Extra steps taken for nuclear backup systems after Fukushima disaster
Bridgeman, Mich. — In March 2011, a powerful earthquake struck off the east coast of northern Japan, setting off a chain of events leading to the worst nuclear power plant disaster since Chernobyl in 1986.
The Fukushima I nuclear power plant was immediately shut down as a precaution. But when a gigantic tsunami triggered by the earthquake hit the coastal power plant about an hour later, the huge wave topped the 19-foot seawall.
The tragic result was that flooding in the plant disabled backup generators used to pump cool water into the reactor cores to prevent overheating. The water did overheat, and in turn caused several explosions. The disaster led to the release of radiation into the sea and into the air.
It didn’t take long for the federal Nuclear Regulatory Commission to analyze what went wrong at the Fukushima plant and learn what could have been done to prevent it.
More importantly, NRC staff wanted to know how the lessons learned from the Japanese disaster could be used to boost domestic nuclear power plant disaster safety.
Within a year of the disaster, the NRC issued additional regulatory orders for U.S. nuclear power plants. All the plants are expected to have the new requirements in place by late 2016, or sooner.
Southwest Michigan’s two nuclear power plants have or are building hardened “bunker” style buildings to house emergency backup equipment such as hoses, diesel generators and backup pumps, as required by the NRC.
The thrust of the new NRC regulations is meant to give nuclear power plants another layer of redundant backup plans in case of a wide range of possible emergencies that could knock out power, including flooding, earthquakes and tornadoes.
Both the Donald C. Cook plant, north of Bridgman, and the Palisades plant in Covert Township are along Lake Michigan.
At the Cook plant, as much as $50 million has been invested by AEP in compliance with the new NRC regulations, said Cook’s engineering vice president Shane Lies.
That includes an estimated $10 million to $15 million for the reinforced bunker that houses the backup generators, pumps, hoses and other emergency equipment. The project was completed this spring during the planned maintenance and refueling outage for Unit 1.
The equipment is on wheels so it can be rapidly deployed to anywhere on site.
“It’s a hardened facility designed to withstand a tornado,” Lies said.
Cook was given the option of having one hardened bunker housing the equipment, or building two separate structures, each with its own set of equipment, Lies said.
No tornado is known to have struck at or near the plant site, but that doesn’t mean it couldn’t happen, Lies said.
“Realistically, we never expect to have to use this stuff,” he said. “But the plant is now well-prepared for any kind of natural disaster.”
“What we have learned as an industry from Fukushima is that you have to think about the risk of probability of natural disasters,” he said.
The outside of the Cook bunker is surrounded by large concrete blocks designed to keep vehicles or other heavy debris from being pushed into the building by a tornado.
The bunker houses trucks that could be used to clear downed power lines or other debris at the plant site. It houses other emergency equipment, including emergency lights and Jaws of Life extrication tools.
All 1,200 Cook employees have received training on the new system, Lies said.
The NRC is requiring several other improvements at Palisades under the same umbrella of regulations said Lindsay Rose, Palisades spokeswoman.
They include additional safeguards to ensure cooling valves are working; installing more places where portable diesel generators and pumps can pump water into the reactor system; installation of electrical quick connection panels; and more instrumentation to measure more reliable water level indications in the spent fuel pool.
Palisades’ investment in the new improvements is expected to be about $50 million, Rose said.