Radiation Protection Dosimetry (2012), Vol. 148, No. 1, pp. 3 8 Advance Access publication 20 February 2011

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1 Radiation Protection Dosimetry (2012), Vol. 148, No. 1, pp. 3 8 Advance Access publication 20 February 2011 doi: /rpd/ncq597 IMPLEMENTATION OF DOSE MANAGEMENT SYSTEM AT RADIATION PROTECTION BOARD OF GHANA ATOMIC ENERGY COMMISSION F. Hasford 1,2, *, J. K. Amoako 1, E. O. Darko 1, G. Emi-Reynolds 1, E. K. Sosu 2, F. Otoo 1 and G. O. Asiedu 1 1 Radiation Protection Institute, Ghana Atomic Energy Commission, PO Box LG 80, Legon-Accra, Ghana *Corresponding author: haspee@yahoo.co.uk Received September , revised December , accepted December The dose management system (DMS) is a computer software developed by the International Atomic Energy Agency for managing data on occupational exposure to radiation sources and intake of radionuclides. It is an integrated system for the user-friendly storage, processing and control of all existing internal and external dosimetry data. The Radiation Protection Board (RPB) of the Ghana Atomic Energy Commission has installed, customised, tested and using the DMS as a comprehensive DMS to improve personnel and area monitoring in the country. Personnel dose records from the RPBs database from 2000 to 2009 are grouped into medical, industrial and education/research sectors. The medical sector dominated the list of monitored institutions in the country over the 10-y period representing 87 %, while the industrial and education/research sectors represent 9 and 4 %, respectively. The number of monitored personnel in the same period follows a similar trend with medical, industrial and education/research sectors representing 74, 17 and 9 %, respectively. Analysis of dose data for 2009 showed that there was no instance of a dose above the annual dose limit of 20 msv, however, 2.7 % of the exposed workers received individual annual doses >1 msv. The highest recorded individual annual dose and total collective dose in all sectors were 4.73 msv and man Sv, respectively. Workers in the medical sector received higher individual doses than in the other two sectors, and average dose per exposed worker in all sectors is 0.25 msv. INTRODUCTION The Radiation Protection Board (RPB) which is mandated to be the national competent authority in Ghana with regulatory, monitoring and advisory responsibilities in matters pertaining to ionising radiation was established in 1993 by the Government of Ghana through the Ghana Atomic Energy Commission (GAEC). The RPB was established by the amendment of the Atomic Energy Act, Act 204 of 1963 by the Provisional National Defence Council Law, Law 308 (1, 2). Act 204 has since been revoked and replaced by Act 588 of 2000 (3). The Primary Law was, however, strengthened by the enactment of the legislative instrument (LI), 1559 in January 1993 (4). The Radiation Protection Institute (RPI) is responsible for the operational functions of the RPB. The institute through the occupational radiation protection sector monitors occupationally exposed workers in Ghana. The activities of the RPB like the National Radiological Protection Board (5) in the UK help to protect occupationally exposed workers from radiation hazards. For all justified practices which could involve occupational exposure, dose limits are imposed so that no worker 2 Present address: Radiological and Medical Sciences Research Institute, Ghana Atomic Energy Commission, PO Box LG 80 Legon-Accra, Ghana. will be subject to an unacceptable risk attributable to the radiation exposure. The term exposed workers refers to all workers who are subject to individual radiation dose assessment (6). These limits are set and specified by the RPB with the backing of the LI 1559 to prevent the occurrence of deterministic effects and to limit the probability of stochastic effects. Occupational exposure of any worker is controlled such that an effective dose of 50 msv, an equivalent dose to the lens of the eye of 150 msv and/or an equivalent dose to the extremities or the skin of 500 msv are not exceeded in any single year. For apprentices and students of y of age who are being trained for employment involving exposure to radiation, occupational exposure is controlled such that an effective dose of 6 msv, an equivalent dose to the lens of the eye of 50 msv and/or an equivalent dose to the extremities or the skin of 150 msv are not exceeded in any single year (7). The dose management system (DMS) has been developed and is being used by the Radiation and Waste Safety Division of the International Atomic Energy Agency (IAEA) as an important system for managing all existing internal and external dosimetry data. This allows for a general analysis of the data under the International Commission on Radiological Protection s (ICRPs) developed concept (8). By design, the DMS has modules for entering and updating employment data, registering # The Author Published by Oxford University Press. All rights reserved. For Permissions, please journals.permissions@oup.com

2 occupationally exposed workers, and their doses resulting from internal and/or external exposure (7, 9, 10). It includes a group of classifiers that facilitate the user s work and a module for producing reports and correlating results. Access into the DMS can be made through either of three available authorisation levels depending on the intent for which an individual wants to use the system. Head of Laboratory is the authorisation level which serves as the system administrator and has total access to all options of the system. Head of Service is the level authorised to enter data into all files of the system, to issue reports and to save data, while Technician is the level authorised to enter data only into the work files of the system. The procedure for storage and processing of dose data of occupationally exposed workers varies from one regulatory body to another. These data are of vital importance to regulatory authorities in terms of radiological protection policies. Such data are useful in epidemiological studies and in studies of risk and potential exposure. There is, however, the need to harmonise systems of dose management in regulatory bodies across the world with the adoption of a common DMS. The DMS developed by the IAEA has been adopted, tried and tested successfully by the RPB of GAEC to serve as a support tool for the national regulatory authority in occupational exposure monitoring services. The system is being used to process dose values and other F. HASFORD ET AL. important quantities obtained by specific dosimetry techniques for monitoring occupational exposure to external radiation sources and exposure due to the intake of radionuclides. The system focuses on the collection, storage, evaluation and management of all data needed by the dosimetry service. METHODOLOGY FOR THE IMPLEMENTATION OF DMS Dose management system After successful installation of the DMS on the RPB s computer system, start-up is achieved by executing the program DMS.exe located in the directory D:\Dmsystem. A shortcut has, however, been created on the desktop in order to speed up the start-up to the DMS. The program comprises a group of linked data files and classifiers as shown in Figure 1 that guarantee the integrity of data entered into the system. New occupationally exposed workers are registered with the DMS by inputting their personal data, employment record and previous dose records, if any. Occupationally exposed workers who are already registered with the system, however, have their dose records updated by entering into appropriate fields the required data. After processing the input data, individual or group monitoring reports as well as area monitoring reports are generated depending on the one which is of need. Figure 1. Input and output data of a newly registered occupationally exposed worker (8). 4

3 The generated report could either be over a particular monitoring period or several monitoring periods accumulated over some time. Implementation The DMS (version 2.0) which is being implemented at the RPB for personal monitoring of occupationally exposed radiation workers is a higher and a relatively new version of an older one, DMS (version 1.0). The software has been installed, customised, tried and tested, and found to be working perfectly in the management of occupational doses. The software is installed on a Pentium IV 3.0 MHz desktop computer with 504 MB RAM and 75 GB hard disk drive, and it works with Access 97 software on Windows XP Professional platform. Personnel dose records of monitored occupationally exposed radiation workers from the year 2000 to 2009 have been obtained from the RPB s database and fed manually into the DM System. Subsequently, personal dose equivalent values H p (0.07) and H p (10) (8, 11) of newly monitored personnel which are read with the Harshaw 6600 TLD reader is fed manually into the system for dose monitoring reports to be generated. Personal dose equivalent values are calculated using in the following equations. Skin dose : H p ð0:07þ ¼½ð1:2958R skin Þþ0:0097Š msv Deep dose : H p ð10þ ¼½ð1:3772R deep Þþ0:0566Š msv; ð1þ ð2þ where R skin (mr) and R deep (mr) are exposure readings from the Harshaw 6600 TLD reader for skin DMS IMPLEMENTATION AT RPB-GAEC and deep doses respectively and they are based on reader calibration to 137 Cs exposure. The TLD reader is operated with WinREMS software installed on the computer system for generating the exposure values (R skin and R deep ) which are used in calculating skin and deep doses. The generated monitoring reports are then sent to recipient individuals or institutions and copies kept at the RPB as reference. DATA ANALYSIS Occupational exposure trend ( ) A survey of monitored institutions that employ the use of ionising radiation in Ghana from 2000 to 2009 has been made. The institutions have been grouped according to the purpose for which the radiation sources are employed. Occupationally exposed workers monitored by the RPB of the GAEC are classed into either one of the three sectors; medical, industrial and education/research. From the dose data extracted from the RPB s database, a number of observations and analyses are made. From Figures 2 and 3, monitored institutions that employ the use of ionising radiations in the medical sector, and number of occupationally exposed workers working in those institutions dominate over those of industrial and education/ research sectors in the 10-y monitoring period. A similar trend is observed by Colgan et al. (6) in their 10-y period of study in Ireland from 1996 to The number of monitored institutions in the medical sector increased from 84.2 % in 2000 to 87.0 % in 2007 in Figure 2, while those in industrial sector showed marginal increase from 10.0 % in 2000 to 10.1 % in The education/research Figure 2. Distribution of institutions using ionising radiation monitored in Ghana. 5

4 F. HASFORD ET AL. Figure 3. Distribution of occupationally exposed workers monitored in Ghana. Table 1. Number of institutions using ionising radiation monitored in Ghana. Sector/year Medical Industry Education/research Total Table 2. Number of occupationally exposed workers monitored in Ghana. Sector/year Medical Industry Education/research Total sector, however, showed a decrease from 5.8 % in 2000 to 2.9 % in Monitored medical institutions decreased from a maximum number of 160 in 2004 to 120 in 2009, after a steady rise from a minimum number of 101 in The gradual decline in the number of monitored medical institutions from 2004 to 2009 could be attributed to the fold up of some of the institutions or inability to monitor all required institutions. The number of monitored occupationally exposed workers has decreased over the 10-y period after consistently increasing from the year 2000 to a maximum in the year In 2009, there were 629 such workers compared with 808 in 2000, showing a decrease of 22.2 %. Highest number of monitored exposed workers was recorded in 2004 with a number of 949. The number of occupationally exposed workers in any given year between 2000 and 2009 is shown in Figure 3. In summary, medical, industrial and educational/ research sectors represent 87.2, 8.9 and 3.9 %, respectively of monitored institutions in the period The number of monitored radiation workers in the same period follows a similar trend with medical, industrial and educational/research sectors representing 73.6, 17.2 and 9.2 %, respectively. The summary of monitored institutions and personnel in Ghana by the RPB in the 10-y period is given in Tables 1 and 2. Dosimetry for 2009 Analysis of individual and cumulative doses has been performed, and Table 3 shows the summary of 6

5 DMS IMPLEMENTATION AT RPB-GAEC Table 3. Summary of dose data for occupational radiation exposure per sector for Sector Institutional averages of effective dose within sectors (msv) Min. Max. Collective dose (man Sv) Workers receiving doses Average dose per worker (msv) Medical Industrial Education/research All sectors dose data for occupational radiation exposure per sector for The averages of effective dose for institutions within the medical, industrial and education/research sectors varied in the range of , and msv, respectively. From the 2009 dose records, there was no instance of a dose above the annual dose limit of 20 msv, however, there were instances whereby workers received individual annual doses.1 msv. Seventeen exposed workers received individual annual doses.1 msv, representing 2.7% of the exposed workers. Out of the 17 patients, 9 (representing 53%) were in the medical sector and 5 (representing 29%) were in the educational/research sector. All except one exposed worker received individual annual doses,3 msv. The highest recorded individual annual dose was 4.73 msv, and this was recorded on a TLD worn by a personnel in a diagnostic radiology department of the medical sector. Investigation into this observation has been requested by the RPB of the GAEC, but the outcome is not readily available. The collective dose of man Sv received by exposed workers in the medical sector is approximately 13-fold more than that of the industrial sector and 22-fold more than that of the education/ research sector. Approximately, 89 % of the entire collective dose of man Sv is from the medical sector, while the educational/research sector contributes the least with 4 %. Average dose per exposed worker in the medical, industrial and educational/ research sectors are calculated to be 0.32, 0.09 and 0.10 msv, respectively, and the average doses per exposed worker in all sectors is 0.25 msv. This indicates that workers in the medical sector receive higher individual doses than in the other sectors. The reason for this observation is not immediately known, but it may be a result of the increased workload in the medical sector when compared with industrial and educational/research sectors. CONCLUSION AND RECOMMENDATION The introduction of the DMS by the RPB is of much importance as it seeks to properly and adequately manage exposure of occupationally exposed workers. The DMS is being used to process the dose values and other important quantities obtained by specific dosimetry techniques for monitoring occupational exposure to external radiation sources and exposure due to the intake of radionuclides. The system makes monitoring of personnel more effective and quite easy as it provides an integrated system, is user-friendly, and is a more dynamic option in dose management. The ability to use the DMS in collecting, storing, evaluating and managing personal (internal, external and unusual) doses of occupationally exposed workers as well as doses in area monitoring makes it a very important tool for the RPB as a regulatory authority in the country. A challenge to the implementation of the system however, is the incompatible nature of the DMS with WinREMS, the installed software for operating the Harshaw 6600 TLD reader. It is recommended that the RPB develop or acquire software which will be compatible with the two programs so as to automatically transfer exposure readings (in mr) from the WinREMS into dose values (in msv) in the DMS as soon as the exposed TLDs are read with the Harshaw FUNDING There was operational support from the Radiation Protection Institute of Ghana Atomic Energy Commission. REFERENCES 1. Atomic Energy Commission Act, Act 2004 (1963). 2. Atomic Energy Commission (Amendment) Law, P.N.D.C.L 308 (1993). 3. Atomic Energy Commission Act, Act 588 (2000). 4. Radiation Protection Instrument, L.I 1559 (1993). 5. O Riordan, M. C. The NRPB era. J. Radiol. Prot. 30, 85 (2010). 6. Colgan, P. A., Currivan, L. and Fenton, D. An assessment of annual whole-body occupational radiation exposure in Ireland ( ). Radiat. Prot. Dosim. 128, (2008). 7. Occupational Radiation Protection. Radiation Protection and Safety Guide. GRPB-G3:2000, RPB, Accra, Ghana (2002). 7

6 8. International Commission on Radiological Protection Recommendations of the ICRP. ICRP Publication 60. Pergamon Press (1990). 9. International Atomic Energy Agency. Dose Management System (version 1.0) user manual. IAEA, NSRW/PPSS (2004). F. HASFORD ET AL. 10. International Atomic Energy Agency. Dose Management System (version 2.0) user manual. IAEA, NSRW/PPSS (2006). 11. International Commission on Radiation Units and Measurements Quantities and units in radiation protection dosimetry. ICRU Report 51. ICRU (1993). 8