Document: NUREG-0800
Document ID: 49aefb86-1adb-4b3c-826f-480e32947595
Document Type: srp
Title: Radiological Consequence Analyses Using Alternative Source Terms
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0037/ML003734190.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.0.1
CFR Part: 
CFR Title: 

Content:
AST, that is, the composition and magnitude of the radioactive material, its chemical and physical form, and the timing of its release. A full implementation replaces the previous accident source term used in all design basis radiological analyses and incorporates the total effective dose equivalent (TEDE) dose criteria. Once a full implementation is approved, all subsequent new or updated analyses would be based on the approved AST and TEDE criteria. • A selective implementation is a modification of the plant design basis that (1) is based on one or more of the characteristics of an AST and/or (2) reevaluates a limited subset of the design basis radiological analyses. An example of an application of selective implementation is one in which a licensee desires to use the release timing insights of an AST to increase the required closure time for a containment isolation valve by a small amount. The licensee would only need to evaluate the impacts of the delay in valve closure. Radiological consequence analyses might not be necessary. The staff’s approval for an AST (and the TEDE criterion, if applicable) would be limited to the particular selective implementation proposed by the licensee. The licensee would be able to make subsequent modifications based on the selected characteristics incorporated into the design basis by the approved initial implementation under the provisions of 10 CFR 50.59. However, use of other characteristics of an AST or use of TEDE criteria which are not part of the approved design basis, and changes to previously approved AST characteristics, requires prior staff approval under 10 CFR 50.67. As an example, a licensee with a timing-only implementation involving relaxed closure time on isolation valves could not use 10 CFR 50.59 as a mechanism to implement a modification involving a reanalysis of the radiological consequences of a DBA LOCA. However, this licensee could extend use of the timing characteristic to adjust the closure time on