The Method of Manufacturing a Pelletized Nuclear Ceramic Fuel

Abstract

The invention is related to nuclear technologies, in particular, to the technology of producing nuclear oxide fuel for fuel elements, this oxide fuel can be used for manufacturing palletized nuclear fuel from uranium dioxide to be consumed by NPPs. The essence of the invention: this method of producing palletized nuclear fuel from uranium dioxide involves preparation of uranium dioxide moulding powder with/without uranium oxide, at this point powdered uranium dioxide is used as a raw material for preparation of moulding powder. Powdered uranium dioxide should be in the following proportion: O/U=2.370.04, it is obtained using a renowned methodby air heating of powdered uranium dioxide (ceramic grade) with the following proportion O/U=2.012.15. The technical result of the invention is increased mechanical strength of sintered pellets and a larger grain size of sintered pellets. 3 appendices, 1 diagram, 2 figures

Claims

1. The method of manufacturing a pelletized nuclear ceramic fuel, including preparation of uranium dioxide moulding powder with or without an addition of concentrated uranium oxide, pressing the moulding powder and sintering the pressed pellets in a reducing atmosphere, wherein as a raw material for the preparation of moulding powder they use uranium dioxide powder with a proportion of oxygen to uranium equal to: 2.370.04, which they preliminary obtain by heating a ceramic grade uranium dioxide powder in air.

Description

EXAMPLE 1

[0029] They pour 300 g of a ceramic grade uranium dioxide powder, obtained by the method of uranium hexafluoride dry conversion (the total specific surface area of the powder is 2.8 m.sup.2/g), as a layer of 10-15 mm in a stainless steel baking tray, place it in a muffle, preheated to a temperature of 16010 C., and keep in it for 3-5 minutes when the muffle door is open. Then they remove a baking tray with the powder out of the muffle and cool it down to the room temperature.

[0030] Thus way obtained the powder with a proportion of O/U=2.370.04 is used for manufacturing of sintered pellets according to standard technology: [0031] they add a 6% solution of polyvinyl alcohol (PVA) with glycerin to the powder as a binder and mix it thoroughly in a porcelain cup; [0032] they press the prepared batch at a specific pressure of 1100-1200 kg/cm.sup.2 in a matrix with a diameter of 20 mm; [0033] they grind up the obtained tiles in a mortar and rubbed through a strainer with a mesh size of 0.63 mm; [0034] prepared thus way moulding powder is pressed at specific pressure of 2100-2200 kg/cm.sup.2 in a matrix of 9.3 mm diameter; [0035] they sinter pressed pellets at a temperature of 1700 C. in an argon-hydrogen mixture; holding at this temperature is equal to 2 hours.
The results of the powder processing are shown in the Table 1 in comparison with the results of regular powder sintering; FIG. 1 shows sintered pellets distribution on the grain size, which was determined using optical microscopy.

Example 2

[0036] They mix the powder with a proportion of O/U=2.370.04, prepared the same as in example 1, with 0.3% 1.2-DISED (distearyl ethylenediamine) with the formula C.sub.38H.sub.76O.sub.2N.sub.2 as a dry lubricant. They manufacture pellets from the prepared mixture, as in the example 1. The results of the powder processing are shown in the Table 1 in comparison with the results of regular powder sintering; FIG. 1 shows sintered pellets distribution on the grain size, which was determined using optical microscopy.

Example 3

[0037] They mix the powder with a proportion of O/U=2.370.04, prepared as in example 1, with 10% of concentrated uranium oxide (specific surface area 8.2 m.sup.2/g), obtained from ammonium polyuranate. Prepared homogeneous mixture is processed as in the example 1.

The results of powder processing are shown in the Table 1; FIG. 2 shows sintered pellets distribution on the grain size, which was determined using optical microscopy.

TABLE-US-00002 TABLE 1 Powder of Pellets density, g/cm.sup.3 uranium dioxide Binder pressed sintered Regular factory-made PVA 6.15-6.20 10.62-10.66 According to the invention 6.15-6.20 10.68 Regular factory-made DISED 5.34-5.36 10.58-10.66 According to the invention 5.57-5.59 10.57 According to the invention PVA 5.81-5.83 10.45 with an addition of concentrated oxide