Study on improvement of availability for fuel handling system of JOYO

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With a purpose of operating effectively JOYO as a fuel irradiation bed, studies have been conducted for reduction of fuel handling time and prevention of troubles resulted in delay of fuel handling time. This report describes of results of following studies. (1)Increase of numbers of fuel assembly received in the transfer rotor tank as a buffer storage (2)Abandonment of fuel cooling pot and addition of fuel transfer pot in the in-vessel storage rack (3)Necessity of the guide sleeve and maintenability of the hold-down mechanism of in-core charge machine (4)Addition of rotating function to the gripper of in-core charge machine (5)Reduction of gas-purge time of the guide sleeve connected with ex-vessel transfer machine (6)Reduction of spent fuel cleaning time and spent fuel canning time. As a result of the above-mentioned studies, the feasibility of increasing numbers of fuel assembly received in the transfer rotor tank was proved and the refueling time undetr reactor shutdown was prospected to reduce as follows; (1)Abandonment of fuel cooling pot reduces about 2.5days per one refueling period. (2)Abandonment of the guide sleeve of in-core charge machine reduces about 2days per one refueling period. (3)Gas-purge time of the guide sleeve connected with ex-vessel transfer machine reduces one half as compared with the present gas-purge time by means of the ex-vessel transfer guide sleeve attached door-valve.