Nuclear fuel elements and method of making same

A method for making a nuclear fuel element for a high temperature gas moderated reactor that has a normal operating temperature of 2000.degree. C., or more, comprising the steps of;

• a) providing a plurality of porous graphite or carbon members that are adapted to have fissionable material impregnated in the pores thereof,
• b) impregnating fissionable fuel material within said pores,
• c) heating said members to cause the fissionable material to melt and react with the carbon wall of said pores, thereby to localize and stabilize the fissionable fuel material within the pores, and
• d) forming a layer of pyrolytic carbon over the outer surface of said members, thereby to seal the pores and to form a barrier against migration of the melted fissionable material from the pores.

A method for making a nuclear fuel element for a high temperature gas-moderated reactor that has a normal operating temperature of 2000.degree. C., or more, comprising the steps:

• a) providing a plurality of porous graphite or carbon members that are adapted to have fissionable fuel material impregnated therein,
• b) impregnating said members with oxidant and heating the members to increase their porosity by causing a controlled reaction with the oxidant,
• c) impregnating said members with a solution of fissionable fuel material and solvent and evaporating the solvent to leave fissionable fuel material deposited in pores of the graphite members,
• d) heating said members to react the fissionable material with the graphite members and to increase porosity of the graphite members,
• e) re-impregnating said members (one or more times) with a solution of fissionable fuel material and solvent and evaporating the solvent,
• f) coating the graphite members with a layer of pyrolytic carbon (or diamond) to further localize the fissionable material within the pores, and
• g) depositing one or more additional layers of pyrolytic carbon or diamond on the outer surface of the graphite or carbon members or on the earlier-applied coatings thereon.