Non-standard, multiple-notch tension specimens made from both annealed and 70 per cent cold-drawn type 347 stainless steel were irradiated for various times in the Experimental Breeder Reactor at the National Reactor Testing Station in Idaho. The tests were originally started for the purpose of monitoring the effects of high-energy neutrons on reactor structural components made from type 347 steel. During irradiation the specimens were in contact with a liquid alloy of sodium and potassium at temperatures between 228 and 316 C. Rockwell A hardnesses and ultimate tensile strengths were determined and compared with similar data from unirradiated specimens.
Hardness and tensile strength of the annealed specimens continued to increase up to the maximum integrated flux, 4.3 × 1020 nvt. A linear relationship is shown to exist between the measured property and the log of the integrated flux. Evidence for an incipient annealing process is discussed, in which the activation energy for thermal healing is shown to be related to integrated flux. The maximum increase in tensile strength was 36 per cent on a base value of 129,700 psi for the unirradiated specimens. The maximum hardness increase was 14 Rockwell A divisions on a base value of 48.
The results of the tests on irradiated specimens made from cold-drawn stock were somewhat erratic. However, the tensile strength initially increased at a higher rate than for the annealed specimens, but indications are that saturation of property changes has occurred at 1.2 × 1020 nvt.