United States Nuclear Regulatory Commission - Protecting People and the Environment

Resolution of Generic Safety Issues: Item C-5: Decay Heat Update (Rev. 1) ( NUREG-0933, Main Report with Supplements 1–34 )


Historical Background

As identified in NUREG-0471,3 this issue involved following the work of research groups in determining best estimate decay heat data and associated uncertainties for use in LOCA calculations.

Safety Significance

No significant change in public risk is attributed to this issue.


In accordance with a DSI memorandum,907 the staff has determined that the 1979 ANSI/ANS Standard 5.1920 is technically acceptable and has allowed the use of this data to justify relaxation of non-required conservatisms in current ECCS evaluation models.908 In addition, the proposed ECCS rule change being developed by the staff will allow the use of this new data. Thus, this issue is a resolved Regulatory Impact issue.

Page Last Reviewed/Updated Thursday, March 29, 2012