Staff of the US Nuclear Regulatory Commission will recommend thatcommissioners impose a requirement that 31 nuclear reactors similar in designto those that experienced core melting at Japan's Fukushima-1 be retrofittedwith containment vent filters that could cost $16 million each to install,officials said Thursday.
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NRC staff is preparing a paper for the five-member commission by the endof November, John Monninger, associate director of the agency's Japan lessonslearned directorate, said during a public meeting at agency headquarters inRockville, Maryland. There is no timetable for the commission to take actionon the measure.
Commissioners told the staff to include the issue of filtered vents inthe agency's immediate response to the Fukushima accident, instead of waitingto decide that issue until later.
Agency staff believe the filters provide a "substantial safetyenhancement" that provides additional defenses for the containment structuresin some General Electric-designed boiling water reactors. Those GE Mark I andMark II containment designs, because they have generally smaller containmentvolumes than other GE-designed units and than pressurized water reactors, aremore vulnerable to excessive pressure during a severe accident, Monningersaid.
The containment structure for a nuclear unit encloses the reactor and keysafety systems, and is sealed from the exterior environment. The containmentstructure is the third of the three main barriers to the release ofradioactive fission products.
Containments at Fukushima were subjected to pressure beyond their designlimit and there were delays in venting them, in part because of concern aboutexposure to the public in the vicinity of the plant, Japanese officials havesaid.
The nuclear industry opposes the requirement, which it believes couldcost even more than NRC estimates, Steven Kraft, the Nuclear EnergyInstitute's senior director of Fukushima response coordination, said at themeeting.
"There's this aura built up around external filters that isunwarranted," Krafts said.
The industry has proposed that NRC set heightened requirements foradditional protection from the release of radioactive materials in anaccident, and allow individual plants to determine whether the filters oranother strategy is the best approach.
However, representatives of environmental groups welcomed the agencystaff recommendation.
Requiring filtered containment vents for the reactors in question is "ano-brainer," said Mary Lambert, head of the group Pilgrim Watch inMassachusetts. Entergy's 728-MW Pilgrim reactor in Plymouth, Massachusetts, isone of the 31 units that would be covered by the proposed order.
Filtered vents would make it easier for reactor operators to make thedecision to vent the containment structures at the right time, Lambert said.Without them, operators would be "hesitant" because they know the ventingwould likely release radioactive materials into the community where they andtheir families live, she said.
Krafts said strict operating procedures and frequent training would meannuclear plant operators would vent when appropriate.
Requiring the vents would put the US in line with most other countriesoperating boiling water reactors, said Jim Riccio, a nuclear policy analystwith Greenpeace in Washington. Currently, US citizens have less protectionthan those in Europe, where filtered vents are common, he said.
--William Freebairn, firstname.lastname@example.org
--Edited by Lisa Miller, email@example.com