PROBLEM TO BE SOLVED: To provide a shield structure capable of replacing liquid for blocking neutron rays.SOLUTION: A shield structure 1 is disposed between an irradiation chamber 2 irradiated with neutron rays and an operation room 3 located outside the irradiation chamber 2, and blocks the neutron rays in the irradiation chamber 2. The shield structure 1 includes: a transparent water tank 11 that separates the irradiation chamber 2 from a space S, and stores transparent liquid E including water； a liquid supply unit 12 for supplying the liquid E into the water tank 11； a heater for heating the liquid E so as to generate upflow F of the liquid E in the water tank 11； and a liquid discharge unit 14 for discharging, from the water tank 11, the liquid E heated by the heater to be elevated.SELECTED DRAWING: Figure 1
