Environmental impact of the leakage of radioactive water into the soil from a subsurface-pipeline on the site of NPP Paks was studied to assess the size of the contaminated area and to estimate the potential migration of radioisotopes. For this aim a comprehensive analysis study was performed on soil samples taken from the contaminated area. The activity concentration of representative radionuclides (such as 137 Cs, 134 Cs, 60 Co, 54 Mn, 7 Be, 3 H and 90 Sr), the composition of soil, the distribution of radioactivity in different grain size fractions and the pH of soil were determined. Dissolving experiments with synthetic acidic rain water was also carried out.Results of the activity-measurements show that the average activity concentrations in the case of all isotopes are below the exemption limit given by the authority. The short-term migration of radioisotopes has been found to be negligible. Since pH of the soil is about natural and the radionuclides are very strongly bounded to the soil, the risk of the long-scale groundwater contamination is low.
Computer Program ILT15 developed to accompany a new leach test for solidified radioactive waste forms in the Hungarian NPP Paks. The program is designed to be used as a tool for performing the calculations necessary to analyse leach test data, a modelling program to determine if diffusion is the operating leaching mechanism (and, if not, to indicate other possible mechanisms), and a means to make extrapolations using the diffusion models. The ILT15 program contains four mathematical models that can be used to represent the data, diffusion through a semi-infinite medium, diffusion through a finite cylinder, diffusion plus partitioning of the source term and solubility limited leaching. The program is written in C++ in the Borland C++ Builder programming environment.A detailed description of application of this modelling computer program is given.
IntroductionFor a number of years increasing attention has been given in Hungary to the management of the low and medium level radioactive wastes (LLW, MLW) being produced in Paks nuclear power plant.Some of these wastes, for example, evaporator bottom concentrates, pond sludge and spent ion exchange media are produced in relatively large volumes. In addition to national programs on the development of immobilization processes, the European Community commissioned programs on the immobilization of LLW and MLW. These wastes are immobilized by incorporating them into cement. In order to optimize these immobilization processes, for example with respect to waste loading, it was necessary to characterize the products with respect to such properties as density, strength, dimensional stability, leach resistance and so on. In this article we report about an accelerated leach test and the developed computer program. Experimental Accelerated leach testsAn accelerated leach test method was used for low-level radioactive waste forms in the Hungarian NPP Paks. The leach test method was designed to minimize experimental artifacts that could be misinterpreted as release mechanisms such as effects of increased ionic concentrations in the leachate. This is particularly important when the data is used for mechanistic interpretations and long-term extrapolations.The test method we used was a semi-dynamic leach test that is the leachant is changed at predefined intervals. The test requires a volume of distilled water that is 10 times the surface area of the sample. The leachant was changed twice on the first day and then daily for 11 more days.These experiments were performed using cylinders of 2.93 cm diameter and 4.96 cm height, prepared form Hungarian cement type CEM I 32,5-LH and CEM III/B 32, N LH/SR. Each cylinder was AbstractAn accelerated leach test method was used for low-level radioactive waste forms in the Hungarian NPP Paks. These experiments were performed using cylinders prepared form Hungarian cement type CEM I 32,5 LH and CEM III/B 32, N-LH/SR. Each cylinder was made using cement or cement plus additive using radioactive waste water. The cemented radioactive material was evaporator bottom residue or sludge as well as evaporator cleaning acid solution, spent ion exchange resin, decontamination solution from NPP Paks, containing 134 C s , 137 C s and 60 C o as main radioactive components. Leach tests were performed according to ASTM C 1308-08 standard. A computer program (ILT15) associated with the accelerated leach test was developed based on the ASTM C 1308-08 standard. Literature test and measured leaching data were analyzed to assess whether the model for diffusion from a finite cylinder describes leaching from cement based waste forms. In this paper some of the experimental and modeling work used to validate the test method are presented.
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