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

Abstract

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.

Liquid scintillation counting of environmental radionuclides: a review of the impact of background reduction

“…However, as shown here by comparison to published methods in use for analysis of environmental radionuclides, the overall analysis time can still be lowered by both lowering the required sample size and reducing the steps required for processing that sample. Pacific Northwest National Laboratory is currently in the process of developing such a low background LSC system to take advantage of the recently opened shallow underground laboratory [4].…”

“…A Quantulus system at Pacific Northwest National Laboratory (PNNL) was housed underground as an early assessment of the potential for background reduction that might be afforded by the additional overburden. The resulting measurements showed there was little background improvement provided by the over-burden of the shallow underground lab [4]. This implies the background rate in this particular Quantulus system was dominated by the ubiquitous radioactivity present either in the laboratory or in the instrument construction materials.…”

“…This implies the background rate in this particular Quantulus system was dominated by the ubiquitous radioactivity present either in the laboratory or in the instrument construction materials. Large reductions in background count rates have been achieved for other radiation detection systems at PNNL through sophisticated designs of active and passive shielding, including siting of a shallow underground laboratory with 30 m water equivalent overburden, and use of high-purity materials [4][5][6][7]. We anticipate that an appropriately designed custom LSC system constructed of low background materials and placed in an underground laboratory could potentially achieve a background reduction on the order of 10-100 times the background rate seen in above ground commercially-available LSC systems.…”

Noble gas migration experiment to support the detection of underground nuclear explosions

“…For each argon measurement, 800 L of this waste gas from the SAUNA system was collected and then processed on the argon separation and purification bench previously documented [10][11][12]. After separation and purification, the argon fraction of the sample(s) was loaded into a gas proportional counter and taken to PNNL's shallow underground laboratory and counted [13].…”

The Majorana Parts Tracking Database

“…An example of the usage of the cosmic ray exposure calculator is provided by the shipment of a mandrel of electroformed copper grown in PNNL's shallow underground laboratory [15] and transported by FedEx Ground Freight to MJD's underground laboratory at SURF. On June 8, 2012 part P34F4 was picked-up in Richland, WA, USA The route taken, as reported by FedEx Tracking, included passing through Pasco, WA → Hermiston, OR → Boise, ID → Denver, CO → Rapid City, SD (all within the continental USA) before arriving in Lead, SD.…”