EURADOS INTERCOMPARISONS FOR INDIVIDUAL MONITORING SERVICES: RESULTS AND CONCLUSIONS FROM THE FIRST THREE EXERCISES

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1 EURADOS INTERCOMPARISONS FOR INDIVIDUAL MONITORING SERVICES: RESULTS AND CONCLUSIONS FROM THE FIRST THREE EXERCISES Stadtmann H. 1, Grimbergen T.W.M. 2, McWhan A. 3* Figel M. 4, Romero A. M. 5 1 Radiation Safety and Application, Doimetry Head, Seiberdorf Labor GmbH, 2444 Seiberdorf, Autria 2 Radiation and Environment Group, NRG, PO Box 934, 68ES, Arnhem, Netherland 3* Berkeley Approved Doimetry Service, Babcock International Group, A11 Berkeley Centre, Berkeley, Glouceterhire, GL13 9FB, United Kingdom 4 Auwertungtelle (Peronal Monitoring Service) Helmholtz-Zentrum Muenchen, Otto- Hahn-Ring 6, D-81739, München, Germany 5 Radiation Doimetry Service, CIEMAT, Avda Complutene, 4, 284-Madrid, Spain ABSTRACT In 28 EURADOS (European Radiation Doimetry Group) tarted a elf utaining programme of regular intercomparion exercie for individual monitoring ervice (IMS) in Europe. With the intercomparion reult, each IMS can tet the performance of their ytem, compare their reult with thoe from other participant and how compliance with the requirement et by regulatory or accreditation bodie. Thu, EURADOS provide a neceary ervice for all European doimetry ervice and contribute to the harmoniation of peronal doimetry in Europe. In thi paper the intercomparion programme organized by EURADOS i preented together with the detail, reult and concluion of the intercomparion held to date: IC28 and IC21 for whole body doemeter and IC29 for extremity doemeter. Key Word: Intercomparion, individual monitoring, doemeter. 1. Introduction. Peronal doimetry intercomparion are conidered an eential tool for the harmoniation of peronal doimetry ervice (alo known a individual monitoring ervice IMS) in Europe. Participation i pecifically recommended in the new "Technical Recommendation for Monitoring Individual Worker Expoed to External Radiation" [1] and in the ection on method validation in ISO/IEC [2], General requirement for the competence of teting and calibration laboratorie. However, up until now only a few European Union countrie have been organiing intercomparion for peronal doimetry and, in general, thee have been limited to IMS within the organiing country. EURADOS (European Radiation Doimetry Group, ) i a non profit aociation that bring together over 2 cientit from over 5 intitution in the European Union, Switzerland and countrie of Central and Eatern Europe and whoe objective i to promote reearch, development and European co-operation in the field of doimetry of ionizing radiation. Recognizing the demand for intercomparion and drawing on the tructure of the large network of it member and the experience gained in organiing previou intercomparion, EURADOS decided to invetigate the poibility of etablihing a utainable program of intercomparion organied periodically, to be financed by fee paid by participant. Thu, EURADOS would contribute to the knowledge of the current tate of doimetry in Europe and the harmoniation between the different 1

2 IMS. Thi tudy wa commiioned by the working group EURADOS 2 (WG2) for the "Harmoniation of peronal doimetry in Europe", preented at the 27 EURADOS Annual Meeting. The frequency wa et at the rate of one intercomparion per year, with whole body doemeter intercomparion held every econd year with extremity or neutron doemeter intercomparion held on alternate year. The intercomparion program wa etablihed taking into account the requirement of ISO [3] in term of qualitie and angle of irradiation, the doe range, the number of doemeter irradiated and background, etc. The choice of laboratory irradiation wa limited to accredited reference laboratorie in order that the intercomparion reult would be ueful for IMS which have ISO/IEC-1725 accreditation [2]. However, ince EURADOS i not approved for the evaluation of IMS, ie for the purpoe ISO [3], it wa decided that the reult of the intercomparion would be preented to the participant a a "Certificate of Participation", accompanied by a certificate iued by the accredited laboratory irradiation. The Certificate of Participation doe not make any aement of the reult becaue the pecified national criteria differ from country to country. 2. Intercomparion Phae The Council appoint a group EURADOS organier (OG) for each intercomparion, one of whom act a co-ordinator. The OG decide the cope of each campaign, define the irradiation plan, hire the laboratory irradiation intercomparion, analye the reult of the participant, prepare individual certificate of participation and prepare the final report. Each intercomparion can be conidered a four phae: 1) preparation, 2) announcement and regitration, 3) execution and 4) reporting. In the preparation phae, the OG develop a propoal for intercomparion in defining the cope, etablihing the irradiation plan (radiation qualitie and doe range) and et the budget and proviional timetable. The OG then contact uitably accredited calibration laboratorie for quote, baed on an outline of the propoed irradiation and the number of expected participant. A EURADOS i a non-profit making organiation, the fee i baed on the total cot and the minimum number of participant to balance income and expenditure. When the quote have been received and the budget ha been finalied, the OG preent the propoal to the EURADOS Council for formal approval. Once the propoal ha been approved, the econd phae tart with the formal announcement of the intercomparion on the EURADOS webite with a copy ent by to all IMS on the OG mailing lit. The announcement include information about the type of intercomparion, the doe range, energie and angle of irradiation and the chedule for the year. Thoe intereted in participating mut complete an application form (which include term and condition). The application form can be downloaded from the EURADOS webite. If the minimum number of participant (et by the budget) ha been reached, the elected irradiation laboratory i formally notified. The third phae begin with participant ending confirmation of participation. Intruction for ending doemeter and the correponding invoice are then ent back to the elected participant. Participant mut label their doemeter and end thee to the co-ordinator. The coordinator receive all the doemeter and attache new label with an organiation code. The doemeter are ent to an irradiation laboratory (or laboratorie). Each hipment i accompanied by an electronic doemeter to monitor the doe received in tranit. When the irradiated doemeter are returned to the co-ordinator, the new OG label are removed and the doemeter are returned to the IMS participant doemeter for evaluation along with intruction for ending reult. 2

3 After receiving the reult, the co-ordinator calculate the value of the repone, R, for each doemeter by dividing the participant' reult, H p, participant, by the reference doe given laboratory H p, reference, according with equation (1). R H p, participant (1) H p, reference The calculated repone value are ent to each participant for the initial check and confirmation (with the opportunity to comment). Thu, each participant i informed of the radiation qualitie and the doe given to their doemeter. Any comment received after that time are dicued by the OG to decide if any application for reult modification can be permitted. A a general rule, the OG only accept change to the reult when it i proven that there ha been an error by the OG or by the irradiation laboratory. In the lat phae, the coordinator prepare the "Certificate of Participation" which are igned by the coordinator and the preident of EURADOS. Thee certificate are iued to participant at the "Participant Meeting" which OG hold at the end of each intercomparion. Finally, the OG prepare and end a quetionnaire to participant to gauge the value of the intercomparion, the need for new intercomparion and area for improvement. All data i treated a trictly confidential and the IMS identification code ued for analying reult i known only to participant and the coordinator. In addition, the irradiation laboratory carrie out the irradiation to each doemeter to a doe value, randomly generated, cloe to the value propoed in the OG irradiation plan. Thi mean that each participant doemeter receive lightly different doe value. The detail of organiation, execution and analyi of reult for each intercomparion are preented in a Final Report which i prepared by the OG when each intercomparion ha been completed. For the analyi of reult required for preparation of report, the OG ue the trumpet curve method et out in ISO [3], for which the tolerance limit are given by equation (2 ) wherein F = 1.5 and H i lower range of doe. 1 2H H 1 R F 1 F H H p, ref 2H H p, ref (2) Following thi methodology, three intercomparion have now been completed: two in 28 and 21 for whole body doemeter, and one in 29 for extremity doemeter. IC212 for whole body doemeter i now under way. A technical overview of the three completed intercomparion i preented below. 3

4 3. EURADOS 28 Intercomparion for whole body doemeter (IC28) [4] Organiing Group: T. Grimbergen, M. Figel, A. M. Romero, H. Stadtmann and A. McWhan, Co-ordinator: T. Grimbergen Participant ubmitted 26 doemeter of which 2 were irradiated with the photon qualitie and value of Hp (1) and Hp (.7) hown in Table 1. The remaining 6 doemeter were ued a pare and background doemeter. The irradiation plan had been etablihed to enable participant to obtain information about the performance of their ytem with repect to linearity, reproducibility, energy dependence and angular meaurement capability in mixed field. Thee irradiation were performed in the Calibration Laboratory of Greek Atomic Energy Commiion (GAEC) in Greece A total of 52 IMS from 24 countrie participated with a total of 62 different doimetric ytem: 1 photographic film (Film), 46 thermoluminecence doemeter (TLD) and 6 other technique (Other) including optically timulated luminecence (OSL), radiophotoluminicence (RPL) and active peronal doemeter (APD). Of the 62 participant, 48 ubmitted reult for both quantitie and the remainder jut ubmitted reult for Hp (1). Table 1: Irradiation Plan for IC28 Quality Hp(1), Hp(,7) (msv) Number of doemeter N N N N-6 + S-C (3 + 1) 2 S-C + N-6 (3 + 1) 2 S-C.5 2 S-C 3 4 S-C 1 2 S-Co 15 2 Figure 1 how the overall reult of all participant a a function of the doe quantitie Hp (1) and Hp (.7) together with the repreentation of the trumpet curve. Mot of the reult (93% and 88%, repectively) are within acceptable limit; film doemeter howed the larget deviation. 1 Trompeta Trompeta TLD Film Otro Trompeta Trompeta TLD Film Otro Figure 1: IC28 reult in term of the doe delivered repreented together with the trumpet curve (H =.85 msv) 4

5 Analyi of the reult depending on the quality of radiation, a hown in Figure 2, how that the median i at a value very cloe to unity in all cae, which mean that the calibration procedure and in particular, traceability to national reference laboratorie, are performing a expected. However, the N6 qualitie ( and 45 ) how the greatet pread of reult: 15% of the repone value fall outide the trumpet curve. Figure 2: Reult of the IC28 depending on the quality of radiation. The value hown are the median ( ), percentile 25% to 75% (bar), the percentile 5% to 95% (vertical line), maximum ( ) and minimum ( ). When the individual reult of Hp (1) are preented for all participating ytem baed on the anonymou ytem identification number(figure 3) it can be oberved that mot of the value outide the range 1/1, 5 R 1.5 come from photographic film doemeter, although it i noted that ome of them howed a good performance, comparable to that of the TLD. TLD baed ytem howed atifactory reult in general (96% of reult within the trumpet curve) and the other ytem preented only 1% of outlier. 5 4 R 3 2 Film TLD Other ytem number Figure 3: Individual reult for Hp(1) for all participant ytem in IC28 5

6 4. EURADOS Intercomparion 29 for extremity doemeter (IC29) [5] Organiing Group: T. Grimbergen, M. Figel, A. M. Romero, H. Stadtmann and A. McWhan Coordinator: T. Grimbergen For IC29, each participant ent 28 extremity doemeter of which 22 were irradiated with the photon qualitie and beta energie for Hp (.7) lited in Table 2. The remaining 6 doemeter were ued a pare and background doemeter. The irradiation plan wa deigned to enable participant to obtain information on their ytem with repect to linearity, reproducibility, energy dependence and angular qualitie for their beta and photon repone. The irradiation were performed in calibration facilitie in Seiberdorf in Autria and the Intitut de Radioprotection et de Sûreté Nucléaire (IRSN) in France. There were a total of 44 IMS from 18 different countrie with 59 doemeter ytem: 46 ring ytem, 4 fingertip and 9 writ / ankle doemeter. Participant could chooe to participate only with photon or beta radiation, or both. 21 IMS choe qualitie ytem involving photon, 37 choe photon and beta and one choe beta only. All participant ued TLD except for one participant who ent RPL gla doemeter. Table 2: Irradiation plan for IC29 Radiation Quality Abreviation Energy max beta / media photon kev H p(.7) msv Number of doemeter Beta 85 Kr; (Kr) Sr/ 9 Y; (Sr) Sr/ 9 Y; 6 (Sr6 ) Photon N-2; (N2) W-8; (W8L) (W8M) (W8H) W-8; 6 (W8M6 ) N-15; (N15) S-C; (C) Figure 4 how the overall reult for all participant baed on the value of Hp (.7) given together with the trumpet curve. About 15% of the reult are outide the trumpet curve; the doemeter irradiated with beta radiation preented the highet deviation. 6

7 1 1 e n o p re Kr-85; Sr-9/Y-9; Sr-9/Y-9; 6 N-2; W-8; W-8; 6 N-15; S-C; F Trumpet Hp(.7) msv Figure 4: Reult for IC29 a a function of the doe repreented together with the trumpet curve (H =1,25 msv) Figure 5 how the reult a a function of the quality of radiation. It mut be noted that all the minimum and maximum value for all of the irradiation with photon are for jut two doimetry ytem that conitently howed value too high or too low. A expected, the repone value were lowet for the lower-energy beta ( 85 Kr; ) and wider angle ( 9 Sr/ 9 Y; 6 ). Both the mean value of beta irradiation 9 Sr/ 9 Y; º and irradiation with photon remain cloe to unity R e n o 2. p r e 1.5 median max min Kr Sr Sr 6 N2 W8L W8M W8M 6 W8H N15 C All radiation quality Figure 5: Reult for IC29 a a function of the radiation quality. The value hown are the median ( ), percentile 25% to 75% (bar), the percentile 5% to 95% (vertical line), maximum ( ) and minimum ( ). If the individual reult of Hp (.7) are preented for all participating ytem baed on the number of anonymou ytem (Figure 6) it can be oberved that mot of the value outide the range 1/1, 5 R 1,5 correpond to the 85 Kr;º and 9 Sr/ 9 Y;6 beta irradiation qualitie. 71% of the ytem deigned for only photon paed the trumpet curve criteria while only 4% of thoe deigned to meaure photon and beta radiation met the criteria trumpet curve criteria in both capacitie. The 7

8 doemeter deigned for beta only wa within the trumpet curve. In total, only 31 of the 59 participating ytem (52%) met the criteria of the trumpet curve. 4 3 e n o p 2 re Kr-85; Sr-9/Y-9; Sr-9/Y-9; 6 N-2; W-8; W-8; 6 N-15; S-C; F=1.5 1/F= Sytem ID Figure 6: Individual reult of Hp (.7) for all ytem participating in the IC EURADOS Intercomparion 21 for whole body doemeter (IC21) Organiing Group: A. McWhan, E. Fantuzzi, M. Figel, T. Grimbergen, A. M. Romero and H. Stadtmann Co-ordinator: A. McWhan For IC21, 26 whole body doemeter were ent by each participant of which 2 were irradiated following the irradiation plan hown in Table 3. The remaining 6 were ued a pare and background doemeter. The irradiation were performed in the Calibration Laboratory BEV in Autria. A total of 7 IMS, from 3 countrie participated with a total of 85 different doimetric ytem: 13 film, 59 TLD, 8 OSL and 5 baed on other technique (Other), ie radiophotoluminecence (RPL), direct ion torage (DIS) or active peronal doemeter (APD). Of the 85 participant, 66 ubmitted reult for both quantitie and the remaining 19 participated only in the magnitude Hp (1). Table 3: Irradiation Plan for IC21 Quality Hp(1), Hp(,7) (msv) Number of Doemeter N-4 3º 1 2 N-4 + S-C 3 2 W X 5 2 W Y 5 2 W-25 + S-C 3 2 S-C.5 2 S-C S-C 12 2 S-Co

9 Figure 7 how the overall reult of all participant a a function of the doe given in the quantitie Hp (1) and Hp (.7) together with the repreentation of trumpet curve. In thi exercie, the increae in OSL-baed ytem allowed the OG to tudy their behaviour a a new category of ytem. It can be een that mot of the reult (95% and 91%, repectively) are within acceptable limit. Some TLD ytem have hown greater deviation than in the IC28 while film performance ha improved. Figure 7: Reult for IC21 a a function of the imparted doe repreented together with the trumpet curve (H=.85 msv). N4 / 3 º N4 / 3 º If we analyze the reult depending on the quality of radiation, a hown in Figure 8, the median i oberved at a value very cloe to unity in all cae but there wa a greater pread of reult for N4;3º quality which i due mainly to the behaviour of TLD which had 1% of reult outide the trumpet curve for thi quality. Figure 8: Reult for IC21 a a function of the radiation quality. The value hown are the median ( ), percentile 25% to 75% (bar), the percentile 5% to 95% (vertical line), maximum ( ) and minimum ( ). Analyi of individual reult how that 74% and 67% of the ytem had reult within the trumpet curve for the quantitie Hp (1) and Hp (.7), repectively. TLD ytem howed table and atifactory reult in general, 76% of ytem without outlier, yielding the pooret reult for the 9

10 quality N-4/3º. Film-baed ytem were ignificantly improved with reult down from 25% outlier in the IC28 to 8% in IC29. OSL doemeter performed well with outlier only for N4/S- C quality. Note that the Other ytem had all value within the trumpet curve for all qualitie teted. 6. Concluion The programme of EURADOS intercomparion ha met the objective for which it wa etablihed. Three elf financed intercomparion have now been completed and thee indicate the contribution of the IC programme to the harmoniation of European IMS. The high number of participant confirm the interet and the need for IMS to participate in international intercomparion exercie to demontrate the competence of their ervice. The reult how a good performance in general, although it can be een that there i ome cope for improvement, in particular for extremity doimetry. The OG i currently working on IC212 for whole body doemeter in photon field and EURADOS i alo organiing an intercomparion pecifically for neutron doemeter in 212. REFERENCES [1] European Commiion. Technical recommendation for monitoring individual occupationally expoed to external radiation. Directorate-General for Energy and Tranport, RP-16 (EC) (29). [2] International Organization for Standardization. General requirement for the competence of teting and calibration laboratorie. ISO 1725 (ISO) (25). [3] International Organization for Standardization. Radiation protection Criteria and performance limit for the periodic evaluation of proceor of peronal doemeter for X and gamma radiation. ISO (ISO) (2). [4] Grimbergen, T., Figel, M., Romero A.M., Stadtmann H., McWhan A. EURADOS elf-utained programme of intercomparion for individual monitoring ervice. Radiat Prot Doimetry (211) 144(1-4): [5] Stadtmann H., Grimbergen, T., Figel, M., Romero A.M., McWhan A. Reult of the EURADOS extremity doemeter intercomparion 29. Radiat Prot Doimetry (211) 144(1-4): [6] Stadtmann H., Grimbergen, T., Figel, M., Romero A.M., McWhan A. EURADOS Intercomparion 28 for Whole body Doemeter in Photon field, EURADOS report 212-1, Braunchweig, January 212, ISSN , ISBN