The following story originally appeared in NEI’s Nuclear Energy Overview.
The industry has urged the Nuclear Regulatory Commission to separate the issue of reliable hardened vents—required for some reactors under a post-Fukushima order issued in March—from the question of whether such vents should be filtered.
Since vent filters are only one of several options for reducing or preventing a release of radioactive materials during an accident, the NRC should consider all the alternatives in a more holistic context, the industry said in a letter to the agency.
The industry believes the commission’s intent in combining the issues was, at least in part, to preclude rework on hardened vents in the event the NRC later decides to require filters, Anthony Pietrangelo, NEI’s senior vice president and chief nuclear officer, said in the May 15 letter. While the commission’s action was well-intended, he said, the industry is concerned that linking the two issues places vent filters in the wrong context.
NEI’s letter notes that while “a reliable hardened containment vent is intended to provide a heat removal path and protection from containment overpressure … [a] vent filter is intended to reduce the impact of potential [radiation] releases during a core damage event.”
“Preliminary analysis shows that there are various means that can effectively mitigate potential releases,” Pietrangelo said, including containment sprays, flooding, venting, alternate containment heat removal and enhanced operator actions. He added that these actions are at the heart of the industry’s severe accident management guidelines.
“The most appropriate question is not whether a vent filter system should be installed,” Pietrangelo said, “but rather what the most effective means are to reduce or preclude potential releases during a severe accident.”
Pietrangelo said the best way to protect people and the environment near nuclear energy facilities is to prevent fuel damage through multiple layers of safety. “To begin the examination of enhanced mitigation strategies with a recommendation and decision on vent filters ignores these principles [of defense in depth] and the tenets of risk-informed regulation.”
The decision should be based on NRC analyses that evaluate the alternatives and take into account the safety enhancements the industry is making in response to other post-Fukushima orders, he said. “Only based on such evaluations can the NRC, the industry and other stakeholders be assured that the optimal approach for enhancing environmental protection is being implemented.”