NEGLIGIBLE CREEP OF P91 STEEL

To avoid inclusion of the possible creep effects during normal service operation in future nuclear plants in the component design, it is important to define temperature, stress and time limits for negligible creep for P91 steel. If these limits can be reliably defined, the component design in the vicinity of these temperatures becomes clearer and the design below limits considerably easier. In the nuclear design rules there are generally accepted negligible creep limits for the austenitic steel 316L(N) but not for P91. The definitions for reference stress used in the codes for 316L(N) steel cannot be applied for P91 steel due to significantly different yield and tensile behaviour of this material. The definition on the negligible creep term itself is under debate. In this paper a series of low temperature creep tests and optimized creep strain models are presented for predicting very low strains at temperatures in the vicinity of the negligible creep limit temperatures (below 400°C). It is shown that limiting the allowed creep strain below 0.2% is counterproductive if there is no clear reason for not allowing negligible deformation from primary creep. This paper strives to pin-point a sensible definition of negligible creep for P91 steel and to give the modelling tools to extrapolate creep strains within a reasonable range of temperatures.

HOLMSTROM Bjorn;  LUZGINOVA Natalia; 

2014-12-17

CSM, Italy

JRC89589

978-88-7484-380-0,   

http://eccc.c-s-m.it/,    https://publications.jrc.ec.europa.eu/repository/handle/JRC89589,