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PubMed1989

Artificial radioactivity in fuel peat and peat ash in Finland after the Chernobyl accident.

The accident at the Chernobyl nuclear power plant in April 1986 caused very uneven deposition of radionuclides in Finland. The deposited radionuclides were found in relatively high concentrations in fuel peat and especially in peat ash because a thin surface layer of peat-production bogs was extracted as fuel peat soon after the fallout occurred. Concentrations of artificial radionuclides in fuel peat and peat ash were measured at six peat-fired power plants in Finland throughout the heating season 1986-87. Concentrations of 137Cs in composite peat samples varied between 30 and 3600 Bq kg-1 dry weight and in ash samples between 600 and 68,000 Bq kg-1. High concentrations in peat ash caused some restrictions to the utilization of peat ash for various purposes.

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PubMed1989

Cesium-137, 134Cs and 110mAg in lambs grazing pasture in NE Scotland contaminated by Chernobyl fallout.

The decline in Cs radioisotope levels has been studied in tissues from lambs grazing lowland pasture. The lambs were slaughtered 18 and 115 d after contamination with Chernobyl fallout. During this time the Cs activity decreased to 13% of the initial amount in animals that had continued to graze contaminated pasture and to 3.5% in animals consuming uncontaminated feed. The 137Cs concentration in grass from the field grazed by the lambs decreased with a half-time of 22 d over the period 11-100 d after contamination. The amounts of Cs radionuclides removed from the pasture by the grazing animals amounted to only 0.01% of the total, the rest remaining in the soil, with over 40% in the upper 10 mm. Small amounts of 110mAg, found in grass, declined with a half-time of 8.9 d, and the radionuclide was found to accumulate in liver tissue.

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PubMed1989

Cesium-137 urinary excretion by northeastern (Pordenone) Italian people following the Chernobyl nuclear accident.

To estimate the radiological consequences in humans due to the Chernobyl nuclear accident (5 May 1986), we have determined both the 137Cs concentration in food and the 137Cs daily urinary excretion on 198 residents of the Pordenone area. The resulting experimental data have been compared with those estimated from the International Commission on Radiological Protection Publication 10A model (ICRP 1971) using a suitable dietary intake, and they were found to be in reasonable agreement.

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PubMed1989

Isotopic composition of high-activity particles released in the Chernobyl accident.

Gamma spectra were measured and activities of the detected isotopes were analyzed for 206 high-activity particles (hot particles, HPs) found in northeastern Poland after the Chernobyl accident. The isotopic composition of HPs observed in gamma-activity is compared with that of the general fallout and core inventory calculations. Particle formation and a process of depletion in Ru and Cs isotopes are discussed. On the basis of a search performed a year later, some comments on the behavior of HPs in the soil are made.

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PubMed1989

Experimental determination of transfer coefficients of 137Cs and 131I from fodder into milk of cows and sheep after the Chernobyl accident.

Following the Chernobyl accident in April 1986, the transfer of 131I and 137Cs from feed to milk was studied under experimental and common agricultural conditions. From measurements in different dairy farms in Southern Bavaria, equilibrium transfer coefficients for cow's milk were calculated to be 0.003 d L-1 (range 0.0015 to 0.005) for 131I and 0.003 d L-1 (range 0.0025 to 0.004) for 137Cs. In feeding experiments with cows and sheep under more controlled conditions, milk transfer coefficients of 0.007 d L-1 (range 0.0055 to 0.0081) for 131I and 0.003 d L-1 (range 0.0023 to 0.0053) for 137Cs were obtained for cows, while for sheep the 137Cs transfer coefficient was higher: 0.06 d L-1. The kinetics of the Cs transfer from fodder to cow's milk can be described by two exponential terms assuming biological half-lives in milk of 1-2 d and 10-20 d. The use of a fast component with 1.5 d and a fraction of 0.8, and a slow component with 15 d, gives a good approximation to the kinetics for all cows in this experiment.

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PubMed1990

Radionuclide concentrations in the northern part of The Netherlands after the Chernobyl reactor accident.

Concentrations of radionuclides originating from the Chernobyl reactor accident were measured as a function of time in air, rainwater, grass, cow's milk, vegetables and dust by means of high-resolution gamma-ray spectroscopy. Special attention was paid to grass and milk originating from the same meadows. Also, milk of cows temporarily kept inside after the accident was monitored until a few days after their release from the stables. Activity ratios in various types of samples and the implication of the sheltering measures for cows are discussed.

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PubMed1990

Measurements of radiocesium transfer to milk and calculation of resulting dose in Brescia, Italy, following the Chernobyl accident.

Results are presented of several measurements on components of the cows' milk chain performed at our Medical Physics Service after the Chernobyl accident. Values were obtained for Cs isotope transfer coefficients, namely, for cows' diet-milk and diet-feces transfers. Other measured parameters were the effective half-life of Cs in milk and the 134Cs:137Cs ratio. In addition, an evaluation of Cs contribution to the absorbed dose to population from milk is performed.

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PubMed1991

Assessment of radiocesium incorporation in Austrians after the Chernobyl accident.

Residents of Vienna, Austria were whole-body counted for radiocesium content due to fallout deposited after the Chernobyl accident. Data for a 2-y period were compared with prior estimates of radiocesium body burden based on food consumption. Our results suggest that the prior estimates be revised and the rejection limit be increased by a factor of 2 for contaminated food.

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PubMed1991

Human postmortem thyroid 131I content and risk estimates in Bratislava, Czechoslovakia following the Chernobyl accident.

From 3 May to 4 August 1986, thyroids of 416 postmortem subjects in Bratislava (population: approximately 400,000) were measured for 131I. Subsequently, dose rates in this organ for the day of exitus were calculated. Mean dose commitments were estimated by integrating linear or quadratic-periodic regression lines drawn through scatterplots of logarithmically transformed daily dose rates. The mean dose-commitment estimates in thyroids of adults were 0.74 and 0.58 mGy for linear and quadratic-periodic regression, respectively. The same for thyroids obtained from donors of fetal to 18 y of age were 1.67 and 1.77 mGy for liner and quadratic-periodic regression, respectively. A comparison of the actual thyroid radiation burden with its theoretical values calculated in the first days of contamination of the environment showed that the models used were safe enough to protect the population. Estimates of absolute risk for thyroid cancer showed that excess incidence that could be expected as a result of the Chernobyl accident shall remain obscured by the "spontaneous" incidence of this disease at geographic localization.

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PubMed1991

Chernobyl fallout in southern and central Finland.

To study the levels and distributions of radionuclides released in the Chernobyl accident, we sampled surface peat from 62 sites in Southern and Central Finland and measured 131I, 134Cs, 137Cs, 132Te, 140Ba, 103Ru, 90Sr, 141Ce, and 95Zr. The distribution of fallout activities was highly uneven, depending on movement of the contaminated air mass and rainfall distribution during the critical days. The highest values observed were 420 kBq m-2 of 131I and 70 kBq m-2 of 137Cs. The nuclide ratios showed wide and partly unexpected variations. The high-boiling-point, or nonvolatile, elements Ce and Zr were spread mostly on a 200-km-wide zone extending across Finland from southwest to northeast. The more volatile elements, I, Ce, and Te, showed quite a different, more widespread, fallout distribution, while an intermediate behavior was observed for Ba, Ru, and possibly Sr. These results can be explained by assuming that pulverized nuclear fuel material released in the reactor explosion on 26 April reached Finland via Poland and the Baltic Sea and traversed the country along the above-mentioned narrow zone, while volatile material, evaporated in the reactor fire from 26 April to 5 May, arrived in several waves and was consequently more widely and evenly spread. From their elemental melting and boiling points, Ru and Mo would appear to belong to the nonvolatile group and Sr to the volatile. Yet, their actual behaviors were opposite; Ru in particular was found in the nonvolatile as well as the volatile fallout, possibly because Ru activities were present in the fuel partly in the metallic state and partly as volatile oxides.

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PubMed1991

Radioiodine retention in ovine thyroids in northwestern Greece following the reactor accident at Chernobyl.

Iodine-131 concentrations were measured throughout the summer of 1986 in thyroids of lambs slaughtered at Ioannina (Northwestern Greece) following the accident at the Chernobyl nuclear reactor. During the survey, 40 thyroids were collected. The highest level of 131I detected was 2471 +/- 339 Bq per thyroid. The thyroids of 20 lambs did not contain detectable 131I concentrations, while the contamination content of the others was greatly variable. The transport of 131I from pasture to thyroids of lambs has been described through a simple model for the retention of 131I in the glands. The transfer coefficient fT, expressing the steady-state equilibrium, was estimated to be 564 +/- 270 kg-1 d. This result reflects the sensitivity of animal thyroids as biological radioiodine monitors.

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PubMed1991

Radiocesium bioavailability: transfer of Chernobyl and tracer radiocesium to goat milk.

The bioavailability of Chernobyl-derived radiocesium in hay, fungal fruit bodies, willow bark, and soil was compared to tracer radiocesium (134CsCl) by measuring transfer coefficients (Fm) to goat milk. The average Fm value from 134CsCl of 11.9 x 10(-2) d L-1 was taken to represent the maximal transfer to milk on the provided diet. In 1986, the Fm value from hay was 35% of that from 134CsCl, thus demonstrating the low bioavailability of recently deposited radiocesium. Values in 1987 were also lower, with a mean of 76% of that from tracer Cs. During 1988 and 1989, maximal Fm values were observed, suggesting increased bioavailability from the year of fallout to the following years. Transfer of radiocesium from two fungal species harvested in 1988 and 1989 were 78% and 87%, respectively, of that from tracer Cs, while bark was lower (62%). Transfer from organic soil was only 7% of tracer radiocesium, and therefore contribution from soil ingestion could only have a small impact on the content of radiocesium in animals. Live monitoring measurements and the excretion of 134Cs in milk, urine, and feces during a 50-d period was adequately described by a two-exponential equation.

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PubMed1991

Multi-fractal nature of radioactivity deposition on soil after the Chernobyl accident.

Fractal analysis is introduced in the field of environmental health physics. In particular, it is applied to the complex and inhomogeneous deposition pattern of radioactivity after the Chernobyl accident. The patchiness of 137Cs hot spots is quantified by a fractal dimension as low as 1. The problem of finding hot spots that might be of health concern is discussed.

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PubMed1991

Seasonal variations of 137Cs content of milk after the Chernobyl accident.

Results are presented on monthly measurements of 137Cs content in cows' milk over a 3-y period after the Chernobyl reactor accident. It was observed that, in an annual cycle of measurements, the 137Cs concentration of milk increased between December and August, peaking in April each year, due to the dependency of the 137Cs content of cattle feed on the fallout activity of 137Cs. There was a consistent correlation between the 137Cs concentration of milk and surface air.

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PubMed1992

Behavior of Chernobyl fallout radionuclides in peat combustion.

The fallout from the explosion and fire at the Chernobyl nuclear power plant concentrated levels of up to 10 kBq 137Cs kg-1 dry weight in the fuel peat harvested during the summer of 1986 in Finland. We investigated the behavior of fallout radionuclides 137Cs, 134Cs, 106Ru, 144Ce, 125Sb, 95Zr, and 110mAg together with naturally occurring 210Pb and 226Ra in the combustion of this contaminated peat in four different power plants. The elements antimony, ruthenium, lead, and cesium were enriched on the smallest particles, indicating that they were in a volatile chemical form, while cerium, zirconium, and radium were nonvolatile at the combustion temperatures. This result confirms the previous finding that ruthenium is volatile in combustion. Although metallic ruthenium requires 2,310 degrees C to melt, some of its oxides melt and evaporate at much lower temperatures.

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PubMed1992

Risk estimation of radioactive contamination after the Chernobyl accident using bioindicators.

After the Chernobyl nuclear accident, game meat and, in particular, sheep meat in the Republic of Croatia showed a high degree of radioactive contamination compared to large livestock. The activity concentrations of 131I, 134Cs, and 137Cs were measured in meat and internal organs (i.e., lung, liver, kidney, and heart) of game (e.g., venison, hare, and wild boar) and sheep that were used as biological indicators of radioactive contamination. In order to estimate the importance of game and sheep as a dietary source of radioactivity, the effective dose equivalent for the average and critical population (hunters and livestock raising families) were calculated. The data indicated that sheep meat represents greater risk for the human population, in case of a nuclear accident, than game meat. The share of meat from sheep (4.4%) prevailed over the share of meat from game (0.5%) when comparing the average intake of meat per inhabitant in Croatia. This result pointed to an increased risk for families who depend mostly on sheep meat in the case of a nuclear accident.

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PubMed1992

Area and time distribution of external and internal doses from Chernobyl fallout: the lack of correlation in Norway.

Population doses from external radiation and internal food-based radioactivity were calculated each month for each municipality for 3 y immediately following the Chernobyl contamination in Norway. The main polluted regions are sparsely populated but comprise important food production areas. The external dose data base was calculated based on fallout deposition and measurements in dwellings, whereas the totally independent internal dose data base was calculated on a large number of food measurements and knowledge of both the food distribution system and the countermeasures taken. The internal dose in the densely populated municipalities was comparably higher than expected from local deposition, despite the fact that countermeasures had some effect. Thus, the correlation between internal and external dose for individual municipalities is rather weak. This study shows that a traditional deposition/transfer factor approach may be inappropriate if used in countries with large variation in population density and agricultural ecosystems and in combination with effective countermeasures.

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PubMed1992

Mathematical model of 137Cs migration in soil: analysis of observations following the Chernobyl accident.

The applicability of traditional mathematical models is studied on the basis of 3 y of observation of the vertical migration of 137Cs fallout after the Chernobyl accident. The most accurate description of the dependence of the radionuclide concentration on the depth of the soil layer is given by a lognormal distribution. The parameters of this distribution are determined and shown to be a solution to the Fokker-Planck equation, a special case of which is the diffusion-convection transport equation.

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