Speaker
Description
Tungsten is chosen as the target material of European Spallation Source (ESS) where it will be irradiated by a high energy (2 GeV) and high power (5 MW) pulsed proton beam to produce neutrons to be used by neutron scattering intruments. For designing a target with a high availability, it is important to determine the development of the temperature and secondary thermal stresses in tungsten during the operation. As irradiation alters material properties, knowledge on the impact of irradiation on thermal diffusivity is crucial to the ESS target design. Using Laser Flash Analysis (LFA) technique, thermal diffusivity of three highly irradiated samples with three different displacement damage doses 9.5, 25.1 and 26.5 dpa were examined. Due to the high radioactivity of the specimens, no surface polishing or blackening could be applied on the samples prior to measurements. Therefore, an attempt was made to study the effect of measured surface roughness on LFA data, and the obtained results for irradiated samples were calibrated accordingly. The data shows a drastic reduction of the thermal diffusivity for all three samples by up to 50%. The thermal diffusivites of the three specimens are overlapping within measurement error uncertainty ranges, independently of the damage dose. Further, the recovery of the thermal diffusivity of irradiated tungsten was also observed after annealing, however this effect was less prounanced compared to the low-dose specimens.
| Themes for the contribution | 3 Post-irradiation examination: |
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