초록 ▼

Methods for manufacturing porous nuclear fuel elements for use in advanced high temperature gas-cooled nuclear reactors (HTGR's). Advanced uranium bi-carbide, uranium tri-carbide and uranium carbonitride nuclear fuels can be used. These fuels have high melting temperatures, high thermal conductivity

Methods for manufacturing porous nuclear fuel elements for use in advanced high temperature gas-cooled nuclear reactors (HTGR's). Advanced uranium bi-carbide, uranium tri-carbide and uranium carbonitride nuclear fuels can be used. These fuels have high melting temperatures, high thermal conductivity, and high resistance to erosion by hot hydrogen gas. Tri-carbide fuels, such as (U,Zr,Nb)C, can be fabricated using chemical vapor infiltration (CVI) to simultaneously deposit each of the three separate carbides, e.g., UC, ZrC, and NbC in a single CVI step. By using CVI, a thin coating of nuclear fuel may be deposited inside of a highly porous skeletal structure made, for example, of reticulated vitreous carbon foam.

대표청구항 ▼

What is claimed is: 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 com

What is claimed is: 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: (UWZrXNbY)CZ, where 0.04<W<0.12, 0.45<X<0.9, 0<Y<0.45, and 0.92<Z<1.0; 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. UCl5+CH4+1/2H2UC+5HCl NbCl5+CH4+1/2H2NbC+5HCl, and ZrCl5+CH4+1/2H2ZrC+5HCl, and 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, BeC2, ZrC2, SiC, pyrolytic carbon, diamond, and diamond-like carbon; and 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.