Abstract: Assuming knowledge of the number and species of gases present within an enclosed environment such as the atmosphere of a containment vessel of a nuclear plant, an apparatus and process for receiving a gas sample from said atmosphere and measuring the percentages of the various known number and species of gases present is disclosed. Assuming N number of gas species present, N-1 discrete chambers are utilized. Each chamber confines the sample gas, includes a discrete permeation cell having an internal volume isolated from the rest of the chamber by a permeable membrane, and has a pressure sensor for measuring the pressure within the permeation cell resulting from gas permeating through the permeable membrane. Each chamber is isothermal and maintained at its own discrete temperature. Sample gas is introduced into each chamber and allowed to come to equilibrium with the temperature of the chamber. When thermal equilibrium is attained, the permeation cell in each chamber is evacuated by a vacuum pump.

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 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.