Medical Physics International

INTERCOMPARISON IN 2016 FOR PERSONAL DOSE EQUIVALENT HP(10) AND HP(0.07) ON PHOTON AND BETA FIELDS IN SOUTHEAST AND SOUTH ASIA REGION V Pungkun1, J Esor2, W Sudchai2, I Kobayashi3, H Sekiguchi3, H Sofyan4, A Kadir5, A Abdullah6, K Romallosa7, J Acuña 8, F Y Hsu9, P Chettasingh10, N Hung11, B Ky12, S Aung13, M Reginaldo14, J Kim15, S Hong16

1Office of Atoms for Peace, Thailand; 2Thailand Institute of Nuclear Technology (Public Organization), Thailand; 3Nagase Landauer Ltd., Japan; 4Center for Radiation Safety Technology and Metrology, Indonesia; 5Malaysian Nuclear Agency (Nuclear Malaysia), Malaysia; 6Asia Lab (Malaysia)Sdn.Bhd., Malaysia; 7Philippine Nuclear Research Institute, Philippines; 8TÜV Rheinland Philippines, Inc., Philippines; 9Nuclear Science and Technology Development Center, Taiwan; 10Bureau of Radiation and Medical devices, Thailand; 11Nuclear Research Institute, Vietnam; 12Institute for Nuclear Science and Technology (INST), Vietnam; 13 Radiation protection department, Myanmar; 14Nagase Philippines Corporation-Dosimetry Laboratory. Philippines; 15 Hanil Nuclear Co., South Korea; 16Pohang Accelerator Laboratory, South Korea

Abstract- Optical Stimulated Luminescence (OSL) the ICRU operational quantities and to provide a unique technology which used for passive personal dosimetry opportunity for regional exchange information. To verify has become illustrious among an Individual Monitoring the compliance with the performance requirements, the IMS Services (IMS) laboratory in Southeast and South Asia laboratories need to provide a regional inercomparison region. The OSL dosimeter evaluated in term of Hp(10), starting with simple photon qualities and ending with mixed Hp(0.07) and Hp(3) is based on whole body dose photon qualities in different irradiation conditions including algorithm accredited by National Voluntary Laboratory rotational field and simulating real work place Accreditation Programme (NVLAP). The conditions[1]. OSL intercomparison has become important intercomparison is a crucial procedure for assessing the after OSL technology was intensively used for personal performance of OSL dosimeters used in IMS laboratory dosimeters for IMS laboratories in Southeast and South according to ISO 17025. The objective of this Asia region instead of film badge and TLD. The Secondary intercomparison programme aimed to reveal confidence Standard Dosimetry Laboratory (SSDL), Office of Atoms between measured dose from IMS laboratories and true for Peace (OAP) has initiated the intercomparison dose from the Secondary Standard Dosimetry programme for InLight (OSL) dosimeters among IMS Laboratory (SSDL), Office of Atoms for Peace (OAP). laboratories which aimed to check the procedure for Fifteen laboratories from nine countries in Southeast assuring the quality of measured dose of radiation workers and South Asia region participated in this programme. in term of Hp(10) and Hp(0.07) which complied with ISO The programme has been designed for the comparison 17025. of Hp(10) and Hp(0.07) for Inlight OSL. The dosimeters were irradiated at beam qualities of Cs-137 for the deep dose (Hp(10)) and Sr-90 for the shallow dose (Hp(0.07)). II. MATERIALS AND METHODS The results showed the performance of the personal dose equivalent evaluation for Hp(10) and Hp(0.07) in photon IAEA-TECDOC-CD-1567, Intercomparison of and beta fields in terms of compliance with the trumpet Measurements of Personal Dose Equivalent Hp(10) in curve. The intercomparison programme will be Photon Fields in the West Asia Region, was used as a continued on a regular basis to develop the quality guideline to set up this OSL dosimeters intercomparison management system and to develop the Personal which followed criteria of RS-G-1.3[2]. The announcement Dosimetry Network of IMS laboratories in Southeast of the Secondary Standard Dosimetry Laboratory (SSDL), and South Asia region. Office of Atoms for Peace (OAP) to notify about the information schedule and instructions were distributed to Key words - intercomparison programme, OSL IMS laboratories in Southeast and South Asia region. An dosimeter, trumpet curve information of OSL reader and dosimeters types for each IMS laboratory was collected. There are fifteen IMS laboratories from nine countries participated in this I. INTRODUCTION intercomparison programme. Thirty five OSL dosimeters were sent to each IMS laboratory which can be divided into The IAEA/RCA (Regional Cooperative Agreement) seven groups. Six groups composed of known and unknown project to strengthen and harmonize radiation protection irradiation doses as in the following, infrastructures in Asian and Pacific region has started since - Group Unknown A : Hp(10) (0.30 - 0.50 mSv) 1998. The objectives of the intercomparison programme - Group Known B : Hp(10) (1.00 mSv) should be included with performance assessment in term of - Group Unknown C : Hp(10) (1.00 - 5.00 mSv)

1 - Group Unknown D : Hp(0.07) (1.00 - 3.00 mSv) - Group Known E: Hp(0.07) (5.00 mSv) Table 1. Statistic evaluation of Cs-137 quality. - Group Unknown F : Hp(0.07) (5.00 - 10.00 mSv) measured dose/ true value dose The last group was additional dosimeters used as 0.35 mSv 1 mSv 3.5 mSv control dosimeters or transport dosimeters. The dosimeters angle 0 degree 0 degree 0 degree were used for evaluation the background and the Max 1.11 1.09 1.04 transportation dose received by the dosimeters before and Min 0.60 0.85 0.91 after their irradiation, when dosimeters were in scanning Average 0.91 0.96 0.97 process at the airports[3]. For the irradiation process, six S.D. 0.14 0.07 0.05 groups of dosimeters of all participants were irradiated by SSDL, OAP at beam qualities of Cs-137 and Sr-90 in term Table 2. Statistic evaluation of Sr-90 quality. of Hp(10) and Hp(0.07) respectively. Irradiations using a Cs- 137 gamma source was carried out at the dose of 0.35, 1.00 measured dose/ true value dose and 3.50 mSv at 0 degree angle of incidence in term of 2.50 mSv 5.00 mSv 8.00 mSv Hp(10). Also, the irradiation doses using Sr-90 source were angle 0 degree 0 degree 0 degree 2.50, 5.00 and 8.00 mSv at 0 degree angle of incidence in Max 1.11 1.12 1.14 term of Hp(0.07). Air kerma for Cs-137 and Absorbed Dose Min 0.79 0.88 0.92 for Sr-90 are traceable to Physikalisch-Techische Average 0.97 1.04 1.04 Bundesanstalt (PTB) in Germany. S.D. 0.09 0.06 0.06 The information of report was composed of irradiation qualities, response values (measured dose from participant divided by true value dose from OAP) and overall uncertainties for all irradiations. For assessing the capability of performance requirement of OSL dosimeters, R, the result of the response was used in the following equation.

R = Hpm Hpw

Where Hpm, value measured by the participant Hpw, conventional true value stated by the irradiating Laboratory Figure 1. Response factor of known dose for Cs-137 dose with 0 degree incidence angle. The results of the intercomparison report were evaluated in terms of compliance with the trumpet curve taken from criteria of RS-G-1.3 which given by equation,

1  2Hp0  Hpm  Hp0  1    1.51  1.5  Hp0  Hpw  Hpw  2Hp0  Hpw 

Hp0, lower limit of dose range, Hp0 = 0.1 mSv for whole body dosimeters

III. RESULTS

The results of measured doses from four participants were Figure 2. Response factor of known dose for Sr-90 high when compare with true value doses. The subtraction dose with 0 degree incidence angle. of control doses was recommended for the assessment of measured doses in term of Hp(10) and Hp(0.07). The results have been recalculated by subtracting their background. The ratios of Hpm/Hpw of all participants were calculated. Table 1. and Table 2. show the summarize of the statistic evaluation for radiation quality of all participants. Figure 1 and 2 illustrate the response, the ratios of Hpm/Hpw, in each participant.

2 Figure 4. The trumpet curve of response factor versus the true dose for Hp(0.07)

. Figure 3. The trumpet curve of response factor versus the true dose for Hp(10)

3 such as daily QC of the readers and calibration periods. The different type of the OSL reader also caused the problem for the intercomparison. Some of participants used Inlight A200 reader, whilst some of them used MicroStar reader. However this comparison activity is the good initiation for the cooperation between IMS laboratories in Southeast and South Asia region for assuring the quality of measurement.

ACKNOWLEDGMENTS

The OSL dosimeters provided by Nagase The statistic evaluation of Cs-137 shows that the Landauer Ltd. and TINT Thailand distributed dosimeters measured dose at the higher level of dose is closer to the for whole participants which highly appreciated. true value dose. The average response factor at 3.5 mSv is 0.97, whilst the average response factor at 1 mSv and 0.35 mSv is 0.96 and 0.91 respectively. Also, the standard References: deviation of response factor at 3.5 mSv is better the lower 1. Murakami H, Takahashi F, Griffith R, (1996), A Personal dose (0.05 at 3.5 mSv, 0.07 at 1 mSv and 0.14 at 0.35 mSv). Dosimetr Intercomparison Study in Asian and Pacific Region. However, the statistic evaluation of Sr-90 shows that there website : www.irpa.net/irpa10/cdrom/00184.pdf 2. Intercomparison of Measurements of Personal Dose Equivalent is no significant different on standard deviation of response Hp(10) in Photon Fields in the West Asia Region, IAEA- factor (0.06 at 8.00 mSv, 0.06 at 5.00 mSv and 0.09 at 2.50 TECDOC-DC-1567. IAEA (2007). mSv). There is also no different on average response factor 3. Arib M, Herrati A, Dari F, Lounis-Mokrani Z, (2015), Intercomparison 2013 on measurements of the personal dose between the dose of 5.00 mSv and 8.00 mSv. equivalents Hp(10) in photon fields in the african region. Radiat For Cs-137 gamma dose intercomparison, the majority Prot Dsimetry, Vol. 163, No 3, pp. 276-283. of the results were underestimated with maximum value 4. International Atomic Energy Agency. Assessment of around 15%, whilst the results of five participants were occupational exposure due to external sources of radiation. Safety Standard Series No RS-G-1.3 IAEA (1999). overestimates with maximum value around 9%. For Sr-90 5. Figel M, Stadtmann H, Grimbergen T, McWhan A, (2016) beta dose intercomparision, most of the participant results Intercomparisons for individual monitoring services in Europe : were overestimated with maximum value around 12%, Organization, experience and results web site : www.rpe.org.in whilst the results of 3 participants were underestimated with maximum value around 12%. The results of the intercomparison are also evaluated in terms of compliance with the trumpet curve. The results show a good agreement between the IMS laboratories. All response factor of Hp(10) and Hp(0.07) are within the trumpet curve. The standard deviation of response factor of low dose is larger than the high dose in both Hp(10) and Hp(0.07).

IV. CONCLUSION

After IAEA/RCA IMS for Asia Pacific in 1998, there was no such intercomparison activity for personal dosimetry, whilst all personal monitoring service providers need to maintain their ISO 17025 accreditations. This was the first intercomparison programme for all OSL service providers in Southeast and South Asia region. The results show a good agreement between the IMS laboratories within 30% of IAEA criteria. The assessment shows that the results of all IMS laboratories are within the trumpet curve. The response factors of IMS laboratories are 0.91-0.97 for Cs-137 quality and 0.97-1.04 for Sr-90 quality. The standard deviation of response factor of IMS laboratories are 0.05-0.14 for Cs-137 quality and 0.06-0.09 for Sr-90 quality. Since the results of high dose irradiation show the better agreement between the response factors of IMS laboratory, the low dose assessment should be improved