Analysis of reaction rate and sample worth measured in simulated LMFBR meltdown cores

An analysis of fission rate, fission rate ratio and sample worth has been made on FCA VIII-2 Assembly built to simulate LMFBR meltdown cores. To check the adoptability of computational methods used in analysing core disruptive accidents, the results obtained by the three methods, transport (Sn), conventional and modified diffusion methods, were compared with the measured ones. Group constants used in the analysis were prepared from JAERI Fast Set Version II. Conventional diffusion theory does not represent the measured fission rates both in the compacted and voided region. The results obtained by transport theory with S4P0 approximation agree fairly well with the measured ones. The use of modified diffusion theory, which changes the diffusion coefficient in the voided region does not significantly improve the agreement. For Pu sample worth, problems still remain partially which need a more detailed analysis, although the use of transport theory improves the agreement to a large extent. (author)