IMPROVED TECHNIQUE OF A COMPLEX ANALYSIS OF CRACK RESISTANCE OF WWER-1000 NUCLEAR REACTOR COLD LEG NOZZLE UNDER TERMAL SHOCK. REPORT 2. BRITTLE STRENGTH

Abstract

This article is devoted to problems of cold nozzle brittle strength evaluation. Brittle strength calculations are considered as a second stage of methodology proposed by authors in report 1.The methodology aims to replace the RELAP 5 thermo-hydraulic calculations with finite elements modelling.

Report 2 defines main steps that should be fulfilled to assess initial crack propagation resistance of the reactor shell material in the area of cold nozzle inlet with help of finite elements modelling. It also provides a validation procedure of presented methodology. The validation procedure consists of following problems: derivation of initial stress field from the area of interest without consideration of initial crack, altering the stress field by implementing the influence of initial crack (influence functions method) and deriving the  values from altered stress field. Then  values derived using finite elements procedure and validation procedure are to be compared. Good agreement between both results means good accuracy of finite elements procedure.

Finite elements calculations were performed in ANSYS 14.5 software with help of a new package that allows stress intensity factors evaluation. ANSYS and analytical procedures have shown excellent agreement.