The NRC’s Commissioners have directed the agency’s technical staff to follow a two-track approach for further improvements to systems for safely venting pressure during potential accidents at 31 U.S. reactors.
The Commission’s Staff Requirements Memorandum calls for enhancing a March 2012 Order requiring “hardened” venting systems at 31 boiling-water reactors with “Mark I” and “Mark II” containments. The memo also starts rulemaking activities to produce requirements for those reactors to cool core debris and retain radioactive material in conjunction with venting during severe accidents.
“In reaching this decision, the Commission engaged in thoughtful deliberation with each other as we each considered these important issues in our post-Fukushima accident review process,” said NRC Chairman Allison Macfarlane. “I compliment my colleagues and the staff for their sustained efforts on this issue and for taking a hard look at a complex matter.”
The Commission has given the staff 60 days to finalize the enhanced Order, which will require the vents to handle the elevated pressures, temperatures and radiation levels from a damaged reactor. The enhanced Order will also ensure plant personnel can operate the vents safely under these accident conditions.
The Commission has also given the staff a year to produce a technical evaluation to support rulemaking on filtering. During that time the staff will gather more public input as it completes its analysis. The Commission directed the staff to consider both the use of a filter to be placed on the vent, as well as a more performance-based approach using existing systems to achieve a similar reduction in radioactive release during an accident. The staff then must develop a draft rule and final rule, all by March 2017.