Hinkley Point 'B' fuel assembly vibration problems - a broad perspective

The problem of severe damage due to vibration in a number of Hinkley 'B' fuel channel units at a late stage of commissioning, has been given top priority in the UK nuclear industry. Initial examination showed that a small number of upper gag units had suffered extensive mechanical damage, including hammering and erosion of the gag plug and/or its drive shaft. Further examination disclosed that a number of bellows had developed cracks in their internal shrouds used to stream-line the gas flow through the bellows sections. The programme of work on the gag plug and bellows shroud is given. (author)