Temperature effects on the mechanical properties of candidate SNS target container materials after proton and neutron irradiation

Abstract

This report presents the tensile properties of EC316LN austenitic stainless steel and 9Cr-2WVTa ferritic/martensitic steel after 800 MeV proton and spallation neutron irradiation to doses in the range 0.54 to 2.53 dpa. Irradiation temperatures were in the range 30 to 100°C. Tensile testing was performed at room temperature (20°C) and 164°C to study the effects of test temperature on the tensile properties. Test materials displayed significant radiation-induced hardening and loss of ductility due to irradiation. The EC316LN stainless steel maintained notable strain-hardening capability after irradiation, while the 9Cr-2WVTa ferritic/martensitic steel posted negative strain hardening. In the EC316LN stainless steel, increasing the test temperature from 20°C to 164°C decreased the strength by 13 to 18% and the ductility by 8 to 36%. The tensile data for the EC316LN stainless steel irradiated in spallation conditions were in line with the values in a database for 316 stainless steels for doses up to 1 dpa irradiated in fission reactors at temperatures below 200 o C. However, extra strengthening induced by helium and hydrogen contents is evident in some specimens irradiated to above about 1 dpa. The effect of test temperature for the 9Cr-2WVTa ferritic/martensitic steel was less significant than for the EC316LN stainless steel.In addition, strain-hardening behaviors were analyzed for EC316LN and 316L stainless steels. The strain-hardening rate of the 316 stainless steels was largely dependent on test temperature. It was estimated that the 316 stainless steels would retain more than 1% true stains to necking at 164 o C after irradiation to 5 dpa. A calculation using reduction of area (RA) measurements and stress-strain data predicted positive strain hardening during plastic instability.

Irradiation hardening behavior of polycrystalline metals after low temperature irradiation

“…However, the generalization of this observation might require more evidence on a larger variety of material conditions. Also, it is interesting to note that the highly ductile metals deformed in a channeling mode when the strain-hardening rate was high and the strain level was well below the plastic instability strain [15,23]. Therefore, we can conclude that the occurrence of channel deformation is not always consistent with plastic instability at yield or with a change in the regime of irradiation hardening.…”

“…Also, the irradiation temperatures in the two facilities were in the ranges 60-100 and 50-160°C, respectively. The details of the irradiation conditions can be found in [14,[21][22][23]. All tensile tests were conducted at room temperature in screw-driven machines at a nominal strain rate of about 10 À3 s À1 .…”

Effects of frequency on fatigue behavior of type 316 low-carbon, nitrogen-added stainless steel in air and mercury for the spallation neutron source

“…However, most of the mechanical data for 316 LN SS have been gathered in monotonic-loading conditions, and relatively less information for fatigueloading conditions has been obtained. [5,6] Some studies have been performed on 316 LN SS by the Oak Ridge National Laboratory, on the tensile behavior of irradiated specimens [7,8] and on 316 L with regard to liquid-metal corrosion and embrittlement, when the metal is in contact with the mercury. Powel et al [9] studied the interaction of 316 L coupons with mercury in thermal convection loops.…”

In-situ Creep Testing Capability Development for Advanced Test Reactor

“…They show no significant shift of ductile to brittle transition temperature by irradiation at low temperatures (below 400°C), although they show low resistance to irradiation swelling and creep above about 400°C. 27 These steels have been not only widely used in conventional nuclear power plants, where operation temperatures are limited below 400°C, but are also selected for advanced reactor components such as the first wall and shield of ITER 28 and the container vessel for the liquid metal target of the spallation neutron source [27][28][29][30] . Table 3-5 also summarizes the fabrication processes and heat treatments applied to specimen data presented in this section.…”