Nuclear fuel assembly holddown apparatus

A nuclear fuel assembly to be located below a core upper alignment plate and on a core support stand, the stand having a square array of projections thereon forming mating surfaces, comprising:

• a. a lower end fitting having an upper portion with an opening therethrough and a lower portion facing the support stand and including a square array of posts for placement adjacent to a respective array of projections;
• b. actuating means extending from the upper end of the assembly through the opening in the lower end fitting and being movable relative thereto, the actuating means including,
• (1) an actuating rod vertically movable in response to the position of the core upper alignment plate,
• (2) rigid arms fixedly connected to the lower end of the actuating rod, each arm extending toward one of the posts, the arms having a lowermost position when the core upper alignment plate is in place;
• c. locking means carried by the lower end fitting adjacent to each of a first set of two proximate posts, the external side of each latching means having a latch adapted to mate with the mating surface on the projections and having an internal side including a vertical land surface directly below the outer end of one of a first set of arms;
• and
• d. bracing spring means carried by each of the other two proximate posts, each bracing means being located below the outer end of one of the second set of arms, and each bracing means having an orientation and spring rate such that when each of the second set of arms is in the lowermost position it biases the bracing spring to
• (1) urge the proximate post into bracing abutment with the adjacent projection, and
• (2) produce a substantially constant horizontal locking force component that is transmitted through the arms whereby one of the latches is urged into locking engagement with the mating surface on the proximate projection.