ES350396A1 - An elemental fuel device suitable for use in a nuclear reactor placed at pressure. (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

A fuel element suitable for use in a pressurized nuclear reactor comprises a plurality of fuel pellets disposed in a cladding with a clearance space therebetween to permit differential thermal expansion and contraction between the pellets and the cladding and a gas-forming compound enclosed within the element and adapted to form a gas at operating temperature to offset exterior fluid pressure on the cladding and thereby reduce premature fatigue failure due to strains during cyclic operation of the reactor. As shown in Fig. 1, 1 a stack of fuel pellets 12 is disposed within a cladding 14 closed by end plugs 16, a plenum chamber 22 being provided at the upper end of the element to accommodate fission product gases. Within the chamber 22, a bodv 24 of a gas-forming compound is mounted between a pair of discs 26, 28 of aluminium oxide on the upper end of the stack of fuel pellets 12. The pellets 12 are held in place by a coil spring 30 located between the uppermost disc 26 and the upper end plug 16. The body 24 may be of an oxalate or a carbonyl decomposing in the temperature range 200 to 600 F. Example of such compounds are Ni(C0 4 ), Fe(C0 5 ), NiC 2 O 4 , Al 2 (C 2 O 4 ) 3 and MnC 2 O 4 . FeC 2 O 4 , which is liquid at normal temperatures may also be used, being absorbed in a carrier such as a molecular sieve or a chelate. The cladding 14 must be inert to the carbon monoxide and carbon dioxide produced on decomposition of the body 24, also the coolant surrounding the fuel element, and may be a Zr-base alloy or an austenitic stainless steel. The amount of gas-forming compound present is sufficient to produce a pressure of 600 to 3500 p.s.i. Alternatively, solid CO 2 is used for the body 24, vaporizing to form CO a gas.