United States Nuclear Regulatory Commission - Protecting People and the Environment

W17  Gas Accumulation and Management: Remaining Issues and their Resolution

A 2013 RIC session addressed progress in resolving the potential loss of systems that are important to safety due to gas accumulation.  More recently, the NRC endorsed NEI 09-10, Revision 1a-A, in a safety evaluation that was the subject of Regulatory Issue Summary 2013-09.  Other accomplishments included publication of Technical Specifications Task Force (TSTF)-523 and meetings with NEI, owners’ groups, and licensee representatives to discuss evolving issues.  This session will focus on issues identified since the 2013 RIC session, their resolution, and the planned resolution of the remaining issues.  The session will address such design-basis and operational-compliance issues as (1) use of correlations to determine usable volume during tank draindown and (2) pump inlet void criteria.  NRC speakers will provide a review and inspection perspective, and industry speakers will discuss plant implications.  Key aspects of achieving closure include (1) licensee modifications, (2) in-depth inspections, and (3) the planned publication of a NUREG that covers (a) the current design basis, (b) determination of operability, (c) origin of gas concerns, (d) gas acceptance criteria, (e) gas movement, and (f) vortexing and critical water level in sumps, tanks, and pipes.  This will be followed by a regulatory guide.




  • Jennifer Whitman, Reactor Systems Engineer, Division of Safety Systems, NRR/NRC tel: 301-415-3253, e-mail: Jennifer.Whitman@nrc.gov
Page Last Reviewed/Updated Friday, June 05, 2015