Radiation damage to the 316 stainless steel target container vessel at SNS

In the past, our calculations of radiation damage (concentrations of displacements, helium atoms, and hydrogen atoms) to the 316 stainless steel (316SS) container vessel at the spallation neutron source (SNS) mercury target dealt with the average damage rates in a volume at the nose of the vessel. This paper describes an attempt to improve the accuracy of estimates of the damage rates at the center of the proton beam where the damage rates are expected to be the highest. Four series of calculations (Series I–IV) were conducted to determine the damage rates within volumes (tally volumes) that varied systematically in location in the vessel. This permitted extrapolation to the rates at the tip of the vessel nose (Z=0) and at the center of the proton beam (X=Y=0). The total damage rates due to protons and neutrons were found to be: 36 dpa/yr, 1400 appmHe/yr, and 20 000 appmH/yr. In addition, insight was gained into how the damage rates vary with position in the vessel nose and at locations further downstream in the vessel.