BCP’s Plant Services Division personnel have designed and built a flux thimble straightening tool that enables a one-entry job, requiring just minutes per thimble. This tool has been used successfully in several nuclear power stations to straighten multiple thimbles. Use of this specialized tooling greatly reduces unnecessary radiation exposure to personnel and the production of radioactive waste materials from thimble
disposal. This repair is effective anytime the bend has not actually “kinked” the thimble and damaged the metal. It most often occurs during Refueling when a thimble is retracted prior to the fuel shuffle, or re-inserted after the core is reloaded. Typically, a short radius bend in an Incore Flux Thimble takes the thimble out of service, and previously has required a plant to replace it. Early attempts to correct these bends (straighten the thimble) have been ineffective, including some previous attempts made
by ourselves. A clamp arrangement would be used to bring the thimble back to ‘straight’, but the memory of the bend would prevent the Flux Detector from passing by. Our revised design was made to specifically answer that problem, and enables us in a very controlled manner to take the bend back ‘over-center’ to overcome the memory of the bend and effect a fix that works properly and continuously. We have used this tool for over 10 years with excellent results.
Should your plant have interest or need for this tooling and service, please contact Tony Stough or Mark Beggs at the new Plant Services Division Offices in Clearwater,Florida at 727 581-9594.
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