Reactor core provided with a device allowing for precise operation of the combustible elements

Reactor core provided with a grate and many combustible caskets each of which made of a number of combustible bars enclosed within a sheating, the grate of the reactor core forming essential reactor core and each field enveloping a group of four combustible caskets separated by slots and arranged so that there should be an elastic mechanical contact betweent their envelopes and the reactor grate as well as between themselves, such slots being intended to receive the four arms of a vertically arranged controll bar of cross-shaped cross-section, characterized in that each slot at the height of the core grate is provided with a non yielding distancing plate the total dimension of which (a+2b=) corresponding to the spacing is equal to or greater than the maximum thickness of the control bar