Assessment of annual whole-body occupational radiation exposure in education, research and industrial sectors in Ghana (2000-09)

Institutions in the education, research and industrial sectors in Ghana are quite few in comparison to the medical sector. Occupational exposure to radiation in the education, research and industrial sectors in Ghana have been analysed for a 10 y period between 2000 and 2009, by extracting dose data from the database of the Radiation Protection Institute, Ghana Atomic Energy Commission. Thirty-four institutions belonging to the three sectors were monitored out of which ～65% were in the industrial sector. During the 10 y study period, monitored institutions ranged from 18 to 23 while the exposed workers ranged from 246 to 156 between 2000 and 2009. Annual collective doses received by all the exposed workers reduced by a factor of 2 between 2000 and 2009. This is seen as a reduction in annual collective doses in education/research and industrial sectors by ～39 and ～62%, respectively, for the 10 y period. Highest and least annual collective doses of 182.0 man mSv and 68.5 man mSv were all recorded in the industrial sector in 2000 and 2009, respectively. Annual average values for dose per institution and dose per exposed worker decreased by 49 and 42.9%, respectively, between 2000 and 2009. Average dose per exposed worker for the 10 y period was least in the industrial sector and highest in the education/research sector with values 0.6 and 3.7 mSv, respectively. The mean of the ratio of annual occupationally exposed worker (OEW) doses for the industrial sector to the annual OEW doses for the education/research sector was 0.67, a suggestion that radiation protection practices are better in the industrial sector than they are in the education/research sector. Range of institutional average effective doses within the education/research and industrial sectors were 0.059-6.029, and 0.110-2.945 mSv, respectively. An average dose per all three sectors of 11.87 mSv and an average dose per exposed worker of 1.12 mSv were realised for the entire study period. The entire study period had 187 instances in which exposed workers received individual annual doses >1 mSv, with exposed workers in the education/research sector primarily receiving most of this individual dose.     

Implementation of dose management system at radiation protection board of Ghana Atomic Energy Commission

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 159.84 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.     

Assessment of annual whole-body occupational radiation exposure in medical practice in Ghana (2000-09)

Occupational exposure to radiation in medical practice in Ghana has been analysed for a 10-y period between 2000 and 2009. Monitored dose data in the medical institution in Ghana from the Radiation Protection Institute's database were extracted and analysed in terms of three categories: diagnostic radiology, radiotherapy and nuclear medicine. One hundred and eighty medical facilities were monitored for the 10-y period, out of which ~98% were diagnostic radiology facilities. Only one nuclear medicine and two radiotherapy facilities have been operational in the country since 2000. During the 10-y study period, monitored medical facilities increased by 18.8%, while the exposed workers decreased by 23.0%. Average exposed worker per entire medical institution for the 10-y study period was 4.3. Annual collective dose received by all the exposed workers reduced by a factor of 4 between 2000 and 2009. This is seen as reduction in annual collective doses in diagnostic radiology, radiotherapy and nuclear medicine facilities by ~76, ~72 and ~55%, respectively, for the 10-y period. Highest annual collective dose of 601.2 man mSv was recorded in 2002 and the least of 142.6 man mSv was recorded in 2009. Annual average values for dose per institution and dose per exposed worker decreased by 79 and 67.6%, respectively between 2000 and 2009. Average dose per exposed worker for the 10-y period was least in radiotherapy and highest in diagnostic radiology with values 0.14 and 1.05 mSv, respectively. Nuclear medicine however recorded average dose per worker of 0.72 mSv. Correspondingly, range of average effective doses within the diagnostic radiology, radiotherapy and nuclear medicine facilities were 0.328-2.614, 0.383-0.728 and 0.448-0.695 mSv, respectively. Throughout the study period, an average dose per medical institution of 3 mSv and an average dose per exposed worker of 0.69 mSv were realised. Exposed workers in diagnostic radiology primarily received most of the individual annual doses >1 mSv. The entire study period had 705 instances in which exposed workers received individual annual doses >1 mSv. On thermoluminescent dosemeter (TLD) return rates, facilities in Volta and Eastern Regions recorded highest return rates of 94.3% each. Ashanti Region recorded the least TLD return rate with 76.7%.     

Occupational exposures of Chinese medical radiation workers in 1986-2000

Data on occupational exposures from medical uses of radiation in China during 1986-2000 are presented. Individual dose monitoring results in the reports of monitoring centres in different provinces in China during 1986-2000 were collected as the basic data. These data were summarised and then analysed. From 1986 to 2000, in diagnostic radiology, nuclear medicine and radiotherapy, the annual collective effective doses varied within the range 122.4-206.6, 5.4-9.3 and 4.1-10.3 man Sv, respectively; the average annual effective dose in these categories varied within the range 1.5-2.2, 1.2-1.6 and 1.0-1.5 mSv, respectively. Almost all the average annual effective doses in medical uses of radiation were <3 mSv in 1986-2000, and no monitored workers were found to have received an occupational exposure >50 mSv in a single year or >100 mSv in a 5-y period. After 1990, the protection status of medical radiation workers in China was sufficient.     

Occupational exposure to external ionising radiation in Poland, 1999

In 1999 about 6208 radiation workers from 389 departments were monitored by CLOR in Poland. The distribution of annual personal doses shows that 85% of controlled workers received doses below the MDL (0.4 mSv) and about 97% controlled workers received doses below 5 mSv. Doses higher than 50 mSv were received by three operators of industrial radiography units. The radiation workers under control are divided into four main work sectors: nuclear industry, research and education, medicine, and general industry. The average annual dose for all workers in each particular sector was 0.22 mSv, 0.22 mSv, 0.30 mSv and 0.80 mSv, respectively. The average annual dose for the entire monitored population was 0.47 mSv. The average annual dose in each particular sector for number of workers receiving E > 0, i.e. Hp(10) > or = 0.4 mSv, amounted to 1.78 mSv, 2.03 mSv, 1.88 mSv and 4.85 mSv, respectively. The average annual dose for the full number of workers receiving E > 0 was 3.21 mSv. This paper contains the detailed analysis of occupational exposure. The distributions of annual occupational exposure in different work sectors are also given.     

Dose level of occupational exposure in China

This paper discusses the dose level of Chinese occupational exposures during 1986-2000. Data on occupational exposures from the main categories in nuclear fuel cycle (uranium enrichment and conversion, fuel fabrication, reactor operation, waste management and research activity, except for uranium mining and milling because of the lack of data), medical uses of radiation (diagnostic radiation, nuclear medicine and radiotherapy) and industrial uses of radiation (industrial radiography and radioisotope production) are presented and summarised in detail. These are the main components of occupational exposures in China. In general, the average annual effective doses show a steady decreasing trend over periods: from 2.16 to 1.16 mSv in medical uses of radiation during 1990-2000; from 1.92 to 1.18 mSv in industrial radiography during 1990-2000; from 8.79 to 2.05 mSv in radioisotope production during the period 1980-2000. Almost all the average annual effective doses in discussed occupations were lower than 5 mSv in recent years (except for well-logging: 6.86 mSv in 1999) and no monitored workers were found to have received the occupational exposure exceeding 50 mSv in a single year or 100 mSv in a five-year period. So the Chinese protection status of occupation exposure has been improved in recent years. However, the average annual effective doses in some occupations, such as diagnostic radiology and coal mining, were still much higher than that of the whole world. There are still needs for further improvement and careful monitoring of occupational exposure to protect every worker from excessive occupational exposure, especially for the workers who were neglected before.     

Analysis of radiation workers' dose records in the Korean National Dose Registry

Data are presented on the externally received personal dose equivalent for radiation workers who used the Korea Radioisotope Association's personal monitoring and dose record keeping service since 1984, and provide initial statistics on Korean workers who have been exposed to ionising radiation in different occupations. The total number of workers registered during the period of 1984 to 1999 was 64,518. The number increased steadily and the accumulated dose also increased. The proportion of radiation workers by occupation was 38.4% for nuclear power plants, 20.3% for industrial organisations and 12.4% for non-destructive industry. The annual collective dose of radiation workers was 31.72 man.Sv in 1999. The mean annual dose by sex was 1.49 mSv for males and 0.56 mSv for females and the mean annual dose for a worker was 1.41 mSv with the highest mean dose being received by non-destructive industry (3.53 mSv). Very few workers (0.8%) received more than 20 mSv (2 rem) and only one more than 50 mSv, the legal limit for an annual dose increase. There has been a steady decline in the mean dose since 1984, showing a significant decrease in dose with time (p<0.001). The data showed that radiation protection in Korea was improving, though annual doses were still higher than other countries.     

Occupational exposure to ionising radiation in the region of Anatolia, Turkey for the period 1995-1999

For this study, the individual annual dose information on classified workers who are occupationally exposed to extended radiation sources in Turkey, was assessed and analysed by the Ankara Nuclear Research and Training Centre dosimetry service at the Turkish Atomic Energy Authority for the years 1995-1999. The radiation workers monitored are divided into three main work sectors: conventional industry (8.24%), medicine (90.20%) and research-education (1.56%). The average annual dose for all workers in each particular sector was 0.14, 0.38 and 0.08 mSv, respectively, in 1995-1999. This paper contains the detailed analysis of occupational exposure. The statistical analysis provided includes the mean annual dose, the collective dose, the distributions of the dose over the different sectors and the number of workers who have exceeded any of the established dose levels.     

Optimization of radiation protection for the control of occupational exposure in Ghana

Investigation of the optimization of protection of occupational exposed workers (OEWs) in Ghana had been carried out on the three practices in the country, namely medical applications, industrial radioisotope applications and research and education from 2002 to 2007. Mean annual effective dose and collective effective dose were estimated from dosimetry records from the Radiation Protection Institute of those occupationally exposed from 2002 to 2007. The mean annual effective dose estimated for about 650 OEWs per year ranged from 0.42 to 0.68 mSv compared with a global value of 0.5 mSv estimated by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR 2008 Report). This implies that efforts should still be made to institute as low as reasonably achievable culture in most practices in Ghana even though trend of doses incurred was low. The collective effective dose for this same period estimated ranged from 0.26 to 0.47 man Sv. A reference monetary value of the man sievert was estimated using the human capital approach for each year from 2002 to 2009; it ranged from 172 to 22 US $ per man Sv, which provided a basis for estimating the cost of averting a unit collective effective dose of 1 man Sv. This value could not be used for quantitative optimization since the range of mean annual effective dose estimated was below 1 mSv.     

Analysis of occupational doses of workers on the dose registry of the Federal Radiation Protection Service in 2000 and 2001

In 2000 and 2001 about 279 and 221 radiation workers, respectively, were monitored by the Federal Radiation Protection Service, University of Ibadan, in Nigeria. The distribution of the occupational doses shows that the majority of workers received doses below 4 mSv in each of the two years. The radiation workers in the two years are classified into two occupational categories: medicine and industry. The mean annual effective doses, collective doses and the collective dose distribution ratios for workers in each category and the entire monitored workers were calculated. The mean annual effective doses were compared with their corresponding worldwide values quoted by UNSCEAR. In each of the two years, a few workers in industry received doses higher than 50 mSv. The collective dose distribution ratio was found to be about 0.49, which is very close to the highest value of 0.5 in the range of values considered by UNSCEAR as normal for this parameter. This suggests that extra measures have to be taken, particularly in industry, to ensure that the proportion of workers at risk does not go outside this normal range. The occupational doses were also modelled by both the log-normal and Weibull distributions. Both distributions were found to describe the data in almost the same way.     

Individual and collective doses from cosmic radiation in Ireland

This paper assesses the individual and collective doses in Ireland due to cosmic radiation. Information on the exposure to cosmic radiation at ground level is reviewed and published data on the frequency of routes flown by Irish residents is used to calculate the dose due to air travel. Occupational exposure of aircrew is also evaluated. Experimental data on cosmic radiation exposure at ground level is in good agreement with international estimates and the average individual dose is calculated as 300 microSv annually. Published data on international air travel by Irish residents shows a 50% increase in the number of flights taken between 2001 and 2005. This increase is primarily on short-haul flights to Europe, but there have been significant percentage increases in all long-haul flights, with the exception of flights to Africa. The additional per capita dose due to air travel is estimated to be 45 muSv, of which 51% is accumulated on European routes and 34% on routes to the United States. Exposure of aircrew to cosmic radiation is now controlled by legislation and all airlines holding an Air Operator's Certificate issued by the Irish Aviation Authority are required to report annually the doses received by their employees in the previous year. There has been a 75% increase in the number of aircrew receiving doses >1 mSv since 2002. In 2004 and 2005 the average individual doses received by Irish aircrew were 1.8 and 2.0, mSv, respectively. The corresponding per caput dose for the entire population is <3 muSv. While this is low compared with the per caput doses from other sources of cosmic radiation, aircrew exposure represents a higher collective dose than any other identified group of exposed workers in Ireland.     

Transition in occupational radiation exposure monitoring methods in diagnostic and interventional radiology

Radiation exposure monitoring is a traditional keystone of occupational radiation safety measures in medical imaging. The aim of this study was to review the data on occupational exposures in a large central university hospital radiology organisation and propose changes in the radiation worker categories and methods of exposure monitoring. An additional objective was to evaluate the development of electronic personal dosimeters and their potential in the digitised radiology environment. The personal equivalent dose of 267 radiation workers (116 radiologists and 151 radiographers) was monitored using personal dosimeters during the years 2006-2010. Accumulated exposure monitoring results exceeding the registration threshold were observed in the personal dosimeters of 73 workers (59 radiologists' doses ranged from 0.1 to 45.1 mSv; 14 radiographers' doses ranged from 0.1 to 1.3 mSv). The accumulated personal equivalent doses are generally very small, only a few angiography radiologists have doses >10 mSv per 5 y. The typical effective doses are <10 μSv y(-1) and the highest value was 0.3 mSv (single interventional radiologist). A revised categorisation of radiation workers based on the working profile of the radiologist and observed accumulated doses is justified. Occupational monitoring can be implemented mostly with group dosimeters. An active real-time dosimetry system is warranted to support radiation protection strategy where optimisation aspects, including improving working methods, are essential.     

Analysis of whole-body doses received by occupationally exposed workers in Ireland (1996-1999)

The work described in this paper is based on the results of routine whole-body measurements carried out by the Radiological Protection Institute of Ireland Dosimetry Service from 1996 to 1999. Data on the occupational radiation exposures of monitored personnel are examined and have been found to follow the skewed distribution reported by UNSCEAR. The annual average effective dose for each major work practice over the 4 years is given and compared with the UNSCEAR reference value of 1.1 mSv per year for all occupations. Evidence suggests that improvements in procedures and the use of better equipment have resulted in a reduction in the numbers of workers receiving measurable doses.     

Occupational radiation exposure during removal of radioactive reactor components from GRR-1 pool

The aim of the study was to control occupational exposure during the removal of radioactive reactor components from a Greek research reactor pool. The method comprised the prediction of the radiation levels, the design of special shielding structures and the occupational dose assessment. Activation calculations were performed using the FISPACT code to predict the source term. Monte Carlo simulations using MCNP code were utilized to estimate the ambient dose equivalent rates. The results of the calculations were verified by measurements and were found to be in good agreement. Thermoluminescence dosemeter (TLD) and electronic personal dosemeter (EPD) were implemented to measure the radiation exposure of the workers. The total collective dose of 14 participating workers was 0.15 man mSv. The maximum individual effective dose was 0.02 mSv, and the maximum extremity equivalent dose was 0.09 mSv. The discussed method provides a useful tool enabling work planning during reactor decommissioning and renovation activities ensuring that exposures will be maintained ALARA.     

Radiation exposure assessment for portsmouth naval shipyard health studies

Occupational radiation exposures of 13,475 civilian nuclear shipyard workers were investigated as part of a retrospective mortality study. Estimates of annual, cumulative and collective doses were tabulated for future dose-response analysis. Record sets were assembled and amended through range checks, examination of distributions and inspection. Methods were developed to adjust for administrative overestimates and dose from previous employment. Uncertainties from doses below the recording threshold were estimated. Low-dose protracted radiation exposures from submarine overhaul and repair predominated. Cumulative doses are best approximated by a hybrid log-normal distribution with arithmetic mean and median values of 20.59 and 3.24 mSv, respectively. The distribution is highly skewed with more than half the workers having cumulative doses <10 mSv and >95% having doses <100 mSv. The maximum cumulative dose is estimated at 649.39 mSv from 15 person-years of exposure. The collective dose was 277.42 person-Sv with 96.8% attributed to employment at Portsmouth Naval Shipyard.     

Estimates of the occupational exposure to tenorm in the phosphoric acid production plant in Iran

Phosphate rock is used world wide for manufacturing phosphoric acid and several chemical fertilisers. It is known that the phosphate rock contains various concentrations of uranium, thorium, radium and their daughters. The subject of this study is the evaluation of the radiation exposure to workers in the phosphoric acid production plant due to technologically enhanced naturally occurring radioactive materials that can result from the presence of naturally occurring radioactive materials in phosphate ores used in the manufacturing of phosphoric acid. Radiation exposure due to direct gamma radiation, dust inhalation and radon gas has been investigated and external and internal doses of exposed workers have been calculated. Natural radioactivity due to (40)K, (226)Ra and (232)Th have been measured in phosphate rock, phosphogypsum, chemical fertilisers and other samples by gamma spectrometry system with a high-purity germanium. The average concentrations of (226)Ra and (40)K observed in the phosphate rock are 760 and 80 Bq kg(-1), respectively. Annual effective dose from external radiation had a mean value of ～0.673 mSv y(-1). Dust sampling revealed greatest values in the storage area. The annual average effective dose from inhalation of long-lived airborne was 0.113 mSv y(-1). Radon gas concentrations in the processing plant and storage area were found to be of the same value as the background. In this study the estimated annual effective doses to workers were below 1 mSv y(-1).     

Current status of personal dosimetry in industry, research and medicine in Lithuania

The personal dosimetry service of the Radiation Protection Centre performs individual monitoring for all the industrial, medical and research radiation workers. The RADOS and DTU TLD systems are used for monitoring of doses. The DTU TLD system is used for measurements of doses to extremities and for measurements of public external exposure. Finger ring TLDs are used in therapy which uses radiopharmaceuticals. The RADOS system is also used for evaluation of patients' doses in selected hospitals. The dosimetry service recently provided individual monitoring of approximately 3000 workers. The average occupational dose was about 1.06 mSv for medical workers and 3.2 mSv for industrial radiography workers in 1999. Detailed analysis of doses received by different categories of workers is performed. A system for the urgent review of work conditions in the case of increased dose has been set up.     

Natural radionuclides in zircon and related radiological impacts in mineral separation plants

The activity concentration of uranium and thorium present in zircon obtained from mineral sand industries are presented. External gamma radiation levels and inhalation of airborne dust are found to be the significant routes of radiation exposure to occupational workers. The annual average dose attributed to zircon processing is estimated to be 2.3 mSv in the plants under study. This paper presents the results of external gamma measurements, estimation of airborne radioactivity in zircon process locations and radon and thoron in the occupational environment of two mineral separation plants in India. Analyses of the solid wastes and liquid effluent generated and resultant environmental impacts are indicated.     

The overview of internal exposure monitoring in Lithuania

This study deals with analysis of situation and results of internal exposure monitoring of radiation workers and population in Lithuania. Radiation workers are assessed for internal exposures by direct methods--whole body counting or organ counting by gamma spectrometry at the Radiation Protection Centre and Ignalina Nuclear Power Plant (INPP). Results of monitoring of INPP and nuclear medicine workers show that no significant activities were detected. The annual committed effective doses of workers are <1 mSv. The measured average activity of 40K in males and females was 3.7 +/- 1.0 and 2.5 +/- 0.7 kBq, respectively. Mixed diet sampled at hospitals in 2001-5 was analysed for (90)Sr and (137)Cs activity concentrations. Average effective dose due to 90Sr and 137Cs in mixed diet was 0.6 +/- 0.2 and 0.47 +/- 0.13 microSv, respectively. Indoor radon measurements were done in multi-storey houses. Average concentration was 15.1 +/- 1.0 Bq m(-3). The annual effective dose aused by radon was 0.38 mSv.     

Occupational exposure in Portugal in 1999

This study reports the occupational radiation doses for external exposure received in 1999 by the radiation workers monitored by the Radiological Protection and Nuclear Safety Department (DPRSN) in Portugal. Occupational exposures arise from conventional industry, research laboratories, the health or medical sector, and mining. There are no nuclear power plants in the country. There are two dosimetry systems running simultaneously at DPRSN, one based on film dosimetry and the other on thermoluminescence dosimetry (TLD). In 1999, 8400 persons were monitored, 3100 with film and 5300 with TLD and the data presented in this report were obtained by using both technologies. The annual mean effective doses received from external radiation in the different fields of activity and the distribution of the annual effective dose by dose intervals are presented. The collective annual dose by field of activity is estimated and the contribution to the total annual collective dose is determined.