Patent Number: 049884735
Section: abstract

A self-latching reactivity-reducing device contains neutron absorbing material and is installable in a guide thimble of a spent fuel assembly for reducing the reactivity of the assembly to allow its storage in an on-site fuel storage facility. The device includes an elongated rod which contains the neutron absorbing material and has a central passage extending between opposite ends of the rod. A self-latching mechanism is disposed on a leading end of the rod and engagable with a lower end portion of the guide thimble upon full insertion of the rod in the guide thimble so as to render the self-latching mechansim unlatchable from the guide thimble without the use of an independent tool inserted solely through the rod passage from a trailing end thereof. A closure plug is removably fastened to the trailing end of the rod for closing the passage therethrough. The self-latching mechanism includes a plurality of latch members being mounted for pivotal movement between displaced latching and releasing positions at the leading end of the rod and biased toward the latching position.