Variable force spring device for sodium pipe system of fast reactor

The invention provides a variable force spring device for a sodium pipe system of a fast reactor. The variable force spring device comprises a top plate, an indicator board assembly, springsin an evennumber, a bolt assembly, a shell assembly and an elastic nut. The top plate is fixedly connected above the shell assembly, the springs are arranged in the shell assembly, the bolt assembly penetratesthe centers of the springs, the upper end of the bolt assembly is connected to the indicator board assembly while the lower end of the bolt assembly is connected to the elastic nut, the indicator board assembly presses the upper ends of the springs, and the springs are arranged in a matrix. The variable force spring device also comprises a tray receiving assembly which is arranged at the middle contact position between the upper and lower springs. By arranging the springs arranged in the matrix, the using strength and the using load of the variable force spring are enhanced, the operating stroke range of the variable