Improvement of replacing frequency for connecting pins of encoder measuring the position of shearing blade and gags by stress analysis

Japan Nuclear Fuel Ltd. (JNFL) is now constructing a commercial nuclear fuel reprocessing plant at Rokkasho Mura, introducing French technology on the main processes of it. Shearing machine, which is one of the most important equipment of the head end process in the reprocessing plant will be also manufactured, based on French technology. The shearing machine cuts a spent fuel element (FE) which is transferred from spent fuel storage pool in about 35 mm length and chopped fuel rods enter into the dissolver. After the FE in the fuel element introduction part of the shearing machine is pushed at a constant pitch to the shearing part, FE is pressed and fixed by the main gag and the auxiliary gag. And then the fuel rods are cut by the shearing blade attached to the blade holder trolley which moves forward. The main gag, auxiliary gag and the blade holder trolley are equipped with encoder through connecting pins in order to measure their positions and to control the their movements. These connecting pins are important parts to operate the shearing machine and they are planned to be replaced periodically. For the purpose of making their replacing frequency longer, strain measuring test during shearing and stress analysis test have been performed about the connecting pins. The data of the strain and acceleration about the connecting pins have been measured when PWR and BWR dummy fuels were sheared by the full scale mock-up shearing machine at the center for R and D of JNFL. Stress analyses corresponding to the above test have been carried out in order to evaluate the analysis method by Mitsubishi Heavy Industries. LTD. and the calculated values agrees with the measured one. According to this analysis method, stress analysis has been carried out for various improved connecting pins of which material and mechanical structure are changed. The result of the test confirmed that the replacing frequency can be made longer for the improved connecting pins. This paper reports the strain measuring test during shearing and stress analysis test for the connecting pins to make their replacing frequency longer. (author)