Fabrication of annular pellet for dual cooled fuel

Fabrication method of an annular pellet with highly precise diametral tolerances has been investigated. On applying a dual cooled annular fuel to a high power density pressurized water reactor, one of the most critical problems is its gap conductance asymmetry, which might be solved with a precise tolerance control of an annular fuel pellet. In order to achieve a better diametral tolerance, a new compaction process which combined a usual double acting pressing and a cold isostatic pressing was tried. A green annular pellet was firstly compacted with a double acting press and then pressed again with a cold isostatic press (CIP) after a precisely machined metal rod was inserted. A sintered annular pellet which is fabricated by the new combined compaction process shows an inner diametral tolerance of less than ±15μm without an inner surface grinding