Failure analysis of a radio-activated accelerator component
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A double-walled, hemispherical metal beam exit window made of alloy 718, used at the Los Alamos Neutron Science Center (LANSCE), developed a crack during service, leading to leakage of coolant. The window had been exposed to radiation damage from 800 MeV protons and a cyclic stress from 600 MPa tensile to near zero induced by numerous temperature cycles calculated to be from 400 to 30 °C. The window was activated to > 200 Sv/h. It was determined, through analysis using remote handling techniques and hot cells, that the crack initiated near a spot weld used to affix thermocouples to the window surface. In addition to analysis of the crack, some of the irradiated material from the window was used to measure mechanical properties. Hot cell techniques for preparation of samples and testing have been developed at both Forschungszentrum Juelich (FZJ) and Los Alamos National Laboratory (LANL). Important and useful data on radiation effects can be obtained from components used in service because they have experienced true operating conditions of radiation, strain, and temperature.
Keywordsaccelerator mechanical tests neutrons protons radiation damage
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