Abstract: Channels running along the cooling tubes, between the cooling tube and the liner to which the tubes are attached, serve to collect leakage gas through lateral openings connecting the channels to the boundary between the liner and the concrete. These channels can be produced in the extrusion of the cooling tubes and provide considerable saving in the construction of the leak monitoring system as well as efficiency in bringing the leakage detecting channels close to the liner. The channels are connected to a known form of piping tree equipped with valves for determining leak location after the presence of a leak has been found with all the branches connected to the detector unit. A conventional set of perforated pipes embedded in the concrete running at right angles to the cooling tubes may be used to complete the detection raster where large surfaces are to be monitored.