J.L. Erchinger, C.E. Aalseth, B.E. Bernacki, M. Douglas, E.S. Fuller, M.E. Keillor, S.M. Morley, C.A. Mullen, J.L. Orrell, M.E. Panisko, G.A. Warren, R.O. Williams, M.E. Wright, “Development of a low background liquid scintillation counter for a shallow underground laboratory”, Applied Radiation and Isotopes, 105 (2015).
Pacific Northwest National Laboratory has recently opened a shallow underground laboratory intended for measurement of low-concentration levels of radioactive isotopes in samples collected from the environment. The development of a low-background liquid scintillation counter is currently underway to further augment the measurement capabilities within this underground laboratory. Liquid scintillation counting is especially useful for measuring charged particle (e.g. β and α) emitting isotopes with no (or very weak) gamma-ray yields. The combination of high-efficiency detection of charged particle emission in a liquid scintillation cocktail coupled with the low-background environment of an appropriately designed shield located in a clean underground laboratory provides the opportunity for increased-sensitivity measurements of a range of isotopes. To take advantage of the 35m-water-equivalent overburden of the underground laboratory, a series of simulations have evaluated the scintillation counter’s shield design requirements to assess the possible background rate achievable. This report presents the design and background evaluation for a shallow underground, low background liquid scintillation counter design for sample measurements.