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:
the material presented i n t h i s chapter f i t s i n t o the overall PTS study. Provide a general description o f the process used t o i d e n t i f y PTS sequences. It should be made clear how the approach used w i l l r e s u l t i n com- pleteness o f i d e n t i f i c a t i o n o f a l l classes o f events t h a t could contribute sig- n i f i c a n t l y t o PTS risk, how specific events are selected f o r more detailed anal- y s i s t o represent each class, and f i n a l l y how the events so analysed are used t o determine t o t a l PTS r i s k a t the plant. 3.2 Sequence Del i neati on Identi f y potential overcool i ng transients i n a we1 1 -def i ned manner, and document them i n such a way t h a t it i s clear t o a reviewer t h a t a l l important potential overcool ing conditions have been considered. Classes o f i n i t i a t o r s 1 should be developed, important variations o f i n i t i a t o r s within each class should be identified, and potential transients resulting from these i n i t i a t o r s should be defined. Operating experience a t the specific plant and a t similar plants should be carefully examined t o a i d i n the i d e n t i f i c a t i o n o f potentially significant PTS i n i t i a t o r s , contributing f a i 1 ures, and potential corrective actions. The ORNL contribution t o Systematic Eva1 uation Program reviews (Ref. 5, f o r example) i s a technique that can be used f o r t h i s purpose. 3.2.1 Development o f Classes o f I n i t i a t o r s Any class o f transients t h a t could lead t o overcool ing o f the reactor ves- sel should be considered i n the analysis. It should, however, be appropriate t o use logical arguments t o eliminate classes o f transients as actual PTS i n i t i a t o r s whenever justifiable. . Examples o f i n i t i a t o r s that should be included are: O Loss-of-coolant accidents ( LOCAs) , i ncl udi ng steam generator tube rupture accidents. * Steam 1 i ne breaks. O Overfeeds. O Combinations of