Automatic measurements with the Pille-ISS thermoluminescent dosimeter system on board the International Space Station (2003-2021).

The health risk of staying in space is a well-known fact, and the radiation doses to the astronauts must be monitored. The Pille-ISS thermoluminescent dosimeter system is present on the International Space Station (ISS) since 2003. We present an analysis of 60000 data points over 19 years from the 90 min automatic measurements and show a 4-day-long segment of 15 min measurements. In the case of the 15 min we show that the mapping of the radiation environment for the orbit of the ISS is possible with the Pille system. From our results the dose rates inside the South Atlantic Anomaly (SAA) are at least 1 magnitude higher than outside. From the 90 min data, we select orbits passing through the SAA. A statistical correlation in the SAA between the ISS altitude and monthly mean dose rate is presented with the Spearman correlation value of ρSAA=0.56. The dose rate and the sunspot number show strong inverse Pearson correlation (R2=-0.90) at a given altitude.

DOSE ASSESSMENT WITH DIFFERENT METHODS AFTER EXPOSURE TO 14C-LABELLED COMPOUNDS.

An accidental intake of 14C-labelled compound has been followed by long-term monitoring of urine samples. First, the intake and the committed effective dose have been calculated by a generally recommended method and as the value exceeded the investigation level, special dose estimation was performed. Recommendations from ICRP Publications were used for analyses but the measurement data did not fit these models, so the recommended parameter values were deemed incorrect for this compound and this exposure situation. With the measurement data, it was possible to set up a case-specific model based on the actual excretion functions. Afterwards, the committed effective dose was obtained from integrating the total number of decays in the body over 50 y. This case shows that 14C-labelled organic compounds could be very unique when they get incorporated into the body and the absorption and deposition parameters should be used with special care when estimating the dose.

Effects of the uncertainty contributions on the methods used for measurement uncertainty evaluation.

Adequate measurement uncertainty evaluation is crucial for supporting basic measurement purposes. However, the most prevalent approach, the uncertainty propagation, may not be validly applicable under certain conditions which require the use of less restricted alternative method (MCM-based propagation of distributions). We demonstrate the effects of major conditions, e.g. non-linear measurement model, non-Gaussian input quantities, on the reliability of uncertainty evaluation methods, highlighting the importance of the less frequently examined impact of uncertainty component contributions to the standard uncertainty of measurand.

Consequences of selecting different subsets of meteorological data to utilize in deterministic safety analysis.

Atmospheric dispersion calculation of radiological releases can be done for different purposes such as deterministic or probabilistic safety analysis, environmental impact assessment, emergency preparedness and response. The characteristics of the weather conditions used in such assessments have a significant effect on the results, thus it is vital to select appropriate meteorological data for the calculation. In this paper, we conduct a study on deterministic safety analysis of radiological releases and investigate the effects of using different subsets of a meteorological database for such assessments. We demonstrate that conducting deterministic dose assessment with a large site specific dataset of meteorological measurements and the use of a dose percentile is more beneficial than using one set of meteorological parameters. This is because variations in the meteorological condition have considerable effect on the dose results when using one set of meteorological parameters (e.g. worst case scenario) and less when a large meteorological database is used. We show that there can be a significant difference in the maximum dose computed with a large (at least annual with hourly resolution) meteorological database when there is a lack of data points or conversion of the parameters is needed, thus the 100th dose percentile is not optimal for verification of safety criteria fulfillment. It is better to use a relatively high percentile (e.g. from 80th to 99th), partly because it behaves more robustly and also because the use of the maximum dose (100th percentile) would be overly conservative. In case of meteorological data not being available for a sufficient temporal domain (e.g. data available for only one year or less), a multiplication factor - determined based on conservative assumptions and extensive studies on the possible spread of meteorological conditions and their effect at a given location - can be used for the comparison of a selected dose percentile with the safety limit. A 5-years long meteorological database provided by a meteorological measurement system was used in this study as an example to demonstrate and calibrate the methodology on a real database. The methods presented in this work are universal, they can be used in deterministic safety analysis of other nuclear facilities, and the results can facilitate the development of optimal meteorological databases.

International intercomparison on internal dose assessment (ICIDOSE 2017).

Internal dose assessment intercomparison exercises are useful tools: to verify the performance of an internal dosimetry service; to promote the harmonisation of dose assessments; and to identify weaknesses where further improvements are necessary. However, no such international intercomparisons have been performed for more than ten years. In the period May 2014-May 2016, the 'Technical Recommendations for Monitoring Individuals for Occupational Intakes of Radionuclides' were developed on the initiative of the European Commission, and later published within the EC Radiation Protection series, as RP188. In 2017 the Working Group 'Internal Dosimetry' of the European Radiation Dosimetry Group (EURADOS) organised a new intercomparison action, named ICIDOSE 2017, with the main aim of testing the practical applicability of these technical recommendations (RP188). Four case studies were proposed to participants: an artificially created case of inhalation of 60Co to simulate a simple special monitoring case; a real case of inhalation of 125I, with simple routine monitoring; a real and more complex case of incorporation of 234+235+238U, featuring both confirmatory and special monitoring; and a complex real case of an accidental incorporation of 241Am, including multiple administrations of diethylenetriamine pentaacetic acid (DTPA). Results were received from 66 participants from 26 countries; these were compared to reference or recommended solutions, developed for each case based on the application of RP188. In cases 1, 2 and 4 only a small number of results were identified as outliers, with the spread of all the results, expressed as the geometric standard deviation (GSD) of the values, assessed as 1.07, 1.04 and 1.43, respectively. This observed spread of the submitted results was improved from those obtained from similar cases in previous intercomparison exercises, showing that the availability of RP188 contributes to the harmonisation of the internal dose assessment process. There was a much wider spread of results for the uranium case: this case was characterised by an absence of any prior knowledge of the exposure scenario, and participants assumed a range of different exposure pathways and patterns.

Evaluation of Hungarian monitoring results and source localization of the 106Ru release in the fall of 2017.

Anthropogenic 106Ru has been detected in the environment from late September to early October 2017 by several European environmental radiological monitoring networks. The paper presents the comprehensive evaluation of Hungarian monitoring results related to the occurrence of 106Ru in various environmental compartments (airborne particulates, deposition, plants, and terrestrial indicators), which was implemented to determine the temporal and spatial variation of the contaminant on a national scale and also to verify the findings based on the data arising from environmental monitoring at a local scale in Budapest. Difficulties in direct comparison of the diverse reported data were also considered; results arising from varied sampling periods were corrected with account taken of the relation between the sampling duration and 4-day-long plume residence (estimation based on the daily monitoring of air and backward trajectory analysis). Integrated analysis of air and deposition measurements and meteorological data was also performed; the deposition processes were investigated by establishing the correlations of activity concentrations measured in the atmosphere and in the deposition samples. In order to study the temporal distribution and spatial localization of the 106Ru contamination and to interpret the measurements at ground level, backward trajectory analysis was performed with HYSPLIT model. The backward trajectory simulations suggested that the release had probably occurred during the last week of September 2017 from the geographical area between Volga and the Urals. In addition, assessment of the doses due to the 106Ru release was implemented considering external exposure from cloudshine and groundshine and internal exposure via inhalation.

Methods, results and dose consequences of 106Ru detection in the environment in Budapest, Hungary.

From late September to early October of 2017, the majority of European networks involved in environmental radiological monitoring - including the environmental monitoring system of the KFKI Campus in Budapest - detected 106Ru isotope of artificial origin in the atmosphere. The reported values higher than the minimum detectable activity (MDA) concentrations were in the range of 0.8 µBq/m3 - 145 mBq/m3. Based on the results of environmental measurements and the available meteorological data, assessments were made to analyze concentration levels of 106Ru activity and to help understand the behavior of radioruthenium in various environmental media. Evaluation of the daily variation of activity levels indicated a maximum of 4 day-long residence time of 106Ru contamination presence in ground level air in Budapest. An average 106Ru activity concentration of 25.6 ±â€¯1.4 mBq/m3 have been observed for the estimated residence time of 106Ru in the air. Deposition of 106Ru was dominantly influenced by rainfall, the major contributor wet deposition which led to an average of 11.3 ±â€¯1.3 Bq/m2 deposition on the ground surface prior to plume passage.

SPACE DOSIMETRY MEASUREMENTS IN THE STRATOSPHERE USING DIFFERENT ACTIVE AND PASSIVE DOSIMETRY SYSTEMS.

Several measurements have been performed on the cosmic radiation field from the surface of the Earth up to the maximum altitudes of research aeroplanes. However, there is only limited information about that between 15 and 30 km altitudes. In order to study the radiation environment in the stratosphere, an experiment was built by students from Hungarian universities that flew on board the BEXUS (Balloon Experiments for University Students) stratospheric balloon in Northern Sweden, from the ESRANGE Space Center. The main technical goals of the experiment were to test at the first time the TRITEL 3D silicon detector telescope system in close to space conditions and to develop a balloon technology platform for advanced cosmic radiation and dosimetric measurements. The main scientific goals were to give an assessment of the cosmic radiation field at the altitude of the BEXUS balloons, to use the TRITEL system to determine dosimetric and radiation quantities during the balloon flight and to intercompare the TRITEL and Pille results to provide a correction factor for the Pille measurements. To fulfil the scientific and technological objectives, several different dosimeter systems were included in the experiment: an advanced version of the TRITEL silicon detector telescope, Geiger-Müller (GM) counters and Pille thermoluminescent dosimeters. The float altitude of the BEXUS balloon was ∼28.6 km; the total flight time was ∼4 h. Measurement data from the active instruments were received in real time by the ground team during the mission. There were no failures in the operation of the system; everything worked as expected. This article presents the scientific goals and results in detail. From the TRITEL measurements, the linear energy transfer spectra, the average quality factor of the cosmic radiation as well as the absorbed dose and the dose equivalent were determined. Estimations for the uncertainty in the TRITEL measurements were given. The deposited energy spectra measured with the TRITEL instrument were compared with the count rates measured with the GM counters. The experiences and results gained in the frame of the project will be used in the evaluation of TRITEL data from measurements on board the International Space Station. As an outlook a short overview is given of the planned rocket radiation experiments based on the system used in the BEXUS programme.

Space dosimetry with the application of a 3D silicon detector telescope: response function and inverse algorithm.

One of the many risks of long-duration space flights is the excessive exposure to cosmic radiation, which has great importance particularly during solar flares and higher sun activity. Monitoring of the cosmic radiation on board space vehicles is carried out on the basis of wide international co-operation. Since space radiation consists mainly of charged heavy particles (protons, alpha and heavier particles), the equivalent dose differs significantly from the absorbed dose. A radiation weighting factor (w(R)) is used to convert absorbed dose (Gy) to equivalent dose (Sv). w(R) is a function of the linear energy transfer of the radiation. Recently used equipment is suitable for measuring certain radiation field parameters changing in space and over time, so a combination of different measurements and calculations is required to characterise the radiation field in terms of dose equivalent. The objectives of this project are to develop and manufacture a three-axis silicon detector telescope, called Tritel, and to develop software for data evaluation of the measured energy deposition spectra. The device will be able to determine absorbed dose and dose equivalent of the space radiation.