Material mixing process and device for preparing (U, Gd) 02 combustible poisonous core block

Abstract

The present invention provides material mixing process and apparatus for preparing combustible poisonous (U, Gd)O2 core block. The mixing process for UO2 powder and Gd2O3 powder prepared through AUC process includes premixing, and ball milling the pre-mixture in a ball milling drum to obtain homogeneous UO2-Gd2O3 powder. The ball milling procedure has ball milled material loading volume ratio of 1 to 3.0-8.0, ball milling time of 4-8 hr, and milling drum rotation speed of 30-80 rpm. The ball milling drum has inner lining of silicone rubber plate and milling balls of 10-25 cm diameter. The combustible poisonous (U, Gd)O2 core block thus produced has high solid solution degree, no free Gd2O3 phase, and physical and chemical performance reaching the requirement of nuclear reactor.

Description

technical field [0001] The invention belongs to the nuclear material (fuel) preparation process, in particular to (U, Gd)O 2 Mixing process for the preparation of burnable poison pellets. Background technique [0002] International nuclear fuel manufacturers widely adopt (U,Gd)O 2 Poison fuel can be burned to compensate the initial reactivity of the reactor, flatten the power distribution of the core, realize the improvement of reactor unloading fuel consumption and prolong the refueling cycle, thereby reducing the operating cost of nuclear power and improving the safety and reliability of operation. Foreign countries began to study (U, Gd)O in the early 1960s 2 Burnable poison fuel was gradually used in pressurized water reactors in the 1990s. The mixing process is (U, Gd)O 2 One of the key processes in the preparation process of burnable poison pellets. The homogeneity of gadolinium is (U,Gd)O 2 It is an important quality control indicator in the manufacturing proces...

AI Technical Summary

Problems solved by technology

Among the above four methods, the chemical co-precipitation method and the sol-gel method are chemical methods. Under the condition of proper process control, the uniformity of gadolinium can be guaranteed, but the disadvantage is that the use of this process route will cause damage to the Pure UO 2 Preparation of poison pollution of chemical conversion process equipment, for which another set of UO must be built 2 Preparation of chemical conversion process line, which is bound to greatly increase equipment and plant investment, so in the world, these two methods are limited to laboratory research, and have not been applied in industrial production. At present, the method of mechanical mixing is generally used in the world

And for (U,Gd)O 2 For the manufacture of burnable poison pellets, ordinary mechanical mixing methods are difficult to meet its requirements. The reason is that due to the presence of gadolinium, in (U, Gd)O 2 During the sintering process of the pellet, in order to obtain a uniform (U,Gd)O 2 Solid solution structure, it is necessary to reduce or even eliminate free Gd as much as possible 2 o 3 Phase and UO 2 phase, so how to make Gd 2 o 3 Powder is better dispersed in UO 2 It is very important in powder

due to Gd 2 o 3 The powder is easy to absorb moisture and cause agglomeration. Due to the low speed of material movement, it is difficult to effectively disperse the agglomeration and obtain the ideal mixing effect by using ordinary mixing methods. This will bring great difficulties to the subsequent sintering process and even cause cores. A large amount of free Gd in the block microstructure 2 o 3 Phase and UO 2 Unqualified product performance due to the existence of the phase