Grant: Collaborative Research and Development Grants

Fuel endplate failures and severe pressure tube wear were discovered in some CANDU reactors only a few years after their commercial operations. Investigations revealed that (i) the fuel endplate failure was caused by the acoustics originated at the primary heat transport pump and (ii) the presence of moderate to severe fretting marks on the inside surfaces of the pressure tubes was caused by the excessive movement (vibration) of the bearing pads. Further investigations showed that fretting of varying degrees was present in all fuel channels. Fuel string fretting thus becomes an integrity concern for the CANDU reactors. The objectives of the proposed research project are to (i) develop efficient, accurate and reliable algorithms for predicting vibration of a CANDU fuel string under reactor conditions, (ii) implement the algorithm into a computer code for assessment of fretting and wear for existing and new CANDU fuels, (iii) test the code against experimental data documented in the Canadian nuclear industry. This is enormously challenging research area where a large number of bodies, large scale dynamic contact and solid-fluid interaction must be dealt with accurately. Completion of the proposed research program will allow the Canadian nuclear industry to advance their understanding of flow-induced vibrations and dynamic contact in a fuel string under operating conditions. The modeling work and the computer program will directly help the Canadian nuclear industry to conduct assessments of fuel bundle fretting and pressure tube wear in fuel design and qualifications. The methodology and algorithms developed in dealing with the vibrations of multibody systems involving contact and interaction with fluid may be used by researchers and engineers in other industries such as power and process industries. In addition, the proposed work is significant in designing future CANDU reactor fuel to meet the wear specifications that are compatible with the overall reactor life and maintenance schedules.