Canada’s National Calibration Reference Centre for Bioassay - Present Programs and Future Directions

In 1983, the Radiation Protection Bureau of the federal Department of Health was formally recognized by the Canadian nuclear industry regulator, the Atomic Energy Control Board (AECB) as the National Calibration Reference Centre (NCRC, the Centre) for Bioassay and In Vivo Measurements. The Centre’s mandate was to provide practical reference standards to the AECB’s licensees for measurements they use to assess doses resulting from radionuclide intakes by their workers. These standards are offered in the form of annual intercomparisons which provide the external verification required by the AECB on a regular basis. In vivo programs are administered by the In Vivo Section, while bioassay programs are administered by the Bioassay Section of the Radiation Protection Bureau. This paper will describe only the intercomparisons and related services offered by the Bioassay Section. Plans for the establishment of new programs will also be described. INTRODUCTION The AECB’s choice of the Bureau to act as the national reference centre for internal dosimetry measurements is based on recognition of its expertise in this area gained through many years of experience in bioassay, in vivo measurements and internal dosimetry. The impetus for the formation of the centre is the desire of the AECB to have a means for obtaining both external verification of licensee monitoring results and assessing the comparability of results submitted to it by its various licensees. PRESENT PROGRAMS Currently, Bioassay Intercomparisons include urinalysis programs for uranium mass measurement, tritium, carbon-14 and fission/activation products. A program where tritium and carbon-14 are simultaneously present (the Dual Spike Program) in the urine matrix is also available. All intercomparisons are offered regularly on an annual basis. PARTICIPANTS Three Canadian provinces meet part of their electrical requirements with power provided by CANDU reactors. Canada’s uranium industry produces uranium for these nuclear stations as well as for export to other nuclear power producing countries. The in-house bioassay laboratories for these facilities participate in the Centre’s programs, as do the laboratories in a tritium-producing facility and an organization that provides bioassay measurements for internal dose assessments for occupational and environmental exposures. Several radiopharmaceutical companies, one Canadian and the rest from the United States, also participate in the NCRC’s Bioassay Intercomparisons. CHARACTERISTICS OF PROGRAMS In all programs, natural human urine is used as the sample matrix. A blank is provided for each spiked urine standard. This urine blank is used by the participant for MDA determinations as well as to matrix-correct their