| 摘要 |
<p>A fuel sub-assemblage incorporates a cluster of fuel pins in a tubular wrapper sepd. by a series of cellular reinforcement grids, each pin occupying a separate cell of each grid. The wrapper has an extension spike at its lower end and a neutron shield at its upper end. Each cell of the reinforcement grid has elastic contact pads to guide the sliding movement of a fuel pin. The pads form a first set which normally supports the pin coaxially in its cell and a second set normally away from the pins, but establishing a second set in case of excessive displacement of the pads of the first gp. Each pin is retained at one end by a cellular retaining grid fixed to an end region of the wrapper. The lower end of each pin has pref. a radial projection to bear against the lower face of the retaining grid. A process for removing a sub-assemblage from a wrapper comprises cutting off the upper and lower end regions of the wrapper to separate the neutron shield and the spike, cutting the wrapper immediately above the retaining grid and extracting from the set formed by the wrapper and reinforcement grids the set which the retaining grid and cluster of fuel pins consitute. The construction facilitates the removal of the wrapper for retreatment of the sub-assemblage after irradiation, for recovery of unused fissile material and sepn. of plutonium.</p> |
