Spectral shift-producing subassembly for use in a nuclear fuel assembly.

摘要

A spectral shift-producing subassembly (12) is composed of a plurality of sealed empty water displacement rodlets (30) incorporating a spectral shift-producing capability. Each of the rodlets (30) includes an elongated tube sealed at its opposite ends and having an axially-extending annular wall section (54) of reduced thickness compared to the thickness of the wall of the remainder of the rodlet (30). The respective reduced thicknesses of the axial wall sections (54) of the rodlets (30) can be varied to adapt the rodlets (30) to rupture at different times and permit water to enter the rodlets to produce an increase in the water/fuel ratio and thereby an increase in reactivity. The rodlets (30) can also have different levels of pressurization to initiate rupture at different times.