August 16, 2022

Concern at Nebraska Reactors as Floodwaters Rise

The reactor, Cooper Station, is one of two nuclear plants on the Missouri River, which has been beset by flooding in recent days. Another reactor, Fort Calhoun, took two steps backward on Sunday. In the pre-dawn hours, a piece of heavy equipment nicked a temporary rubber berm, 8 feet high and 2,000 feet long, and it deflated. And water there began to approach the switchyard, where grid power enters the complex, so operators started up their diesel generators.

But both reactors appear well set up to weather the flooding, their operators and government regulators say. Fort Calhoun shut down in April for refueling and stayed closed because of predictions of flooding, so its cooling requirements are much smaller now. It is “designed to remain secure” at a reiver level of up to 1,014 feet above sea level, and the river level is stable now at 1,006.5 feet ,according to the Omaha Public Power District, the operator.

Cooper, owned by the Nebraska Public Power District, is still running. Managers brought in two tanker-loads full of extra diesel fuel and have stocked up on all the other “consumable” materials the plant uses, including hydrogen and carbon dioxide, in case truck access becomes difficult.

At Cooper on Sunday, plant officials led Gregory Jaczko, the N.R.C. chairman, led him past thousands of feet of new berms that would hold back the river if it overtopped the levees, past buildings where every doorway was barricaded with four-foot high water barriers that are intended to survive even if an earthquake hits during a flood, and into the building that holds the diesel generators, which would supply vital electricity if the water knocked out the power grid.

Getting into that space required some doing. First, Mr. Jaczko climbed over a makeshift metal staircase to get over the flood barrier at the entrance to the building. Then, past a security guard with a military-style rifle, he stepped through a doorway into a small hallway blocked with a four-foot high flood barrier. Visitors climbed three steps up a plastic-and-aluminum A-frame ladder, and then took a long step unto a temporary wooden platform, stepped over the four-foot-high barrier unto another platform, and then down a ladder on the other side.

“And if the water gets in here, what would be the result?” asked Mr. Jaczko.

“We’ve got a sump pump over here,” said Dan Goodman, the assistant operations manager, leading him around to the other side of the giant diesel generator which is the size of a tractor-trailer truck.

Twice an hour, 48 times a day, a technician with a tape measure looks at the water level at the water intake building, and other operators check the level recorded by the Army Corps of Engineers four miles upstream, in Brownville. Plant workers walk the levees near the river and intermittently add sandbags where they find soft spots leaks. They watch for “sand boils,” places where water begins to leak through.

Flooding is always a potential problem for nuclear reactors, but the threat has a higher profile lately because of the tsunami that hit the Fukushima Daiichi reactors in northeastern Japan on March 11. Nuclear reactors require electric power to pump cooling water even when they are shut down, and at Fukushima, the tsunami destroyed the connection to the electric grid, flooded the emergency diesel generators, washed away the extra tanks of diesel fuel and damaged the switches that would have controlled the flow of electricity from the emergency generators to pumps, valves and other vital equipment.

Unlike a tsunami, the challenges posed by the Missouri River was obvious for days in advance. At Cooper, the plant’s license specifies that it would have to shut down if the river reached 902 feet above sea level, and it came close, but then a levee on the Missouri side broke on Thursday night, and the water level fell precipitously.

Cooper went into service in July 1974, and is the largest generator in Nebraska. Its design is similar to Fukushima’s.

The trip to the disaster scene may be almost a relief for Mr. Jaczko, because it gets him out of Washington, where Republicans in the House and his own agency’s inspector general have been seeking to pillory him over decisions he made about Yucca Mountain, the proposed nuclear waste repository.

Mr. Jaczko ordered the Commission’s staff to drop work on evaluating whether the Yucca project should get a license, but in early June, the inspector general found said the chairman was “not forthcoming” with the other four commissioners about what he was doing, and quoted colleagues were critical of his management style.

And on June 24, four long-time members of the Commission staff complained bitterly in testimony to a House subcommittee that years of their work had been discarded. Mr. Jaczko said that since the Energy Department was trying to withdraw its application to build the repository, and since Congress had not appropriated money for the evaluation work, terminating the work was the only sensible option.

Article source: http://feeds.nytimes.com/click.phdo?i=f520e040f39540fd552920b28bb49920

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