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:
evaluation should be performed using a human reliability methodology. The acceptability of this methodology for the purpose should be justified by the licensee (Refs. 9 through 13). 3.5 Event Tree Col lapse Collapse the event trees using a frequency screening criterion to form a l i s t of specific sequences and a set of residual groups to be analyzed. T h i s i s important since the event trees may generate thousands of end states that cannot be individual ly analyzed. A screening value of 1.0E-7/reactor year i s recommended. This value should ensure that important sequences are treated individually, and i t should also help to keep the size of the residual small. This i s particularly important since i t may be necessary t o t r e a t the residual using a bounding consequence condition. 3.5.1 Specific Sequences Those sequences that survive the frequency screening should be defined and their frequency noted. I t i s recommended that some identification be assigned t o each sequence t o enhance i t s traceability through the remainder of the anal- ysis. Grouping and identifying each sequence w i t h respect to initiator type may also prove helpful. 3.5.2 Residual Groups Those sequences that do not survive the frequency screening must also be considered. They should be grouped together based on transient characteristics to form a s e t of residual groups. The residual groups should be reviewed to identify sequences that should be grouped with previously defined sequences because of transient similarity or should be specifically evaluated because of their severe consequence. I t i s important to attempt to reduce the size of each residual group since i t will be necessary to assign a bounding consequence that would apply within each group. Each residual group should be defined and i t s frequency noted. 4. THERMAL-HYDRAULIC ANALYSIS \[ This chapter is to present the reactor coolant pressures, temperatures, and heat transfer coefficients at the vessel's interior