PURPOSE: To reduce material cost and fabrication cost of simulated fuel pellets, when fabricating the simulated fuel pellets which constitute a weight simulated fuel assembly.

CONSTITUTION: In stead of the ordinary W pellets having hollow part, simulated fuel pellets consisting of weight simulated fuel assembly, which are a combination of different kinds of materials such as W pellets and stainless steel pellets both of which density are lower than that of a tungsten, in a manner that the tight of the combination coincides to that of actual UO2 pellets, for instance, the W pellets 1 and the stainless steel pellets with controlling both height thereof, are inserted into and fill a fuel clad tube 3.