February 15, 2017

TEPCO gave inaccurate explanations about seismic capacity of nuke plant

http://mainichi.jp/english/articles/20170215/p2a/00m/0na/014000c

Tokyo Electric Power Co. (TEPCO) has revealed that it had explained that the seismic capacity of a quake-absorbing structure called an "important anti-seismic building" at its Kashiwazaki-Kariwa Nuclear Power Plant in Niigata Prefecture was higher than it actually was, now saying that it "cannot withstand all types of shaking."

TEPCO made the revelation at a Nuclear Regulation Authority (NRA) safety screening session on the plant's No. 6 and 7 reactors on Feb. 14. The "important anti-seismic building" is supposed to serve as a frontline base in the event of a nuclear accident. The NRA demanded TEPCO give detailed explanations about how and why it provided the wrong information, saying harshly, "We cannot overlook this."

According to the NRA and other sources, of the so-called "standard earthquake vibrations," the strongest seismic shaking the important anti-seismic building is assumed to withstand, TEPCO had said that the structure would not be able to withstand some types of seismic shaking. But the utility reversed its previous explanations at the latest meeting, saying, "It cannot withstand all types of shaking." TEPCO said that it had given the wrong explanation because the facts had not been conveyed from its section that analyzed the seismic capacity of the building in 2014 to the division in charge of attending safety screening session meetings.

A TEPCO official apologized at the meeting, saying, "We are sorry that our information sharing was insufficient."

Key Niigata nuclear plant building may not be quake-proof

http://www.asahi.com/ajw/articles/AJ201702150042.html

THE ASAHI SHIMBUN

Tokyo Electric Power Co. has revealed that a key building at its Kashiwazaki-Kariwa nuclear power plant may not be able to withstand even half of the assumed strongest seismic shaking, contrary to its earlier assurances.

TEPCO's disclosure came Feb. 14 during a screening by the Nuclear Regulation Authority (NRA) for the restart of the No. 6 and No. 7 reactors at the nuclear power plant in Niigata Prefecture, which is the world’s largest.

The utility became aware of the possibility in 2014, but the information was not shared within the company. TEPCO reported to the NRA that the building can withstand temblors of 7, the highest category on the Japanese seismic intensity scale.

The building is designed to serve as an on-site emergency headquarters in the event of a severe accident, such as one caused by an earthquake.

An earthquake that occurred off the Chuetsu region of Niigata Prefecture in 2007 badly damaged the Kashiwazaki-Kariwa plant.

In response, TEPCO constructed the building in question in 2009. At that time, it said the structure could withstand the assed biggest earthquake motions that are 1.5 times stronger than those described in the Building Standards Law.

In 2014, the utility checked the building’s anti-quake capabilities again. It found that it may not be able to withstand horizontal movements triggered by even half the anticipated strongest earthquake, and that it could collapse into the side of an adjacent building.

That information was not conveyed to the company’s division in charge of the NRA’s screening, and thus escaped notice from NRA inspections.

Takafumi Anegawa, managing executive officer of TEPCO, apologized, saying, “We did not conceal the possibility. The in-house liaison was insufficient.”

An NRA official said, “Information is not shared in the company. Lessons from the accident at the Fukushima No. 1 nuclear power plant are not utilized.”