109th day!
I. Recapping on the water purification system
With the day light, TEPCO investigated the water leak location and found that the 10 cm dia vinyl hose came off. The temporary hose is designed with 10 kg/cm2 pressure. The operational pressure was approximately 8 kg/cm2, however, it may went up by adjusting a valve. The leakage was said to be limited to just one cubic meters, lasting for 2 minutes. TEPCO is checking all the valves with the similar pipe fittings. From their explanation, I got an impression that a hose clamp came off due to the high pressure. By replacing the faulty hose, the system went back into operation at 2:36 PM. Currently 14 tons/h of the purified water and additional 2 tons/h from the river water taken at nearby dam are being injected into the 1F1-3.
Obviously more robust pipeline should be constructed, such as by using a hard plastic piping, since the water injection line is in a safety class for the current accident management. Since another water line is available from the nearby dam to the pure water tank, redundancy is barely sufficient. It is anticipated that TEPCO may be using the water purification system for years and I believe more reliable setup is going to be necessary.
TEPCO also released a set of schematics of the water purification system as attached (in Japanese,http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110627_03-j.pdf) There are few new issues I did not realize. One is that there is an independent oil separator in front of the Kurion’s SMZ sorption tank. If the degradation of the DF in past several days came from oil impregnates, whether this stage is working properly should be investigated. We need very high grade oil removal for adequate operation of the cesium adsorption and co-deposition processes. The detailed spec has not been released yet for this part of the process.
Secondly, it is stated that the AREVA’s process and Kurion’s process can be switched only by manipulation of valves. I believe it strongly depends on the worker doses received during replacement of sober in the Kurion’s process. According to their operational log, the following maintenance outages are recorded; 23 June 13:00-14:44; 24 June 10:00-12:50: 25 June 10:00-15:00; 26 June 10:00-18:10. During these outage time, the system was flushed by lower contaminated water before changing sober. Estimated availability appears like 80%, which is not so high. More importantly, a daily maintenance for manual exchange of sober became necessary, resulting in the low availability. If the worker dose is not so high during this maintenance, say in a range of 100-200 microSv a day, it might be tolerable. If it is much more than this, TEPCO should seriously consider switching the AREVA’s and Kurion’s processes. This will not only reduce the worker doses, but also improve availability by reducing the frequency of flushing operation.
As of the evening of June 27, as much as 7610 tons of highly contaminated water has been purified.
II. Recapping on recovery of the secondary containment system for 1F1
I introduced this issue in Earthquake (96). This is a kind of Fukushima version of the infamous Chernobyl “sarcophagus” and is called “cover” this time in Japan.
Today, TEPCO announced that the on-site construction of cover has started, scheduled to be completed in late September. This cover is of the size of 41x45x52(H) meters. There will be assembled by using two 750 ton remote operation crawler cranes.
III. Recapping on nitrogen gas injection in 1F2.
TEPCO started today injection of nitrogen gas into the 1F2 pressure containment system for prevention of hydrogen explosion, as soon as a permission is obtained from NISA. A similar operation has been started in 1F1 since April.
Well, let me stop here tonight.
Gen Saji
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(Previous e-mail sent at 11:15 PM on June 27 as Earthquake (108))
Dear Colleagues:
108th day!
I. Recapping on the water purification system
At 4:20 PM of June 27, TEPCO announced that they have started to inject the purified water into the reactor vessels of 1F1-3, thus closing the water cooling chain and preventing an increase in the volume of highly contaminated water so far accumulated to more than 110,000 tons. The purified water line was laid out in parallel to the pure water line so far used by extracting natural water from a nearby dam. TEPCO also commented that the unanticipated high dose rate in Kurion’s system calls for reevaluation of replacement procedures. I think TEPCO need to find solution for the first stage SMZ sorption tanks for removal of oil contamination. It appears that oil contamination also affects DF of the AREVA’s co-precipitation process. The operation itself is a R&D with cut and try.
However, the operation had to be suspended at 5:55 PM due to a water leakage found in its 4 km pipe line. TEPCO plans to fix the leakage tomorrow. During suspension, the water injection has been switched back to the old tank from the dam.
II. Recapping on accumulation of “radioactive” sludge and ashes
I introduced this issue more recently in Earthquake (95) and (97). The National Center of Counter Measures for Nuclear Disasters introduced a new guideline for disposal of “radioactive” sludge on June 16. The new guideline specifies, for incineration of sludge, furnaces should have filtration to prevent releasing radioactivity. The sludge and ash should be kept in a shielded facility when the activity is higher than 100,000 Bq/kg. The way for ultimate disposal is being investigated. The lower activation wastes can be disposed in the municipal disposal facility with dose to the individual of the nearby residents will not receive more than 10 microSv/y, when the activity level exceed 8000 Bq/kg but less than 100,000 Bq/kg. For very low activation wastes, lower than 8,000 Bq/kg, can be used for land fill purposes, not for residence purposes, after water proofing.
I do not know how this guideline was developed. However, it is becoming obvious that this kind of deterministic graded guideline does not work in the real world. This should have been a risk approach with adequate exposure scenario, without showing safe/unsafe borderline, since there is no such distinct boundary in the radiation safety. There were a few municipal waste water treatment facilities that own the waste treatment facilities with a final fused disposal process. Most of them have been selling sludge for making composts for farmers. However, the manufactures refused to accept the “contaminated sewage wastes”, even if the activity level is of the order of 1000 Bq/kg, lower than the guideline of 5000 Bq/kg for soil used for allowing planting rice sprout. Many of the municipal sewage facilities are forced to urgently construct in-site storage facilities but it is near their limit. For example, the North Fukushima Central Water Treatment Facility has already accumulated a stock of 1200 tons. There is no immediate solution in sight. They are crying that the national government take responsibility of disposal of the “radioactive” sewage wastes, not just making a guideline.
This issue is glowing to reveal affecting much wider areas than expected. Later today it was announced from Tokyo Metropolitan Sanitary Stations that a fly ash sample from Edogawa Ward showed 9740 Bq/kg.
III. Recapping on City-wide radiation health assessment in Fukushima
I started to monitor this issue in my Earhquke (77) and (99). The Fukushima Prefecture Government is preparing to initiate radiation health assessment for their entire population of 2.02 million people, for monitoring their radiation health as long as for coming 30 years. Today their “preceding survey” has been started to measure internal exposure, mainly thyroid doses, by selecting 120 residents out of 28,000 villagers living in the highly contaminated region (within “scheduled (and organized) evacuation” zone) from Iidate-mura, Namie-machi and a part of Kawamata-cho. These samples were picked to avoid the ‘selection effect’, to designate evenly distributed cohort group considering life pattern and activities at the time of the plume passage. Their ages were distributed from 4 to 69 years old. The early “preceding survey” is obviously needed, in view of half life of 8.04d for I-131. It is generally recognized that I-131 detection should be performed within 10 half life period, to be able to estimate the thyroid doses received at the time of plume passage. The measurement is performed by using a “whole body counter” with a gun-shaped scintillator detector at the National Institute of Radiological Sciences (NIRS?in Chiba. Ten people went through this assessment today. NIRA intend to develop a computer system to estimate thyroid doses without actually surveying the entire population by the whole body counters. The dose assessment of the entire population will be made on the basis of questioners to be practical.
In comparison with this, I respect Russian scientists at the time of the Chernobyl accident. By May 5, 1986 (the accident occurred on 26 April), at Bragin District, as many as 4000 people went through the thyroid dose measurement, by using a makeshift lead cover to reduce background below patient’s shoulder (Ref. The International Chernobyl Project: Technical Report, IAEA (1991). I am greatly concerned whether meaningful monitoring results can become available after 14 times of the half life! As a matter of fact I tried to estimate release fraction of soil samples a few weeks ago, but I had to give up since the results were unreasonable.
IV Amelioration of farm land
The Ministry of Agriculture, Forestry and Fishery (MAFF) initiated a new project at Kawamata-cho for amelioration of farm land by planting Kenaf (Hibiscus cannabinus), a kind of hemp, Amaranthus (there are 42 different species. Perhaps it corresponds to Amaranthus caudatus?) and Quínua (It was reported by the word “kinua” but it seems to correspond to Chenopodium quino). MAFF has already started another amelioration project by planting sunflower and rape seed at Iidate-mura in late May. The sunflower was tested very effective in the amelioration of Chernobyl contaminated farm land in Ukraine. The Cs-137 is concentrated in its roots and strontium in its seed coat. The bio-oil can be extracted from the seed without contamination of radioactive species. The effectiveness of this method was very widely reported in Japan through Far East Research Corporation ( http://www.ntv.co.jp/FERC/200x_index.html , in Japanese ) in F.E.R.C Research Report - File No.1045 ( http://www.ntv.co.jp/FERC/research/20001203/f1045.html , in Japanese) This method is being developed to extract gold from the soil. It is an controversial new technology called “PHYTOREM” ( In situ remediation of contaminated soil by plants "PHYTOREM" web site (http://www.ensaia.u-nancy.fr/Recherche/solenviro/phytorem.htm). I did not know this new science frontier and found very interesting.
V Contamination of fish in Fukushima
The government ordered to suspend marketing Plecoglossus altivelis altivelis caught from the river streams from the Abukuma Mountain Chains, on which the highly contaminated corridor stretches from Fukushima Daiichi through Namie-cho and Iidate-mura. The fish samples from Abukuma River, Mano-gawa and Nitta-gawa showed 1260, 3300 and 4400 Bq, respectively.
On the other hands, no strontium contamination was found from the sea water fish samples of Sardinops melanostictus, Engraulis japonica and Ammodytes personatus. It is perhaps due to the fact that release of strontium is much reduced this time due to the decontamination effect of the suppression pool water before environmental release compared with the case of the Chernobyl accident. Where this measurement made was not disclosed.
It was also reported today from Nuclear Safety Commission that 140 Bq/kg of Sr-89 was detected first time in the sea bottom sludge samples taken at 3 km off shore of the Fukushima Daiichi. They are asking for investigation of crustaceans and fish living at the sea bottom. Among such fish, Pleuronectiformes is a favorite fish for many Japanese people.
Well, let me stop here tonight.
Genn Saji
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(Previous e-mail sent at 00:54 AM on June 27 as Earthquake (107))
Dear Colleagues:
107th day!
I. Recapping on the water purification system
TEPCO made an announcement today that they plan to start the water injection operation by using the purified water as early as Monday afternoon, June 27, by saying that the mission objectives of the water purification system have been successfully completed. If successful, this will close the water cooling chain to prevent an increase in the volume of highly contaminated water so far accumulated to more than 110,000 tons. On June 25, they inspected the system as well as replaced the sober from the US Kurion’s process. TEPCO is said to be planning to make an overall judgment for the future operational schedule and procedures on Monday.
For my memory sake, I developed the attached memo which explains the amount of nuclear species released to the highly contaminated water. It is to develop an equivalence of Table 2: Estimates of the principal radionuclides released in the accident, in Annex J of UNSCEAR 2000, Exposure and effects of the Chernobyl accident. The memo assumes that some portion of “intermediate” and “refractory species (including the fuel particles) can have settled down at the bottom of the pool of contaminated water accumulated in the basements of Reactor Buildings, Turbine Halls, as well as “trenches). In developing the memo, I realized an importance of future sampling of the contaminated water sludge, which is likely rich in “intermediate” and “refractory” species, including fuel particles. Currently TEPCO is trying to introduce a new robot “Quince”, developed by a Japanese team, which has a capability of sampling water. Please visit http://www.tepco.co.jp/en/news/110311/index-e.html to download Robot:Quince(4.95MB) (videoed on Jun 16, 2011)
II. Boron in the 1F3 SFP
TEPCO announced that they are pouring 90 tons of 2% borated water into the 1F3 spent fuel pool (SFP). This operation is said to prevent the alkalization of the pool due to accumulation of concrete debris. The pH measured last month was as high as 11.2. In the SFP, there are aluminum racks which should be kept in a neutral to slightly acidic condition. A similar operation is also being planned in 1F1.
Also, TEPCO announced that the external air cooler are being installed to the 1F3 SFP and scheduled to be ready by June 30, following with the 1F2, which has been working since May 31.
III. Nitrogen gas injection ready in 1F2.
TEPCO has been saying that they are ready to start injecting nitrogen gas into the 1F2 pressure containment system for prevention of hydrogen explosion, as soon as a permission is obtained from NISA. By filling the containment vessel with nitrogen, some amount of radioactive materials are expected to be released to the environment. In 1F1, the nitrogen gas charging have been performed since April. I think this is a prudent operation, however, the situation is a bit different from the successful operation in 1F1. It is because the damage to the reactor pressure boundary as well as to the pressure contaiment vessel seem to be different for 1F1 and 1F3. By struggling to install the temporary level gauge into 1F2, the reactor vessel pressure was only 0.1 kg/cm2 and there can be a larger crack. Also, the color of highly contaminated water observed in the 1F2 a few days ago indicated a heavy contamination with hematite (Fe2O3). This indicate a leakage from unknown region where there was a heavy accumulation of hematite. I am puzzled where this much of hematite came from. In 1F1 and 1F3, the color of the highly contaminated water in the basement of the reactor buildings looked yellowish, indicating a presence of strontium in the water. When metallic strontium reacts with water, it will dissolve into the water by changing the color slightly yellowish. TEPCO should be prepared in the situation that the the containment vessel is much leaky than in the case of 1F1.
IV. 1F1 Pool water sampling data released
I overlooked to introduced this data released on June 24. TEPCO showed that the results of the pool water sampling data (sampled on June 22) from 1F1 as follows:
Species Half Life Concentration (Bq/cm3)
Cs-134 2a 12,000
Cs-137 30a 14,000
I-131 8.04d 68
The activation is very likely came from contaminated debris fallen into the pool and is not due to damage of the fuels. Sith this, all four data indicate that the gross fuel damage did not occur in any of the SFPs.
Well, let me stop here tonight.
Genn Saji
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