J. Erchinger, “Development of an Ultra-Low Background Liquid Scintillation Counter for Trace Level Analysis”, INMM 56th Annual Meeting, Indian Wells, California, 12-16 July 2015.
Low-level liquid scintillation counting (LSC) has been established as one of the radiation detection techniques useful in elucidating environmental processes and environmental monitoring around nuclear facilities. The Ultra-Low Background Liquid Scintillation Counter (ULBLSC) under construction in the Shallow Underground Laboratory at Pacific Northwest National Laboratory aims to further reduce the MDAs and required sample processing as an ultra-trace level detection system. Through layers of passive shielding in conjunction with an active veto and 30 meters water equivalent overburden, the background reduction is expected to be 10 to 100 times below current low background liquid scintillation systems. Simulations have shown an expected background of around 14 counts per day. A novel approach to the light guide will use a coated hollow light guide cut into the inner copper shielding. Demonstration LSC measurements will show lowenergy detection, spectral deconvolution, and alpha/beta discrimination capabilities, from trials with standards of tritium, strontium-90, and actinium-227, respectively. An overview of the system design and expected demonstration measurements will emphasize the potential applications of the ULB-LSC in environmental monitoring for treaty verification, reach-back sample analysis, and facility inspections.