Nuclear Regulatory Commission Grants Oyster Creek Request For 'Relaxation' Of Vents In Plant's Drywell

The federal Nuclear Regulatory Commission has granted the owner of the Oyster Creek Nuclear Plant in Lacey permission for "relaxation" of its order that of the aging plant's hardened vents be upgraded since the plant will cease operation at the end of 2019.

The hardened vents cope with the aftermath of a severe nuclear accident by relieving pressure and combustible gases inside the plant's reactor containment building, said NRC spokesman Neil R. Sheehan.

The NRC ordered that all nuclear plant owners with Mark 1 and 2 boiling water reactors upgrade the vents in both the wetwell and the drywell in the nuclear reactor building back in March 2011, after the Fukushima disaster.

More specifically, these plants were ordered to have reliable hardened vents from both the wetwell (the torus, or donut-shaped reservoir of cooling water at the base of the reactor building) and the drywell (the enclosure around the reactor).

Oyster Creek was required to be in compliance with the wetwell requirement (Phase 1 of the order) by the fall 2016 and the drywell requirement (Phase 2) by the fall of 2018.

Exelon asked the NRC back in 2011 to relax the upgrade vent order, Sheehan said.

"This extension request was based on the limited remaining operational time for the plant; existing plant safety features; existing containment vent enhancements to address venting under severe accident conditions; and FLEX equipment and strategies put in place at the plant under a separate NRC post-Fukushima requirement.

The NRC approved the Oyster Creek Phase 1 relaxation request on Nov. 16, 2015, after carefully reviewing the information provided by Exelon. The Phase 2 request was also recently approved, he said.

“The NRC staff evaluated Exelon’s proposed venting strategy and associated water management guidance and concluded that the guidance and containment venting strategy, including preservation of the containment wetwell vent path, will make it unlikely that Oyster Creek would need to vent from the containment drywell during severe accident conditions, or during an extended loss of alternating current power event.”

Oyster Creek is the oldest nuclear plant in the United States. It went online on Dec. 23, 1969.

Image: Patricia A. Miller