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Quality assurance for 14C and 3H measurements by GPC and LSC counting meethods in the Zagreb Laboratory

Laboratory for Measurements of Low-level Radioactivity of the Rudjer Bošković Institute in Zagreb, Croatia, has been measuring 14C since 1968 and 3H since 1976 by applying gas (CH4) proportional counting (GPC) technique. By purchasing a Quantulus 1220 ultra low-level liquid scintillation counter (LSC) in 2002 two methods of chemical preparation of 14C samples have been implemented: a CO2 absorption method and a benzene synthesis method [1]. The procedures for LSC measurement of both isotopes have been established. A "good laboratory practice" was introduced since the beginning of the measurements in the Laboratory. The Laboratory Manual issued in 1994 covered most technical procedures required by the QC/QA system and management, including calibration of measurements, traceability, trackability and statistical evaluation of results. Laboratory participated in 4 radiocarbon and five tritium interlaboratory comparisons [2, 3]. A great progress in implementation of quality system was achieved during the participation in the IAEA project RER/2/004 "Quality Control and Quality Assurance of Nuclear Analytical Techniques" (1999-2001) [4]. The new Quality Assurance Manual includes the following documents conformed with ISO 17025 requirements: 6 administrative documents, 3 technical documents, 5 administrative procedures, 14 technical procedures, 3 documents of method validations, description of 3 programs and databases, 12 forms, 14 log books, 2 action plans, 3 lists of equipment and expenditures, and documentation on Laboratory personnel [5]. Laboratory took part in three IAEA audits and two proficiency tests, and a constant progress was established [4]. During the participation in the IAEA project a specific problem was the non-existence of implementation of quality system at the Institute level. Last year a new quality manager of the Institute was designated and the first version of the new Institute Quality Manual in accordance with ISO 17025 requirements was issued. Harmonization of the Laboratory quality assurance system with that of the Institute is in course. Although the accreditation of the laboratory is still not required by our authorities, preparation of documentation necessary for this step is in progress.

quality control; quality assurance; methods; GPC; LSC

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