Document: NRC Regulatory Guide
Document ID: 4d46a966-d280-43da-9b03-8b0abe7b29ce
Document Type: regulatory_guide
Title: Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2120/ML21204A065.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.183
CFR Part: 
CFR Title: 

Content:
nt is assumed to correspond to the following two cases in the standard technical specifications for the nuclear steam supply system vendor: D-2.1 The concentration that is the maximum value (typically 4.0 microcuries per gram (μCi/g) dose equivalent (DE) iodine (I)-131 (DE I-131)) permitted and corresponds to the conditions of an assumed pre-accident spike, and D-2.2 The concentration that is the maximum equilibrium value (typically 0.2 μCi/g DE I-131) permitted for continued full-power operation. D-3. The activity released from the fuel should be assumed to mix instantaneously and homogeneously in the reactor coolant. The release from the breached fuel is based on Regulatory Position 3.2 of this guide and the estimate of the number of fuel rods breached. Noble gases should be assumed to enter the steam phase instantaneously. Transport D-4. Assumptions acceptable to the NRC staff related to the transport, reduction, and release of radioactive material to the environment are as follows: D-4.1 The main steamline isolation valves should be assumed to close in the maximum time allowed by technical specifications. D-4.2 The total mass of coolant released should be assumed to be that amount in the steamline and connecting lines at the time of the break plus the amount that passes through the valves before closure. 1 “Minimal fuel breach” is defined for use in this appendix as an amount of damage that will yield reactor coolant system activity concentration levels less than the maximum technical specification limits. The activity assumed in the analysis should be based on the activity associated with the projected fuel damage or the maximum technical specification values, whichever maximizes the radiological consequences. In determining DE I-131, only the radioiodine associated with normal operations or iodine spikes should be included. Activity from projected fuel damage should not be included. DG-1389, Appendix D, Page D-2 D-4.3 All radioactivity in the released