Abstract: Disclosed is a neutron detector, provided with a sealed chamber having two spaced apart electrodes, hermetically sealed in the chamber with a seal which is located in an environment of at least two decades less neutron flux than that experienced by the detector. An ionizable gas is placed within the space between the electrodes, and pressurized to a pressure above one atmosphere. A layer of a mixture of an active material and a breeding material are positioned within the chamber, the active material and breeding material being respectively U-235 and U-234, which layer has a thickness of at least 0.2 milligrams per square centimeter.

Abstract: A rhodium self-powered detector, a fission chamber, and appropriate electronic circuitry for combining the output of the self-powered detector and the fission chamber are disclosed in combination wherein the combined output of the self-powered detector and the fission chamber is always proportional to the local reactor power level or neutron flux density in a nuclear reactor.

Abstract: A liquid level detector, or detector array, for insertion into the pressure vessel of a nuclear reactor, or into any liquid-containing vessel, for that matter. A coaxial cable supports the detector, which includes a sensing element having a positive temperature-coefficient of electrical resistivity. The detector is driven by a constant current source of electricity and the presence of liquid is determined by making a resistance measurement.

Abstract: A hydrogen sensing device for determining the concentration of hydrogen in a fluid atmosphere consists of a sealed chamber formed with a window which selectively allows diffusion of hydrogen into the chamber. Alpha particles from a source contained in the chamber ionize the hydrogen and a pair of polarized electrodes collect the resulting electrons to provide a current which is a function of the hydrogen concentration in the chamber. A second window permeable to helium allows escape of the helium from the chamber that is formed by the combination of electrons with alpha particles therein.

Abstract: An ion chamber type neutron detector is disclosed which has a greatly extended lifespan. The detector includes a fission chamber containing a mixture of active and breeding material and a neutron shielding material. The breeding and shielding materials are selected to have similar or substantially matching neutron capture cross-sections so that their individual effects on increased detector life are mutually enhanced.

Abstract: In a moderated nuclear reactor core, an in-core neutron detector assembly with means for fixing the location of the detectors and for displacing the moderator in the vicinity of the detectors to thereby flatten and reduce the thermal neutron flux to which the neutron detectors are exposed.