Cooling device at shut-down

Purpose: To provide a cooling device at shut-down which can perform cleaning and warming-up and can operate safely without discharging reactor water outside the system. Constitution: This arrangement comprises a pressurizing device and a heat-removing device disposed at the external of a container surrounding a pressure vessel in a reactor, said pressure vessel being connected to said pressurizing device and said heat-removing device, and a pipe connected to a water pipe at the external of said container. A pipe, which takes water from the reactor and returns it to the pressure vessel through the pressurizing device and the heat-removing device, is provided with a flow detector and a stop valve, an orifice disposed by by-passing thereof and a stop valve. (Nakamura, S.)