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:
expected to be the bounding cases (i. e. , the most severe), calculations for an entire class of overcooling scenarios may be deemed unnecessary if the bounding case is not of PTS concern. Similarly, careful selection -of the first set of scenarios to be evaluated can permit simple extrapolation or interpolation of the results to other scenarios that share common controlling thermal-hydraulic phenomena. During the analysis, the sequence identification analyst and the thermal - hydraulic analyst should coordinate activities to ensure that pertinent details of the delineated sequences are thoroughly understood. Similarly, close coor- dination must be maintained between the thermal-hydraulic analyst and the frac- ture mechanics analyst so that the transient fluid conditions are calculated at the appropriate vessel locations. 4.2 Thermal-Hydraulic Models Thjs section and supporting appendices should present a detailed descrip- tion of the thermal-hydraulic computer models used in this analysis. The models should include an accurate representation of the pertinent parts of the primary and secondary systems. This includes the condensate system, the main and auxil- iary feedwater systems, and parts of the steam system. The model should include appropriate secondary-side metal heat capacity. Particular attention should be given to the modeling of control system logic and characteristics such as valve closure times and liquid level measurements. References 14 through 17 illustrate some of the modeling details included in such a study. The thermal-hydraulic models should be capable of predicting single and two-phase flow behavior and critical flow as required. The models should be capable of predicting plant behavior for LOCAs, steamline breaks, and steam generator tube ruptures. In general, a one-dimensional code is suitable for most overcooling transient calculations. However, if any of the control systems are dependent solely on the fluid conditions in a single loop