Abstract: Disclosed herein are a collagen-based matrix for use as a restorative material and a method for the preparation thereof. An atelocollagen dispersion is spread at a predetermined thickness over a plate and freeze-dried to form a porous collagen membrane. An atelocollagen dispersion is separately spread over a plate and pressurized to form a dense collagen membrane. This is overlaid with the porous collagen membrane and immersed in an EDS solution in ethanol to crosslink the two membranes with each other. From the bilayer structure thus constructed, EDS is removed, followed by lyophilization and cutting into an appropriate size.

Abstract: Disclosed herein is a joining structure between a top nozzle and guide thimbles in a nuclear fuel assembly, which can prevent a rotation of inner insertion tube bodies when the top nozzle is separated from the nuclear fuel assembly and promote convenience in assembling and disassembling the top nozzle and the guide thimbles.