High Temperature Detector for Material Accounting in Advanced Reactors

High-temperature-capable detectors are essential for nuclear material accounting in advanced fuel cycles like Molten Salt Reactors (MSRs). Dual-mode scintillators, capable of detecting gamma-rays and neutrons simultaneously, are highly advantageous for such environments. They enhance measurement accuracy and efficiency. $\mathrm{Cs}_{2} \mathrm{LiLa}(\mathrm{Br}, \mathrm{Cl})_{6}$ (CLLBC) is a notable dual-mode scintillator, renowned for its excellent gamma detection and ability to discriminate gamma-rays from neutrons. It’s readily available commercially from RMD. At room temperature, CLLBC shows a $3.0 \%$ energy resolution at 662 keV and a light yield of approximately $45,000 \mathrm{ph} / \mathrm{MeV}$. Its gamma-neutron pulse shape discrimination figure of merit stands at about 3.5 at room temperature. A high temperature (HT) detector was designed and manufactured using the CLLBC scintillator and a high temperature PMT (R1288AH-27) from Hamamatsu. The detector was characterized from $25^{\circ} \mathrm{C}$ to $175^{\circ} \mathrm{C}$ with various gamma sources and digital pulse processing MCA. The 662 keV energy resolution was measured to be $5 \%$ at RT and $7.8 \%$ at $175^{\circ} \mathrm{C}$. We were able to resolve gamma energies from 60 keV to 1.5 MeV when a combination of multiple sources was used. In this presentation we will discuss the data and the significance of radioisotope identification and quantification for NMA applications at high temperatures and count rates.