Abstract: A heat exchanger for transferring heat from primary fluid to secondary fluid and particularly one which is especially suitable for cooling a fast breeder nuclear reactor is disclosed herein. The heat exchanger includes a plurality of thermally conductive, concentric shells spaced apart from one another so as to define a number of primary annular spaces and physically isolated secondary annular spaces therebetween. The primary fluid is directed in a continuous flow through the primary annuli, while at the same time the secondary fluid is directed in a continuous flow through the secondary annular spaces.

Abstract: An apparatus for sealing a rotatable shield plug in a nuclear reactor having liquid metal coolant. The apparatus includes a dip-ring seal adapted to provide a fluid barrier between the liquid metal and the atmosphere and to permit rotation of the shield plug. The apparatus also includes a static seal for the rotatable shield plug located between the dip-ring seal and the liquid metal. The static seal isolates the dip-ring seal from the liquid metal vapor during operation at power and can be disengaged for rotation of the shield plug.