Possible Release Of Radionuclides Research Articles

Hydrogeologic assessment of the Amchitka Island nuclear test site (Alaska) with magnetotellurics

Amchitka Island, in Alaska, was used for underground nuclear testing from 1965 to 1971. Since the test program concluded, there have been concerns about the possible release of radionuclides into the marine environment of the Aleutian Islands. The hydrogeology of islands such as Amchitka is characterized by a layer of freshwater overlying a saltwater layer, with the salinity increasing across a transition zone (TZ). Hydrogeologic modeling can provide an estimate of the timing and amount of radionuclide release from the explosions beneath Amchitka Island. This modeling is inconclusive because of a lack of information regarding subsurface structure. To address this problem, magnetotelluric (MT) data were collected on Amchitka Island in 2004. Broadband MT data were recorded on profiles passing through three explosion sites to give information about subsurface porosity and salinity. A 2D MT inversion produced models of sub-surface electrical resistivity and showed a pattern of increasing, decreasing, and increasing resistivity with depth at each test site. The depth at which resistivity begins to decrease defines the top of the TZ. The deeper increase in resistivity approximates the base of the TZ. The depths of the top and bottom of the TZ were determined as follows: Cannikin 900–2500 m; Long Shot 600–1700 m; Milrow 900–1700 m. Uncertainties were estimated for these depths. Effective porosities were also estimated and ranged from 10%–20% at the surface to 1%–3% at 3-km depth. These porosities are higher than those assumed in several hydrogeologic models, and give longer transit times from the explosion to the marine environment. Subject to the limits of the analysis, it appears that each of the cavities resulting from underground nuclear explosions is located in the TZ from fresh to saltwater. This implies shorter transit times to the marine environment than if the detonations had been located in the saltwater layer.

Migration of 134Cs in unsaturated soils at a site in Egypt

To demonstrate the safety performance assessment for the disposal of 134Cs radionuclide in a geological formation, several investigations were required to calculate the possible release of radionuclides into groundwater. This research examined the sorption behavior of radioactive cesium (134Cs) in natural groundwater. Cesium chloride (10-6 to 10-2 mol.l-1) was used as a carrier, traced with 134Cs radionuclide. Distribution coefficients of radiocesium for sorption and desorption were measured on natural soil samples of different grain size fractions (l400 to l36 mm). Cesium sorption and desorption were found reversible at cesium chloride concentrations between 10-6 mol.l-1 to less than 10-3 mol.l-1. Sequential extraction procedures showed that the cesium sorption on soils were of various types: those easily desorbed, ion-exchanged, bound to carbonate, iron oxides, and organic matter. To demonstrate the safety performance assessment for the disposal of 134Cs radionuclide in a geological formation, several investigations were required to calculate the possible release of radionuclides into groundwater. This research examined the sorption behavior of radioactive cesium (134Cs) in natural groundwater. Cesium chloride (10-6 to 10-2 mol.l-1) was used as a carrier, traced with 134Cs radionuclide. Distribution coefficients of radiocesium for sorption and desorption were measured on natural soil samples of different grain size fractions (l400 to l36 mm). Cesium sorption and desorption were found reversible at cesium chloride concentrations between 10-6 mol.l-1 to less than 10-3 mol.l-1. Sequential extraction procedures showed that the cesium sorption on soils were of various types: those easily desorbed, ion-exchanged, bound to carbonate, iron oxides, and organic matter.

Calculation of fission product behaviour in an advanced containment in case of a severe accident

The aim of the present work is to demonstrate the applicability of the MELCOR- and CONTAIN-computer programs, respectively, to determine the radiological source terms (RST) of a pressurized water reactor under conservative release conditions based on preliminary reactor data from the European Pressurized Water Reactor Conceptional Design Phase. The determination of the RST means the quantification of the possible release of radionuclides from the plant (mostly from the containment) into the environment in case of a severe accident. This contribution gives an outline of the procedures by which the RST can be estimated conservatively. Such procedures have to be known if the ‘harmful effects of ionizing radiation’ outside the reactor plant, as mentioned in legislation, are determined in a proper way. It is demonstrated that the computer codes available at Forschungszentrum Karlsruhe can be used for the complete analyses of the containment behaviour and the accident consequences, provided that the design data of the nuclear reactor and information on the initiating phase of the accident are available. The first 12 h of a postulated Large Break Loss-of-Coolant Accident are analysed and a time dependent RST to the environment is calculated, which can be used as input for the COSYMA code system for the assessment of the accident consequences.

Three-dimensional model of radionuclide dispersion in estuaries and shelf seas

The 3-D model THREETOX was developed for the assessment of contamination in coastal seas and inland water bodies. It includes a high resolution numerical hydrodynamic submodel, a dynamic–thermodynamic ice submodel, and submodels for suspended sediment and pollution transport. The results of two case studies are described. The first case concerns a 2-year simulation of the Chernobyl radionuclide contamination of the Dnieper–Bug estuary to validate the model. In the second case study, simulations were performed for the assessment of the consequences of the possible release of radionuclides from scuttled reactors and containers with liquid radioactive wastes in the Novaya Zemlya fjords and the East Novaya Zemlya Trough of the Kara Sea. The simulated results demonstrated the capability of the THREETOX model to describe a wide spatial and temporal range of radionuclide transport processes in the ocean.

The dissolution of a glass in an infinite volume of water

The release of a species from a solid that is dissolving in water is of particular interest in scenarios that describe the possible release of radionuclides from glasses that contain immobilized nuclear fuel wastes. The simplest scenario is that of release from a glass that is dissolving congruently in an infinite volume of water. In a previous work, the hypothesis that the dissolution of a glass is a consequence of the diffusion of water into it was used to obtain an approximate expression for the time-dependence of the dissolution. In this present work, the approximate solution is compared with a more rigorous solution, obtained by use of the linear diffusion equation.

The release of a diffusing species by leaching in a closed solid/liquid system

Diffusion of a species from a solid matrix into a limited volume of water is of interest in scenarios that describe the possible release of radionuclides from solids containing immobilized nuclear wastes, buried in disposal vaults within geological strata. A rigorous solution is given for the case of diffusive release from a nondissolving matrix into a finite volume of leachant. The rigorous solution is compared with a previous solution that had been obtained by means of an approximation.