April 22, 2013

Apr 22, 2013 | Fukushima Accident Updates

  • Tepco briefly shut off cooling flow to F. Daiichi’s unit #2 spent fuel pool today for inspection of the temporary power supply. Two dead mice were found inside the portable enclosure. No damage to the internal transformer or switchgear occurred. A protective cover was placed over the device to keep any other rodents out and #2 SFP cooling flow was restarted. The shutdown lasted about four and a half hours. SFP temperature increased roughly 0.1oC during the cooling stoppage. However, some Japanese news media reported this as yet another SFP power loss due to “rats”. Contrary to Tepco’s news release, the Press says the company has not yet taken measures to keep rats out of the temporary power supply for unit #2 SFP. (Tepco News Release, Japan Today; NHK World)
  • The International Atomic Energy Agency has inspected F. Daiichi. IAEA team leader Juan Carlos Lentijo said, “Extraordinarily committed workers have made significant accomplishments at Fukushima Daiichi since the March 2011 accident, but Japan continues to face difficult challenges as it works to decommission the site. We saw that TEPCO has achieved the stable cooling of the reactors and spent fuel pools at the site.” He added that Tepco should replace all temporary devices with permanent ones, but the F. Daiichi staff’s prompt response to problems has been exemplary. Much of the Japanese Press focused on a specific portion of the IAEA summary report referring to the recent SFP power losses and waste water reservoir leaks. For example, NHK World said that Lentijo urged the government and Tepco to boost management of wastewater, plus examine and explain the impact on the plant’s immediate environment. Kyodo News quoted the following from the IAEA summary, “Measures should continue to improve management issues regarding radiation releases and exposure from the site, particularly issues created by the storage of accumulated water.” Japan Times posted, “Tepco should continue its efforts to improve the reliability of essential systems, to assess the structural integrity of site facilities and to enhance protection against external hazards.” In all three cases, Lentijo’s actual statement was not included. (IAEA Public Information; NHK World; Kyodo News; Japan Times)
  • The seismic fault issue with two Japanese nukes has resurfaced. First, Japan’s Nuclear Regulatory Authority has rejected Tohoku Electric Co. contention that the “crush zones” running under the Higashadori nuclear station, Aomori Prefecture, are not seismic. Tohoku Electric says the zone has “lithified” [hardened], which could not have happened if the seam had moved within the NRA-specified time-frame. NRA commissioner Kunihiko Shimazaki accused Tohoku Electric of merely trying to change the NRA’s conclusion that the anomalies might be seismic. He stressed that just because the zone has not moved in the past few hundred thousand years does not mean it will not move in the future. The second issue concerns Japan Atomic Power’s Tsuruga nuclear station, Fukui Prefecture. In December last year, the NRA said there was a possibility that the D-1 crush zone directly beneath unit #2 was an active fault. Japco criticized this finding, saying it lacked scientific backing and the investigation had been one-sided. However, the NRA says Japco’s counter-argument is “unclear” and insufficient to reverse the watchdog agency’s prior judgment.  (Jiji Press; Mainichi Shimbun)
  • Four mayors of municipalities near the Hamaoka nuclear station say they will firmly oppose restarts. Elections were held in Kakegawa and Fukuroi, with the winners stating their antinuclear positions. Kakegawa winner, incumbent Saburo Matsui, said “it’s very hard to say that this is really the place for a nuclear plant,” and, “I will not recognize a restart until the safety of the plant has been confirmed.” Fukuroi winner, incumbent Hideyuki Harada, said “Even when the new safety measures (at the plant) are completed, I still will not approve reactor restarts.” Concurrently, the mayors of nearby Kikugawa and Yaizu also declared they “will not recognize” any move by plant owner Chubu Electric Co. to restart the Hamaoka station. A Chubu Electric executive said they will “refrain from commenting on the election results, but [the company] is developing thorough safety measures that we hope will lead to local public approval for reactor restarts.” The Hamaoka station is about 200 kilometers from Tokyo. It has been the focus of antinuclear activism since former PM Naoto Kan shut the plant down due to fears that a Fukushima-type accident at Hamaoka would force him to evacuate the Tokyo metropolitan area. (Mainichi Shimbun)
  • Official assessments of Fukushima resident’s radiation exposure have been over-estimated. A collaborative study by experts from four universities in Japan reveals that the Fukushima populace has experienced much lower exposures due to Cesium than previously thought. The team believes prior assessments were based on Chernobyl-area findings after the Ukraine nuclear accident in 1986. However, it seems the Chernobyl methodology calculated that internal exposures in excess of several millisieverts would be common in Fukushima. However, “…internal exposure levels of [Fukushima] residents are much lower than estimated. In particular, the first sampling-bias-free assessment of internal exposure of children in the town of Miharu, Fukushima, shows that the Cs137 body burdens of all children were below the detection limit of 300 Bq/body in the fall of 2012.” The team studied Whole-Body-Counter examination data covering more than 100,000 individuals from June 2011 through December, 2012. Prior official assessments were calculated based on contamination levels found in various Fukushima communities, assuming everyone ate locally-produced foods contaminated with radioactive Cesium. However, that was not the case. Residents were very careful about their eating choices and produced the extremely low internal exposures measured by Whole-Body-Count. For the complete report, go to…  https://www.jstage.jst.go.jp/article/pjab/89/4/89_PJA8904B-01/_pdf