Wrapper tube for fuel assembly

Purpose: To prevent a wrapper tube from being bent due to the irradiation of fast neutrons in a FBR type reactor fuel assembly. Constitution: The right half of a wrapper tube with a regular hexagonal cross section if formed of a stainless steel-316 member, and the left half thereof is formed of a member in which a low swelling additive is added to stainless steel-316. When such a wrapper tube is disposed so that the low swelling side is directed to confront the center of the reactor core, no deformation accident occurs due to the difference between the amount of fast neutron irradiation in the portion near to the center of the reactor core and the portion far therefrom, but uniform swelling will be obtained, and so the bending of the wrapper tube can be prevented. (Kamimura, M.)