REUSE OF CONDITIONALLY RELEASED RADIOACTIVE MATERIALS FROM NPP DECOMMISSIONING APPLIED IN MOTORWAY BRIDGES CONSTRUCTION

摘要

During the operation and especially during decommissioning of nuclear installation is produced considerable amount of solid materials (metals, non-metals, building structures) that can fix radioactivity in forms of contamination or activation. The materials present radioactive waste, part of radioactive waste may just slightly exceed limits for unconditional release of materials into the environment. On the other side, there is possible, after proving of defined safety limits fulfillment, to conditionally release radioactive waste for special purpose. In opposite case it would be inevitable to dispose radioactive waste in radioactive waste repository.Approaches of different countries to release of materials vary and the extent of this issue processing is related to each approach. Requirements set down in Slovak Republic legislation are given in the paper.Before the conditional release of materials there must be done consistent analysis of the materials impact on the inhabitants and the environment in short and long time period. The analysis comprises the evaluation of considered scenarios of specific utilization of conditionally released materials. This analysis necessarily precedes the realization of utilization. Scenarios describing utilization of radioactive waste carbon steel in the motorway bridge building process is stated in the paper. Radioactive steel can be utilized in many parts of the bridge. In the paper it is described its use as reinforcement of piles. Short time period external irradiation of workers and inhabitants is taken into account. Critical group (i.e. the group that gets the highest accumulated dose) of workers orinhabitants is chosen. Specific mass activity of released radioactive waste carbon steel is related to individual effective dose taken by critical group. Following legislation rules, annual effective dose taken by critical group must not overstep the limit of 10 μSv/year. The determination of value of the specific mass activity is the target of scenarios evaluating. Evaluation of model scenarios can be realized with the appropriate calculation tool. In the paper VISIPLAN 3D ALARA planning tool was chosen.