The role of analogues in radioecology.

If no data are available for a specific radionuclide its analogue could be used in radioecological models. They might be used not only in the frame of screening modelling. Relevant processes and features have to be known, such as time scales of these processes, physical, chemical and biological properties of the environment and relevant media. An analogue could only be proven to be valid by comparing its behaviour in the conditions of interest, while confidence in the validity of an analogue will increase as the quality of the justification increases, there will always be some residual uncertainty. Several main types of analogy can be used when measured or recommended values are not available: the same parameter obtained for another isotope of the same element; the same parameter obtained for another element; a different parameter obtained for the same element. There are several cases, when analogues might be applied as indicators of the determining processes in the radioecological studies.

Regulations for radioisotope content in food- and feedstuffs.

The regulation of contamination levels in food and feed should be made in connection to each other, and described here is a guideline level system with decision rules for radionuclide content in foodstuffs and feedstuffs. Levels for foodstuffs are derived from the general dose limits established by the International Committee of Radiological Protection. For foodstuffs, two levels are suggested: tolerance level for normal situations based on 0.1 mSv/year ingestion dose, and acceptance level for prolonged emergency situations based on 1 mSv/year committed effective dose, with the application of a protection factor of 5 and 3, for children younger than one year and adults, respectively. Current legislation does not contain any derived limits for normal everyday use; however, it is necessary to incorporate limits soon, not only because of the wide use of nuclear technology but also the threat of violent events where foodstuffs are as a vehicle. In addition, technologically enhanced natural isotopes can also cause problems. The derivation of the acceptance level in feedstuffs is based on the suggested acceptance level in foodstuffs, in addition to the latest literature review of transfer coefficients performed in the frame of the Environmental Modelling for Radiation Safety program of the International Atomic Energy Authority.

Plutonium isotopes in the Hungarian environment.

More than 50 soil samples were analysed from different parts of the country, the activity concentration of 239+240Pu was in the range of 0.01-0.84 Bq/kg dry soil with the average of 0.10 Bq/kg. 238Pu could be detected only in few moss samples and 238Pu/239+240Pu ratio determines the origin of plutonium. 241Pu was determined by liquid scintillation spectrometry. The activity concentration of this isotope in the soil is between 0.04 and 3.74 Bq/kg with the average of 0.82 Bq/kg, while in the moss is also similar 0.01-2.07 Bq/kg fresh mass with the average of 0.43 Bq/kg. Significant difference could not be observed between the different types of soils occurring in the country, but the results could be sorted according to the sampling carried out on undisturbed or cultivated area. The isotope ratios 241Pu/239+240Pu prove that the origin of the plutonium in Hungary is the global fallout determined by the atmospheric nuclear weapon tests.

Determination of 241Pu in the environmental samples.

More than 70 soil samples were analysed in the last several years; results are in the range 0.10-3.74 Bq/kg dry soil, with a median of 0.49 and mean of 0.59 Bq/kg dry soil. From the analysis of more than 40 moss samples, the range of activity concentration was found to be 0.002-2.80 Bq/kg fresh mass with median 1.00 and mean value 0.30 Bq/kg fresh mass. In Hungary, the plutonium contamination comes from global fallout determined by the nuclear weapon tests, while is confirmed by plutonium isotope ratios.