A fast and simple approach for the estimation of a radiological source from localised measurements after the explosion of a radiological dispersal device.

After an explosion of a radiological dispersal device, decision-makers need to implement countermeasures as soon as possible to minimise the radiation-induced risks to the population. In this work, the authors present a tool, which can help providing information about the approximate size of source term and radioactive contamination based on a Gaussian Plume model with the use of available measurements for liquid or aerosolised radioactivity. For two-field tests, the source term and spatial distribution of deposited radioactivity are estimated. A sensitivity analysis of the dependence on deposition velocity is carried out. In case of weak winds, a diffusive process along the wind direction is retained in the model.

Field tests using radioactive matter 2.

Results of field tests with explosive dispersal of a radioactive substance (RaS) are presented. The paper deals with tests exploiting artificial obstacles as a continuation and expansion of the tests used in this study performed in free area described previously. The essential goal of the tests was to estimate the distribution of the released RaS in the case of intentional abuse of radioactive sources and to get a set of data applicable to testing physical or mathematical models of propagation. Effects of different geometrical and meteorological conditions on the distribution of dispersed RaS were studied via the assessment of dose rate, surface and volume activities, aerosol mass and activity aerodynamic diameters. The principal results can be summarised as follows: the prevalent proportion of the activity of the radionuclide dispersed by an explosion (born by the blast wave and by air convection) is transferred to the detection system/collecting pads essentially within the first minute. Enhanced aerosol mass concentrations were also detected within the same period. The RaS carried by the blast wave passed through the polygon (50 m) within <1 s. An expected crucial impact of meteorological conditions at the moment of the explosion and shortly after was proved by the tests.

Field tests using radioactive matter.

During recent years, the assessment of possible radiological consequences of a terrorist attack associated with a release of radioactive substances (RaS) has been in the focus of interest of emergency preparedness and radiation protection specialists, as well as experts dealing with the dispersion of harmful substances in the atmosphere. Suitable tools for these analyses are applications of mathematical and physical models and simulation of this attack under 'realistic' conditions. The work presented here summarises the results of four tests, in which a RaS (a Tc-99 m solution) was dispersed over a free area with the use of an industrial explosive. Detection methods and techniques employed in these tests are described and values characterising the RaS dispersion--dose rates, surface activities in horizontal and vertical directions, volume activities, their space and time distributions and mass concentrations of aerosols produced after the explosion are presented and compared. These data will be applied to a comparison of outcomes of models used for the assessment of radiation accidents as well as in future field tests carried out under conditions of more complex geometry (indoor environment, terrain obstacles, etc.).

The Austria-Czech Republic co-operation in the field of radiation-emergency preparedness.

An overview on the long-term information exchange and co-operation between Austria and the Czech Republic in the field of radiation emergency preparedness and evaluation of radiological consequences of NPP accidents is provided. Initiated by the 'Melk Protocol' between the Czech and Austrian governments in December 2000 and its follow-up activities, the information exchange and co-operation between the Czech Republic and Austria in the field of radiation-emergency preparedness have been extended. Among others, a Working Group to compare radiological consequences of Beyond Design Basis Accident with a detailed inter-comparison program concerning atmospheric dispersion models, dose assessment methods and counter- measures was established. Based on this experience, an area for future co-operation in the field of emergency preparedness and information exchange between the Czech Republic and Austria is discussed.

The system of personal monitoring and the evaluation of occupational exposure in the Czech Republic.

New legislation concerning radiation protection, which was effective in the Czech Republic from 1997, followed from the recommendations of ICRP Publication 60 and the IAEA BSS, and included all new basic principles for the protection of radiation workers given in these documents. The requirements for the personal monitoring of category A workers and the recognition of the capacity of dosimetry services were identified as being very significant for radiation practice, and will be licensed by the State Office for Nuclear Safety (SONS). The license application will include the methodology of effective dose evaluation, the description of QA and QC of the service, the system of customer communication and dose recording and reporting. In accordance with legislation requirements, the licensee is obliged to report the personal and dosimetry data of category A radiation workers to SONS. For the purpose of data collection, SONS is developing the central registration system of occupational radiation exposure (CROE). Personal monitoring is managed for about 20,000 workers in 1500 workplaces. The paper describes in detail all current aspects of external monitoring of workers in the Czech Republic.

Medical radiation exposure of the Czech Republic paediatric population due to diagnostic nuclear medicine.

BACKGROUND: The information on the results of the survey of collective effective dose SE to children in the Czech Republic (CR) due to nuclear medicine examinations performed during the one-year period July 1995-June 1996. METHODS: The estimate of SE was based on the annual frequency of nuclear medicine procedures and the type and amount of administered radiopharmaceuticals provided by the General Health Insurance Company covering 75% of the CR population. RESULTS: In the period considered, 15,281 examinations of children younger than 18 years were performed, which represented 7.5% of total nuclear medicine examinations in the CR. The annual SE 43.8 man Sv formed 5.1% of the collective effective dose to all patients examined by nuclear medicine procedures in the CR. The contributions of procedures in various body systems of children to the annual SE: urinary tract 32.8%, bone 30.4%, brain 12.8 %, cardiovascular 6.4%, GIT 6.0%, thyroid 4.4%, lungs 3.0%, other 4.2%. In comparison with a similar survey performed in the CR in 1987 (based on a questionnaire) there was an increase in SE to children younger than 15 years by a factor of 2.8, mainly due to the expansion of kidney and bone investigations. CONCLUSIONS: The mean effective dose per exam to children younger than 15 years was 60% of that for adults, which was in agreement with the requirement that the radiation burden of children should not exceed that of adults. The use of data from the Insurance Company for regular conducting of such surveys appeared to be not as cumbersome and time-consuming as questionnaire surveys.

Early warning system in the Czech Republic.

Since the 1950's early warning networks (EWN) for monitoring of the radiation situation on the state territory have been established in the most European countries. In the Czech republic the radiation monitoring network exists, but new requirements, especially after accident at the Chernobyl nuclear power plants, called for restructure of EWN so that be able of permanent and telemetrized measurements. Based on these requirements, the program of the EWN establishment in the Czech republic is prepared. The realization is planned in two phases--in the first one 40 telemetrized measuring places in professional observatories of the Czech Hydrometereological Institute and in the network of measuring points of air contamination will be established. In the second phase EWN will be supplemented with selected (about 30) measuring stations of Automatic Immission Monitoring and measuring points of the Czech Army.