Corrections and Apologies: When re-cheking my estimation of thyroid doses as reported in Earthquake (175, Jan 20-27, 2012) with the attachment: Estimation of Thyroid Doses from Land Contamination Maps for the Fukushima Disaster, ICONE20-55048, I found an embarrassing confusion in incorporating the difference in dose conversion methods between the Chernobyl accident and Fukushima. After the initial explosion, followed with graphite fire, a prolonged radioactive iodine release occurred for ten days in Chernobyl. Whereas at Fukushima, the releases were series of "puff releases", sometimes accompanied with hydrogen explosions. In the dose conversion process, I was confused in estimating the time-integrated radioactive intake and failed to correctly use the ventilation rates for the "puff release" cases. Please discard the previous version and substitute into the new one. The changes are indicated with red fonts. I also receive a scientific comment from Dr. Rosalie Bertell, who touched on hypothyroidism. I revised the Chapter IV DISCUSSIONS completely, focusing on health effects of thyroid intakes. Dear Colleagues: 322nd - 329th day! I. Upate of estimation of thyroid doses and effects of low level exposure I received a couple of comments and questions related with my draft paper: Estimation of Thyroid Doses from Land Contamination Maps for the Fukushima Disaster, ICONE20-55048 In the attached revised draft, Chapter IV Discussions has been totally revised to focus on health effects of intakes of radioactive iodine. One unthinkable news related with this issue is reported in the Yomiuri Newspaper (in Japanese, http://www.yomiuri.co.jp/feature/20110316-866921/news/20120207-OYT1T01085.htm). TEPCO prescribed about 15,000 iodine tablets to radiation workers between March 13 to October 12. Among them, 226 workers who took more than 1 gram were screened for blood tests of thyroid hormones. Three of them were identified with low level in the hormone but went back to a normal level after termination of prescription. The stable iodine dosing may have been effective for a few weeks, after March 11, especially during the 10 days of active phase, but such a prolonged dosages to radiation workers cannot be rationalized, I believe. The unnecessary dosage can induce negative side effects, as well known in thyroid illness. II. Update of Chernobyl experiences In Earthquake (176, Jan 27 - Feb 3, 2012), I introduced the news of three Ukraine scientists visited Japan to give a series of lectures on Ukraine experiences for amelioration of the aftermath of the Chernobyl accident: Dr. Oleksandr KLIUCHNYKOV Mr.Viktor KRASNOV Dr. Valerii KASHPAROV Dr. Kashparov kindly confirmed my explanation as copied in the following text: "I was very glad to meet you during my last visit to Japan. You have really understood the main statements of my presentation: iodine mainly was uptaken by children with the consumed milk. In that time in the regions of Ukraine and Belarus adjacent to the accident area the weather was very warm, and cows were grazing on the pastures. However, the grass was not well developed, and each cow had to eat grass from the big area and thus consumed the big amounts of iodine; the resulting specific activities in milk reached hundreds kBq/L. In Russia that period was rather cold weather, and the cows were mainly kept in stalls (not at the pastures). Thus in Russia there was no big rise of the thyroid cancers." Indeed, this is one of the key issues. Let me quote the relevant statement from my previous paper (Genn Saji, 2005. A Scoping Study on the Environmental Releases from the Chernobyl Accident (Part II): Iodine. In. International Topical Meeting on Probabilistic Safety Analysis, PSA’05 11-15 September 2005, San Francisco, California, USA. Available from ANS Store.) "Makhonko and his colleagues of the Experimental Meteorology Institute of S.-I.C. ‘Tayfoon’ (Russia) also found that the putting of milk cattle out to pasture has not begun at the moment of the arrival of the radioactive plume in the northern areas at the time of the Chernobyl Accident, which occurred on the 26th of April, 1986. For example, in Kaluga region, Makhonko and his coworkers report that the best estimated time for the beginning of pasturing is between the 5th to the 10th of May, when the grass height exceeds 5 – 6 cm; whereas the I-131 fallouts in Obninsk have started as early as on the 28th of April, two days after the accident. The spring was abnormally warm in 1986, therefore it was decided that the 5th of May was more than likely the beginning of pasturing period in this region. Further to the south, the pasturing may have started at the time of the arrival of the plume: [Makhonko, K. P. and Kim, V. M., The Calculation of the Dose Load for the Thyroid Gland by Consumption of Milk after the Chernobyl Accident, The Experimental Meteorology Institute of S.-I.C., Russian Journal ‘Atomnaya Energia’ v.83, Issue 1, July, p. 134 (1997), (in Russian, a private English translation is available upon request)" III. Mysterious temperature rise in 1F2 I introduced this issue in Earthquake (176, Jan 27 - Feb 3, 2012). On February 11, TEPCO reported that this mysterious temperature behavior still continues even after an increase in water injection rates as quoted below from http://www.tepco.co.jp/en/press/corp-com/release/12021105-e.html "From February 2, water-injection to Unit2 reactor was increased and the temperature tendency was monitored as the tendency of temperature rise at the bottom of PCV was observed, but the temperature have been high value (around 70.0°C). As a result of the sampling for the Gas Control System of the Unit 2 on February 6 to make sure there is no re-criticality state, we confirmed that the concentration of Xe-135 was below the detectible limit at the system's inlet, meaning that it falls below the re-criticality criteria of 1 Bq/cm3. In order not to raise the possibility of re-criticality state due to the high density of water in the reactor by injecting cold water rapidly, we injected boric acid into the reactor from 0:19 am to 3:20 am on February 7, in advance of increasing water injection amount, as a safety countermeasures against the re-criticality, and changed the amount of the core spray system injection water from 3.7m3/h to 6.7m3/h at 4:24 am (the amount of the feed water system injection is 6.8m3/h). Currently, the temperature is approx. 70°C (2/11 11:00) and we continuously monitor the tendency." I have been worrying, for the last several months, a possibility of fuel channel blockage with corrosion products occurring with poor water chemistry management since the beginning of water injection. The corrosion products blockage seems to be occurring frequently in the water purification lines, especially at filters. With radiation, the reactor core region becomes cathodic, which tends to invite deposition of corrosion products in anion states. When the cooling line can be made into a compact recirculation loop, it is possible to adjust the water chemistry. However, with such a gigantic water purification system, it is going to be impossible. If it is really due to fuel channel blockage, one possibility for amelioration is chemical decontamination. In the Japanese BWR community, including TEPCO, the CORD technology (Siemens, KWU) has been used. The method essentially chemically dissolve CRUD (Chalk River Unidentified Deposits, corrosion products in the primary system) by a strong acid at pH of around 2.1-2.4, followed with acidic neutralization process and removal processes of added chemicals. Although this technology has been applied to BWRs to reduce worker doses, its application to the damaged core should be a new challenge. However, at least a feasibility study is urgently waited for. IV. 1F4 SPF video On February 10, TEPCO posted a recent video of 1F4 SFP to confirm a transparency (in a sense purity) of the pool water in http://www.tepco.co.jp/en/news/110311/index-e.html where the methodology is illustrated http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120210_03-e.pdf A 38MB video can be downloaded from the homepage, showing fuel racks covered with concrete debris. The top of individual fuel rods can be observed in the video, showing there is no apparent fuel melting events. V. Recent photos of Fukushima Dai-ichi Current Status of Fukushima Daiichi Nuclear Power Station by photographs: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120120_02-e.pdf For Fukushima Dai-ni, a good presentation is also available, however, it appears to be released only in Japanese. http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120208_06-j.pdf Well, let me stop here today! Genn Saji
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