nuclear-news

The filtered vents would be required on two of the oldest reactor designs sold by General Electric. The idea is that their containments could be opened early in an accident to vent a puff of slightly radioactive gas and explosive hydrogen and thus prevent a buildup in pressure or explosions as an accident unfolds. The reactors did not have such vents originally, but most of the oldest models, equipped with Mark I containments, added vents in the early 1990’s.

After the Fukushima accident of March 2011, the commission ordered that vents be added to Mark II reactors as well but told its staff to quickly study whether filtered ones were necessary.

The United States has 23 Mark I reactors, all of which now have vents, and eight Mark II reactors, none of which have vents. None have filtered vents…..

Jim Riccio of Greenpeace told the advisory committee, “This is the only country except for perhaps Slovenia that is not moving to put these filters in place.’’

In fact, an N.R.C. document he cited shows that Mexico and India are also in that nonadopter category. Others are installing them.

Another opponent, Mary Lampert of Pilgrim Watch in Massachusetts, addressed the group by speakerphone. “We have seen three core melt accidents in real time,’’ she said, referring to Fukushima, Chernobyl and Three Mile Island. Speaking of the staff’s use of probabilistic risk assessment, she said, “It’s time to learn from real experience, not P.R.A. theoretical games.’’

A filtered vent is a “no-brainer,” she said.

The staff is somewhat less emphatic; it will present the commission with a range of options, including a performance-based approach that could leave some plants installing filters and others demonstrating that the water provides adequate filtration. http://green.blogs.nytimes.com/2012/11/02/a-hard-look-at-u-s-reactor-hardware-after-fukushima/