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PubMed2003

Conversion factors for a mobile survey method by car in the Chernobyl area.

Conversion factors for the purpose of mobile survey by car in the Chernobyl area have been evaluated using simulation calculations. In the calculations, the width of road is assumed as being 4 m, 10 m and 20 m and the surrounding area is divided into ten zones contaminated homogeneously by 137Cs with different depth profiles in the ground. The air kerma contribution from all zones to the road is simulated. A conversion factor is calculated by dividing the air kerma rate in typical land-use adjacent to the road by that on the road. Conversion factors in various land uses around the roads are examined. The calculated conversion factors agree with the conversion factors measured in the Chernobyl area within an accuracy of 20%. Further, basic data, needed for composing conversion factors appropriate to other contaminated regions with different depth distributions from the Chernobyl area, are also indicated.

Air Pollutants, Radioactive↗

PubMed2001

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.

Gamma Rays↗

PubMed2001

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.

Adult↗

PubMed2004

International exchange of emergency phase information and assessments: an aid to national/international decision makers.

This paper discusses a collaborative project (1) to demonstrate the feasibility and benefit of a system seeking early review, in a 'quasi peer review' mode, of nuclear accident plume and dose assessment predictions by four major international nuclear accident emergency response systems before release of calculations to respective national authorities followed by (2) sharing these results with responsible national/international authorities, (3) development of an affordable/accessible system to distribute results to countries without prediction capabilities and (4) utilisation for exercises and collaboration studies. The project exploits Internet browser technology and low-cost PC hardware, incorporates an Internet node, with access control, for depositing a minimal set of XML-based graphics files for presentation in an identical map format. Side-by-side viewing and televideo conferencing will permit rapid evaluation, data elaboration and recalculation (if necessary) and should produce strong consensus among decision makers. Successful completion affords easy utilisation by national/international organisations and non-nuclear states at risk of trans-boundary incursion.

Decision Support Systems, Management↗

PubMed2004

Demonstrating the European capability for airborne gamma spectrometry: results from the eccomags exercise.

Airborne gamma spectrometry (AGS) is being increasingly recognised as an important means for mapping environmental radioactivity in emergency response. Progress has been made in recent years towards methodological convergence and cooperation between European teams. Recently, an international comparison was undertaken in SW Scotland in 2002 to evaluate AGS and ground-based methods. Teams from 18 institutions in 10 European countries attended, collecting some 140,000 AGS spectra, with 750 laboratory gamma spectrometry analyses and 120 in situ observations from the ground sites. Comparisons between AGS and ground-based methods have confirmed the validity of AGS protocols. A composite mapping task, where AGS teams recorded data over adjacent parts of a 90 x 40 km2 area within a few days, confirmed the ability of teams to work together in an effective manner. This paper provides a summary of the results of the exercise. These demonstrate the operational capabilities of European AGS teams and confirm the quantitative nature of the method.

Aircraft↗

PubMed2004

Airborne gamma spectrometry--towards integration of European operational capability.

Airborne gamma spectrometry is an excellent tool for finding out in a timely manner the extent and magnitude of the dispersion of radioactive materials resulting from a nuclear disaster. To utilise existing European airborne monitoring capabilities for multilateral assistance in an accident is a complex administrative and technical matter. Several international exercises have been organised demonstrating the capability to cooperate. However, efficient mutual assistance between European countries requires conceptual work, standards and harmonisation of software. A unified radiological vocabulary and data exchange format in XML need to be developed. A comprehensive database is essential for data assimilation. An operations centre is needed for management and planning of surveys.

Aircraft↗

PubMed2004

Can the confidence in long range atmospheric transport models be increased? The pan-european experience of ensemble.

Is atmospheric dispersion forecasting an important asset of the early-phase nuclear emergency response management? Is there a 'perfect atmospheric dispersion model'? Is there a way to make the results of dispersion models more reliable and trustworthy? While seeking to answer these questions the multi-model ensemble dispersion forecast system ENSEMBLE will be presented.

Air Movements↗

PubMed2004

Dose due to mushroom ingestion in Spain.

The dose due to ingestion of mushrooms depends on their radioactive content. However, not all the mass of the mushroom ingested is digested and assimilated completely by man. To analyse the degree of assimilation of the radioactive content of mushrooms, we have carried out culture under controlled laboratory conditions for Pleurotus eryngii mushrooms to which we added known activities of 134Cs, 85Sr and 239Pu. We then applied the Van Soest method to the fruiting bodies, which were obtained in order to determine the fraction of these radionuclides associated with the major components of the cell that are assimilable by man. Finally, on the basis of the results, we determined the dose due to 137Cs, 90Sr and (239+240)Pu for several mushroom species collected in different natural and semi-natural ecosystems in Spain.

Agaricales↗

PubMed2004

Measurements of environmental background radiation at location of coal-fired power plants.

Environmental radiation monitoring in the vicinity of coal-fired power plants which are used primarily to determine the variability in measured background exposures are presented in this article; this is in order to estimate the contribution due to the plants' operation. Measurements have been done using a multi-element, high sensitive dosemeter system composed of three solid, properly filtered, sintered CaSO4:Dy thermoluminescent detectors, and one low-atomic number, MgB4O7:Dy,Na thermoluminiscencent detector produced at the Vinca Institute. The dosemeters were deployed quarterly 1 m above ground level at locations within 20 km of the power plants. Twenty urban and suburban measured stations were established. Measurements were carried out over one year period, from the beginning of the summer of 1995 to the end of the spring of 1996. The registered annual absorbed dose in air, from all of the 20 stations, vary from 0.91 to 1.46 mGy a(-1). One of the highest values of the annual absorbed dose was measured at the station near to the plant, i.e. at the place the most exposed to the lighter fly ash from the plant stack, as it was expected. The annual absorbed dose registered at the measuring stations that were selected as a control because they were situated practically away from possible influence of the plants were from 0.91 to 0.98 mGy a(-1). The above values of absorbed doses become very important, by concurrence of the circumstances, because they represent the zero background radiation level before the incidence of depleted uranium over former Yougoslav territory in the Kosovo region in the spring of 1999. These measured absorbed dose exposures have to be compared with corresponding absorbed dose rates from the natural sources, such as soil having an exposure of 18-93 nGy h(-1) (average 35 nGy h(-1)) according to the UNSCEAR 2000 Report. This investigation has been primarily done in order to check the impact of coal-fired power plants on the background radiation level in its vicinity. According to the experimental results, influence was confirmed both qualitatively and quantitatively.

Air Pollution, Radioactive↗

PubMed2004

Influence of radionuclides distributed in the whole body on the thyroid dose estimates obtained from direct thyroid measurements made in Belarus after the Chernobyl accident.

Thyroid dose reconstruction is most accurate when using the results of direct thyroid measurements, in which gamma radiation emitted by radionuclides present in the thyroid and in the remainder of the body is recorded by means of a radiation detector positioned against the neck. A large number of such measurements were performed in Belarus in May-June 1986. Owing to the short half-life of 131I and to the intake and accumulation of caesium radioisotopes (mainly 134Cs and 137Cs) in the body, the thyroid doses derived from thyroid measurements made after the beginning of June 1986 have so far been often considered to be unreliable. To evaluate the influence of the caesium radioisotopes to the signal recorded by an instrument performing measurement of 131I activity in the thyroid, a Monte Carlo method was used to calculate the calibration factors of that instrument. These calculations were made for males of six reference ages: newborn, 1, 5, 10 and 15 years old, and adult. The calibration factors were combined with estimated time-dependent intake functions for 131I and caesium radioisotopes. The fractions of the instrument indications that were due to 131I in thyroid were thus estimated as a function of the age of the subject that was measured and of the time elapsed since the accident. Using this information when processing the thyroid measurements made in May 1986 would improve the accuracy of the thyroid dose estimates, and may make it possible to use a larger proportion of the thyroid measurements made in June 1986.

Adolescent↗

PubMed2005

Comparative study of Dutch and German emergency-management models for near border nuclear accidents.

Four institutes, all of which are involved in nuclear-emergency management in the Dutch-German border region, have compared their short-range dispersion and radiological dose models using scenarios consisting of single-station meteorology and two dispersed radionuclides. After adjustment of some of the parameters, the consequence of the differences in parameters on the effective dose was quantified at several stages from source to exposure. Results for the neutral stability class agreed within a factor of four. Variations in wet deposition of radioactive material, giving rise to external radiation from the ground, can cause significant variations to the effective dose. Furthermore, the way the different emergency-management tools model the atmospheric dispersion for a stable stability class in the horizontal plane can generate large differences. Finally, the methodology of calculating cloudshine is not comparable among the models, which causes the effective dose near the source to show large deviations for high emission sources.

Accidents↗

PubMed2006

Dosimetry of environmental radiation--a report on the achievements of EURADOS WG3.

Owing to the fact that a nuclear accident is a border-crossing problem, all national active monitoring systems should measure the same quantity with a comparable level of precision. Also, the sensitivity of the systems must be such that sudden changes in the environmental dose rate are recognised and a radiological incident is clearly identified. Thus, international intercomparisons of the so-called Early Warning Systems are the best method to assure high quality measurements. Supported by the European Commission within the scope of the 4th and 5th Framework Programmes, intercomparisons of these Early Warning Systems were organised by European Radiation Dosimetry (EURADOS) Working Group 3 (WG3) in 1999 and 2002. The methods developed for this purpose are based on controlled irradiation of the systems and the determination of their responses to secondary cosmic radiation. One of the major problems turned out to be the correct subtraction of the internal background. Investigating this problem was only possible by carrying out measurements at almost zero dose rate, as available in the Underground Laboratory for Dosimetry and Spectrometry (UDO) maintained by Physikalisch-Technische Bundesanstalt. Progress was also achieved with regard to including in situ gamma spectroscopy systems in the 2002 intercomparison. For these systems, the UDO irradiation facility provides a unique possibility to measure the spectral responses to monoenergetic photons.

Air Pollution, Radioactive↗

PubMed2006

The second EURADOS intercomparison of national network systems used to provide early warning of a nuclear accident.

In 1999 and 2002, the EURADOS Working Group on Environmental Monitoring organised two European intercomparison exercises of national network systems used to provide early warning in case of a nuclear accident. In total, 12 European countries, represented by more than 40 scientists, participated in these two intercomparisons with more than 35 different dose rate detectors. In addition, an in situ gamma spectrometry intercomparison was performed by a group of European scientists during the 2002 exercise. Results of these spectrometry measurements will be reported elsewhere. This report summarises the results of the second intercomparison, performed in 2002, at the environmental dosimetry facilities of the Physikalisch-Technische Bundesanstalt (PTB) in Germany. The unique combination of the ultra-low background Underground Laboratory (UDO) and two free-field sites (a floating platform on a lake showing an almost pure cosmic radiation field and a free-field gamma ray irradiation facility) provide the particular opportunity to precisely quantify the inherent background of the detectors and to calibrate them almost free of any background and traceable to PTB's primary standards. In addition, the intercomparison comprised investigations on the energy and dose rate dependence of the detectors' response to gamma radiation as well as on the response to cosmic radiation. Finally, the sensitivity of the detector systems to small dose rate variations, similar to that caused by a passing overhead radioactive plume, was studied under realistic free-field conditions. Following the Council Directive 96/29/EURATOM, the participants of the 2002 intercomparison were asked to report their results in terms of the operational quantity ambient dose equivalent, H(*)(10). Although the verification of the individual calibrations showed smaller discrepancies than those in the 1999 intercomparison, in a few cases, these discrepancies would be still unacceptably high in the case of a real emergency situation as demonstrated by the plume results. This shows the clear need for further efforts towards a European harmonisation in environmental dosimetry. For this purpose, a further intercomparison shall be held at the PTB in 2006, especially with the participation of new members of the European Union.

Air Pollution, Radioactive↗

PubMed1965