Radiochemical Analysis at Hanford, the Past 30 years

Matt Lardy

STL-Richland

Richland, Washington

Over the past 30 years or more, interesting and challenging changes have occurred in the handling, processing and analysis of environmental and bioassay samples for radionuclides. In some ways the nature of the radiochemical laboratory has changed little and in other ways there has been significant change. In the early 1960’s, at Richland the short-lived radionuclides Si-31, Mn-56, Zn-69m, Ga-72 and As-76 once included with the analytical protocol for Hanford water samples are no longer required because their sources, the single pass reactors at Hanford, have long since been closed. Later, in the 1970s, soil sample analyses for Sr-90, U-234, U-235 and U-238, Pu-238, Pu-239/240 and Am-241 were added. The addition of soil analyses necessitated development and testing of a soil preparation procedure using large (50-100 gram) sample sizes. New analytical techniques such as extraction chromatographic resins have been developed that provide improved selectivity, produce less waste and have faster separation times. One example is use of the extraction disk for Tc-99 analysis. Previously the classical ion exchange procedure required two or more days to complete the chemical separation, but with the extraction disk the separation can be performed in one day. Change is evident in other areas of the analytical process; because of its greater resolution capability and increased size, the germanium detector has replaced sodium iodide as the preferred detector for gamma spectroscopy. Autoradiography was used for plutonium analysis and was capable of achieving a Minimum Detectable Activity of approximately 0.05 dpm. However it was not possible to resolve the energies of the various plutonium isotopes. Consequently it was also impossible to use a tracer to measure chemical recovery. Alpha spectroscopy, using the silicon diode, resolved that problem.

Government regulations and national consensus standards have also caused significant changes in radiochemical analytical laboratories. Government regulations began with the initiation of certification of laboratories analyzing drinking water under the Safe Drinking Water Act and the publication of the U. S. Nuclear Regulatory Guide 4.15, Quality Assurance for Radiological Monitoring Programs. The two most recent government directives are NELAC and Integrated Contractor Procurement Team (ICPT) programs initiated by the Environmental Protection Agency and the Department of Energy respectively. In addition, required national consensus standards are HPS N13.30, Performance Criteria for Radiobioassay and ANSI N 42.23, American National Standard Measurement and Associated Instrumentation Quality Assurance for Radioassay Laboratories.

Added to the complexity are market forces that influence a commercial laboratory. These forces include items such as competition, pricing, and laboratory mergers and acquisitions. The Laboratory in Richland where I am currently employed has undergone a fourth ownership change, while the number of laboratories performing radiochemical analyses in the United States continues to decrease.

All in all, the effect of change has contributed to progress: the analytical laboratory provides a better product and improved service.

This presentation will more fully describe the items discussed above as I remember them, include more examples, compare past changes to the current practice and thoughts about the future. The remarks are based on my experience in a commercial radiochemical analysis laboratory. However, other laboratories have experienced similar significant changes.

The assistance of Mike Buvinghausen, ThermoRetec, for providing technical and supporting information, is acknowledged.