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.
This paper presents ongoing results of the project presented at ICEM 10 [paper 40071] related to the topics of the reuse of conditionally released materials arising from decommissioning of nuclear installations. The subject of the presented paper is modelling of motorway tunnels, which reuse the conditionally released steel in form of reinforcing nets and bars for the concrete construction of tunnels. The general approach for the project was presented at ICEM 10. The activities of the project continued in evaluating the impact of the nuclide composition contained in the conditionally released steel on calculated individual effective doses from the external exposure (the internal exposure will be evaluated in next stages of the project). Mentioned radioactive steel arises during decommissioning and would be reused in motorway tunnels. Evaluated scenarios are related to critical groups of public (driver’s scenarios) and for professionals constructing the tunnels and performing the maintenance of tunnels (worker’s scenarios). The computer code VISIPLAN 4.0 3D ALARA planning tool was used for the calculation of individual effective doses for worker and for public groups. Various limits of the individual effective dose are used for public and for professionals. The aim of the ongoing modelling is to develop a set of data of the maximal radioactivity concentration for individual radionuclides contained in the conditionally released steel used in tunnel model constructions in order not to exceed the limits for the individual effective dose.
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