| 摘要 |
933,500. Nuclear fuel elements. NUCLEAR MATERIALS & EQUIPMENT CORPORATION. Aug. 9, 1961 [Aug. 23, 1960], No. 28733/61. Class 39 (4). A nuclear fuel element comprises a compacted mass of pellets of fissile material, each pellet having a coating of at least one layer of a material which protects the fissile material from corrosion (which may occur as a result of leakage of the cladding, particularly at welded joints), helps to retain fission products, and provides additional mechanical strength to improve dimensional stability under irradiation, the coatings being deformed but not broken during the compacting process so that the compacted mass has a lattice of the deformed but unbroken coatings with the fissile material contained in the lattice cavities, and the pellets being deformed so that the density of the element approaches that of a solid block of the fissile material, e.g. in excess of 90%. One method of manufacture is illustrated in Fig. 2, a dense mass 15 of the pellets enclosed in a tube 17 of Zr, Nb, Zr-Nb alloy, or stainless steel closed by rubber stoppers 19 being passed through a swaging machine where it is repeatedly impacted by dies 21. The compacting may also be effected by hot or cold extrusion. The stoppers 19 are subsequently removed and metallic end plugs inserted and welded in place. Suitable materials for the pellet coatings are; Al, Cu, Ni, Fe, Si, Cr, Nb, V, W, Mo, Zr, Ti, Yt, Mg, Be, C, V-Nb alloy, Mo-W alloy, Mg-Be alloy, Fe-Cr alloy, stainless steel, Al 2 O 3 , Yt 2 O 3 , ZrO 2 , SiC, and BeO. The coatings may be single layers or several layers of different materials, one encasing the other, each layer including at least one of the above materials. |
