Radioactive waste may arise throughout the lifetime of any type of nuclear facility. This waste has to be isolated from the environment using the engineered and natural barriers of near surface or deep geological radioactive waste repository. Before final disposal, the waste volume is reduced in the treatment process and then it is immobilized into the stable matrix. In Slovakia, the treated radioactive waste is conditioned into fibre-reinforced concrete containers using a cementation technology. These containers are the only overpacks approved for near surface disposal in the National Radioactive Waste Repository located at Mochovce nuclearsite (Slovakia). Every filled container has to fulfill the defined limits and conditions for safe transport and disposal. The dose parameters, determining the safety of personnel handling a container, are one of them. Basically, the doses are measured on the container walls’ outer surfaces and on the lid of the container. The dose monitoring in 1 meter distance from the container walls and from the lid of the container is performed before transportation as well. The calculation code VISIPLAN 3D ALARA is a planning tool and it calculates dose parameters also for the above mentioned positions concerning the fibre-reinforced concrete container which contains waste with different physical or radiological characteristics. In the paper, calculated data are compared with in-situ measurements. Using VISIPLAN 3D ALARA planning tool, various scenarios are evaluated. Finally, the optimization leading to the lowest radiation exposure of personnel handling the filled fibre-reinforced containers is discussed.
Considerable amount of solid radioactive waste with radioactivity slightly above the limits for unconditional release is generated during the decommissioning of the nuclear installations. Conditional release deals with precisely this type of materials with activity slightly above limits in order to save considerable financial resources, which would be otherwise spend on treatment, conditioning and disposal of these materials at appropriate repository. The basic principles of conditional release as well as possibilities of reusing of the conditionally released materials are described. One of these possibilities of the reusing was chosen and application proposal of conditional release of metal waste - steel reinforcement in the concrete, which could be used for construction of motorway tunnels, was created. The computer code Visiplan 4.0 3D ALARA planning tool software was used for the calculation of effective individual dose for personnel constructing the tunnel and for critical group related to scenario. Particular models for individual scenarios of conditional release have been developed within the scope of this software code. The aim of the paper is to determine a level of the radioactivity of conditional released materials to avoid over exceeding the value of annual individual effective dose 10μSv/year established by international recommendations.
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