NRC: Reactors Must Upgrade Vents

Monday, June 10, 2013 @ 06:06 PM gHale

Owners of almost a third of all U.S. nuclear reactors must upgrade the units in the next four years to guard against pressure-induced explosions.

The Nuclear Regulatory Commission (NRC) directed operators of the 31 units, among the oldest of 104 U.S. reactors, to overhaul vent systems to prevent a build-up of hydrogen and limit the rise of temperatures in containment buildings, according to a statement. The NRC’s decision adds to a 2012 order and makes fixes to the units potentially more expensive.

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“Strengthened vents will help these plants continue to protect the public and the environment even if emergency systems can’t immediately stop an accident,” NRC Chairman Allison Macfarlane said. “By safely releasing built-up pressure and hydrogen, the plants will preserve the buildings that contain radioactive material.”

The NRC is considering rules to improve U.S. safety after an earthquake and tsunami in March 2011 triggered a triple meltdown at Japan’s Fukushima Dai-ichi nuclear power plant. The U.S. reactors covered by the agency’s decision have General Electric Co.-designed containment buildings similar to the structures damaged at Fukushima.

The NRC told owners to upgrade, starting in June 2014, the “wetwell” structures that condense steam and control pressure. By June 2017, the owners must begin installing vents for the larger “drywell” surrounding a reactor, if an analysis deems the changes necessary, according to the statement.

The ruling supersedes the March 2012 order for the 31 units to have or improve their “hardened” vents that can withstand extremely high temperatures during an accident, according to the statement.

The agency in March delayed until 2017 action on a staff recommendation that the 31 reactors be equipped with radiation-scrubbing filters on the venting systems. Those changes may have cost reactor owners as much as $20 million per unit, according to industry estimates.

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