Development of a European Procedure for Assessment of High Cycle Thermal Fatigue in Light Water Reactors: Final Report of the NESC-Thermal Fatigue Project

In nuclear plant piping systems thermal fatigue damage can arise at locations where there is turbulent mixing of different temperature flows. The severity of this phenomenon can be difficult to assess via plant instrumentation due to the high frequencies involved. In Europe the existing approaches to high cycle thermal fatigue have been successful in providing margins against pipe ruptures. Nonetheless there have been instances of thermal fatigue damage and over the last 10 years several recent R&D programmes have been devoted to developing better understanding of the induced thermal loads and associated damage mechanisms. To exploit this work, in 2003 the Network for Evaluation of Structural Components (NESC) set up a project involving both utilities and R&D organizations. Its aim was to produce a consensus methodology for assessing high cycle thermal fatigue in piping components, with special attention to turbulent mixing phenomena at mixing tees in light water reactor systems. It has involved the collaboration of over 10 organisations from 5 European countries. All have participated on an 100% in-kind basis. Wherever possible, advantage has been taken of recent R&D work at national, European and international levels. The work programme focused on two main aspects: a) creating a database of service and mock-up data for better understanding thermal fatigue damage mechanisms and for validating the procedure. b) developing a European multi-level thermal fatigue damage procedure, which should reflect the multi-disciplinarity of the phenomenon (thermo hydraulic, material, strain evaluation through FEA, damage analysis, fracture mechanic, ISI performance).

NILSSON Karl-Fredrik;  TAYLOR Nigel;  DAHLBERG M.;  FAIDY C.;  WILKE U;  CHAPULIOT S;  KALKHOF D;  BRETHERTON I;  CHURCH M;  SOLIN J;  CATALANO J; 

2007-06-11

European Commission

JRC37258

EUR 22763 EN,