Abstract: A method and means of non-invasively determining the liquid level and density in a nuclear power reactor pressure vessel is disclosed. In general the method consists of detecting neutron levels external of the pressure vessel at least at positions adjacent the bottom of the fuel core, the center of the fuel core and the top of the fuel core; and the detected neutron level signals are directed to monitoring means.The detecting means may comprise fission chambers and monitoring means may comprise simple electric meters.

Abstract: A system for determining whether a self-sustaining neutron chain reaction (i.e., criticality) may occur as each successive nuclear fuel element is added to a liquid-filled tank. This is accomplished by determining whether a multiplication factor, k, approaches unity after each element is added to the tank in accordance with the equation:CR=(.alpha.S)/(1-k)where:S is the emission rate of the neutron source;.alpha. is a term that reflects the detector sensitivity as well as the attenuation of the neutron between source and detector and various geometric considerations in the tank;CR is the counting rate from a neutron detector; andk is a multiplication factor of the assembly at any given time for any given element configuration.

Abstract: An apparatus for collecting pollutants in which a passageway is formed to define a path for industrial gases passing therethrough. A plurality of isotope sources extend along at least a portion of the path followed by the industrial gases to provide a continuing irradiation zone for pollutants in the gases. Collecting electrode plates are associated with such an irradiation zone to efficiently collect particulates as a result of an electrostatic field established between such plates, particularly very small particulates. The series of isotope sources are extended for a length sufficient to attain material improvement in the efficiency of collecting the pollutants. Such an effective length is established along a substantially unidirectional path of the gases, or preferrably a reversing path in a folded conduit assembly to attain further efficiency by allowing more compact apparatus structures.