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:
ptures. 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 (e.g., reactor coolant pump restart crite- ria), a method of estimating the three-dimensional effects in the downcomer may be necessary for some of the asymmetric cooldown scenarios encountered in the PTS study. Sensitivity of calculated results to the nodalization schemes used should be discussed. The thermal-hydraulic models should be coupled, where appropriate, with neutronic models that have the capability to analyze pressure surges resulting from any relevant sequences involving recriticality. This section of the report must also present the results of benchmarking the computer models against suitable plant data or data from experimental facilities or incorporate this information by reference to an NRC-approved topical report. As a minimum, the plant data comparison should fully exercise the modeling features that are employed in the thermal-hydraulic computer pro- grams such as the pressurizer (including heaters and sprays), feedwater heaters and liquid level controls, the steam generator liquid level controls, and the turbine bypass (i . e. , steam dump) controls under steady-state and transient con- ditions. If overcooling transients have occurred at the plant or at a similar plant, they should be benchmarked against the computer models. The licensee is encouraged to use codes and methods accepted by the NRC at the time the calcula- tion is performed. The models should be capable of accurately predicting condensation at all steam-water interfaces in the primary system, especially in the pressurizer during the repressurization phase of an overcool ing event or during 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