Nuclear fuel pellet manufacturing method

Molibdenum dioxide powders are added to uranium dioxide powders and put to press molding. Then, heat processing applied at a temperature and in an atmosphere that an oxygen potential is lower than -350KJ/mol. In this case, molybdenum dioxide is reduced along with the sintering of uranium dioxide to deposit metal molybdenum. Then gas bubbles occupy about one-half of the volume occupied by the molybdenum dioxide. Accordingly, the difference of expansion or shrinkage between uranium dioxide and molybdenum due to the difference of linear expansion coefficient between them is absorbed by the gas bubbles. Therefore, no stresses are caused and no cracks are formed. Molybdenum is activated to be a getter, to absorb iodine and oxygen formed in the fuel pellet. With such a constitution, corrosion cracks of cladding tube and reduction of heat conductivity can be inhibited. (I.N.)