The Influence of Heterogeneity in Gamma Spectroscopy Analysis of Soil Contaminated with Weapons Grade Plutonium at the BOMARC Missile Accident Site, McGuire AFB, NJ
Abstract
The BOMARC Missile Site contains weapons grade plutonium (WGP) as the result of a nuclear weapon accident that occurred in 1960. Numerous environmental investigations have been performed on the site during the 40 years post accident. Many of the investigations have been focused on the location of the residual WGP and activity concentrations. WGP in the environment is notorious for its heterogeneous distribution in soils. Past characterization efforts have noted this characteristic for the WGP at the BOMARC site and the difficulties it presented in accurate description of site conditions. Direct measurement of WGP in soils can be accomplished through gamma- and alpha-spectroscopy. Due to the low-energy and low-frequency of the photons emitted from Pu-239/240, gamma spectroscopy is difficult and error prone. Direct measurement by the expensive and time-consuming process of dissolution, chemical extraction, and alpha-spectroscopy analysis is also error prone for heterogeneously distributed plutonium. A less costly and considerably more timely laboratory analysis consists of evaluation of the 60 KeV gamma-ray emitted by Am-241, a decay product of WGP. This process relies on a known relationship between the Am-241 and the Pu-239/240. This report describes the errors inherent in this method for WGP from the BOMARC site and the reduction of errors from a conjugate counting methodology. The findings demonstrated that many of the soils were laden with heterogeneity that affected measurement accuracy. A sizeable fraction, however, had little observable heterogeneity. In addition, vertical distributions and correlation coefficients to a portable in-situ gamma-radiation measurement device are provided.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2001
- Accession Number
- ADA397752
Entities
People
- Steven E. Rademacher