A comparison of different detection techniques for 137Cs measurements of cattle in vivo.

Agricultural lands with farm animals (e.g. cattle) can be significantly affected by radioactive contamination following nuclear or radiation accidents. In order to optimise the techniques for measuring 137Cs in contaminated cattle, selected radiation detectors have been tested and calibrated using volumetric radiation sources. In addition, a mathematical phantom of a cow was created within Monte Carlo simulations. The main aim of the research was to propose a method for making rapid measurements of 137Cs in cattle in vivo/in situ and to select the most suitable measurement set-up. Measurements of contaminated cattle in vivo were carried out in Belarus with one selected detector, and were then compared with measurements of meat in a laboratory and with measurements of a control group of cows. The proposed measurement method was also tested on measurements of 137Cs in wild boars in Czechia with higher levels of the 137Cs activity.

ACTIVITY OF 137CS IN HUMAN BODY OF INHABITANTS OF THE CZECH REPUBLIC.

The time course of 137Cs activity in general population of the Czech Republic has been systematically followed since the Chernobyl accident in 1986. Either whole body counting or the determination of 137Cs content in 24-hour urine samples were used as a method of determination of body activity. Environmental and effective half-lives were calculated from the data. In the time period from 1986 to 1990 the effective half-life was 1.3 years; since 1990 up to present the half-life is 15 years. The older data on whole body activity of 137Cs from 1965 to 1985 were compiled and are presented as well. Apart from the general population, a group of people who have special dietary habits in terms of increased game meat consumption, namely wild boar meat, has been monitored since 2000. In this group, the body content of 137Cs is about two orders of magnitude higher than in the general population.

238U CONTENT IN URINE OF URANIUM MINERS AND ITS MODELED VALUES.

The aim of the study is to make a comparison of daily 238U excretion in urine among 115 active uranium miners and its modeled values obtained from inhalation intake of long-lived alpha emitters as measured by personal dosemeters and assessed by biokinetic models for different absorption parameters settings for inhaled uranium. A total of 144 spot samples of urine were collected. The 238U content was measured using high-resolution inductively coupled plasma mass spectrometry method. To obtain estimates of the daily excreted values, the daily values were calculated according to the expected daily excretion of creatinine assessed individually for each miner. When determining the relation between the experimentally found data and the modeled data, a high emphasis was placed on uncertainty of the both compared quantities. All the tested absorption parameters settings produced in average 1.4-4.7-fold higher values than the experimentally found values in the urine.

Ingestion intakes of 137Cs by the Czech population: Comparison of different approaches.

Ingestion intakes of 137Cs of the Czech population were calculated in two different ways - either from the measured activity of 137Cs in components of food in combination with statistical data about consumption rates or from retention of 137Cs in the human body obtained by whole body counting or calculated from daily urinary excretion of 137Cs. Data from the time period since 1986 to 2015 are used. The daily ingestion intake was about 25 Bq d-1 in 1986 and is around 0.1 Bq d-1 at present. Both approaches of ingestion intake calculation have their advantages and disadvantages. Ingestion intake calculated from 137Cs body content was assumed to be the most accurate as it requires fewer assumptions than the calculation from food consumption. However, calculation of 137Cs intake from food consumption is an important tool for prediction doses after the release of radionuclides into environment. The best agreement exceeding the intakes from urine measurement 5 times at maximum was achieved when intakes calculated from food also included products from the natural environment. Without this, the ingestion intake could be under-predicted seriously up to 6 times, especially in the longer time after the release of 137Cs into environment. Ingestion intakes up to 11 Bq d-1 in a group of people with significant consumption of game meat containing elevated activity of 137Cs activity were included as a special case. Various groups of foodstuffs had varying effects on the total committed effective dose from 137Cs. Dose estimates for the Czech population from 137Cs ingestion intake achieved 80 µSv in 1986 and not more than 2 µSv currently and were similar to those incurred by the population of neighbouring countries.

MONTE CARLO CALIBRATION OF THE WHOLE-BODY COUNTING DETECTION SYSTEM FOR IN VIVO MEASUREMENT OF PEOPLE INTERNALLY CONTAMINATED WITH 90SR.

This work is focused on numerical calibrations of the body counter for in vivo measurement of pure beta emitters through the produced bremsstrahlung radiation. Calibrations were performed using the UPh-02T block whole-body phantom and the Lawrence Livermore National Laboratory (LLNL) realistic torso phantom. Neither of these physical phantoms is appropriate for such calibrations; therefore, specific 90Sr sources have been manufactured to be used with the UPh-02T phantom for experimental measurement followed with Monte Carlo (MC) simulations. Calibrations with the LLNL torso phantom were carried out solely using MC technique. Different scenarios of the 90Sr distribution in the human tissues were considered for the spectrometer calibrations. MC simulations with the LLNL confirmed the applicability of the UPh-02T with specific 90Sr/90Y sources for experimental calibrations of the body counters for measurement of pure beta emitters. Differences in count rates in 50-200 keV for UPh-02T and LLNL were not >25% for all considered scenarios.

Urinary excretion of uranium in adult inhabitants of the Czech Republic.

The main aim of this study was to determine and evaluate urinary excretion of uranium in the general public of the Czech Republic. This value should serve as a baseline for distinguishing possible increase in uranium content in population living near legacy sites of mining and processing uranium ores and also to help to distinguish the proportion of the uranium content in urine among uranium miners resulting from inhaled dust. The geometric mean of the uranium concentration in urine of 74 inhabitants of the Czech Republic was 0.091 mBq/L (7.4 ng/L) with the 95% confidence interval 0.071-0.12 mBq/L (5.7-9.6 ng/L) respectively. The geometric mean of the daily excretion was 0.15 mBq/d (12.4 ng/d) with the 95% confidence interval 0.12-0.20 mBq/d (9.5-16.1 ng/d) respectively. Despite the legacy of uranium mines and plants processing uranium ore in the Czech Republic, the levels of uranium in urine and therefore, also human body content of uranium, is similar to other countries, esp. Germany, Slovenia and USA. Significant difference in the daily urinary excretion of uranium was found between individuals using public supply and private water wells as a source of drinking water. Age dependence of daily urinary excretion of uranium was not found. Mean values and their range are comparable to other countries, esp. Germany, Slovenia and USA.

Estimation of intakes of 131I, 137Cs and 134Cs after the Chernobyl accident.

Activities of (131)I and (137)Cs excreted in urine from two healthy males during May 1986, when contaminated air masses from Chernobyl arrived on the territory of the Czech Republic, were determined by bioassay. The data were used to estimate the intakes and committed effective doses from these radionuclides. The results for inhalation intakes are of particular interest, in the absence of sufficient contemporary data for airborne activity. They are found to be higher than initial estimates based on air sampling.

Twelve years of follow up of cases with old 241Am internal contamination.

A group of workers internally contaminated with Am have been followed for about 12 years. The source of contamination was AmO2 powder used for production of AmBe neutron sources and other applications. The production of some radionuclide sources included chemical treatment of the original material, which transformed the americium into the nitrate, but mostly powder metallurgy was used for production of sources for smoke detectors. In vivo measurement of the workers was performed with two LEGe detectors placed near the head of the measured person. Calibration was performed with four different physical skull phantoms of different origin and a voxel phantom with Monte Carlo simulation, which was developed to fit the head sizes of individual persons. Samples of urine and feces were analyzed by means of radiochemical separation followed by alpha-spectrometry. Separation of 241Am from mineralized excreta was performed by combined anion exchange and extraction chromatographic techniques. As a tracer, 243Am was used. When the measured data (83 data on skeletal activity, activity in 389 bioassay samples) were compared with International Commission on Radiological Protection's and Leggett's biokinetic models of americium, it was found that in most cases, after more than 15 y since the intake, the excretion rate was lower (or skeletal activity higher) than predicted. On the other hand, the ratio of excreted activity in urine and feces agrees well with model predictions.

Dissolution behaviour of 238U, 234U and 230Th deposited on filters from personal dosemeters.

Kinetics of dissolution of (238)U, (234)U and (230)Th dust deposited on filters from personal alpha dosemeters was studied by means of a 26-d in vitro dissolution test with a serum ultrafiltrate simulant. Dosemeters had been used by miners at the uranium mine 'Dolní Rozínka' at Rozná, Czech Republic. The sampling flow-rate as declared by the producer is 4 l h(-1) and the sampling period is typically 1 month. Studied filters contained 125 +/- 6 mBq (238)U in equilibrium with (234)U and (230)Th; no (232)Th series nuclides were found. Half-time of rapid dissolution of 1.4 d for (238)U and (234)U and slow dissolution half-times of 173 and 116 d were found for (238)U and (234)U, respectively. No detectable dissolution of (230)Th was found.