Abstract: A nuclear fuel assembly comprising a plurality of fuel rods, each fuel rod comprising a cladding tube closed at both ends and filled with cylindrical nuclear fuel pellets such as sintered uranium dioxide or uranium plutonium dioxide. All or nearly all of the cylindrical pellets are coated with a refractory boride coating of sufficient thickness to prevent mechanical interaction between the pellets and the tube. The isotopic composition of the boron in the refractory boride is adjusted for each batch of fuel pellets, rods, or assemblage of rods so that the initial excess reactivity, k, of the batch, when assembled in a reactor core, is nearly zero.

Abstract: A cadmium oxide glazed nuclear fuel pellet and glazing composition therefor is disclosed which controls the reactivity and extends the operating life cycle of a nuclear reactor while increasing the rate of burnout of the burnable absorber and reducing the amount of undersirable gases produced therefrom. The glaze forming composition comprises at least about 0.5 percent by weight cadmium oxide as a burnable absorber, i.e., cadmium-113 isotope, and at least one glaze forming oxide. The glaze constituents are formed into a slurry and a nuclear fuel pellet is dipped into the slurry to produce a hard refractory glaze upon firing and cooling.

Abstract: A method and apparatus for identifying those fuel rods (32) of a multiple-rod nuclear fuel assembly (30) which contain leaks, are described. The longitudinal position of the leak in the fuel assembly is determined by moving a first test probe (62) longitudinally along the length of the fuel assembly while drawing coolant surrounding the fuel rods into the probe and sampling the radioactive product content of such coolant. The exact position of the leaking fuel rod is then determined by using second (63) and third (64) test probes to logically subdivide the fuel rods of the fuel assembly at such longitudinal position into successively smaller groups while sampling the radioactive content of coolant surrounding the smaller rod groups, until the leaking fuel rod is isolated. A test probe configuration (60) for subdividing and isolating selective groups of the fuel rods for the coolant sampling is disclosed.

Abstract: An annular burnable absorber rod which minimizes the displacement of cooling water from a nuclear reactor core is disclosed. The rod is constructed from a pair of concentric tubes providing a sealed annular space therebetween. A tubular support having a layer of zirconium diboride deposited by chemical vapor deposition is located within the annular space and protected against corrosion.

Abstract: A method for coating a uranium dioxide nuclear fuel with a zirconium diboride burnable poison. First, a layer of niobium is bonded to the nuclear fuel. Then, a layer of zirconium diboride is deposited by chemical vapor deposition on the niobium layer. A zirconium diboride coated nuclear fuel having a layer of niobium between a uranium dioxide substrate and the zirconium diboride layer also is disclosed.

Abstract: An improved nuclear fuel composition characterized as a mixture of the dioxide of uranium and plutonium with pores of specified sizes and volumes of each size. The volume of pores of each size are adjusted so that as each group of pores of each size is removed by the nuclear fission induced process of densification, the volume removed is balanced by the volume added by the nuclear fission induced process of solid state swelling. This fuel composition is dimensionally stable in-pile to high burnups because the rate of pore removal is matched to the rate of swelling.