On April 26, Nuclear Regulatory Commission staff did a safety "walkdown" of the Diablo Canyon nuclear power plant on southern California's coast, part of NRC inspections of all U.S. reactors that were triggered by the Fukushima Daiichi nuclear plant disaster in Japan.

The NRC's inspection report, released Friday, did not flag the plant's owner, Pacific Gas & Electric Co. (PG&E) for a serious violation of the rules the commission has imposed to assure the plant's safe shutdown in an anticipated emergency.

But it did list more than a half-dozen issues that could jeopardize the plant if it were confronted with the kind of chain reaction of unexpected and unplanned-for calamities that struck the Fukushima nuclear complex.

The NRC investigators reported:
• The plant had a single diesel-driven pump to provide emergency cooling water to a single reactor in case an earthquake cut off normal water flow. The pump could not have serviced both of the plant's reactors if they lost normal water supply simultaneously, the NRC staff said.

• Some doors at the plant required to protect against flooding of major safety equipment would not self-latch as required. One latch was "degraded," they said.

• The plant's six emergency diesel generators were located in the same plant area, and thus vulnerable to a "common mode" failure.

• An earthquake could cause a structural failure in the building where the fire truck is stored, and debris could block crews from using the truck.

• PG&E planned for a contractor to provide seawater for emergency cooling, but had no backup plan if an earthquake and tsunami blocked highways to the plant. PG&E intended to rely on the California National Guard to deliver diesel fuel for emergency generators if roads were impassable, but had no memorandum of understanding in place for the deliveries.

• Four 20-foot extension cables, used to operate fans that cool portable generators, were missing from their storage location.

Vulnerabilities found at dozens of U.S. reactors
Something under one-third of the 104 U.S. reactors were found to have some vulnerabilities to extreme emergencies, according to the NRC, which is preparing a summary of its post-Fukushima findings.

The NRC says that all issues have been fixed or put on schedule for correction, and that the safety of the reactors was not compromised.

PG&E spokesman Paul Flake said issues reported by the NRC had been identified by the company's own review after Fukushima, and an inspection by the Institute for Nuclear Power Operations, the industry's confidential safety monitor. "All of the issues identified in the [NRC] inspection report are being addressed. We continue to work with the NRC to introduce safety improvements" required to protect the plant, he said.

"Our inspectors found all the reactors would be kept safe even in the event their regular safety systems were affected by these events, although a few plants have to do a better job maintaining the necessary resources and procedures," said Eric Leeds, director of the NRC's Office of Nuclear Reactor Regulation.

But the U.S. plants are now being reviewed in Fukushima's harsher light, that of a disaster far greater than planned for, which spread confusion among plant operators.

"We'll review the plants' responses [to the inspections] to see if they need to take any additional actions to meet our existing requirements, along with seeing what the NRC might need to do to enhance those requirements and continue to protect public health and safety," NRC Chairman Gregory Jaczko said last week.

At a time when the NRC and industry leaders are calling for a rigorous safety culture within the U.S. nuclear industry, the inspection findings raise questions about whether some plants were following the letter of requirements but not prepared for "unthinkable" events.

1 Comments

1. 1. sault 12:50 PM 5/19/11

   It is apparent from the Japanese Earthquake and subsequent tsunami that these "beyond design basis" events are possible and WILL cause nuclear disasters in the future. With the consequences of Chernobyl and Fukushima-level disasters so grave and costly to society, reactors MUST be designed to handle these types of threats. We MUST ignore the complaints from the nuclear industry that they are being strangled by red tape since this article highlights their safety shortcomings even after going through the review processes they are hoping to short-circuit. Finally, people have to realize that the costs to build a nuclear plant that can handle every conceivable, and sometimes inconceivable, event over its 80-year lifespan make nuclear power a very high-cost option for generating low-carbon electricity.

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