Document: NRC Regulatory Guide
Document ID: 7e57474b-e9b7-4add-afd3-4b3269b1a0cb
Document Type: regulatory_guide
Title: Assumptions Used for Evaluating the Potential Radiological Consequences of a Radioactive Offgas System Failure in a Boiling Water Reactor
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1605/ML16053A354.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.98
CFR Part: 
CFR Title: 

Content:
licensees to select and justify their own levels. The RG states that specific release fractions are to be provided at a later date; however, this additional information was never published. Section C to RG 1.98, Rev. 0, provides a noble gas release rate at the steam jet air ejectors of 350,000 microcuries per second (µCi/sec) (after 30 minute decay) for a period of 30 days preceding the accident, and 100,000 µCi/sec (after 30 minute decay) for times earlier than 30 days. These rates apply to a 3,500 megawatt thermal (MWt) reactor and should be scaled in a linear manner based on reactor power. However, the more current NRC Branch Technical Position (BTP) 11-5, “Postulated Radioactive Releases due to a Waste Gas System Leak or Failure,” of the NUREG-0800 (Standard Review Plan), Chapter 11.3, “Gaseous Waste Management System,” assumes a fission product release that is consistent with a noble gas release to the reactor coolant of 100 µCi/sec per MWt (after 30 minute decay). Additionally, BTP 11-5 allows licensees to apply techniques described in RG 1.112, Rev. 1, “Calculation of Releases of Radioactive - 2 - Materials in Gaseous and Liquid Effluents from Light-Water-Cooled Power Reactors,” for source term determination. Furthermore, RG 1.98, Rev. 0, states that activation gases and iodine should be neglected; however, BTP 11-5 states that the inclusion of radioiodine in the source term should be determined by the type of event and whether the failed component could lead to the release of radioiodine. The guidance applicable to atmospheric diffusion in Section C to RG 1.98, Rev. 0, refers to dated documents that may not be widely available. The source, or technical basis, for the figures at the end of the RG is not provided. In the techniques discussed in RG 1.145, Rev. 1, “Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants,” for example, the consideration of a meandering plume at, or, near ground