syndrome in the health effects of Chernobyl in the Rupandin's book as "Chernobyl Sickness" (Chernobyl: Have the Prognoses Come True? Russian Journal PRIRODA (Nature), #9, 1992, pp. 70-74. His paper has been distributed previously, let me attach a private English translation once more for your convenience). Although it is very difficult to quantify such difficulties, we should be cautious in the cerebral damage due to low-level radiation. Mr. R. Hirokawa is a journalist and was a Representative of Fund for Chernobyl Children, who has been following the TMI and the Chernobyl accident. In the book, he performed a followup study of 25,564 evacuees from Pripyat City and Chernobyl City, Districts, villages and suburbs. The cohort comprises approximately 1/4 of the population of these two cities. For the control group, questions and answers from residents of Moscow (316 total) were also collected. His group made the survey by distributing questioners, in which 45 questions were grouped into 6 categories. They consist of (1) What did you feel or see during the first week of the accident; (2) Did you notice some physical changes during the first weak?; (3) What kind of food and drink did you take during the first week?: (4) Were you hospitalized?; (5) Explain your current health conditions; (6) Do you think there is some correlation between your current health conditions and the accident?. Let me only introduce summary of Group 2 and Group 5 responses from former residents of Pripyat (9501total answers), the closest city to the Unit 4. From the complaints as summarized in Group (2), I got an impression that they were suffering a typical near subacute radiation sickness syndrome which appears after receiving a fraction of Sv. (2) Did you notice some physical changes during the first weak? Pripyat headache 60.6% nausea 43.8 sour throat 40.7 dermis pain, burnt feeling 6.2 nosebleed 19.3 fainting 9.3 unusual tiredness feeling 56.3 behaving like intoxicated 19.2 others 10.3 (5) Explain your current health conditions Pripyat Moscow healthy 1.7% 54.7% headache 74.3 16.8 sour throat 38.0 8.5 anaemia 18.1 1.9 dizziness 51.1 7.0 nosebleed 19.3 3.2 easy to get tired 21.2 21.2 tend to catch cold 59.6 17.7 pain in bones of hands/feet 61.1 7.3 eyesight problems 29.2 16.1 thyroid anomaly 38.1 3.5 leukemia 0.5 0.6 tumor 4.6 2.5 borne with defects 0.4 0.0 others 18.1 7.0 II. Secondary confinement system and environmental qualification The US NRC accepted, on November 10, a petition of UCS (Union of Concerned Sientists), demanding for Request for Information (DFI) to a number of BWRs licensees with Mark I and II Containment Vessel Design, compelling each licensee to describe how the each facility complies with GDC (General Design Criteria) 44 "Cooling Water" and with 10CFR Part 50, Section 49 "Environmental Qualification of Electric Equipment Important to Safety of Nuclear Power Plants. The Petition Review Board (PRB) identified that the topic of the petition "the effects of the spent fuel pool during accident" as part of the lessons-learned from the Fukushima event. athttp://adamswebsearch2.nrc.gov/IDMWS/ViewDocByAccession.asp?AccessionNumber=ML11213A030. This issue is worth studied also in Japan, since the outcome of this issue may impact some of the aged BWRs. The SFP in BWRs with Mark I and II containment vessel is located at the top floor of Reactor Building (RB) also called as the Secondary Containment. Such a layout results from the Pressure Suppression System (PSS) located at the bottom of the RCV. The PSS helps reducing the size of RCV, Also, the control rods should be located at the bottom of the reactor pressure vessel, due to neutron flux distribution, in BWRs. These characteristics lead to the BWR design with Mark I and II RCV, which looks very efficient. However, the rooms in RB are interconnected either by heating and ventilation ducts as well as ladders in Fukushima Dai-ichi. This resulted in spreading the leakage of the radioactive species throughout the RB, making it extremely restrictive for the current amelioration efforts. In addition, some of the essential engineered safety feature pumps were flooded due to leakage of the injected water, since they were located at the bottom of "triangular corner" of the reactor buildings in Fukushima Dai-ichi, making it impossible to recover. For progress of this discussion, it is essential to establish the root cause of hydrogen explosion of 1F4 SFP. TEPCO's "official" position is "the reverse flow of hydrogen through venting in 1F3. " I am suspecting involvement of dissolved hydrogen gas (DH) release from the boiling SFP water, the DH induced by water radiolysis and accumulated before the accident. III. Behavior of 1F1 Isolation Condensers after arrival of tsunami On November 22, TEPCP released an interesting handout (in Japanese) analyzing the behavior of Isolation Condensers (IC) soon after the arrival of tsunami through http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111122_03-e.pdf. There are redundant ICs installed in 1F1, which was later improved into the turbine-driven Reactor Core Isolation Cooling (RCIC) system in 1F2 and 1F3, to cope with the higher power duty. The IC is a natural circulation condenser on the primary side, whose secondary side (heat sink, shell side) uses Reactor Components Cooling Water System. Upon station blackout, the secondary side lost its heat removal capability. For operation of valves, DC power source was necessary, however, their failure mode appears to be "fail as is" upon loss of the DC power, from my observation obtained in following TEPCO's reports. On October 18, TEPCO's crew could inspect the current status of ICs by entering into the Reactor Building and found that the system did not seem to be seriously damaged, in spite of the hydrogen explosion. (http://www.tepco.co.jp/en/news/110311/images/111021_3.wmv) This motivated TEPCO to re-assess the behavior of IC during the accident. By the on-site examination, it was found that the secondary side water remained 65% in IC-A but 85% in IC-B, in which the normal water inventory is 80%. The water level indicates that IC-A should have worked, at least partially. It was concluded that IC-B has been manually tripped soon after the start of ICs, due to too rapid cooling rate exceeding 55℃/h (100°F/h). Due to the loss of the heat sink, the shell side water temperature gradually increased from the initial 23.0℃ to 100℃ around the arrival time of the tsunami. It is likely that the water inventory inside IC-A was not lost. (This is a bit strange, since before the arrival of tsunami, the Reactor Component Cooling Water System should have been working, removing heat from the secondary side, though.) Since the availability of IC could not be confirmed due to the station blackout, at 21:30 of March 11, the valves connected to IC-A were made open, whereas those connected to IC-B were closed. The decrease of water inventory in IC-A indicates that a part of the decay heat should have been removed, by boiling off the secondary side water inventory of IC-A. In reading the TEPCO's assessment, I found again their explanation ignores a capability of the "feed and bleed" operation. By boiling off the water inventory of the 1F-A, part of the decay heat should have been removed, although the stopping of IC-B made it impossible to make used of the precious heat removal capability through boiling heat transfer. The heat removal through boiling is far more efficient than using the specific heat of water. I also believe that the cooling the reactor faster than 55℃/h, which is to minimize thermal stress for heavy components in general, is far more important for the severe accident management. IV. Nitrogen gas injection into the Reactor Pressure Vessel On November 24, TEPCO announced their planning of nitrogen gas injection into the RPV (Reactor Pressure Vessel) of 1F1 through 1F3, in order to reduce hydrogen concentration in the PCV (Primary Containment Vessel), identified through operation of the Gas Control Facility. The newly installed gas control facility extracts the PCV atmosphere to remove radioactivity. The hydrogen gas concentration in 1F2, soon after the commissioning of 1F2 gas control facility went down to 0.9% from the initial high of 2.9%. After establishing negative pressure, TEPCO started to suspect that the hydrogen gas accumulated inside of the RPV started to leak into the PCV, since the RPV does not seem to be full with water, in spite of prolonged water injection of approximately 10 m3/h into the RPV. TEPCO intends to keep the hydrogen concentration below inflammable limit even in the condition without steam. Although no radiological assessment has been released, this operation will likely release Kr-85, accumulated inside of the RPV into the environment. http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111124_03-e.pdf http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111124_02-e.pdf V. Radiation monitoring methods used at the Fukushima Dai-ichi On November 19, TEPCO released a set of illustrative presentations (in English) of the health physics equipment being used at Fukushima Dai-ichi, through: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111119_04-e.pdf In the presentation, I noticed the methodologies used for detection of plutonium, strontium and tritium. The following treatment procedures are being used before α/β spectroscopy: Pu: Incineration at electro furnace⇒heat ⇒filtration⇒liquid concentration⇒boil⇒cool⇒filtration⇒elution by ion exchange⇒evapolation solidification ⇒heat/melt⇒electrodeposition⇒bake Sr: Incineration at electro furnace⇒heat ⇒filtration⇒liquid concentration⇒boil⇒cool⇒filtration⇒elution by ion exchange⇒evapolation solidification ⇒heat/melt⇒electrodeposition⇒bake⇒Y-90 milking T: distillation⇒mixed with liquid scintillator in a 9ml low-potassium vial Since these methods appear to be significantly different from those used in Russia and Ukraine at the time of the Chernobyl accident, it is interesting to know how the international colleagues may say about these method. I have been appealing for TEPCO to arrange an international benchmark exercise in view of significance of there species for radiation protection purposes. In connection with this, the reported earlier detection of strontium in Yokohama, the detection performed by Radio-Isotppe Research Institute (http://www.radio-isotope.jp/index.html) (no English site), was recently denied by another independent measurement performed by Japan Chemical Analysis Center ( http://www.jcac.or.jp/index2.html) (no English site) by saying "there is a possibility to detect another isotope in the analysis method performed by the other way. I think the use of "elution by ion exchange" seems to be making the difference. it appears JCAC is supporting TEPCO's analysis needs. VI. Completion of removal of solid debris from the ground TEPCO announced completion of removal of solid debris scattered on the ground of Fukushima Dai-ichi site on November 19: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111119_02-e.pdf The statistics were as follows: ・Term: 4/10~11/17 ・Area: approx. 56,000 m2 (not including debris inside of the buildings) ・Amount: approx. 20,000 m3 This will help facilitate remediation and decommissioning activities. For removal of highly contaminated debris collected near the reactor buildings, the debris above 1 mSv/h were stored in 730 containers of 8 cubic meters capacity. Those collected off the reactor buildings, the debris were classified at 10 mSv/h. For removal of highly contaminated debris, heavy construction vehicles with remote operation capabilities were employed. VII. Amelioration and decontamination On November 22, the Life Supporting Team for Affected People compiled a Handbook of Decontamination (in Japanese), through http://www.meti.go.jp/earthquake/nuclear/pdf/20111122nisa.pdf The handbook incorporates various experiences obtained through pilot decontamination activities, including the Government-contracted (to JAEA) pilot research for Establishing Guidelines for Decontamination of Fukushima Prefecture, EURANOS (Generic Handbook for Assisting in the Management of Contaminated Inhabited Areas in Europe following a Radiological Emergency) as well as the recent report distributed through Cleanup Subcommittee of Atomic Energy Society of Japan. In general, removal of surface soil, sludge, fallen leaves, moss, mud and dirts is effective, although the DF (decontamination factor) depends strongly on local environmental characteristics. It also depends on timing of decontamination. For example, in earlier experiments performed in June, the high pressure water blast technique was found effective and economical. However, in the recent experiments, it is not so when it applied to roofs or pavement. It appears that these loose deposits have already been washed away by rainfalls. Now it is found that wire-brushing with water is necessary to remove the radioactivity which is tightly bound on the surface of structures and pavement. It is necessary to develop a kind of rotary wire-brushing "shop-vac" with a recovery tank for the contaminated water. The "special disposition law of decontamination of radioactivities release by the east Japan great earthquake" was approved by the congress and will be in force starting January, 2012. It specifies that those areas with a dose rate between 1 to 20 mSv/y should be decontaminated by the local governments and those areas exceeding 20 mSv/y will be performed by the national Government. Both of them have launched pilot feasibility study activities. For example, Fukushima Prefecture has started "horizontal deployment (regional) decontamination" starting October 18 at Ohnami district to ameliorate 10 hr (10,000 m2). In this district, there is a variety of landscape, housings, a community house, orchard, paddy fields and forests. The local government is making a detailed soil contamination map of 2m x 2m mesh for the residential districts, and every 10m x 10m mesh at non-residential districts. In the pilot research activity, the local government planned to decontaminate all of the 367 housings by the end of this year. However, a pilot decontamination of six houses showed difficulties in reducing dose. Although 70% reduction in dose rates was achieved in gardens soils and unpaved/pebble-covered parking space, the DF went down to only 25% at the roof and paved garden, resulting in only 22% reduction inside of the houses in average. Well, let me stop here tonight! Genn Saji ______________________________________________________________________________________________________ (Previous e-mail sent on Nov 18 as Earthquake (164, Nov 11-18) Dear Colleagues: 245th-252nd day! I. INPO Special Report Recently, INPO released Special Report on the Accident at Fukushima Dai-ichi (INPO 11-005 November 2011) open to the public through several websites, including http://www.nei.org/filefolder/11_005_Special_Report_on_Fukushima_Daiichi_MASTER_11_08_11_1.pdf. This 104 page report is well written, summarizing the general understanding of the engineers in the nuclear community in Japan. Although their references are limited to official documentation of the Government, TEPCO and several other organizations in Japan, there are not much new information for me. Nevertheless, it helped a lot to clarify some of my misunderstandings and some un-awared-of issues. The report is easier to read in good English by summarizing the essential issues only in the first 45 pages, followed with "Chapter 7. Additional Information" and "Chapter 8. Event Progression and Time-Line". At the International Symposium on Nuclear Safety (iSONS 2011) held in Tokyo (Oct 31- Nov 1), Mr. Lee Gard (INPO USA) explained, in particular, that the Chapter 8 was developed by confirming line by line with TEPCO people as done also by JANTI in http://www.gengikyo.jp/english/shokai/Tohoku_Jishin/report.pdf These reports start with the Government Reports to IAEA, released through http://www.meti.go.jp/english/earthquake/nuclear/index.html#iaea Through these reports, the Chronology/Timeline of the event sequences are now confirmed well, I believe. However, I still feel there remain a lot of unknowns in the root causes of the accident sequences. For example, in the INPO report, it is stated that "There are various theories regarding the cause of the hydrogen explosion in Unit 4. .... The most widely accepted theory is associated with the back-flow of gases from Unit 3 during venting." Although it is true that most people seem to accept this theory, however, this kind of issues cannot be decided by a majority vote. It is very strange that the hydrogen explosion in Unit 4 occurred one day after the venting from 1F3. I have been suspecting the role of water radiolysis, where the dissolved hydrogen was released from the H2-saturated pool water due to boiling. I mentioned "the general understanding of the engineers in the nuclear community in Japan". In general, the Japanese public as well as most of the scientists outside of the nuclear community seem to have distrustful views against the Japanese nuclear community. It is often mentioned in blogs that "The Government's and TEPCO's report made no reference at all to the true consequences of the Fukushima accident. Shades of wartime Imperial Headquarters censorship." I think what is missing in these reports are scientific bases of facts leading to the important conclusions. In all of these reports, scientific bases are seldom published and only conclusions are advocated first through media. In most cases, it is impossible for me to follow their scientific bases or to reproduce their analytical steps, at least by performing independent "back of an envelope" calculations. II. Radiation release to the marine environment Due to the station blackout, which wiped out all of the on-site radiation monitoring stations, it is difficult to estimate the total amount of radionuclides introduced to the environment from data obtained from the instrumentation in the plant. Following explosions and steam venting of the reactor containments, an atmospheric plume of contaminated aerosols was transported mainly to the sea between March 12 and March 23. Contamination of the marine environment following the Fukushima Dai-ichi accident results firstly from dry and wet deposition processes, from an atmospheric contaminated plume directed mainly toward the sea between March 12 and March 23 during the active phase of the accident; secondly from direct releases of highly contaminated waters into the sea; and thirdly of the transport of radioactive pollution by leaching through contaminated soil. On the sea, it is very difficult to assess atmospheric deposition, which involves large surfaces and was quickly advected and dispersed. Only seawater measurements performed a few days after the release could give an estimation of the quantities. Moreover, atmospheric models have large uncertainties with respect to the dispersion and deposition parameters onto the sea. The influence of direct release of the highly contaminated water was particularly significant from March 26 to April 8 in the vicinity of the power station (mean concentration of 15 716 Bq/liter for Cs-137, maximum of 68 000 Bq/liter near the surface. Dr. Ko-ichi Nakamura, a marine geologist, introduced me the following two reports, one from CREPI (Central Research Electric Power Institute, http://criepi.denken.or.jp/en/index.html) and the other from IRSN, http://www.irsn.fr/FR/Actualites_presse/Actualites/Pages/20111027_Accident-fukushima_impact-rejets-radioactifs-milieu-marin.aspx): (1) Tsumune, D., T. Tsubono, M. Aoyama and K. Hirose, (2011b). Distribution of oceanic 137Cs from the Fukushima Daiichi Nuclear Power Plant simulated numerically by a regional ocean model, Journal of Environmental Radioactivity, doi:10.1016/j.jenvrad.2011.10.007, in press. (2) Bailly du Bois, P., Laguionie, P. , Boust, D., Korsakissok, I., Didier, D., Firvet , B. 2011. Estimation of marine source-term following Fukushima Dai-ichi accident (http://www.irsn.fr/FR/Actualites_presse/Actualites/Pages/20111027_Accident-fukushima_impact-rejets-radioactifs-milieu-marin.aspx) Both of them estimated the total amount of the environmental releases as follows: Authors Fukushima direct release Fukushima fallout Tsumune 3.5±0.7 PBq some portion of 15 PBq Bailly 27 PBq 0.076 PBq Since only concentrations near the surface sampling are available, the vertical distribution concentration of radio-actioactive species depends much on technical judgement of authors. Dr. Bailey assumed 35 meter deep mixed layer, whereas Dr. Tsumune incorporated a shoaling beach topology near the Fukushima Daiichi with an average depth of 10 meters. The differences in the depth of mixing layer appear to account for a factor of 3 in their difference. Another difference seems to come from the treatment of varied concentration during April 1 to April 8. After April 8, the concentration near the discharge point showed a gradual decay pattern. The direct leakage of the highly contaminated water occurred during April 1 to 6, releasing 0.96 PBq of Cs-137. There were two peaks during this period. Another large difference appears to results from specifying the total amount of releases at April 8. Dr. Bailly obtained by extrapolation of the regression curve at the date of the April 8 to estimating the total amount of Cs-137 discharged at the end of the main release period (March 26 – April 8). The regression curve uses data from eight sampling points, taken at more than 5 km points, each of them recorded different time span, ranging from a starting time of April 11 to an ending time of July 4. The estimated quantity was 22.0 PBq. A 95% confidence interval gives values between 20.8 and 23.1 PBq. On the other hand, Dr. Tumune relies more heavily on the sampling data taken near the discharge points and assumes a sloping release rate curve with flat portion at both ends. I believe closer the release point, the more reliable the source term can be. As to the estimation of the fallout, the 15 PBq value Dr. Tsumune used is the official value released from the Nuclear Safety Commission, obtained by a reverse engineering of the dispersion calculation by SPEEDI. I do not think this value is correct, due to the inevitable uncertainties induced by atmospheric dispersion calculation. However, Dr. Tumune was successful in differentiating two major release pathways by analyzing observed I-131/Cs-137 activity ratios, direct release and atmospheric deposition. They found the I-131/Cs-137 activity ratios before 25 March were scattered and do not fall on the decay curve of I-131; therefore, before that date, the observed Cs137 concentrations originated from atmospheric deposition. They conclude that the contribution of direct release to the observed Cs-137 concentrations was larger than that of atmospheric deposition. I think this conclusion is very important. Based on the DOE/NNEA land contamination map of Cs-134 + Cs-137, the integrated deposition of Cs-137 to the land was 3.0 PBq, as introduced in Earthquake (159, Oct 7-11) in October 12, although in my estimation, the coverage of the contaminated areas were limited to Fukushima. I believe the actual measurements of the environmental release data does not support the Government designation of INES Level 7, rather it should have been in Level 6. I believe such a designation should have not been made without robust environmental contamination data. In both of these works, they ignored the radioactive terrestrial deposits partially leached by rainwater and then transported to the sea by run-off. The land deposition occurred during the dispersion of the atmospheric releases from the Fukushima Daiichi plant. The most recent information observed was that the leached radioactive cesium reacts with fine particular suspension of cray in the liver water, transported with stream and gradually depositing at estuaries. For example, along the Nitta-gawa river flowing N-W direction of Fukushima, the cesium concentration measured at a upstream, near Iidate-mura recorded 3.2 kBq/kg of sediments, whereas at Minami-Souma-shi, located at the downstream near the estuary, 13 kBq/kg was recorded. The upstream concentration was reduced to 1/5 whereas the down-stream concentration increased three times, compared with the activity measured in May. These contaminated sediments will deposit at the seabed for many years along the coast line but input to the bulk of sea water may be negligible. III. Internal exposure from Cs-137 in livestock An interesting assessment was published by Dr. Manabu Fukumoto, MD, of Institute of Development, Aging and Cancer of Tohoku University pertaining to the internal exposure from Cs-137 (http://www.idac.tohoku.ac.jp/index.en.php). Before evacuation, as many as 3,500 livestock were release to the field, which became a kind of wild livestock. The Government decided to put down these animals, although less than 10% of them have been caught. Dr. Fukumoto and his team investigated 26 of such animals and measured the distribution of Cs-137 in various organs. When the Cs-137 concentration is 60 Bq/kg in blood, the following concentrations were identified in organs: Organs Cs-137 (Bq/kg) blood 60 femule (thigh) 1800 tangs and livers 600