Operation report on experimental fast reactor "JOYO" investigation of the trouble and the unknown imprity on plugging meter in JOYO secondary auxiliary cooling system

not registered; not registered; not registered; Kotaka, Yoshinori; not registered; not registered; not registered

The Plugging Meter is used in JOYO Secondary Auxiliary Cooling System to monitor the sodium purity. This Plugging Meter have been operated more than 12 years since the coolant sodium was charged into JOYO Secondary Auxiliary Cooling System in 1975. Since its operation, some trouble conditions were observed and countermeasures have been taken. For these presume, the state of occurrence trouble conditions were investigated from 100MW 1st cycle operation to 100MW 14th cycle operation. The cause of some trouble conditions are as follows. (1)Increase of Plugging temperature during Reactor operation is supposed to be caused by unknown impurity precipitations except oxygen or hydrogen one. The unknown impurity is transfered from piping and component material in Secondary Auxiliary Cooling System after Reactor Power-up. (2)Sodium flow changes in Plugging Meter, like electric nois, are caused by gas into system sodium flow. (3)Sodium flow changes in Plugging Meter, in case that is not concerned with impurity precipitation, are caused by output voltage changes of the electromagnetic flow meter. This output voltage is shifted by sodium temperature changes. The researches and investigations of Plugging Meter in this system are continued to clear above and other specified matters, and take basically countermeasures.