Method for preparing UO
A method for preparing a UO 2 mixture powder for nuclear fuel manufacturing, comprises the steps of: (a) weighing and sieving, by means of an automatic injection device, a UO 2 powder, a porogen and a lubricant, and injecting same into a UC container; and (b) mixing the UO 2 powder, the porogen and the lubricant by means of an IBC blender. According to a method for preparing a UO 2 mixture powder for nuclear fuel manufacturing, mixing time is short, and degrees of mixing and homogeneity of a prepared UO 2 mixture powder are excellent.
1 . A method of preparing a UO 2 powder mixture for nuclear fuel manufacturing, the method comprising:
(a) weighing and sieving a porogen and a lubricant using an automatic injection device; and injecting the porogen and lubricant together at an initial stage into a container containing UO 2 powder; and
(b) mixing the UO 2 powder, the porogen, and the lubricant using a blender,
wherein the mixing in the (b) comprises:
forward mixing performed under conditions in which:
a rotation speed of the blender is in a range of 10 to 14 rpm,
a container filling rate of the powder is in a range of 50 to 70 vol %, and
a mixing time is in a range of 20 to 30 minutes, and
backward mixing performed under conditions in which:
a rotation speed of the blender is in a range of 10 to 14 rpm, and
a mixing time is about 10 minutes, and
wherein the UO 2 powder is contained in an amount of 10 to 500 kg, and 0.08 to 10 parts by weight of the porogen and 0.05 to 1 part by weight of the lubricant are contained with respect to 100 parts by weight of the UO2 powder.
2 . The method of claim 1 , wherein the porogen is U 3 O 8 powder or azodicarbonamide (ADCA, C 2 H 4 N 4 O 2 ).
3 . The method of claim 1 , wherein the lubricant is Acrawax (ethylene distearamide, C 38 H 76 N 2 O 2 ) or zinc stearate (Zn—C 36 H 70 O 4 ).
4 . The method of claim 1 , wherein the automatic injection device comprises a 300-μm sieving machine and removes granules present in the porogen and the lubricant, and
the porogen and the lubricant are added in a weight ratio set according to the weight of the UO 2 powder.
5 . A method of manufacturing a UO 2 nuclear fuel, the method comprising:
preparing a UO 2 powder mixture by:
(a) weighing and sieving a porogen and a lubricant using an automatic injection device; and injecting the porogen and lubricant together at an initial stage into a container containing UO 2 powder; and
(b) mixing the UO 2 powder, the porogen, and the lubricant using a blender,
wherein the mixing in the (b) comprises:
forward mixing performed under conditions in which:
a rotation speed of the blender is in a range of 10 to 14 rpm,
a container filling rate of the powder is in a range of 50 to 70 vol %, and
a mixing time is in a range of 20 to 30 minutes, and
backward mixing performed under conditions in which:
a rotation speed of the blender is in a range of 10 to 14 rpm, and
a mixing time is about 10 minutes, and
wherein the UO 2 powder is contained in an amount of 10 to 500 kg, and 0.08 to 10 parts by weight of the porogen and 0.05 to 1 part by weight of the lubricant are contained with respect to 100 parts by weight of the UO2 powder;
manufacturing a UO 2 molded pellet by pressing the UO 2 powder mixture;
manufacturing a UO 2 sintered pellet by sintering the UO 2 molded pellet; and
manufacturing a UO 2 ground pellet by grinding the sintered pellet so that the sintered pellet maintains a uniform diameter,
wherein a defect rate is 5% or less, and the sintered pellet has a density of 10.30 to 10.58 g/cm 3 .