The following news article originally appeared in NEI’s Nuclear Energy Overview.
The NRC’s Advisory Committee on Reactor Safeguards said last week it does not support an agency staff position that would require the 31 U.S. boiling water reactors with Mark I and II containments to install external containment vent filters. Instead, the ACRS said in a Nov. 8 letter to NRC Chairwoman Allison Macfarlane, it prefers more general “performance-based standards” that would give plant operators scope to decide on more innovative strategies to mitigate radiation releases in a severe accident.
The ACRS letter is a response to an as-yet unreleased staff paper on the subject. The draft paper recommends the installation of external filtered vents as the staff’s preferred option for minimizing the release of radiation in a severe accident where nuclear fuel has been damaged. The ACRS letter instead recommends an outcome-based approach, which it says “allows more scope for innovation and may result in more effective solutions.”
The ACRS said the staff paper recognizes that quantitative measures such as cost-benefit and risk analyses would not support installing filtered vents.
“[NRC] staff concluded that their recommended option … would not meet a quantitative cost-benefit test,” the ACRS said. “Additional measures for accident source-term [radioactivity release] mitigation in Mark I and Mark II containments are not justified by risk-informed cost-benefit analyses that rely on the generic probabilistic risk assessment models, risk metrics, estimates of averted costs, and uncertainties that were examined by the staff.”
The ACRS said the NRC staff recommended filtered vents based instead on “qualitative considerations” such as defense in depth.
The ACRS’s preference for the performance-based option, it said, would allow for the use of alternative technologies and procedures to meet objective criteria. In other words, it would not be based on applying a particular technology but on achieving a certain outcome. The ACRS said that course of action “will identify acceptable performance objectives and requirements for these [Mark I and II boiling water reactor] containments so that their severe accident management response capabilities can be evaluated. Equipment additions and procedural enhancements, including filtered ventilation systems, would be evaluated and implemented to meet these objectives.”
The five-member commission will decide the agency’s course of action after receiving the final version of the staff paper later this month.
The Advisory Committee on Reactor Safeguards is an independent forum of technical experts that advises the NRC on a range of issues.