The Proficiency Testing for The Calibration of Radiation Measurement Instrument with Photon Radiation

Radiation monitoring and inspecting instruments are important tools for the measurement of radiation dose rate or radioactivity. Now in Taiwan, there are five laboratories (processors) capable of providing calibrations for radiation monitoring and inspecting instruments. All these five laboratories have been accredited by the Chinese National Laboratory Accreditation (CNLA). In the past, there were five accreditation categories in the ionization radiation (IR) field and the calibration of radiation monitoring and inspecting instruments (IB) was one of them. According to the requirements of CNLA to the ionization radiation accreditation field, a laboratory should pass the proficiency testing before being accreditated by the CNLA. Thus, the National Radiation Standard Laboratory (NRSL) of the Institute of Nuclear Energy Research held the 1 proficiency testing for radiation monitoring and inspecting instruments in 1999[1]. Five laboratories participated in that activity and all the five successfully passed the proficiency testing program. 1. Preface Since the effective time of the laboratory accreditation certificate was three years, the NRSL organized the 2 proficiency testing in November 2002. The proficiency testing in 2002 was different from that in 1999 by moving the accreditation field from Testing (IR) to Calibration (KK), and the category from IB to KK10; using ordinary survey meters as the transfer item among the laboratories. In this proficiency testing, the radionuclide Cs was used. The testing method went mainly as passing four survey meters of different types in turns to the tested laboratories. The tested laboratories, after having calibrated the survey meters, provided the calibration results including calibration factors and expanded uncertainties (k=2). The NRSL calculated the En values of itself and the tested laboratories according to the ISO/IEC Guide 43-1[2] recommendations. The results showed that all the En values were less than 1. This meant that all the tested laboratories passed the 2 proficiency testing. Before the first radiation survey meters proficiency testing, NRSL did not find any criteria and plans of this kind which could be referred to. Thus, NRSL discussed with each calibration laboratory on plans and test methods of the proficiency testing and decided that NRSL would send personnel to each calibration laboratory to measure the dose rate of its standard radiation field. The measured values by NRSL would be compared with those measured by the laboratory itself. The calibration competence of the laboratory would be assessed according to the En value which was suggested in ISO/IEC Guide 43-1[2]. 2. Test method NRSL tested several radiation survey meters for their stability and selected four photon radiation survey meters which performed best in stability and covered the calibration capabilities of existing calibration laboratories. Theses four were to be used as transfer items and to be calibrated by the tested laboratories. To meet the actual calibration demands, NRSL provided four kinds of radiation dose detectors (including high dose rate detectors, medium dose rate detectors, low dose rate detectors and electronic personnel dosimeters) as transfer items: (1) The specifications of the transfer radiation survey meters were as Table I. (2) According to the performance criteria of ANSI N42.17A (1989)[3] for easy-held instruments of radiation protection level, the differences for stability and accuracy were 10 % and ± 15 %. The performance criteria of ANSI N42.20 (1995)[4] for active personal radiation monitor, the differences for stability and accuracy were required within ± 5 % and ±15 %.