Effects of Neutron Irradiations at Temperatures Below 500°C on the Properties of Cold Worked 316 Stainless Steels: A Review

Abstract

Many components used in the pressure vessel of French pressurized water reactors are made of austenitic stainless steels : 316L for screws, 304L for core barrel and baffle assembly, etc. Among these components, the most irradiated ones undergo an average damage rate of about 1 dpa/an at temperatures which may reach about 400°C. Such irradiations may have very detrimental effects on the in-service behaviour of austenitic steels. In order to forecast these effects, Electricité de France has defined important programmes of studies. In the framework of these programmes, we have carried out a review concerning the effects of irradiations at relatively low temperatures (i. e. 500°C) on cold-worked 316 stainless steel. We were particularly interested in the evolution of microstructure as well as tensile (with or without notch), creep, fatigue (with or without creep) and fracture toughness properties. In some cases, we have also analysed the influence of cold-work level, irradiation temperature and test temperature. For some mechanical properties, the data was sufficient to qualitatively predict the properties of cold worked 316 stainless steels after long — term irradiations under PWR conditions.

Radiation-Induced Segregation and Void Swelling in 304 Stainless Steel

“…The peak displaceme~t rate for the materials in the SURV subassemblies was approximately 6.5x1 0-8dpa/s. This displacement rate is about two orders of magnitude lower than used in a typical accelerated reactor materials test but within the range of displacement rates experienced by commercial light-water reactor (LWR) core components [4].…”

“…Performance of 304 stainless steel under long-time, low dose rate irradiation is important to extended life operation. The dose rates for typical pressurized water reactor (PWR) components rtige horn about 1.4x10-7 dpa/s for components in the inner core region to 1.4x10-10dptis for the core barrel (these displacement rates are calculated using fast neutron fluences from [2] converted to dpa using 0.7x1021n/cm2=l dpa [3]), with thicker components reaching temperatures up to 400"C [4].…”

Overview of ageing and degradation issues in light water reactors (LWRs)

“…They undergo irradiation-induced creep and stress relaxation. 102 In some PWRs the core baffl e consists of sheets and formers. The sheets are separated by small gaps (0.2-0.4 mm).…”

Methodology for Pressurized Thermal Shock Analysis in Nuclear Power Plant

“…[9] are highly irradiated; the most irradiated areas of some of these components may be exposed to doses reaching around 80 dpa after 40 years of operation. This neutron irradiation changes their microstructure and their mechanical properties, so they harden, lose ductility and toughness, suffer irradiation creep [9][10] [11] [12]. In addition, these changes seem to be the basis of increased sensitivity to stress corrosion [13].…”