Temperature and fluence limits for a type 316 stainless-steel controlled thermonuclear reactor first wall

Results of a series of neutron irradiation experiments conducted on annealed and 20 percent cold-worked Type 316 stainless steel in a high-flux mixed-spectrum fission reactor to simulate a controlled thermonuclear reactor (CTR) first wall displacement per atom (dpa) and helium production are reviewed. Estimates of temperature and fluence limits for this alloy are made. Cold working effectively suppressed swelling up to 550 to 6000C. Using a criterion of 10 percent swelling and limited data on the fluence dependence of swelling, a first wall life of 16.5 (MW-y)/m2 (at 5300C) for 20 percent cold-worked Type 316 stainless steel is estimated. Embrittlement may be the property that limits first wall life. At 3500C acceptable ductility was retained in the cold-worked steel to very high damage levels (49 dpa, 3320 appM helium), and it appears that the 0.5 percent uniform strain criterion will not be limiting. At higher temperatures, however, this is not the situation. At 6500C the uniform and total plastic strain were zero in samples irradiated to 61 dpa and 4140 appM helium. At 5750C, 0.5 percent uniform strain was retained in the cold-worked material to relatively high damage levels; however, the fractures were intergranular. The creep-rupture life at 550 and 45,000 psi was reduced by 5 x 104 compared to the unirradiated property. Generally greater embrittlement in the solution-annealed material suggests that cold-worked material would be preferred for CTR first wall structures