Abstract: A method and an apparatus for ultrasonically inspecting the welds which attach the differential pressure and liquid poison nozzles to the bottom head of the reactor pressure vessel in a boiling water reactor. The scanning apparatus is seated on the upper taper of the nozzle outer tube and incorporates a stationary frame having a cutaway section which allows installation from the side. The apparatus has vertical and circumferential positioning mechanisms which are operated remotely to scan an ultrasonic transducer package over the circumferential welds and heat-affected zones thereof. The rotating frame has a transducer carriage mounted thereon which is vertically displaceable relative to the rotating frame. The vertical and angular motion motors can be controlled together to provide the desired path for the ultrasonic transducer around the stub tube. The tool also includes a vessel contour follower which follows the contour of the inclined surfaces of the reactor pressure vessel bottom head.

Abstract: A technique for reducing the shadow corrosion effect in zirconium-based alloys caused by .beta.-particles emitted by adjacent components containing one or more elements that emit .beta.-particle flux when activated by neutron capture. The technique entails providing a coating capable of absorbing .beta.-particles, so as to mitigate the adverse effect of .beta.-particle bombardment of a zirconium-based alloy. Preferred coating materials include beryllia, beryllium, tin, zinc, chromium and cadmium. The coatings can be applied to various nuclear reactor structural alloys, such as stainless steel and nickel, platinum, copper, hafnium and yttrium-based alloys containing 0.2 weight percent manganese or more.

Abstract: A means for damping a low-friction azimuth resolver by use of an array of small magnets acting on a metallic pendulum attached to the resolver shaft. The magnetic field acts on the pendulum motion to induce a motional electromotive force and associated currents, which produce forces opposed to the motion, thereby acting as a non-contact damper on the resolver shaft. When the resolver shaft is at rest, no "eddy currents" are produced in the static magnetic field and no damping force exists. If the shaft moves, the attached pendulum cuts the magnetic flux lines and produces a drag force proportional to the shaft angular speed. The pendulum is typically made of diamagnetic material, such as lead or copper, thereby assuring that the induced forces arise solely from the motion. The magnetic field is produced by an array of small, but intense, samarium-cobalt magnets contained in a compact package providing for uniform damping throughout 360.degree. of resolver motion.

Abstract: A method for stabilizing direct current generated by neutron activation of a plurality of interconnected .beta.-emitter (nuclear decay electron) cells, which are placed in a specific position in the out-of-core region of a light water nuclear reactor. The method entails a synergistic combination of neutron-absorbing isotopes, in specific relationship to each other, the amount of each absorber and their respective locations in the neutron flux field being chosen to render the total current-time characteristic substantially constant over a significant number of reactor full-power-years. The method enhances the current output and lifetime of the current generator by greatly deferring burn-up of the neutron absorbers. If configured as a DC voltage source for powering radiation-hardened, high-temperature integrated circuitry contained in the reactor pressure vessel, voltage regulation circuitry is not necessary.