[en] The activities which deal with the utilization of ionizing radiation in the fields of medicine, industrial and agricultural in this country are expanding from time to time. Therefore, it requires a reliable radiation protection service for radiation workers, and a facility for the calibration and checking of the radiation measuring instruments. Recognising the importance of radiation protection services for ensuring the safety of radiation workers, a national Secondary Standard Dosimetry Laboratory which is recognised by the Government and the IAEA/WHO was established at the Nuclear Energy Unit. A number of facilities which include irradiation rooms, calibration benches and various radiation sources as X-ray, gamma ray, beta and neutron were provided to facilitate radiation metrology activities in this country. Beside providing calibration services which cover the environmental up to therapy level and area/personnel monitoring, the laboratory also can provide irradiation as well as dosimetry services to the appropriate users throughout the country. (author)

[en] The uncertainty of dose measurements is obtained based on a number of factors that are inevitable. Therefore, the uncertainty must be determined carefully to ensure the reliability of dose measurements within a certain confidence level. The uncertainty of a secondary instrument NPL 2560 for X-ray dose measurements at this Secondary Standards Dosimetry Laboratory was 22%. This is the best uncertainty value that can be offered by this laboratory for calibration of radiation detecting instruments in Malaysia. (author)

[en] Beta radiations from the nuclides of Sr-90/Y-90 are calibrated at specified distances, with and without beam flattening filters. The extrapolation ionization chamber is used to determine the absorbed dose from the beta sources. The standard readings obtained from the measurements are then compared with the standard values given by the Physikalisch Technische Bundesanstalt (M), the national standard laboratory of Germany. Results showed that the discrepancy of measurements performed at the Secondary Standard Dosimetry Laboratory (SSDL) is less than 2%. The standard absorbed doses are used to calibrate radiation survey meters and personal dosimeters such as film and TLD badges used in the country. (Author)

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[en] J.L. Shepherd Cobalt-60 irradiator is the gamma source facilities to calibrate the dosimeter Ceric-cerous which the effective dose ranging from 5-50 kGy for industrial radiation processing usage. The ferrous sulphate dosimeter or known as Fricke dosimeter was used to determined the dose rate distribution in the gamma chamber, J.L. Shepherd which dimension are 15 cm diameter and 20 cm height. Polystyrene material was used to placed the Fricke dosimeter in the gamma chamber. Dose distribution in the gamma chamber was done at three different height i.e. 7 cm, 10 cm and 14 cm. The result shows that the dose rate decreased about 3% and 1% at the height of 14 cm and 7 cm respectively. The lead which various shielding thickness i.e. 10.98 mm, 18.62 mm and 19.43 were used to determined dose rate distribution in the gamma chamber. (Author)

[en] The personal and area dose monitoring is one of the mandatory requirements enshrined in the Atomic Energy Licensing Act 1984 (Act 304). Personal dose monitoring is essential to ensure that each radiation workers comply with the annual radiation dose limits set of 20 mSv per year while the area dose monitoring is necessary to enable the implementation of appropriate controls on the identified controlled areas. Secondary Standard Dosimetry Laboratory (SSDL), provides two types of dosimeters namely film badge and thermoluminescent dosimeter (TLD) for the purpose of these monitoring. The film badges and TLDs that supplied by SSDL must be returned for dose evaluation at the latest within two months from the date of supply. This paper aims to examine the extent to which users comply the returning period of the film and TLD dosimeters for dose evaluation in SSDL. Statistics of data obtained from the e-SSDL system indicated that the average of film badges returned within two month after supply in 2011 and 2012 is 42 % and 46 % respectively. The overall average return of film badges supplied in 2011 and 2012 is 94 % and 91 % respectively. Statistics of TLD in 2012 (February to December) indicated that the average of TLDs returned within two months after supply is 54 % while the overall average return of TLDs supplied in 2012 is 78 %. (author)

[en] Dose intercomparison on an international basis has become an important component of quality assurance measurement i.e. to check the performance of absorbed dose measurements in radiation therapy. The absorbed dose to water measurements for radiation therapy at the SSDL, MINT have been regularly compared through international intercomparison programmes organised by the IAEA Dosimetry Laboratory, Seibersdorf, Austria such as IAEA/WHO TLD postal dose quality audits and the Intercomparison of therapy level ionisation chamber calibration factors in terms of air kerma and absorbed dose to water calibration factors. The results of these intercomparison in terms of percentage deviations for Cobalt 60 gamma radiation and megavoltage x-ray from medical linear accelerators participated by the SSDL-MINT during the year 1985-2001 are within the acceptance limit. (Author)

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[en] Although radiation causes an alarming effect to living organism, it has been accepted for diagnostic and therapy in medicine as well as quality control and test method in industry. Due to the benefit gained, public at large is willing to accept the risk on condition that proper protection and safety standard is implemented and practised. Instrument plays a very important role not only in generation radiation but also measuring it. Therefore to ensure safety it is fair to say that all instrument must be calibrated to a certain standard and maintained to operate to its design specifications from time to time. (author)