23 Novembre 2016
November 22, 2016
Japanese nuclear regulators have accepted power companies' assessment of the durability of steel parts for their nuclear plants.
The Nuclear Regulation Authority asked 11 domestic utilities to check on steel parts made by a method called forging.
The move came after it was found that steel for nuclear plant parts made by the same method in France contained more carbon than it should. Steel with a high carbon concentration can break down easily.
Japanese utilities said last month that steel for their plant parts is unlikely to contain much carbon. [??????]
The authority on Tuesday judged the assessment as appropriate.
It also decided to review the method of inspection to make it easier to detect the amount of carbon in steel.
The authority plans to continue seeking updates on the investigation in France, where regulators have ordered some plants halted for safety checks.
The Nuclear Regulation Authority says potentially weak steel components manufactured by a Japanese company have not been used in domestic nuclear facilities, after its French counterpart ordered reactors that used the company’s parts to be checked.
The NRA determined at a regular meeting Tuesday there is no comparable risk at the domestic nuclear facilities of 11 companies as portions of steel with excessive carbon concentrations had been removed from the components manufactured by Kitakyushu-based Japan Casting & Forging Corp.
The NRA concluded that the removal of portions with higher levels of carbon was insufficient in the components used in the French reactors.
The authority also determined there were no problems with critical parts at domestic facilities that were manufactured by other companies, including Tokyo-based Japan Steel Works Ltd.
The French Nuclear Safety Authority said in June it had found potential weaknesses at a number of nuclear facilities due to steel with higher levels of impurities supplied by Japan Casting & Forging, prompting the NRA to commence its own investigation.
Utilities in Japan checked their facilities and submitted reports to the NRA last month.
According to the reports, Japan Casting & Forging manufactured pressure vessel lids for 11 reactors at seven nuclear power stations, including the No. 2 reactor at Kansai Electric Power Co.’s Takahama power plant in Fukui Prefecture.
The company’s pressure vessel lids were also used at the No. 2 reactor at Kansai Electric’s Mihama plant in Fukui Prefecture and the No. 1 reactor at Kyushu Electric Power Co.’s Genkai plant in Saga Prefecture, both of which are set to be decommissioned.