Tokyo Electric Power (Tepco) staff manipulated main steam valves to reduce leak rates during containment testing in 1991 and 1992, the company has admitted.
Tepco admitted the "dishonest acts" in a press release on 25 October. The company said that during the two annual inspections at Fukushima Daiichi 1 (Fukushima I-1), plant staff knew that the containment leak rate was too high. When government inspectors carried out the leak tightness test the staff injected air via the main steam isolation valves to reduce the leak rate. It is reporteed elsewhere that the real rate was 2% per day compared to the allowed maximum of 0.45% per day. By manipulating the valve, the rate was reduced to 0.12% per day.
Tepco said the plant had been shut down for additional leak rate inspections, and an external commission comprising five specialist lawyers had been assigned to oversee the investigation. The company could not say whether "dishonest acts were conducted in the leakage inspections at all Tepco's nuclear power stations other than the above-mentioned two inspections"; nor could it say whether other tests at that plant had been falsified. All the company's leak tests are now being examined.
Once again, the power company found itself saying: "Tepco sincerely regrets and apologises that such dishonest acts were conducted." Tsunehisa Katsumata has taken over as head of Tepco following the resignation of Nobuya Minami. At a press conference Katsumata said the data falsification was "the gravest crisis since the company was established", and that the company had lost so much "it should start again from zero". Shigemi Tamura is to be promoted to chairman, replacing Hiroshi Araki.
Meanwhile, additional cases of covered up crack findings were also reported by Tepco. According to data Tepco provided to METI, these cases involve flaws found in recirculation pumps and piping connecting the pumps to the primary circuit at Fukushima I-1 to I-5, at Fukushima II-3, and at Kashiwazaki-Kariwa 1 and 2. Unlike previously disclosed cases of concealed inspection results, the inspections at these reactors were carried out by Hitachi and Toshiba, rather than by GE.
In one case, Hitachi has acknowledged that, while under contract for BWR inspection work for Tepco in 1992, it found cracks in neutron-measuring equipment at a BWR at Fukushima. Tepco officials then asked Hitachi personnel to delete the crack finds from reports that they wrote. According to a Hitachi spokesman, a senior official in Hitachi's nuclear plant design division agreed to Tepco's request because Tepco was a Hitachi client.
As a consequence of these revelations, plans to build six new reactors totalling 9000MWe at three sites have been indefinitely frozen. This will halt over half the new nuclear capacity that Japan had intended to have in place soon after 2010, including Japan's first two APWRs.
Tepco announced that it would postpone plans to build new ABWRs at Fukushima I-7 and I-8, and the first two units in Aomori Prefecture, Higashidori 1 and 2. In addition, Yukio Kurita, the governor of Fukui Prefecture, has announced that he has withdrawn his approval of construction by Japan Atomic Power Company (JAPC) to build Japan's first APWRs at Tsuruga 3 and 4. According to Kurita, permission for the new reactors was withdrawn because of the prefecture's "loss of trust" in nuclear energy following the cover-up disclosures. Industry sources say that this reaction was "political".
METI is considering whether to start criminal proceedings against Tepco officials.
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