Japan orders more geologic surveys of nuclear reactors.


The Asahi Shimbun Japan
August 25 2012.

The Nuclear and Industrial Safety Agency plans to order geological fault surveys at two additional nuclear power facilities, which could lead to a decommissioning of both facilities.

The nuclear watchdog said Aug. 24 that surveys, including excavations, are necessary at Kansai Electric Power Co.’s Mihama nuclear plant and Japan Atomic Energy Agency’s Monju prototype fast breeder reactor, both in Fukui Prefecture.

The two companies have said that faults running directly below their reactor buildings are not active, but NISA concluded that more information is needed.

“We need to take into account earthquakes that are not normally expected,” said Shinji Toda, a NISA panel member and Kyoto University associate professor, referring to the March 2011 Great East Japan Earthquake. “Past documents provide only insufficient data.”

A nuclear reactor cannot be installed above an active fault under the government’s quake-resistance standards for nuclear power plants.

NISA had already ordered fault re-examinations at four nuclear power plants: Japan Atomic Power Co.’s Tsuruga plant; Hokuriku Electric Power Co.’s Shika plant; Kansai Electric Power Co.’s Oi plant; and Tohoku Electric Power Co.’s Higashidori plant.

NISA has inspected faults at 18 nuclear power facilities in Japan since its expert panel said in April that a fault running directly below a reactor building at the Tsuruga plant in Fukui Prefecture may be active.

The agency concluded that additional geological surveys are necessary at the six facilities, saying faults under the premises may be active.

Experts say a fault running directly below a reactor building at the Shika plant in Ishikawa Prefecture may be active.

Kansai Electric and Tohoku Electric have said faults at the Oi plant in Fukui Prefecture and the Higashidori plant in Aomori Prefecture are not active, but NISA ordered follow-up surveys.

NISA said further fault studies are necessary for three nuclear power plants–Tokyo Electric Power Co.’s Kashiwazaki-Kariwa plant, Chubu Electric Power Co.’s Hamaoka plant and Kansai Electric’s Takahama plant–but said additional geological surveys are not required at present.

TEPCO, operator of the stricken Fukushima No. 1 nuclear power plant, plans to conduct a voluntary geological survey at the Kashiwazaki-Kariwa plant in Niigata Prefecture in an attempt to reactivate it at an early date.

NISA said no problems have been found at the remaining nine nuclear facilities.
end quote.

The risk posed by the fault running beneath Monju has been raised in Japan by local residents and others for many years. The official response has been, up to now, to treat such people with disrespect.

“On May 30, 2005 the Supreme Court reversed the Nagoya High Court decision on the narrow grounds that NSC’s safety assessment was “not unreasonable” and that it did not “contain flaws that could not be overlooked”. However, the Supreme Court did not say that Monju was safe to operate.

Shortly before the Supreme Court verdict, on February 7, 2005, Fukui Governor, Issei Nishikawa, granted approval for the start of modifications to Monju. The modifications began on September 1, 2005 after the reactor had been shut down for nearly ten years and were completed on August 30, 2007. Modifications included the following: removal and replacement of the temperature gauge that was the cause of the accident; modification of the sodium drainage system; installation of insulation on walls and ceilings, nitrogen gas infusion apparatus, and a comprehensive video monitoring system; and measures to deal with a water-sodium reaction accident arising from a water leak from the steam generator heat transfer tubes. These measures mainly relate to sodium, but other dangers inherent to the Monju design, including the possibility of a run-away chain reaction and problems related to seismic safety, remain unchanged.

The danger of a loss of control over reactivity leading to collapse of the reactor core is much greater in FBRs than in light water reactors (LWR). FBR fuel assemblies are packed much more densely than in LWRs. If the fuel assemblies bend for any reason, the distance between them is reduced even further, increasing core reactivity and creating the risk of a runaway chain reaction and core melt down. FBRs of Monju class and larger have the additional weakness of a “positive void”, meaning that if bubbles form in the coolant, core reactivity tends to increase. Although not an FBR, a positive void was instrumental in causing the 1986 Chernobyl accident. Both these weaknesses could come into play if a loss of electric power caused the primary coolant pumps to stop working.

In regard to seismic safety, there are problems with the design of Monju’s piping system. To cope with sudden temperature changes due to the high heat conductivity of sodium, Monju’s piping is much thinner than in light water reactors. Also, it is not fixed and it is not straight. Instead, it winds around above the reactor. This represents a very real danger in earthquake-prone Japan, especially given that the Headquarters for Earthquake Research Promotion discovered a previously unknown active fault. The Urasoko fault connects with the Yanagaseyama fault on the ocean floor of Tsuruga Bay, with the latter extending to Shiga Prefecture. The seismic safety assessment is now being redone by a subcommittee of the Nuclear Industrial and Safety Agency (NISA).

The original target date for restart was February 2008, but this date has been delayed on four occasions. The main reasons for the delay are JAEA’s inability to rectify problems with its sodium leak detectors, corrosion in the exhaust duct and the need to replace degraded fuel. The leak detectors have gone off repeatedly in various locations, even though there was no sodium leak. The exhaust duct had not been inspected for ten years, because no inspection plan had been prepared. The problem with the fuel was that since it was first fabricated over half of the original “fissile” plutonium-241 had decayed into americium-241. In order for Monju to reach criticality, new fuel assemblies had to be fabricated….Conclusions
Monju shares the same problems of nuclear proliferation, safety and cost that have plagued fast breeder reactors in other countries. There is no sign that the benefits that are supposed to compensate for these dangers, namely breeding of plutonium as an inexhaustible civilian energy source and transmutation of radioactive waste, will ever be viable. The Japanese government will try to trumpet the value of Monju for international transmutation research, but it is highly unlikely that Monju will be used as a breeder reactor.

Japan’s fuel cycle program, of which Monju is a key part, represents a serious nuclear proliferation problem. The rationale for Japan separating plutonium from spent nuclear fuel was to supply its FBR program, but there were warnings from all around the world about the massive stockpile of surplus plutonium that Japan would accumulate in the process. (See for example an article in NIT 20, Nov./Dec. 1990 by Jinzaburo Takagi entitled “Plutonium: 50 Years on”.) These warnings were proved correct. Japan now has about 47 tons of separated plutonium, nearly 10 tons of which is stockpiled in Japan. The rest is held in France and the UK. Regardless of Japan’s own intentions, this plutonium stockpile sets a bad example for other would-be nuclear proliferators.

From a safety perspective, if anything the danger of operating Monju is even greater than it was before the sodium accident. During the fourteen years that Monju has been sitting idle, pipes and equipment would have degraded. However, it is impossible to check for cracks and holes throughout the whole plant, especially where sodium prevents visual inspection. Furthermore, JAEA’s attitude has not changed. Its instinct is still to cover up problems, as evidenced by its proposal not to report false alarms of sodium leaks. The condition of the plant and the nature of the operator bot” http://cnic.jp/english/newsletter/nit134/nit134articles/monju.html CNIC, Japan. Restarting Monju – Like Playing Russian Roulette, circa 2010.

One Response to “Japan orders more geologic surveys of nuclear reactors.”

  1. CaptD Says:

    These “inspections” are yet another “dodge” used by the Japanese Gov’t. to delay decommissioning these reactors…

    Each day they wait the costs go up and the RISK of yet another Fukushima grows…

    THe Japanese people now understand this and that is why they are taking to the streets EVERY Friday in ever larger numbers!

    PM Noda is losing face by supporting the Nuclear Industry instead of the people of Japan, maybe it is time for Ex-PM Kan to get elected, at least he listens to the people!

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