Good Practice Handbook for PTS Evaluation (Result of the IAEA Co-Ordinated Project on PTS)

Integrity and lifetime of reactor pressure vessels are practically determined by their behavior during “pressurized thermal shock” (PTS) emergency regimes as the most severe regimes during reactor operation. Assessment of these potential regimes is carried out mostly in deterministic way but used procedures are different in different countries. Proper and reliable evaluation of these PTS regimes depends on many parameters and approaches used during computations. During the period 2005 – 2008, the Coordinated Research Project 9 (CRP 9) “Review and Benchmark of Calculation Methods for Structural Integrity Assessment of RPVs During PTS” was organised by the IAEA. The overall objective of this Coordinated Research Project was to perform benchmark deterministic calculations of a typical pressurised thermal shock (PTS) regime and finally to recommend the best practice for PTS assessment. This paper describes main results and collected experience within this project that were bases for the preparation of the “Good Practice Handbook for Deterministic Evaluation of the Integrity of a Reactor Pressure Vessel during a Pressurised Thermal Shock” that will be issued as an IAEA TECDOC. Main parameters discussed in this handbook are: - selection of overcooling sequences; - thermal-hydraulics analyses; - temperature and stress field calculations; - crack tip loading incl.K estimations; - integrity assessment; - analyses of nozzles; - national practices; - results from sensitivity studies. Finally, recommendations for reliable and correct PTS evaluation are given.