Abstract: In an electrical safety system primarily for controlling the insertion of absorber rods into a nuclear reactor core in response to a trip signal, two groups of switches are connected between a power supply and the rod magnets. One group of switches is controlled by signal converters which receive input signals from respective guardlines. The other group of switches is controlled by opto-isolator/photo-detector links which also receive the input signals from the guardlines. If fault conditions in the reactor are sensed by more than one of a group of fault sensors, the feeding of the input signals to the signal converters and the optical links is inhibited, and the switches open, thereby deenergizing the magnets.

Abstract: A method of repairing a defective tube in a heat exchanger of the tube-in-shell type comprises inserting a tubular sleeve into the defective tube and extending through the tube from one tubeplate to the other, and bonding the sleeve to each tubeplate. The extremities of the sleeve are preferably welded to the outer surface of the respective tubeplate. In repairing a defective tube which has one end which is bonded to a tubular tubeplate boss having a bore which is of larger diameter than the external diameter of the tube, the diameter of a poriton of the sleeve is preferably expanded to fit the bore of the tubeplate boss after insertion of the sleeve into the tube.

Abstract: In a system for detecting abnormal movement of a part of a gas-cooled nuclear reactor, for example abnormal tilting of a boiler unit caused by failure of a boiler support, a tracer material is released into the gas coolant path in response to the movement. The releasing of the material may be effected by causing a gas canister to be pierced as a result of the movement. The presence of the tracer material in the coolant is detected by the coolant monitoring system.

Abstract: A method and apparatus for non-destructively examining cylindrical material by electromagnetic induction use primary coils separated by an annular gap. The primary coils are excited oppositely so that the respective magnetic fields thereby generated are in boosting relationship in the gap. Close electromagnetic coupling of the primary coils with the material under examination is effected, and detectors, such as secondary coils are disposed in the gap to detect flux perturbations caused by variation in the properties of the material under examination.

Abstract: In a shell and tube boiler for use, in particular, in a liquid-metal-cooled fast-breeder nuclear reactor, the shell is formed as two vertical side-by-side units joined at their upper ends by a chamber. This "folding" of the unit considerably shortens the overall height of the boiler. Each tube is formed in two sections, each comprising a vertical limb with a curved portion at its upper end. The sections are joined by welding together the ends of the curved portions. This reduces the tube lengths which must be manufactured and transported to the site. In use of the boiler, the liquid sodium level in the chamber is maintained below the level of the tube welds. The chamber region above the sodium level may be filled with a blanket gas, such as argon.

Abstract: A mixed-flow impeller pump, which may be used, for example, as a primary pump for circulating sodium as the primary coolant in a fast nuclear reactor, comprises an impeller with evenly-spaced blades. Some of the blades, which are symmetrically disposed around the axis of rotation of the impeller, extend beyond the ends of the other blades towards the suction side of the pump to form an inducer. The channels defined between the extensions of the extended blades follow helical paths parallel to the axis of rotation. The leading edges of the unextended blades are interposed between the extended blades in the region of divergence of flow from the axis of rotation. The provision of the inducer reduces the risk of cavitation in the pump, which could cause rapid wear of the impeller.

Abstract: Heat transfer between a surface and an environment, such as a steam/air mixture in a pressure vessel, is determined by directing heat transferred to the surface to a location away from the environment by use of a heat pipe. The heat content of the working fluid of the heat pipe is determined by causing a fluid to flow through a jacket encircling the condensation part of the heat pipe and measuring the mass flow of the fluid and the temperature change. The method is particularly useful in determining heat transfer coefficients for use in safety analysis for pressurized water reactor power stations.