Abstract: A nuclear fuel rod, which comprises:a cladding tube filled with an inert gas or liquid metal and sealed at both ends in airtightness; anda plurality of nuclear fuel pellets piled one atop another in the cladding tube,and wherein an adsorbent carrying a tag gas for monitoring a nuclear fuel rod failure is received in the inner space of the cladding tube defined at least above or below the nuclear fuel pellet pile.

Abstract: A fuel element for a high temperature gas cooled nuclear reactor which aims at reducing the temperature difference between the fuel center and the coolant has a reduced thickness of heat transfer path and means for eliminating discontinuities therein. The fuel element has flat plates each having a inner fuel bearing sheet of coated nuclear fuel particles dispersed in a carbonaceous matrix material clad by preformed relatively thin artefacts of unfuelled carbonaceous material which have been platen pressed on to the external surfaces of the fuel sheet while both the fuel sheet and the artefacts are in the green state.

Abstract: A fuel element contains a tag gas serving to detect breakage of a cladding tube. Pellets of a fuel material and a metal foil having a tag gas implanted thereinto by ion implantation method are loaded in a cladding tube.

Abstract: Rupture of boiling water reactor nuclear fuel cladding resulting from embrittlement caused by fission product cadmium is prevented by adding the stoichiometrically equivalent amount of CuFe.sub.2 O.sub.4 or CuTiO.sub.3 to the fuel.

Abstract: Rupture of boiling water reactor nuclear fuel cladding resulting from embrittlement by fission product cadmium is prevented by adding the stoichiometrically equivalent amount of V.sub.2 O.sub.4 or V.sub.2 O.sub.5 to the fuel.