Robust Kr-85 Detectors for New Waste Cask Design

Dry cask storage systems (DCSS) are used to store spent nuclear fuel from nuclear power plants. Without a long term storage solution in place, storage for decades in casks may be required. High burnup fuel rods may become brittle over time presenting problems for eventual transport of the spent fuel from reactor sites to a central storage facility. It is desired to passively determine the structural integrity of spent fuel assemblies by monitoring conditions inside the casks including temperatures, pressures, corrosion products and radioactive decay elements. RMD will investigate diamond detectors for monitoring radiation inside storage casks. In particular we will determine the feasibility of detecting beta particles from 85Kr in the presence of background gamma rays. Diamond is a wide band gap semiconductor that can operate at elevated temperatures and under high radiation conditions. Diamond also has high mobility of both electrons and holes enabling high count rate detection. The Phase I work plan is to fabricate diamond detectors from state-of-the-art diamond substrates, characterize electronic properties of the detectors, demonstrate beta particle detection in the presence of a gamma-ray background and employ coincidence methods to maximize signal-to-noise ratio. Measurements will be conducted as a function of temperature and gamma-ray flux. Commercial Applications and Other Benefits: In addition to monitoring status of nuclear waste inside storage casks, non-destructive evaluation, particle physics and homeland security are also possible areas that would benefit from a rad hard beta particle detector that can operate at elevated temperatures. Bore hole logging is another application suited to diamond detectors. Due to its high density of nuclei, diamond is promising for fast neutron detection. Because the effective atomic number of tissue is approximately 6, diamond is well suited for tissue equivalent dosimeter applications.