Radiation flux and damage at accelerator-driven spallation neutron sources

Radiation damage (displacement, helium, and hydrogen production) at proton-driven spallation neutron sources is analyzed and compared for SNS SB (316SS at the nose of the Hg-container vessel), SNS PEW (Al6061 at a hypothetical proton entrance window), and SINQ EW (Al–3 wt% Mg entrance window at Target 5). Spallation neutrons at the three components exhibit differential fluxes, ϕ′, that increase monotonically with decreasing energy E. For SINQ EW, ϕ’ is roughly proportional to 1/E, which is attributed to the moderating effect of the D2O coolant and moderator tank. For 316SS at SNS SB, the calculated total displacement production rate due to protons and neutrons is 34 dpa/yr at full power, with about 37% due to protons. For the Al at SNS PEW and SINQ EW, however, the total rate is 4–5 dpa/yr, with about 90% due to protons. He and H production in all three components is dominated by the incident protons. For He, comparison of experimental and calculated production cross sections for protons on 316SS and Al indicates the need to employ the non-default Jülich ILVDEN option in running LAHET. The resulting total production rates for SNS SB, SNS PEW, and SINQ EW are about 3000, 2400, and 1900 appmHe/yr, respectively. These rates are 1.5–2 times the rates previously calculated using the default GCCI ILVDEN option. The high mobility of H atoms promotes H escape from thin targets of 316SS and Al. For 0.1 cm-thick samples, we tallied the H where it comes to rest using IOPT 14, and obtained production rates at SNS SB, SNS PEW, and SINQ EW of 11500, 4300, and 3500 appmH/yr, respectively.