Summary report on the Alloy Development Intercorrelation Program experiment

The Alloy Development Intercorrelation Program is a national intercorrelation program designed to refine charged-particle irradiation techniques employed in the simulation of neutron-induced swelling of metals. Using a simple well characterized Fe-15Cr-25Ni alloy with a low level of impurities, comparative irradiations were performed using 1.0 MeV electrons, 0.75 MeV protons and nickel ions at three incident energies, 2.8, 3.5 and 5.0 MeV. Fast reactor neutron irradiation is also proceeding on this material. The observed differences in swelling behavior are not closely related to the identity or energy of the bombarding species, although light charged particles are considerably more effective in the creation of voidage per displaced atom. The incubation period preceding the onset of steady-state swelling was found to be quite sensitive to experimental variables related to the softness of the metal and the proximity and method of preparation of the specimen surface. The presence or absence of displacement cascades had no measurable influence on the nucleation of voids. There appears to be an intrinsic swelling rate for this alloy which is dependent only on temperature and displacement flux, and which is independent of the duration of the incubation period. The displacement dose and dose rates calculated by standard procedures cannot be used to correlate the magnitude of the swelling caused by various charged particles. An effective dose concept is defined, with experimental measurements providing good estimates of dose equivalences for electrons, nickel ions and eventually for neutrons. The displacement effectiveness for proton irradiations is larger than anticipated, with the experiment yielding only an approximate dose equivalency factor