Method and apparatus for obtaining a water sample from the core of a boiling water reactor

This patent describes a process for the evacuation of water sample from a boiling water reactor in the core bypass region at the vicinity of the top guide. It comprises: providing a tube having a first end for insertion to the vicinity of the top guide in the core bypass region of the nuclear reactor and have a second end at a location remote from the reactor; inserting the first end of the tube in a local power range monitor conduit in the core bypass region with the open end of the tube exposed to nearly saturated water adjacent the top guide; reducing the pressure in the tube from the second end of the tube whereby the water adjacent the open end of the tube flashes to a steam water mixture of high specific volume and rapidly passes through the tube; and condensing the steam at the remote end for analyzing the contents of the water