The preparation and utilization of performance evaluation soils for evaluating radioassay laboratories engaged in site remediation work

Abstract

Site remediation projects dealing with uranium, thorium or radium require the services of a radioassay laboratory during the site characterization, remediation and final site survey/verification phases. In the U.S., regulatory agencies and industry guidelines recommend that the remediation contractor conduct an external laboratory QC program to ensure the quality of the analytical results. The commercial availability of certified natural soil matrices is extremely limited not only by nuclide and nuclide concentration but also by soil type. In most cases, the applicability of these materials for an external QC program is questionable since the chemical constituents of the certified soil may not be representative of the remediation soil type. Also, such materials are typically only suitable as single blind performance evaluation (PE) samples. The Yankee Atomic Environmental Laboratory (YAEL) has characterized soil materials from several uranium mining and milling sites for use in two laboratory PE programs. The site specific PE materials were prepared in accordance with their intended use and quality performance requirements. One PE material was dried, pulverized to a particle size of approximately 10 microns and homogeneously blended. The second PE material (total of 1,024 kg) was methodically field blended and aliquoted to produce 1,000 separate homogeneous 1 kg samples. Both PE materials were characterized for radionuclide concentration and heterogeneity or sample distribution. A summary of the characterization studies of the different PE materials as well as the quality performance criteria developed for evaluating the laboratory's performance and the advantages and disadvantages of using each PE material will be discussed and summarized.