The diffusivity of hydrogen is an important property of light water nuclear reactor (LWR) fuel cladding. LWR cladding absorbs hydrogen during normal operation, a contributing factor to embrittlement that decreases the lifetime of the fuel. Mass transport of hydrogen is dictated by an Arrhenius behavior typical of solid state diffusion and the associated activation energy is therefore a property relevant to LWR fuel performance. We have used incoherent quasi-elastic neutron scattering (QENS) to directly measure the diffusivity of hydrogen in recrystallized Zircaloy 2 with a hydrogen concentration of . We rely upon the low-Q expansion for long-range diffusion to determine diffusivity as a function of temperature between 572 and 780 K. We find the diffusivity is given by exp (-0.461 eV/kT) [cm/s] below 670 K and by exp (-0.36 eV/kT) [cm/s] above 670 K. Our activation energy below 670 K agrees with the value typically used to assess hydrogen diffusivity in LWR cladding [Kearns, Journal of Nuclear Materials 43 (1972) 330], but is approximately 20% lower above 670 K. The two different activation barriers are attributed to impurity trapping of hydrogen solutes at lower temperature that ceases to influence diffusivity at higher temperature. The application of the Oriani model for diffusion with impurity trapping to our system demonstrates the plausibility of this hypothesis. We believe this mechanism may be responsible for historical discrepancies of measured hydrogen diffusivity in Zr-based alloys. The elastic intensity versus temperature in fixed window scans exhibit inflection points that are in good agreement with the published terminal solid solution solubility limits for hydrogen in Zircaloy 2.

Thin nanocrystalline ZrC and ZrN films (<400 nm), grown on (100) Si substrates at a substrate temperature of 500 °C by the pulsed laser deposition (PLD) technique, were irradiated by 800 keV Ar ion irradiation with fluences from 1 × 10 at/cm up to 2 × 10 at/cm. Optical reflectance data, acquired from as-deposited and irradiated films, in the range of 500 - 50000 cm (0.06 - 6 eV), was used to assess the effect of irradiation on the optical and electronic properties. Both in ZrC and ZrN films we observed that irradiation affects the optical properties of the films mostly at low frequencies, which is dominated by the free carriers response. In both materials, we found a significant reduction in the free carriers scattering rate, i.e. possible increase in mobility, at higher irradiation flux. This is consistent with our previous findings that irradiation affects the crystallite size and the micro-strain, but it does not induce major structural changes.

In this work a fully kinetic model of the JET SOL with tungsten divertor plates has been developed. It includes the dynamics of main-ions (D) and electrons, the neutrals (D, C, W) and the impurity particles (C, W). Our simulations show extremely low concentration of W impurity. We identify two reasons which are responsible for this effect: (1) for low temperature divertor plasma the energy of most of the main-ions and the impurities in a low-ionization state impinging the divertor plates is below the W-sputtering threshold energy; (2) with increasing temperature the W-sputtering increases, but the potential drop across the divertor plasma increases too, so that most of the W ions are reabsorbed at the divertors.

We present results of massively parallel kinetic simulations of the triple Langmuir probes at JET. These results indicate that the probes under certain conditions, e.g. during ELMs, can significantly under/over estimate the electron temperature.

Understanding the chemical durability of neutron shielding materials is necessary when assessing their long-term service potential. In this study, the chemical durability of a Li enriched neutron shielding glass that has been exposed to natural, near-operational conditions is assessed by Prompt Gamma Activation Analysis (PGAA) and Neutron Depth Profiling (NDP). These non-destructive, nuclear analysis techniques are sensitive to Li, and PGAA is uniquely able to detect H in low quantities in solids. It was determined that the enriched alumino-silicate glass can alter within 2 months of exposure to the natural environment. This exposure resulted in an average surface alteration layer thickness of ≈22 μm. The alteration layer contained ≈47% less Li than the bulk glass. Alternatively, a 3 years exposed sample of the glass had a surface alteration depth of ≈30 μm and Li depletion levels in the alteration layer were between 47% and 75% less Li than the bulk glass. When the alteration layer on the 3 years sample was removed, the H content of the glass's surface was nearly eliminated. This sample also showed variable Li concentrations throughout the alteration volume, which contrasts with near static Li concentration in the alteration volume of the 2 months sample. From these findings it was determined that the depletion in Li at the surface of the glass will not affect the glass's neutron shielding properties, but it may change the mechanical stability of the glass's surface and, due to increased H content in the alteration layer, make it an inappropriate material for the lining of certain neutron analysis instruments.