Patent ID: 7666463
Filing Date: 2010-02-23
Classification: G21C,Y02E

Abstract:
1. A process for fabricating a nuclear fuel element, comprising: a) infiltrating an open-celled precursor foam material with a carbon-bearing resin; b) pyrolyzing the resin-infiltrated precursor foam material to form a porous, open-celled, carbon-bearing reticulated skeleton comprising a three-dimensional, reticulated network of interconnected structural ligaments; c) heating the carbon-bearing reticulated skeleton in the range of about 1000 C to about 1200 C; and d) flowing a reactant gas comprising the nuclear fuel through the heated skeleton, reacting the reactant gas, and depositing a coating of the nuclear fuel comprising uranium tri-carbide on top of the heated ligaments of the skeleton; and thereby forming a single-phase, solid-solution uranium tri-carbide alloy coating having the following composition: (U wherein the reactant gas comprises a mixture of niobium pentachloride, zirconium pentachloride, uranium pentachloride, methane, and hydrogen; the mixture being made by chlorinating a pellet of niobium metal to form niobium pentachloride gas; by chlorinating a pellet of zirconium metal to form zirconium pentachloride gas; by chlorinating a pellet of uranium metal to form uranium pentachloride gas; and mixing the niobium pentachloride gas, zirconium pentachloride gas, and uranium pentachloride gas together with methane and hydrogen prior to flowing the reactant gas through the heated carbon-bearing reticulated skeleton; and wherein uranium carbide, UC, niobium carbide, NbC, and zirconium carbide, ZrC are simultaneously deposited on the carbon-bearing reticulated skeleton via the following reactions, at a temperature of about 1000 to 1200 C. e) further comprising vapor depositing a protective coating on top of the nuclear fuel; wherein the protective coating comprises one or more materials selected from the group consisting of SiC, NbC, ZrC, BeO, BeC wherein the open-celled precursor foam material comprises polyurethane foam; and wherein the carbon-bearing reticulated skeleton is selected from the group consisting of carbon bonded carbon fiber (CBCF) foam, reticulated vitreous carbon (RVC) foam, pitch derived carbon foam (PDCF), and graphite foam; and wherein the nuclear fuel element has a total porosity greater than about 77% and less than about 85%; and wherein the total porosity of the open-celled precursor foam material, not including the nuclear fuel, is greater than about 95%; and wherein the coating of nuclear fuel has a thickness less than or equal to about 50 microns; and finally wherein the process further comprises: after the skeleton has been coated with the nuclear fuel in step d), removing the carbon-bearing reticulated skeleton from inside of the ligaments by baking the coated skeleton in an atmosphere comprising oxygen or hydrogen or both oxygen and hydrogen; thereby leaving a hollow central core space inside of the ligaments.