Long-term prediction of the migration of radionuclides from solid radwaste storage sites at the Siberian Chemical Works

Abstract

The results of a calculation of the migration of radionuclides from a repository for solid radioactive wastes from the reactor plant of the Siberian Chemical Works, performed using a method recommended by IAEA with the AMBER 4.4 computer program and by finding an analytical solution, are presented. Three scenarios for migration of radionuclides from the repository are described and estimates of their specific activity in the uppermost water layer and the results on an analysis of the sensitivity of models to a change in the input parameters are presented.A repository for solid radioactive wastes is part of the reactor plant of the Siberian Chemical Works. The inadequate capacity of the facility and the fact that the storage sites which are being operated there do not accept wastes from the reactor plant make it necessary to design and build a new repository for such wastes on the territory of the reactor plant. A new repository has been built and is ready for operation. It consists of three modules with total waste storage volume 6850 m 3 (Fig. 1). Each 2280 m 3 module consists of a rectangular reinforced concrete structure with dimensions 18.8 × 30.6 m (along the axes) and depth 5.4 m is divided into twelve 190 m 3 compartments. Waterproofing materials penetron, foam polystyrene role flowmate 200, a water insulating membrane EPDM, and flat asbestos cement sheets are used to increase the effectiveness of the isolation of the radioactive wastes.This repository is intended for centralized collection and storage of solid radioactive nontechnological wastes, which consist of metallic cuttings, production trash, individual protection means, and wastes from construction and repair work, which are formed as a result of the production work. Before being placed into the repository, the wastes are packed into polyethylene packages or bags. The following data characterize the content of radionuclides in the wastes: the specific activity of β emitters does not exceed 10 6 Bq/kg, the exposure dose rate from γ emitters does not exceed 198 µSv/h 10 cm from the surface of the wastes in the standard packaging; the composition is as follows (%): 14 C 4, 32 P 19, 90 Sr 1, 51 Cr 65, 60 Co 1, 58 Co 1.5, 65 Zn 5, 56 Mn 1.5, 59 Fe 1, 137 Cs 1.Solid wastes are loaded into the compartments of the repository in three successive layers, each 1.5 m thick. A cement solution is poured onto each layer and then a 100 mm thick layer of concrete is placed on top. After the last (third) layer solidifies, it is covered with an additional 300 mm thick layer of concrete, after which the compartment is closed with plates and waterproofed.