An integrated equipment for massive segmentation and packaging of control Rod Guide Tubes - 15161

Over time, some utilities have decided to undergo safety upgrades that include replacement of some ageing components like control rod guide tubes (GT's). GT's are safety related components because they control the path of the control rods into and out of the core. These components are usually stored underwater in interim storage pools to decay their radioactivity. When the interim storage facility reaches saturation, treatment and final disposal of the retired Guide Tubes needs to be performed. Based on more than 30 years of experience and lessons learned in the development of segmentation and packaging technologies for nuclear components, Westinghouse has designed, commissioned and will operate a dedicated system for cutting and packaging retired GT's from 900 MW plants, currently stored in a EDF maintenance facility located in the south of France. The first main technical challenge was the waste volume optimization. Two separate waste streams had to be considered for coping with the highly irradiated portion of the GT's (lower part) and the very low level waste sections (upper part). The segmentation plan has been designed to minimize the waste volume of the highly irradiated waste and therefore develop a process which could be adapted to the container size specified by EDF. Metallic baskets have been designed to optimize the packaging and storage density in the containers. All cutting techniques previously used by Westinghouse in similar applications were assessed and underwater mechanical cutting with a band saw was selected as the preferred method. A turning stand positions the GT in front of the band saw. When the cut is completed, the remnant GT is inserted into the next turning stand for the next cut. Each cell of the turning stand positions the GT at the pre-defined cutting height. An integrated water filtration system is used to ensure good visibility during the cutting operations and to minimize water volume and limit the final liquid effluents. The whole process of GT insertion, cutting, packaging and waste conditioning is carried out in a hot cell and controlled remotely. The operator can therefore follow the packaging plan accurately and safely by using a four axis pick and place unit, while keeping personal radiation exposure low. This innovative process allows cutting and packaging large quantities of GT's in a safe and efficient manner. The pilot project covers the segmentation of 93 GT's but it can be further used for cutting larger quantities of retired GT's resulting from the upcoming GT replacement campaigns. (authors)