Nippon Nuclear Fuel Development Co., Ltd.

Ryoichi Yuda

Kenichi Ito

Hiroshi Masuda

This invention provides nuclear fuel pellets including fission substance of UO.sub.2 or UO.sub.2 having Gd.sub.2 O.sub.3 added thereto, the pellets comprising a satisfactory solid-solution state (homogeneous state), large grain diameters, and a second precipitation phase deposited in grain boundaries, and still having a sufficiently high density. This invention also provides a method of manufacturing the above-described nuclear fuel pellets. The nuclear fuel pellets of this invention comprise UO.sub.2 or (U, Gd) O.sub.2 grains and an aluminosilicate precipitation phase, the precipitation phase being a glass state or a crystalline state, the grains having an average grain diameter of about 20 .mu.m through about 60 .mu.m, the aluminosilicate precipitation phase having a composition including SiO.sub.2 of about 40 wt % through about 80 wt % and Al.sub.2 O.sub.3 of the residual on average, the amount of the alumina and silica being about 10 ppm through about 500 ppm with respect to the total amount of the nuclear fuel pellets, the pellets having porosity of 5 vol % at a maximum.

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Mito, Japan

Ryoichi Yuda