Differential scanning calorimetry of heavy ion bombarded synthetic monazite

Abstract

Specimens of synthetic monazite, CeP04, were rendered metamict by bombardment with 3 MeV Argon ions at fluences of 4 ions nm-z or greater. Differential scanning calorimetry (DSC) was applied to the annealing of these specimens over a temperature range 550-720 K. The stored energy is shown to be 7.3h0.3 cal g-I, independent of the fluence from 4 to 10 ion nm-2. The activation energy of annealing of the damage is 2.7A0.3 eV and the temperature dependent rate constant isThe application of DSC to the study of annealing of radiation damage in materials is discussed briefly. The saturation value of the stored energy with fluence of 3 MeV Argon ions is compared to the approach to a saturation level observed in some glasses used to store radioactive wastes.

Radiation effects in crystalline ceramics for the immobilization of high-level nuclear waste and plutonium

“…The cumulative a-decay dose in ceramics for 239 Pu immobilization reaches a temporary plateau after 100,000 years, but increases over much longer time periods due to the 235 U decay series, as shown in Fig. 2 for several 239 Pu concentrations in a ceramic host phase.…”

“…1 is the cumulative a-decay dose for a ceramic containing 10 wt. % 239 Pu, which reaches significantly larger values relative to DOE tank wastes or non-USA commercial HLW. The cumulative a-decay dose in ceramics for 239 Pu immobilization reaches a temporary plateau after 100,000 years, but increases over much longer time periods due to the 235 U decay series, as shown in Fig.…”

“…The a-particles emitted by actinide decay in HLW ceramics have energies of 4.5 to 5.8 MeV, and the recoil nuclei (a-recoils) have energies of 70 to 100 keV. In the case of Pu ceramics, a 5.2 MeV aparticle and an 86 keV 235 U recoil are released by the decay of the 239 Pu (a-particles and a-recoils of similar energies are released during the decay of the 235 U series).…”

“…In an a-decay event, the a-particle and a-recoil particle are released in opposite directions and produce distinct damage regions separated by several microns. Based on full cascade Monte Carlo calculations using TRIM-96 (assuming a threshold displacement energy of 25 eV), the average number of atomic displacements generated in a ceramic, such as zircon, by the 5.2 MeV a-particle and the 86 keV 235 U recoil released in the decay of 239 Pu are 220 and 1180, respectively. The average number of displacements generated per a-decay event by the decay of the actinides in HLW ceramics is expected to be similar and is estimated to be 1400 displacements per a-decay event.…”

Crystalline Ceramics: Waste Forms for the Disposal of Weapons Plutonium

“…The apparent stability of natural monazite is attributed to this relatively low temperature of recovery of the radiation damage. Differential scanning calorimetry @SC) measurements of natural [57] and synthetic [57,58] monazites irradiated with 3 MeV Ar+ ions have been performed.…”