The invention discloses a drainage
system and a drainage method for an underground
nuclear power plant cavern group. The drainage method comprises the steps that accumulated water in an underground
nuclear power plant cavern flowing out via a drainage hopper is monitored by means of a radioactivity monitor, a controller shuts off a first
isolation valve when the radioactivity monitor monitors that the accumulated water is radioactive, the controller opens a second
isolation valve, the radioactive accumulated water enters a drainage
branch associated with radioactivity, and is discharged into a
siphon well after being treated by a radioactive substances
treatment room; when the radioactivity monitor does not monitor that the accumulated water is radioactive, the controller shuts off the second
isolation valve and opens the first isolation valve, and the non-radioactive accumulated water is discharged into the
siphon well; and the accumulated water is discharged to rivers outside a mounting by means of the
siphon well. According to the drainage
system and the drainage method, the passive drainage
system is constructed by utilizing a siphon pipeline and the siphon well, negative pressure formed in a siphon device forces water in the pipeline to flow under pressure, the flow velocity is accelerated, the drainage effect is good, and the drainage system can
discharge the accumulated water out of the
underground cavern in an organized and efficient manner regardless of accidental water accumulation or serious accident conditions.