Nuclear reactor assembly having a reversible weldless connection between a casing and an element inserted therein

An assembly to be inserted into a nuclear reactor, such as a liquid sodium-cooled fast neutron reactor, includes an assembly hollow body of elongate shape along a longitudinal axis X. The wall of the hollow body includes at least one through-opening. The assembly also includes an assembly element inserted into the hollow body. The assembly element includes at least one flexible blade of which the free end is shaped into a clip-fastening hook collaborating in clip-fastening fashion with the through-opening from inside the hollow body, so as to connect the assembly element to the hollow body. The assembly also includes at least one removable structure for locking the flexible blade clip-fastened into the through-opening. The removable locking structure makes it possible to prevent the flexible blade from flexing and thus the removable locking structure makes it possible to lock a connection between the assembly element and the hollow body.