Document: NRC Regulatory Guide
Document ID: da2e0703-3488-44b0-b6d0-089aac7cae3d
Document Type: regulatory_guide
Title: Format and Content of Plant-Specific Pressurized Thermal Shock Safety Analysis Reports for Pressurized Water Reactors
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003740028.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.154
CFR Part: 
CFR Title: 

Content:
ing refi 11 ing of the primary system with cold safety-injection water. The effects of noncon- densible gases, if present, on system pressure and temperature calculations should be addressed. All code input and modeling assumptions should be documented and available for NRC review during the analysis review period (normally starting 3 years before the plant exceeds the screening limit and continuing until the evaluation results and any requisite actions are approved by the Commission). Simplified Analysis Methods This section should present the technical bases for any simplified analysis methods that are applied in the study. This includes the grouping of similar sequences by controlling phenomena and any extrapolations used to modify exist- ing calculations. If a simplified thermal-hydraulic plant model is used to pre- dict portions of the plant transients, all the simplifying assumptions inherent t o t h i s model should be stated and j u s t i f i e d . Reference 18 provides examples of how t o group sequences and develop a simplified thermal-hydraulic model suitable i f o r portions o f the analysis. i 4.4 Thermal S t r a t i f i c a t i o n Effects Transient thermal-hydraulic computer programs available t o analyze LWR response t o overcooling scenarios do not model f l u i d behavior with s u f f i c i e n t d e t a i l t o predict the onset o f H P I thermal f l u i d s t r a t i f i c a t i o n i n the cold leg and the subsequent cold l e g and downcomer behavior. As a result, additional analysis methods may be needed t o determine which transients are affected by thermal s t r a t i f i c a t i o n and the extent o f such effects. This section should describe and j u s t i f y the thermal f l u i d mixing analysis methods t h a t have been applied i n the study. References 19 through 24 describe the results o f recent mixing analyses and experiments. Reference 19 i d e n t i f i e s a useful s t r a t i f i c a t i o n c r i t e r i o n t o determine which