Calorimetric measurements of nuclear heating in small probes of plasma-facing materials

Total nuclear heating rates have been measured in simulated D-T fusion neutron environment under a USDOE-JAERI collaborative program. An automated, microcalorimetric technique was developed for on-line measurements of total nuclear heating in a mixed neutron plus photon field. Irradiated probe materials included graphite, titanium, stainless steel 304, molybdenum, and tungsten, among others. Analysis of the measurements has revealed large deviations between calculations and experiments. An approach based on sensitivity theory is sketched for estimating uncertainty on total nuclear heating. Also, we observe that calculation-to-experiment (CE) ratio data for all libraries and materials can be consolidated to obtain a probability density distribution of CE ratios that roughly resembles a gaussian distribution centred at 1.04.