External doses in the environment from the Tokai-mura criticality accident

On 30 September 1999, a criticality accident occurred at a uranium processing plant operated by JCO in Tokai-mura, Japan and the criticality remained for about 20 h. Almost all doses to the neighbouring residents were brought by neutrons and gamma rays emitted from the facility rather than fission products released to the environment. External doses in the environment were evaluated using radiation monitoring data and radiation transport calculation. A pattern of the dose rate evolution was modelled based on the records of gamma ray monitors in the JCO facilities. Relations between the ambient dose equivalent rates of neutrons/gamma rays and the distance from the facility were determined from the monitoring data obtained around the accident site. Conversion from the ambient dose equivalent to the effective dose equivalent was made assuming the energy spectra calculated by the radiation transport code, ANISN. It was estimated that the people who stayed outside the 350 m zone would receive doses of less than 1 mSv.     

An estimate of the effect of FMVSS 301—fuel system integrity

Federal Motor Safety Standard No. 301—Fuel System Integrity—was first promulgated, effective 1 January 1968. Its purpose was to reduce the fatalities, injuries and damage caused by fires occurring in automobile crashes. It was subsequently strengthened (1 September 1975 and again 1 September 1976) and extended to all four wheel vehicles of Gross Vehicle Weight less than 10,000 pounds (1 September 1976). This paper uses existing police accident and fire department data from a total of 10 states to estimate the effects of FMVSS 301 on the passenger car crash population. Only very limited information on the rates of fuel spillage were found, so the paper concentrates on the rate of fires in crashes involving passenger cars. Some information on fatalities from the Fatal Accident Reporting System (FARS) is also used. Post-crash passenger car fires are rare. Reported rates ranged from less than one per thousand crashes up to nearly five per thousand crashes. Rates averaged about two fires per thousand police reported crashes or about three fires per thousand towaway crashes. Fatalities are also quite rare. In 1976, 814 persons were killed in 683 vehicles that caught fire after a crash. In 1977, 982 persons died in 858 such vehicles. Fire department data proved only of supplemental use, because a car fire could not be identified with a crash. Police accident data showed smaller post-crash fire rates with newer model year cars. While this is consistent with a beneficial effect of FMVSS 301, it could also be caused by an increasing likelihood of fire in a crash for older cars. A linear trend in age for ear fire rates was statistically significant only in the Illinois data. Combining the data from 6 states showed a 16% reduction in post-crash passenger car fire rates coincident with the first promulgation of the FMVSS 301 in 1968. An additional 14% reduction occurred coincidently with the later versions starting with the 1976 model year. A total reduction of 25% was estimated comparing pre-standard models with the current standard. These reductions were all statistically significant. While it was not possible to eliminate the possibility that aging contributed to the observed reductions, or that other factors could have influenced these reductions, it seems reasonable to conclude that some of the benefit resulted from the standard.     

Contribution of different foodstuffs to the internal exposure of rural inhabitants in Russia after the Chernobyl accident

In a large village, Veprin of the Bryansk region of Russia contaminated with radionuclides as a result of the Chernobyl accident, 137Cs concentration in food products of agricultural produce and natural origin was regularly measured, local inhabitants were polled on the composition of their diet, and the 137Cs content in their bodies was measured at the same time. These results were used as the basis for calculation of annual effective doses of internal exposure to inhabitants and for reconstruction of the dose during the entire period after the accident (1986-1996). The efficiency of countermeasures performed for reduction of the internal dose was assessed. The internal dose in inhabitants during the 10 years after the accident was shown to be reduced by countermeasures by a factor of 2, namely down to 35 mSv instead of the expected 70 mSv. The dose of external gamma radiation during the same time period is close to the obtained dose of internal exposure. The presence of peat and water-meadow soils in the vicinity of this village that are characterised by high transfer factors for radionuclides from soil to vegetation causes a high contribution of internal exposure to the total dose of population exposure. The contribution of natural products to the internal dose increased from 6% in 1987 increased to 25% in 1996. The individual content of 137Cs in the body of inhabitants reliably correlates with consumption of milk in the initial period after the accident and with consumption of forest mushrooms in the subsequent period.     

Three Mile Island epidemiologic radiation dose assessment revisited: 25 years after the accident

Over the past 25 years, public health concerns following the Three Mile Island (TMI) accident prompted several epidemiologic investigations in the vicinity of TMI. One of these studies is ongoing. This commentary suggests that the major source of radiation exposure to the population has been ignored as a potential confounding factor or effect modifying factor in previous and ongoing TMI epidemiologic studies that explore whether or not TMI accidental plant radiation releases caused an increase in lung cancer in the community around TMI. The commentary also documents the observation that the counties around TMI have the highest regional radon potential in the United States and concludes that radon progeny exposure should be included as part of the overall radiation dose assessment in future studies of radiation-induced lung cancer resulting from the TMI accident.     

Radiation dose to members of public residing around uranium mining complex, Jaduguda, Jharkhand, India

Uranium mining activities in the Jaduguda region of Jharkhand state, India have been carried out for the last five decades. Radioactive releases from mines, ore processing facility and tailings pond may increase the natural radiation dose to members of the public residing around the complex. It is, therefore, imperative to investigate the radiological condition around the uranium mining complex and assess the dose received by them. In the present study, it was estimated that the average radiation dose from all exposure pathways to the public living in villages around the mining complex is 2.5 mSv y(-1) and around 50 % contributed due to inhalation of radon and its progeny. The external radiation dose due to terrestrial and cosmic activity is estimated to be 1.1 mSv y(-1), which is 40 % of the total dose and ingestion dose contributes only 3% to the total dose.     

Radon exposure in uranium mining industry vs. exposure in tourist caves

There is a fairly general consensus among health physicists and radiation professionals that exposure to radon progeny is the largest and most variable contribution to the population's exposure to natural sources of radiation. However, this exposure is the subject of continuing debate concerning the validity of risk assessment and recommendations on how to act in radon-prone areas. The purpose of this contribution is to situate the radon issue in Spain in two very different settings. The first is a uranium mining industry located in Saelices el Chico (Salamanca), which is under strict control of the Spanish Nuclear Safety Council (CSN). We have measured radon concentrations in different workplaces in this mine over a five-year period. The second setting comprises four tourist caves, three of which are located in the province of Cantabria and the fourth on the Canary Island of Lanzarote. These caves are not subject to any administrative control of radiation exposure. Measured air 222Rn concentrations were used to estimate annual effective doses due to radon inhalation in the two settings, and dose values were found to be from 2 to 10 times lower in the uranium mine than in the tourist caves. These results were analysed in the context of the new European Basic Safety Standards Directive (EU-BSS, 1996).     

Time and distance to first accident and driving patterns of young drivers with pay-as-you-drive insurance

We conducted a study of approximately 16,000 drivers under the age of 30 that had purchased a pay-as-you-drive insurance policy, where their risk of being involved in a crash was analyzed from vehicle tracking data using a global positioning system. The comparison of novice vs. experienced young drivers shows that vehicle usage differs significantly between these groups and that the time to the first crash is shorter for those drivers with less experience. Driving at night and a higher proportion of speed limit violations reduces the time to the first crash for both novice and experienced young drivers, while urban driving reduces the distance traveled to the first crash for both groups. Gender differences are also observed in relation to the influence of driving patterns on the risk of accident. Nighttime driving reduces the time to the first accident in the case of women, but not for men. The risk of an accident increases with excessive speed, but the effect of speed is significantly higher for men than it is for women among the more experienced drivers.     

Utilizing the eigenvectors of freeway loop data spatiotemporal schematic for real time crash prediction

The concept of crash precursor identification is gaining more practicality due to the recent advancements in Advanced Transportation Management and Information Systems. Investigating the shortcomings of the existing models, this paper proposes a new method to model the real time crash likelihood based on loop data through schematic eigenvectors. Firstly, traffic volume, occupancy and density spatiotemporal schematics in certain duration before an accident occurrence were constructed to describe the traffic flow status. Secondly, eigenvectors and eigenvalues of the spatiotemporal schematics were extracted to represent traffic volume, occupancy and density situation before the crash occurrence. Thirdly, by setting the vectors in crash time as case and those at crash free time as control, a logistic model is constructed to identify the crash precursors. Results show that both the eigenvectors and eigenvalues can significantly impact the accident likelihood compared to the previous study, the proposed model has the advantage of avoiding multicollinearity, better reflection of the overall traffic flow status before the crash, and improving missing data problem of loop detectors.     

Is the radon risk overestimated? Neglected doses in the estimation of the risk of lung cancer in uranium underground miners

Only the exposure to inhaled radon decay products is usually taken into account in the determination of the risk of radiogenic lung cancer in uranium miners. However, the elevated lung cancer risk in uranium miners is due to the total dose of radiation received by that organ, not to the dose from inhaled radon-222 decay products (222Rn D.P.) alone. Lung doses from sources other than 222Rn D.P. may reach 25% to 75% of total effective dose, absorbed dose or equivalent lung dose, are correlated to 222Rn D.P. doses and are quite variable between facilities. Therefore, to neglect these doses leads to a systematic overestimation of the risk of lung cancer per unit 222Rn D.P. exposure, both through dose underestimation and dose misclassification. Correction for neglected doses and dose misclassification would pull the risk per unit radon exposure downward by a factor of at least two or three and bring the overall dose-effect relationship towards the no-effect null hypothesis, thereby increasing the likelihood of thresholds for lung cancer risk at indoor and today's uranium mine exposures.     

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.     

An evaluation of responsibility analysis for assessing alcohol and drug crash effects

This paper evaluates judgments of driver crash responsibility to estimate alcohol and drug impairment effects when exposure data are unavailable to calculate crash risks. Previous studies using responsibility judgments provided some evidence that responsibility is related to BAC. Other studies, some inferring responsibility, indicated a relation between responsibility and relative crash risk. Data are presented showing that responsibility judgments with a rating scale have high interrater reliability, and systematic relations with BAC suggest some validity in the ratings. A method is demonstrated for estimating relative crash risk from responsibility judgments with accident data, and the limitations of responsibility analysis are discussed. While alcohol and drug impairment effects are best determined with relative crash risks determined from accident and exposure data. responsibility analysis may provide useful indications in the absence of exposure data.     

Drug use and the severity of a traffic accident

Several studies have showed that driving under the influence of alcohol and/or certain illicit or medicinal drugs increases the risk of a (severe) crash. Data with respect to the question whether this also leads to a more severe accident are sparse. This study examines the relationship between the use of alcohol, illicit drugs and/or medicinal drugs and the severity of an accident within a group of drivers that were involved in a crash in The Netherlands. Blood samples of 993 drivers, collected in the period from October 1998 through September 1999, were linked to accident characteristics as available from the National Transport Research Centre. The outcome measure was the severity of the accident. An accident was considered severe when the accident had resulted in hospital admission or death. All the blood samples obtained after the accident were screened for the presence of alcohol, illicit drugs (opiates, amphetamines and amphetamine-like substances, cocaine and metabolites, methadone, cannabinoids) and medicinal drugs (benzodiazepines, barbiturates and tricyclic antidepressants). The strength of the associations between exposure to the different classes of alcohol/drugs/medicines and the severity of the accident was evaluated using logistic regression analysis and were expressed as odds ratios (OR), adjusted for age, gender, time of the day, day of the week and urban area. The most frequently detected drugs were cannabinoids, benzodiazepines and cocaine. Our results showed no clear association between the use of alcohol, illicit drug and/or medicinal drug use and the severity of the accident. Given the process of obtaining blood samples from drivers involved in accidents and the retrospective nature of the study, we cannot rule out the occurrence of selection bias. Therefore, our findings need further confirmation.     

Measuring aerosols generated inside armoured vehicles perforated by depleted uranium ammunition

In response to questions raised after the Gulf War about the health significance of exposure to depleted uranium (DU), the US Department of Defense initiated a study designed to provide an improved scientific basis for assessment of possible health effects on soldiers in vehicles struck by these munitions. As part of this study, a series of DU penetrators were fired at an Abrams tank and a Bradley fighting vehicle, and the aerosols generated by vehicle perforation were collected and characterised. A robust sampling system was designed to collect aerosols in this difficult environment and monitor continuously the sampler flow rates. The aerosol samplers selected for these tests included filter cassettes, cascade impactors, a five-stage cyclone and a moving filter. Sampler redundancy was an integral part of the sampling system to offset losses from fragment damage. Wipe surveys and deposition trays collected removable deposited particulate matter. Interior aerosols were analysed for uranium concentration and particle size distribution as a function of time. They were also analysed for uranium oxide phases, particle morphology and dissolution in vitro. These data, currently under independent peer review, will provide input for future prospective and retrospective dose and health risk assessments of inhaled or ingested DU aerosols. This paper briefly discusses the target vehicles, firing trajectories, aerosol samplers and instrumentation control systems, and the types of analyses conducted on the samples.     

Dosimetric models used in the Alpha-Risk project to quantify exposure of uranium miners to radon gas and its progeny

The European project Alpha-Risk aims to quantify the cancer and non-cancer risks associated with multiple chronic radiation exposures by epidemiological studies, organ dose calculation and risk assessment. In the framework of this project, mathematical models have been applied to the organ dosimetry of uranium miners who are internally exposed to radon and its progeny as well as to long-lived radionuclides present in the uranium ore. This paper describes the methodology and the dosimetric models used to calculate the absorbed doses to specific organs arising from exposure to radon and its progeny in the uranium mines. The results of dose calculations are also presented.     

Dosimetric calculations for uranium miners for epidemiological studies

Epidemiological studies on uranium miners are being carried out to quantify the risk of cancer based on organ dose calculations. Mathematical models have been applied to calculate the annual absorbed doses to regions of the lung, red bone marrow, liver, kidney and stomach for each individual miner arising from exposure to radon gas, radon progeny and long-lived radionuclides (LLR) present in the uranium ore dust and to external gamma radiation. The methodology and dosimetric models used to calculate these organ doses are described and the resulting doses for unit exposure to each source (radon gas, radon progeny and LLR) are presented. The results of dosimetric calculations for a typical German miner are also given. For this miner, the absorbed dose to the central regions of the lung is dominated by the dose arising from exposure to radon progeny, whereas the absorbed dose to the red bone marrow is dominated by the external gamma dose. The uncertainties in the absorbed dose to regions of the lung arising from unit exposure to radon progeny are also discussed. These dose estimates are being used in epidemiological studies of cancer in uranium miners.     

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.     

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.     

A feasibility study for transportable 241Am-in-lung and 241Am-in-nose-blow monitoring systems for use following a weapons accident

In a nuclear weapon accident involving fire or conventional explosion, most of the radiation dose received by people in the immediate vicinity would result from inhalation of 239Pu. This is accompanied by the nuclide 241Am, which is much easier to determine by external counting because of the 60 keV gamma ray emission. In the event of an accident, a priority would be to identify any people who have had intakes of 239Pu which were so large that decorporation therapy should be considered. Direct measurement of lung content provides the most rapid and convenient method for assessing intakes by inhalation. A transportable system has been considered as this could be deployed close to the site of the accident and would allow rapid measurements to be made. The feasibility of a transportable 241Am-in-nose-blow and nasal swab measurement system has also been considered. This would be used to help select people for 241Am-in-lung measurements.     

Radiation exposure to the population of Europe following the Chernobyl accident

On the occasion of the 20th anniversary of the Chernobyl accident an attempt has been made to evaluate the impact of the Chernobyl accident on the global burden of human cancer in Europe. This required the estimation of radiation doses in each of the 40 European countries. Dose estimation was based on the analysis and compilation of data either published in the scientific literature or provided by local experts. Considerable variability has been observed in exposure levels among the European populations. The average individual doses to the thyroid from the intake of (131)I for children aged 1 y were found to vary from approximately 0.01 mGy in Portugal up to 750 mGy in Gomel Oblast (Belarus). Thyroid doses to adults were consistently lower than the doses received by young children. The average individual effective doses from external exposure and ingestion of long-lived radiocaesium accrued in the period 1986-2005 varied from approximately 0 in Portugal to approximately 10 mSv in Gomel Oblast (Belarus) and Bryansk Oblast (Russia). The uncertainties in the dose estimates were subjectively estimated on the basis of the availability and reliability of the radiation data that were used for dose reconstruction in each country.