Occupational radiation exposure during inspection and maintenance of the ITER water cooling system. A comparison between two working strategies

The international thermonuclear experimental reactor water cooling system (ITER WCS) is divided into 20 loops with the aim to reduce the consequences of a loss of coolant accident (LOCA). This makes the ITER WCS a very complicated system with many components requiring periodical inspection and maintenance. The main radiological concern for the staff involved in such activities is due to the activated corrosion products (ACPs) generated by corrosion of the inner wall of the piping under the neutron flux. In the present study the collective dose due to the ACP for one loop of the ITER WCS is assessed. Two different maintenance and inspection (M/I) approaches (or working strategies) for the ITER WCS components are to be considered. The first one is usually applied in American and European designs of pressurised water reactors (PWRs) that have cooling loops similar to those envisaged in ITER. The other one is the strategy proposed by the ITER WCS designers that takes into account the actual plant layout and technology. Both strategies have been implemented in the occupational radiation exposure (ORE) assessment process and two results have been obtained. The similarity is then performed pointing out the differences between the two approaches, trying to indicate what is the best one from the ORE point of view.