| 摘要 |
The invention concerns a method of making safe the discharge of residual heat from a nuclear power plant reactor when the filling level in the primary circuit of the reactor cooling system has dropped. According to the invention, the reactor is first shut down and a first cooling and pressure-reduction phase is effected in the cooling system primary circuit. An aftercooler is then switched on in order to take over the discharge of heat from the primary circuit, discharge in this state no longer being ensured by the steam-generating system. In a subsequent step, the pressure is relieved completely and the filling level in the reactor cooling system drops to the centre loop level of the main coolant pipe. A coolant reservoir (7) is also provided for refilling the reactor primary circuit and aftercooler system as necessary. In order to prevent the aftercooler circuit from drying up in the event of unacceptable drops in the aftercooler circuit filling level, the coolant reservoir (7) is connected to the aftercooler system connection pipe (6) at the inlet end via an additional safety flooding pipe (15) which is provided with a nonreturn valve (17) and is opened as filling levels drop. When there is no pressure in the reactor cooling system, the nonreturn valve (17) opens as a function of its closure force as the filling level in the intake line drops, and coolant flows from the coolant reservoir (7) into the intake line. When the reactor cooling system is evacuated in order to degasify the coolant, the closure force of the nonreturn valve (17) is increased by actuating a precontrol valve (20) and is thereby adapted to the modified pressure conditions in the evacuated reactor cooling system. |
