Evaluation of in-pile and out-of-pile stress relaxation in 316L stainless steel under uniaxial loading

Stress relaxation of tensile type specimens under fast neutron irradiation at 288 degreesC has been studied for 316L stainless steel (SS) in the Japan Materials Testing Reactor. In-pile stress-relaxation tests were carried out at fast neutron fluence levels of 1.3 x 10(24), 5.5 x 10(24) and 1.5 x 10(25) n/m(2) (E > 1 MeV). These tests were carried out at the applied total strain levels of 0.06%, 0.1%, 0.3% and 0.75%. In order to evaluate the thermal stress-relaxation behavior and to distinguish it from the irradiation induced stress-relaxation behavior, out-of-pile stress-relaxation tests were also performed at 288 degreesC in air using an electric furnace. This paper describes results of in-pile and out-of-pile stress-relaxation tests on 316L SS tensile specimens. These results are compared with the literature data by Foster et al. [J. Nucl. Mater. 252 (1998) 89] which were mainly obtained from bend beam specimens. Moreover, these experimental results are compared with analytical results obtained using Nagakawa's model [J. Nucl. Mater. 212-215 (1994) 541]. (C) 2002 Elsevier Science B.V. All rights reserved.