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Are PWR safer?

June 20, 2013


Utilities set to apply for screening of pressurized-water reactors under new safety rules



The Nuclear Regulation Authority announced on June 19 its new nuclear reactor safety requirements, which are aimed at averting disasters like that which hit the Fukushima No. 1 Nuclear Power Plant.

The NRA will begin accepting applications for permission to reactivate idled nuclear reactors on July 8, when the new regulations take effect after receiving Cabinet approval. Based on the results of the Mainichi's inquiries into 10 power companies nationwide, four utilities are expected to submit applications for a total of 12 reactors at six nuclear power stations by the end of July.

Numerous pressurized-water reactors (PWRs) mostly in western Japan are a different type than those which existed at the troubled Fukushima No. a plant. Because utilities will be given a longer time under the new regulations to implement some of the required safety measures for PWRs than for other types of reactors, more applications will likely be filed from power firms in western Japan than in eastern Japan. In addition to the new regulations, the 40-year operational limit for all nuclear reactors nationwide will in principle take effect simultaneously. Therefore, the overall process to drop aging reactors will gain momentum.

The 12 nuclear reactors for which the four utilities are expected to apply for the NRA safety screening are as follows: reactors Nos. 1 to 3 at the Tomari Nuclear Power Plant in Hokkaido (Hokkaido Electric Power Co); reactors Nos. 3 and 4 at the Takahama Nuclear Power Plant, and reactors Nos. 3 and 4 at the Oi Nuclear Power Plant in Fukui Prefecture (Kansai Electric Power Co.); the No. 3 reactor at the Ikata Nuclear Power Plant in Ehime Prefecture (Shikoku Electric Power Co.); reactors Nos. 3 and 4 at the Genkai Nuclear Power Plant in Saga Prefecture, and reactors Nos. 1 and 2 at the Sendai Nuclear Power Plant in Kagoshima Prefecture (Kyushu Electric Power Co.). All of the reactors are PWRs that had been in operation for less than 30 years. There are a total of 24 PWRs in the country, mainly in western Japan. Under the new regulations, power companies are given five years to equip their PWRs with filtered venting systems designed to prevent the outflow of radioactive substances into the atmosphere.

There are 26 boiling water reactors (BWRs) in the country that are the same type as those of the troubled Fukushima reactors. The cubic content of the BWR's containment vessel is smaller than that of the PWR, and it could plunge into a critical situation quickly due to increased pressure in the vessel. Therefore, no grace period is given under the new regulations to equip BWRs with filtered venting systems. Tohoku Electric said it was not sure when and whether it would be able to apply for safety screening for BWR reactors at its Higashidori Nuclear Power Plant in Aomori Prefecture and its Onagawa Nuclear Power Plant in Miyagi Prefecture.

Tokyo Electric, Hokuriku Electric, Chubu Electric, Chugoku Electric and Japan Atomic Power Co. (JAPC) all said that it was too early to say when they could apply for the safety screening. It costs billions of yen to install a filtered venting system, and with the exception of the No. 2 reactor at JAPC's Tsuruga Nuclear Power Plant, all of their reactors are BWRs. Clearly, the types of reactors will affect the outcomes of safety screenings.

The NRA will set up three teams within its secretariat to conduct the screenings. If the regulators determine that the reactors meet the new safety requirements, the government will decide whether to reactivate them after securing the consent of concerned local municipalities. The new regulations will also oblige power companies to take measures to deal with severe accidents. Previously, such measures had only to be undertaken as "voluntary efforts." The new regulations will also require utilities to set up "specific safety facilities" to be used to cool down reactors by remote control in case of disaster.

The new regulations will forbid power firms from setting up key facilities such as reactor buildings directly above active faults. The regulations will ask operators of nuclear power plants to conduct surveys, if necessary, regarding whether faults have moved during the past 400,000 years -- as opposed to the past stipulation of 120,000- 130,000 years. In addition, power firms will be required to beef up measures against fires, including the replacement of flammable cables that are often seen in aging reactors. A 40-year operational limit for all nuclear reactors will also be introduced, and extension of this period will require a widened scope of inspections.

"Electric power companies will likely emphasize cost-effectiveness, and make capital investments in younger nuclear reactors with larger power output," commented Takuya Hattori, president of the Japan Atomic Industrial Forum Inc. (JAIF).

NRA Chairman Shunichi Tanaka said during a news conference on June 19, "There will be clashes (between the NRA and power companies) over the screening outcomes."



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