Brian D. Glasgow

A shallow underground laboratory for low-background radiation measurements and materials development.

Pacific Northwest National Laboratory recently commissioned a new shallow underground laboratory, located at a depth of approximately 30 meters-water-equivalent. This new addition to the small class of radiation measurement laboratories located at modest underground depths houses the latest generation of custom-made, high-efficiency, low-background gamma-ray spectrometers and gas proportional counters. This paper describes the unique capabilities present in the shallow underground laboratory; these include large-scale ultra-pure materials production and a suite of radiation detection systems. Reported data characterize the degree of background reduction achieved through a combination of underground location, graded shielding, and rejection of cosmic-ray events. We conclude by presenting measurement targets and future opportunities.

Assay methods for 238U, 232Th, and 210Pb in lead and calibration of 210Bi bremsstrahlung emission from lead

Methods for measuring 238U, 232Th, and 210Pb in refined lead are presented. The 238U and 232Th concentrations are determined using isotope dilution inductively coupled plasma mass spectrometry after anion exchange column separation of dissolved lead samples. The 210Pb concentration is inferred through α-spectroscopy of a daughter isotope, 210Po, after precipitation separation of dissolved lead samples. Subsequent to the 210Po α-spectroscopy measurement, a method for evaluating 210Pb concentrations was developed via measurement of bremsstrahlung radiation from β-decay of a daughter isotope, 210Bi, using a 14-crystal array of high purity germanium detectors. Ten sources of refined lead were assayed and results are presented.

Empirical correction of crosstalk in a low-background germanium γ–γ analysis system

The Pacific Northwest National Laboratory (PNNL) is currently developing a custom software suite capable of automating many of the tasks required to accurately analyze coincident signals within gamma spectrometer arrays. During the course of this work, significant crosstalk was identified in the energy determination for spectra collected with a new low-background intrinsic germanium (HPGe) array at PNNL. The HPGe array is designed for high detection efficiency, ultra-low-background performance, and sensitive γ–γ coincidence detection. The first half of the array, a single cryostat containing seven HPGe crystals, was recently installed into a new shallow underground laboratory facility. This update will present a brief review of the germanium array, describe the observed crosstalk, and present a straight-forward empirical correction that significantly reduces the impact of this crosstalk on the spectroscopic performance of the system.

MARS June 2012 Flight Data: Natural Background and Point Source Spectra

Abstract This brief document describes the electronic data that were collected by the Multi-sensor Aerial Radiation Survey (MARS) detector in June 2012 while mounted onboard the RSL Bell-412 helicopter. A copy of the data is included as an electronic appendix.