핵연료 용기의 일체형 단조공정 개발에 관한 연구

Abstract

Cask is required for the transfer of spent nuclear fuel. Cask is consisted with flange, shell and bottom part. Generally, the diameter of the cask is 2000 mm and height is over than 5000 mm. The shell, flange and base are generally separately manufactured and fabricated by welding them together. These each products are manufactured by hot forging process

Nowadays, monolithic forging of cask is required continuously. Body-base monolithic forging of cask is advantageous as an economical manufacturing process and better reliability for nuclear applications. Backward extrusion is the simplest method to make a body-base monolithic forging cask. But, because of large size of the cask, forging load is higher than capacity of press of 12,000 tons.

Thus, we suggest piercing method is suggested and using two different type of performs. Squared and circular bar are used.

The important point of the piercing process is friction load supported by container. For the successful forming, the value of friction load should be larger than the compression load on bottom die.

Through the finite element analysis and parametric study of design variables , those are die angle, groove length and flange thickness, the optimal dimensions of preform and die sets are determined in order to develop a suitable forging process for body-base monolithic forging.

To verify the result of finite element analysis, the physical model of 1/30 scale of actual product using plasticine was carried out. The result of this experiment, deformed shapes were very similar to the finite element analysis

As a result of this work, the special piercing method was developed using blank material consisting of a flange, groove and squared part.