RTS and BNFL have completed the exchange of dissolver baskets at Sellafield's Thorp plant to time and cost.
The re-usable dissolver baskets hold spent fuel while it is dissolved in nitric acid and then transfer the leached fuel hulls to the waste handling system. The basket handling system is inside a thick concrete cell and although a penetration was included to replace the baskets no mechanical plant had been provided.
RTS carried out a ten-week feasibility study into the basket exchange and developed four different solutions, finally deciding that a 'flask and gate' option was the best. A flask was positioned vertically over the penetration in the cell roof and lowered inside onto supports. A hoist temporarily housed in the top of the flask was then used with a sequence grapple to lift the basket into the flask before removal, monitoring and transfer to a storage facility. The procedure was repeated for seven baskets and the project was completed within the ten-week schedule.
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