| Abstract: | A computer code marse has been developed to analyze structural behaviors of fast breeder reactor (FBR) fuel subassemblies under irradiation conditions, especially of wire spaced fuel pin bundles.The first concept specifically considered is to model on pin oval deformation and dispersion phenomena which were found to occur in highly irradiated fuel pin bundles. Every fuel pin is modeled by three-dimensional finite element method beams with trusses at contact points. Almost all phenomena which would occur under irradiation induced bundle-to-duct interaction (BDI) conditions are included in the marse code; these include bending, expansion, oval deformation and dispersion.The second point is to reduce computing time because the BDI analysis requires much computing time if a conventional solving scheme is applied. This problem is resolved by using only a small stiffness matrix of each pin successively to treat interactions with other pins or ducts as outer forces.The marse code has been applied to BDI analyses and has been confirmed to be applicable to any types of FBR fuel pin bundles with high accuracy and a small computing time. |
