Development of a new fuel handling machine suitable for an Upper inner structure with a slit

Large and Medium scale sodium cooled reactors which has a upper inner structure (UIS) with a slit have been developed in the 'Feasibility Study on Commercialized Fast Breeder Reactor Cycle Systems'. In this study, a new fuel handling machine (FHM) which is suitable for the UIS with a slit has been developed. In the FY2004 study, 1/10 scale bearing tests have been performed and a test rig for real scale bearing have been manufactured. Angular contact ball bearings which can reduce clearance at bearing are selected since the FHM deflection reduction in earthquake is important to prevent contact between UIS and FHM. As a result of 1/10 scale bearding test, the lubrication specification is selected to be a combination of stainless steel rings with MoS2 coating and ceramics balls. In the case of 20000 cycle swing operation which is equivalent to 10 fuel exchanges for large reactor and 20 for middle scale, the limit surface pressure is evaluated to be 1800 MPa which is lower than the design surface pressure of the fuel handling machine (1580 MPa) and the pessimistic design surface pressure (1745 MPa). The surface pressure of the real scale experiment in FY2005 is selected to be 1745 MPa to demonstrate bearing reliability considering uncertainty. (author)