Abstract: A proportion of the liquid metal flow passing through a fast reactor steam generator unit (SGU) is diverted past the outlet to a quiescent zone in the region of immersed tube-to-tubeplate welds at the water entry ends of the tubes, into which zone are given off any hydrogen bubbles which may result from a water leak into the liquid metal. The liquid metal in this zone is caused to flow through a weir system above which there is a gas space for collection of hydrogen, suitable means being provided for detection of hydrogen in this space. The hydrogen is entrained at the water inlet tube plate, the invention making use of the slow solution rate of hydrogen in sodium at lower temperatures prevailing in the quiescent zone at the water inlet end.

Abstract: A tube-in-shell heat exchanger for effecting heat exchange between steam conducted by the heat exchange tubes and liquid metal conducted through the shell. The tubes penetrate the tube sheet by means of clearance apertures and are sealed thereto with thermal sleeves which are brazed to the tubes so that fusion welds are avoided in the sodium/water barrier.