OPERATIONAL EXPERIENCE OF ULTRASONIC SEALING BOLTS FOR SAFEGUARDS CONTAINMENT OF MULTI-ELEMENT BOTTLES IN BRITISH NUCLEAR FUEL'S THORP SPENT FUEL STORAGE PONDS

Following verification of the presence of Light Water Reactor fuel stored in multi-element bottles (MEBs), in British Nuclear Fuel's (BNFL), Thermal Oxide Reprocessing Plant (THORP) fuel storage pond by Euratom and the IAEA, one lid bolt is replaced by an Ultrasonic Sealing Bolt. This safeguards seal, developed by Euratom's Joint Research Centre at Ispra, Italy, has been field tested at Sellafield over several years and applied in volume since 1994. The use of sealing bolts and video surveillance provides dual containment/surveillance on the THORP storage ponds, and brings significant savings in time and hence cost to the operator at the annual inventory verification. Time savings of up to 80% are achievable compared to fuel verification using a collimated gamma detector.