Low-pressure leakage flow rate measuring device and measuring method of shaft sealing pump for nuclear power plant

The invention provides a low-pressure leakage flow rate measuring device and method of a shaft sealing pump for a nuclear power plant. A measuring cavity is formed inside the measuring device; the measuring cavity communicates with a leakage gap of the measuring device; the leakage gap is connected with a liquid inlet pipe; a throttle hole is formed in the measuring cavity, and communicates with the measuring cavity and the inside space of the measuring device; the measuring device also comprises a liquid discharging pipe and a liquid level meter; the liquid discharging pipe communicates withthe inside of the measuring device; and the liquid level meter is arranged on the measuring device, and is used for measuring the height H of fluid in the measuring cavity. The measuring method comprises the following steps of 1, installing the measuring device on a low-pressure flow rate leakage pipeline; 2, measuring the height H of leaked fluid in the measuring cavity by using the liquid levelmeter; and 3, calculating