Comparison of compression properties and swelling of beryllium irradiated at various temperatures

Abstract

A beryllium cylinder irradiated *<n Experimental Breeder Reactor (EBR-II) for four years at 700 to 760 K to a neutron fluence of 8.13 x i0" n/cm 2 (total) or 1 x 10 z<! n/cn> 2 (E > 1 MeV) was cut into samples and tested. Yield strength and plastic strain was determined in compression tests at 300, 723, 823 K and after annealing at 1173 K for one hour. The Immersion density and helium content were measured on samples. An equation for swelling was derived from the data by regression analysis. The microstructure showed agglomeration of helium in voids or bubble:, at the grain boundaries.

Impact of HFIR LEU Conversion on Beryllium Reflector Degradation Factors

“…For a comparison with more recent results, the total amount of gas from each isotope produced in the beryllium reflector was calculated after 21 cycles of irradiation and it was found that the amounts of 3 T, 3 He, and 4 He are, respectively, 9.57, 0.00621, and 94.0 g. These results, especially for the…”

“…However, monitoring 3 He, as well as 6 Li, is important because these isotopes are strong thermal neutron absorbers and could potentially lead to degradation of the beryllium properties as a neutron reflector.…”

“…This means that the conditions for higher gas production are created in regions where the fastneutron flux is higher, such as in the removable reflector. Low-energy neutronic channels exist for gas production also, such as the 3 T/ 3 He production and the α production that originate from 6 Li. However, unless this 6 Li isotope already exists (such as an impurity), it must be produced via the…”

“…Earlier studies, both experimental and theoretical, that were performed in support of fusion programs [3,4] showed that the swelling is a function of the neutron fluence in the material. Accumulation of microvoids and bubbles in beryllium can lead to cracking with the release of tritium, a radioactive gas with a half-life of just over 12 years.…”

“…The procedure used the ORIGEN module of the SCALE package [8] to estimate the total amount of 3 He and 6 Li produced in the reactor as a function of time.…”