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 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.     

An assessment of annual whole-body occupational radiation exposure in Ireland (1996-2005)

Whole-body occupational exposure to artificial radiation sources in Ireland for the years 1996-2005 has been reviewed. Dose data have been extracted from the database of the Radiological Protection Institute of Ireland, which contains data on >95% of monitored workers. The data have been divided into three sectors: medical, industrial and education/research. Data on exposure to radon in underground mines and show caves for the years 2001-05 are also presented. There has been a continuous increase in the number of exposed workers from 5980 in 1996 to 9892 in 2005. Over the same time period, the number of exposed workers receiving measurable doses has decreased from 676 in 1996 to 189 in 2005 and the collective dose has also decreased from 227.1 to 110.3 man millisievert (man mSv). The collective dose to workers in the medical sector has consistently declined over the 10-y period of the study while that attributable to the industrial sector has remained reasonably static. In the education/research sector, the collective dose typically represents 5% or less of the total collective dose from all practices. Over the 10 y of the study, a total of 77 914 annual dose records have been accumulated, but only 4040 (<6%) of these represent measurable radiation doses in any given year. Over the same time period, there were 283 instances in which exposed workers received individual annual doses >1 mSv and 21 of these exceeded 5 mSv. Most of the doses >1 mSv were received by individuals working in diagnostic radiology (which also includes interventional radiology) in hospitals and site industrial radiography. There has been only one instance of a dose above the annual dose limit of 20 mSv. Evaluating the data for the period 2001-05 separately, the average annual collective dose from the medical, industrial and educational/research sectors are approximately 60, 70 and 2 man mSv with the average dose per exposed worker who received a measurable dose being 0.32, 0.79 and 0.24 mSv, respectively. Diagnostic radiology and site industrial radiography each represents >60% of the collective dose in their respective sectors. Available data on radon exposure in one underground mine and in three show caves indicate an annual collective dose of 75 man mSv from these work activities. By comparison, previous estimates of exposure of Irish air crew to cosmic radiation have given rise to an estimated collective dose of 12 000 man mSv. It can be concluded therefore that the natural radioactivity sources account for well >90% of all occupational exposure in Ireland. This evaluation does not include an estimate of exposure to radon in above-ground workplaces-these data are currently being evaluated and their inclusion will increase both the total occupational collective dose as well as the percentage of that dose due to natural radiation.     

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.     

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.     

Occupational radiation protection dosimetry in Nigeria

The general features of occupational radiation protection dosimetry in Nigeria within the period 1990-1999 have been summarised. About 640 personnel, representing about 25% of the estimated number of radiation workers in Nigeria, were monitored by the TL dosimetry technique during the period, with the majority being the personnel of the teaching hospitals across the country. Most private establishments, especially the X ray diagnostic centres, operate without dosimetry coverage or supervision by a regulatory authority. The weighted mean of the annual effective dose ranged between 0 and 28.97 mSv with the upper limit of collective effective dose being 18.47 man.Sv per year. The individual risk estimate due to this is about 1.5 x 10(-3) per year and this was among the medical personnel. The value could be more if all radiation workers in the country were monitored.     

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.     

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.     

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 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.     

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.     

Radiation protection for accompanying person and radiation workers in PET/CT

The purposes of the present study are to measure the total radiation doses for the radiation workers and for the accompanying person to the patients in positron emission tomography (PET)/computed tomography (CT) imaging. Urines samples from the patients were collected at 43, 62, 87, 117, 238, 362 min after the 555-MBq (18)flour-fluorodeoxyglucose ((18)F-FDG) injection and activities were measured. Dose rates were recorded using a Geiger-Muller counter and the total radiation doses were measured with using an electronic personnel dosemeter. According to the results here, 18.4 % of (18)F-FDG was excreted in the urine in 117 min after injection. At 117th min after injection, dose rates were determined as 345, 220, 140, 50 and 15 μSv h(-1), at proposed distances. The radiation doses after 117 min were measured as 3.92 mSv at 0.1 m, 2.11 mSv at 0.25 m and 1.08 mSv at 0.5 m. In conclusion, radiation protection will be sufficient within 2 h after (18)F-FDG injection for PET/CT imaging in daily practice.     

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.     

Personal dose monitoring of employees at the institute of modern physics, China

The radiation field at the accelerator facility consists of radiation produced immediately and of secondary radiation induced by activation etc. As the accelerator building and the experimental hall are closed and inaccessible during accelerator operation, the exposure received by the employees at the IMP (Institute of Modern Physics) comes almost totally from the induced radiation. The methods and the results of personal dose monitoring from 1986 to 1999 at the IMP are presented. During the period, the total number of monitored individuals was 1960, and the average annual effective dose was 0.10 mSv. The number recording less than 0.1 mSv of effective dose was 1471 individuals. amounting to 77% of the total. Only six individuals had received effective doses between 5.0 mSv and 10 mSv. The maximum effective dose of 10 mSv was received by workers repairing the accelerator.     

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.     

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.     

A study of environmental radioactivity measurements for Cankiri, Turkey

This study is the first to assess the level of background radiation for the Cankiri province of Turkey. Indoor air radon concentrations were determined using Columbia Resin-39 nuclear track detectors and the average (222)Rn activity was found to be 44 Bq m(-3) (equivalent to an annual effective dose of 1.1 mSv). Measurements of gamma doses in outdoor air were performed using a portable plastic scintillation detector and the average gamma absorbed dose rate was found to be 8 μR h(-1) (corresponding to an annual effective dose of 87.7 μSv). Radionuclide activity concentrations in soil samples were measured through gamma-ray spectrometry and the average activities were determined as 17.7, 22.3, 357 and 4.1 Bq kg(-1) for the radionuclides (238)U, (232)Th, (40)K and (137)Cs, respectively. The average annual effective dose from the natural radioactivity sources ((238)U series, (232)Th series and (40)K) was calculated to be 44.4 μSv. Radioactivity levels of drinking water samples were carried out using a low-background proportional counter and the average gross alpha and beta activities were obtained as 0.25 and 0.26 Bq l(-1), respectively (equivalent to an annual effective dose of 184 μSv). The average radon concentrations in indoor air and the average radionuclide activities in soil were found to be lower than most Turkish cities while higher levels of outdoor gamma dose rate and water radioactivity were observed. The results of this study showed that the region's background radioactivity level differs considerably from the reported data for Turkish cities.     

Hand exposure in nuclear medicine workers

As a result of the gamma radiation emitted by radioactive elements (e.g. 99mTc and 131I) used in nuclear medicine laboratories for diagnostic and therapeutic purposes, nuclear medicine workers are exposed to whole-body doses. These doses arc usually measured by using individual film dosemeters. Lead or lead glass shields used during the handling of radioisotopes minimise the whole-body doses received. Nevertheless, part of the job has to be performed manually, hence the hands are more exposed to radiation. This paper presents the results of measuring the equivalent dose to the hands of workers employed in five selected nuclear medicine laboratories where technetium and iodine radioisotopes are in common use. Sixty workers, including physicians, nurses, radiopharmacists and technicians, were included in the study. Doses were measured at 1 month intervals. The study indicated that, in some instances, the danger of radiation dose to the hand may be significant. Monthly doses exceeded 50 mSv, which may suggest that an annual dose may be higher than 500 mSv.     

Occupational exposure to ionising radiation with thermoluminescence dosimetry system in Turkey, in 2003

The individual annual dose information on classified workers who are occupationally exposed to extended radiation sources by using thermoluminescence dosimetry system, in Turkey, was assessed and analysed by the Ankara Nuclear Research and Training Centre (ANAEM) dosimetry service at the Turkish Atomic Energy Authority (TAEK) for the year 2003. A total of 3721 persons were monitored with TLD and the data presented in this report were obtained by using TLD technology in 2003. The annual mean effective doses received from external radiation in different fields of activities 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.