Monitoring of gross alpha, gross beta and actinides activities in exhaust air released from the waste isolation pilot plant

Abstract

The simultaneous measurements of gross alpha and beta activities is one of the simplest radioanalytical technique used as a method for screening samples of both high and low activities of alpha and beta emitting radionuclides in environmental and bioassay samples. Such measurements are of great interest from both a radiological, waste disposal viewpoint, and to establish a trend of radioactivity based on long term monitoring. At the WIPP (Waste Isolation Pilot Plant) site, unfiltered exhaust air from the underground repository is the most important effluent. As part of its monitoring program, the particulates from WIPP exhaust air are collected everyday at a location typically called the Fixed Air Sampler (FAS) site or Station A, this site is located at the release point for aerosol effluents from the underground to the environment. The measurements of gross alpha and beta activity on air filter samples were performed using an ultra low level counter, PIC-MPC 9604-α/β, from Protean Instrument Corporation. The high sensitivity of the gross alpha and beta instrument enables detection of low value activity from the air filters. In 2009, the values of gross alpha and beta activity concentrations ranged from <MDC (≈0.1 mBq/m(3)) to 1.03 mBq/m(3) and <MDC (≈0.2 mBq/m(3)) to 15.8 mBq/m(3); the density varied from <MDC (≈0.9 Bq/g) to 63.5 Bq/g and <MDC (≈1.7 Bq/g) to 114 Bq/g.