Elpasolite scintillators show great promise for dual mode neutron-gamma radiation detection and imaging but the impact of high dose radiation on performance characteristics has not been evaluated. Crystalline (Cs,Tl)2LiLaBr6:Ce (CTLLB) materials are grown. After growth the 1-inch diameter crystals are processed and packaged. Prior to the irradiation sequence at SRNL, the detector performance of the encapsulated crystal is measured with gamma-ray check sources including 137Cs and 152Eu. Properties such as energy resolution, light yield, proportionality behavior, and decay times are measured. The packaged crystal is irradiated four times at dose rates of 1, 10, 100 and 1,000 Gy of absorbed dose in a 60Co irradiation and the performance of the crystal is evaluated before and after each radiation treatment. Cumulative dose rates between irradiation were 1, 11, 111 and 1,111 Gy. Initial results show a decreased measured light yield after each radiation exposure, however further analysis on the packaging materials will be pursued.
Structural health monitoring (SHM) is in urgent need and must be integrated into the nuclear-spent fuel storage systems to guarantee the safe operation. The dry cask storage system (DCSS) is such storage facility, which is licensed for temporary storage for nuclear-spent fuel at the independent spent fuel storage installations (ISFSIs) for certain predetermined period of time. Gamma radiation is one of the major radiation sources near DCSS. Therefore, a detailed experimental investigation was completed on the gamma radiation endurance of piezoelectric wafer active sensors (PWAS) transducers for SHM applications to the DCSS system. The irradiation test was done in a Co-60 gamma irradiator. Lead Zirconate Titanate (PZT) and Gallium Orthophosphate (GaPO4) PWAS transducers were exposed to 40.7 kGy gamma radiation. Total radiation dose was achieved in two different radiation dose rates: (a) slower radiation rate at 0.1 kGy/hr for 20 hours (b) accelerated radiation rate at 1.233 kGy/hr for 32 hours. The total cumulative radiation dose of 40.7 kGy is equivalent to 45 years of operation in DCSS system. Electro-mechanical impedance and admittance (EMIA) signatures and electrical capacitance were measured to evaluate the PWAS performance after each gamma radiation exposure. The change in resonance frequency of PZT-PWAS transducer for both in-plane and thickness mode was observed. The GaPO4-PWAS EMIA spectra do not show a significant shift in resonance frequency after gamma irradiation exposure. Radiation endurance of new high-temperature HPZ-HiT PWAS transducer was also evaluated. The HPZ-HiT transducers were exposed to gamma radiation at 1.233 kGy/hr for 160 hours with 80 hours interval. Therefore, the total accumulated gamma radiation dose is 184 kGy. No significant change in impedance spectra was observed due to gamma radiation exposure.
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