Diablo Canyon digs into the details to ensure safety

Plant operators seek to keep the Central Coast safe with the help of lessons learned from Japan’s nuclear disaster

dsneed@thetribunenews.comMarch 9, 2012 

One year ago Sunday, Japan suffered one of the world’s worst nuclear disasters — a triple reactor meltdown at the Fukushima Dai-ichi power plant.

The effects of that disaster are still reverberating worldwide. In San Luis Obispo County, the operators of PG&E’s Diablo Canyon nuclear power plant have embarked on a series of improvements that will help it better withstand the kind of massive, unanticipated natural disaster that occurred in Japan.

“That’s what you have to do to be safe,” said Jim Becker, Diablo Canyon plant manager. “You learn from mistakes and you make improvements based upon experience.”

A powerful offshore earthquake caused the Fukushima plant to be inundated by a tsunami that left it without power. This triggered meltdowns in three of the plant’s six reactors, which in turn forced the evacuation of 80,000 people from an area affected by leaking radiation.

It could have been worse. A recent report by a private policy group in Japan says government officials feared a “demonic chain reaction” would force the evacuation of tens of millions of people from the capital city of Tokyo.

The anti-nuclear group San Luis Obispo Mothers for Peace has several events planned to mark the one-year anniversary of the tragedy. The intent is to honor the victims of the disaster, many of whom have not returned to their homes and have been dealing with contaminated food and water.

“On the one-year anniversary of the tragic events in Fukushima, San Luis Obispo Mothers for Peace remembers the victims and expresses its support for the survivors,” said Jane Swanson, a spokeswoman for the group. “The disaster triggered by a combination of the unanticipated size of the earthquake and the ensuing tsunami is not over.”

In the weeks following the disaster, the Nuclear Regulatory Commission and individual plant operators were quick to reassure the public that the 104 reactors in the United States were safe and that it was highly unlikely a natural disaster would cause a similar cascade of compounding failures here. Diablo Canyon sits 85 feet above sea level, and the many earthquake faults in the area are not the type likely to cause tsunamis.

However, the industry quickly re-examined its emergency response capabilities and began looking at what lessons could be learned from the Japanese debacle.

One overarching lesson emerged: Nuclear plants cannot tolerate extended power outages and must have much more redundant equipment stored at multiple locations that allow them to keep reactor cores and spent fuel pools supplied with cooling water.

“At Fukushima, all the standard equipment was useless to them,” said Murrell Evans, a systems operator at Diablo Canyon who heads the Fukushima response team.

This week, the federal Nuclear Regulatory Commission announced new requirements that all nuclear plants must meet over the next five years to deal with severe natural disasters such as earthquakes, tsunamis, floods and hurricanes. Among the requirements: purchasing additional backup emergency equipment including diesel-driven pumps, electric generators, pipes, hoses, diesel refueling equipment, ventilation fans, communications gear and emergency food and drinking water.

Diablo Canyon is now equipped with four new emergency saltwater pumps and 8,000 feet of steel pipe that would provide cooling water from the ocean if an earthquake were to damage the plant’s standard pumps. A year ago, that equipment was on standby and only would have been brought to the plant in the event of an emergency, Evans said.

Nationwide, more than 300 pieces of additional safety equipment have been purchased in the past year, according to the Nuclear Energy Institute, the industry lobbying group.

Plant managers at Diablo Canyon expect to spend $1.5 million in initial equipment purchases and a total of $50 million over the next three years to meet all of the NRC’s post-Fukushima requirements, said Jearl Strickland, a governmental relations manager at the plant. Longer-term improvements planned by the NRC include installation of sprinkler systems for spent fuel pools and additional venting to prevent the buildup of explosive hydrogen gas within containment domes.

Beefing up emergency equipment is not the only response at Diablo Canyon to the Fukushima accident. Three other improvements are also planned or under way:

Seismic studies: PG&E is spending $64 million to study the earthquake faults surrounding Diablo Canyon. In response to Fukushima, state and federal regulators have required that these studies be completed before PG&E can be allowed to proceed with proposals to renew the plant’s two operating licenses.

The utility has completed two-dimensional mapping, both onshore and offshore of the plant. Higher-energy three-dimensional mapping is planned for late this year, pending the necessary federal and state permits. “I still hope to get a boat in the water this year,” Strickland said.

Spent fuel pool instrumentation: Another of the NRC’s post-Fukushima requirements is that all spent fuel pools be equipped with instruments that remotely tell reactor operators how much water is in the pools and its temperature.

In addition to the reactors, the pools that store used fuel assemblies can contain tons of highly radioactive material. Used fuel can melt down and spew radiation into the environment if the water in the pools drains out or boils off as a result of a natural disaster.

Reactor coolant pump seals: Independent of any NRC requirement, PG&E will install new, more durable seals on its reactor coolant pumps, which are key pieces of safety equipment. The new seals will be installed during upcoming refueling shutdowns and will significantly increase the amount of time the pumps can operate during an emergency by preventing leakage of cooling water, Becker said.

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