Radiation Damage Studies of USn

ABSTRACTUranium stannide, the most stable intermetallic compound in the Uranium/Sn system, has the Cu3Au(LI2 ) structure, and is paramagnetic to liquid He temperature. The magnetic susceptibility data are consistent with 5f band states rather than a localized electronic structure. Samples of this compound have been prepared both with depleted and 235U enriched, as well as 119Sn enriched starting material. Detailed 119mSn Mössbauer effect studies have been carried out over the temperature range 78≤T≤300 K on 60Co gamma ray irradiated, thermal neutron irradiated (depleted), and thermal neutron irradiated (enriched) samples, using the V 10 position of the Brookhaven HFR facility for the neutron irradiations (thermal/fast >3.6×102). The Mössbauer hyperfine parameters are: IS(78) = 2.45 mm/sec, Q.S.(78) 1.38 mm/sec for the unirradiated samples, consistent with the metallic nature of Sn in the USn3 structure. No anomalous charge states have been identified in the Mössbauer spectra of the gamma or neutron irradiated samples. The free-atom lattice temperature is ∼250 K for the unirradiated sample, and shows only minor changes with 60Co–γ radiation to a total dose of 1000 Megarad. Thermal neutron radiation (nvt ∼5×1016 ) of the depleted sample results in a lowering of the lattice temperature to ∼240 K. Two hours heating at 800°C are sufficient to anneal the radiation damage as judged by lattice dynamical data. A sample enriched to 99.94% 235U and irradiated to a fluence of ∼5×1015 slow neutrons/cm2 showed an increase in the freeatom lattice temperature to ∼275 K. A two hour anneal at 800°C restored this parameter to its original value. Resistivity data for these samples and their relationship to spin fluctuation temperatures will also be discussed.