Abstract: Disclosed is a method of monitoring the neutron sensitivity of a neutron detector. Voltage having a predetermined potential difference is applied between an anode and a cathode without irradiating the neutron detector with neutrons to permit an &agr;-ray to be emitted from the nuclear fission substance. The &agr;-ray ionizes the ionizing gas to form an &agr;-ray current (I&agr;) flowing between the anode and the cathode. The current (I&agr;) thus formed is monitored. Also, with the monitoring region in which the applied voltage and the &agr;-ray current (I&agr;) bear a substantially proportional relationship, obtained is an extrapolated zero-volt &agr;-ray current (I&agr;0) at 0V of the applied voltage between the anode and the cathode from the proportional relationship by an extrapolating method, and the extrapolated zero-volt &agr;-ray current (I&agr;0) is correlated with the neutron sensitivity.

Abstract: A neutron spectrometer is provided by a series of substrates covered by a solid-state detector stacked on an absorbing layer. As many as 12 substrates that convert neutrons to protons are covered by a layer of absorbing material, acting as a proton absorber, with the detector placed within the layer to count protons passing through the absorbing layer. By using 12 detectors the range of neutron energies are covered. The preferred dodecahedron embodiment of the neutron spectrometer is a solid, polyethylene dodecahedron assembly with 12 surface facets covered by a solid-state detector stacked on an absorbing layer composed of titanium. Each absorbing layer is constructed with a different thickness according to the minimum and maximum energies of neutrons in the spectrum.

Abstract: A neutron spectrometer for spacecraft is provided by a series of substrates covered by a solid-state detector stacked on an absorbing layer. As many as 12 substrates that convert neutrons to protons are covered by a layer of absorbing material, acting as a proton absorber, with the detector placed within the layer to count protons passing through the absorbing layer. By using 12 detectors the range of neutron energies are covered. The preferred dodecahedron embodiment of the neutron spectrometer is a solid, polyethylene dodecahedron assembly with 12 surface facets covered by a solid-state detector stacked on an absorbing layer composed of aluminum. Each absorbing layer is constructed with a different thickness according to the minimum and maximum energies of neutrons in the spectrum.

Abstract: A solid state semiconductor neutron detector that automatically varies its sensitivity to provide a pulsed output over the entire range of operation of a nuclear reactor. The sensitivity is varied by changing the thickness or makeup of a converter layer that emits charged particles to the active region of the semiconductor surface.

Abstract: A neutron rem meter utilizing proton recoil and thermal neutron scintillators to provide neutron detection and dose measurement. In using both fast scintillators and a thermal neutron scintillator the meter provides a wide range of sensitivity, uniform directional response, and uniform dose response. The scintillators output light to a photomultiplier tube that produces an electrical signal to an external neutron counter.

Abstract: A solid state semiconductor neutron detector that automatically varies its sensitivity to provide a pulsed output over the entire range of operation of a nuclear reactor. The sensitivity is varied by changing the thickness or makeup of a converter layer that emits charged particles to the active region of the semiconductor surface.

Abstract: The invention considers the frequency distributions of singles, doubles and triple neutron emission events from a sample under assay. The count rates are equated to mathematical functions related to the spontaneous fission rate, self-induced fission rate, detection efficiency and &agr;,n rate with probability distribution assigned to each of those factors, the value of the product of all the probability distributions being increased to give an optimised solution and so provide a value of the spontaneous fission rate which is linked to the mass of the neutron source. The technique aims to provide increased accuracy and certainty compared with neutron coincidence counting based techniques.

Abstract: The invention relates a device for measuring the relative proportions of uranium and plutonium in a radioactive package (16), having: a source of photons (10) for irradiating the package, at least one delayed neutron detector (18) able to deliver counting signals for neutrons emitted by the package, means (22, 30) of acquiring counting signals, able to establish a decrease over time in the neutrons emitted, characteristic of the radioactive package, calculation means (32) for comparing the decay characteristic of the radioactive package with the respective characteristic decays of uranium and plutonium and for establishing relative proportions of uranium and plutonium in the package.

Abstract: A neutron spectrometer is provided by a series of substrates covered by a solid-state detector stacked on an absorbing layer. As many as 12 substrates that convert neutrons to protons are covered by a layer of absorbing material, acting as a proton absorber, with the detector placed within the layer to count protons passing through the absorbing layer. By using 12 detectors the range of neutron energies are covered. The preferred dodecahedron embodiment of the neutron spectrometer comprises a solid, polyethylene dodecahedron assembly with 12 surface facets covered by a solid-state detector stacked on an absorbing layer. In this arrangement, each of 12 surface pentagon-shaped facets provides a polyethylene substrate to convert neutrons to protons, covered by a layer of absorbing material, acting as a proton absorber, with the detector stacked on the absorbing layer to count protons passing through the absorbing layer.

Abstract: This invention relates to a method and apparatus for improving the precision of at least one of neutron coincidence counting and neutron multiplicity counting. The method includes the steps of: (1) sampling the real and accidental coincident pulses at the incoming pulse rate; and (b) sampling the accidental coincidences at a clock rate, wherein the clock rate is much faster than the pulse rate. The clock rate is faster than the pulse rate by a factor of 5 to 10 (in the preferred embodiment, approximately 4 MHz).

Abstract: According to the present invention, a system for measuring a thermal neutron emission from a neutron source, has a reflector/moderator proximate the neutron source that reflects and moderates neutrons from the neutron source. The reflector/moderator further directs thermal neutrons toward an unmoderated thermal neutron detector.

Abstract: The present invention concerns a monitor for measuring both the gamma spectrum and neutrons emitted by an object such as a spent nuclear fuel pin or pin assembly or nuclear waste material. According to the invention, it comprises a lead block (1) presenting a front face (8) intended to be brought close to said pin (7) or assembly to be measured and incorporatinga gamma detector (2) for gamma spectroscopy located close to a rear face of said block and associated with a collimator (4) extending from said front face to said gamma detector,two neutron detectors (3) which extend parallelly to each other and to said front face and are disposed symmetrically on either side of the axis of said collimator (4) close to said front face (8).

Abstract: An neutron detector composed of fissionable material having ions of lithium, uranium, thorium, plutonium, or neptunium, contained within a glass film fabricated using a sol-gel method combined with a particle detector is disclosed. When the glass film is bombarded with neutrons, the fissionable material emits fission particles and electrons. Prompt emitting activated elements yielding a high energy electron contained within a sol-gel glass film in combination with a particle detector is also disclosed. The emissions resulting from neutron bombardment can then be detected using standard UV and particle detection methods well known in the art, such as microchannel plates, channeltrons, and silicon avalanche photodiodes.

Abstract: A neutron detector array is capable of measuring a wide range of neutron fluxes. The array includes multiple semiconductor neutron detectors. Each detector has a semiconductor active region that is resistant to radiation damage. In one embodiment, the array preferably has a relatively small size, making it possible to place the array in confined locations. The ability of the array to detect a wide range of neutron fluxes is highly advantageous for many applications such as detecting neutron flux during start up, ramp up and full power of nuclear reactors.

Abstract: Proportional counters for thermal neutron counting are described. In one embodiment, a proportional counter includes a lead wire, a coil spring and an anode wire. The coil spring includes two opposite ends and a substantially cylindrical opening extending between the two ends. The lead wire at least partially extends into the spring opening so that one end of the lead wire is within the spring opening. One end of the spring is secured to the lead wire, and the other end of the spring is secured to the anode wire.

Abstract: A self-powered fixed incore detector for a nuclear reactor has a neutron sensitive emitter element having a low neutron absorption cross section, such as a vanadium element, which extends the length of the active fuel region and generates a full length signal representative of full length power. A number of gamma sensitive emitter elements, preferably platinum but alternatively zirconium, cerium, tantalum, or osmium elements, provide sequentially increasing overlap with the neutron sensitive emitter element to define axial regions of the active fuel region and generate apportioning signals. The portion of the full length signal generated by the neutron sensitive emitter element attributable to each of the axial regions of the core are determined from ratios of the apportioning signals generated by the gamma sensitive elements.

Abstract: A thermal neutron detector comprises an enclosure containing a helium-xenon gas mixture, an optical fiber, and an electrode arranged to detect ion particles. The optical fiber detects photons generated by a reaction of the gas mixture with neutrons passing through the enclosure. The reaction also generates ion particles that are detected by the electrode. A coincidence detector generates an output signal corresponding to the correlation of ion detections from the electrode with photon detections from the optical fiber, rejecting signals generated from the electric field that are not correlated with photon detections.

Abstract: The instant invention is a method for making and using an apparatus for detecting neutrons. Scintillating optical fibers are fabricated by melting SiO.sub.2 with a thermal neutron capturing substance and a scintillating material in a reducing atmosphere. The melt is then drawn into fibers in an anoxic atmosphere. The fibers may then be coated and used directly in a neutron detection apparatus, or assembled into a geometrical array in a second, hydrogen-rich, scintillating material such as a polymer. Photons generated by interaction with thermal neutrons are trapped within the coated fibers and are directed to photoelectric converters. A measurable electronic signal is generated for each thermal neutron interaction within the fiber. These electronic signals are then manipulated, stored, and interpreted by normal methods to infer the quality and quantity of incident radiation.

Abstract: The present invention provides a method for identifying failed fuel elements and the scale of damage accurately, quickly and at low cost without disassembling a fuel assembly and without discharging radioactive waste. Radiation detector(s) for measurement of gamma radiation emitted from surface of the irradiated fuel assembly and the fuel assembly are rotated and translated relative to each other, the dectected data of the radiation emitted from the surface of the fuel assembly is acquired, processed, a tomographic image is constructed from the radiation intensity distribution and is prepared and displayed, and a failed fuel element is finally confirmed from the tomographic image of the fuel assembly cross-section.

Abstract: A radiation gauge is provided which comprises a casing having an evacuated inside, a pair of electrode plates contained within the casing, and an insulating material of aluminum oxide disposed between the pair of electrode plates, the insulating material undergoing an induced conduction phenomenon when ionizing radiation is illuminated thereon, whereby intensity of ionizing radiation can be measured based on the induced conduction phenomenon of the insulating material.

Abstract: An apparatus to survey subsurface formations includes a sonde which is configured to move through a borehole. The sonde includes a neutron generator that emits neutrons into the subsurface formations. A crystal detector connected to the sonde monitors the neutron output of the neutron generator. The crystal detector can comprise an yttrium silicate crystal, an yttrium aluminate crystal, a lanthanum phosphate crystal, or a lutetium phosphate crystal. A lanthanum phosphate crystal or a lutetium phosphate crystal can also be used to detect photons coming from the subsurface formations. The sonde pressure casing can be fabricated from borated stainless steel to shield the internals of the sonde from thermal neutrons.

Abstract: Invention comprises an instrument in which momentum flux onto a biasable target plate is transferred via a suspended quartz tube onto a sensitive force transducer--a capacitance-type pressure gauge. The transducer is protected from thermal damage, arcing and sputtering, and materials used in the target and pendulum are electrically insulating, rigid even at elevated temperatures, and have low thermal conductivity. The instrument enables measurement of small forces (10.sup.-5 to 10.sup.3 N) accompanied by high heat fluxes which are transmitted by energetic particles with 10's of eV of kinetic energy in a intense magnetic field and pulsed plasma environment.

Abstract: A neutron detection device is housed in a metal enclosure containing a first detector with a high-sensitivity fission chamber, and a second detector having a low-sensitivity fission chamber and a boron-lined ionization chamber compensated for gamma radiation. The detection device is useful for extended range measurement of the neutron fluence rate outside the core of a nuclear reactor.

Abstract: A light water nuclear reactor test assembly for emulating the performance of a nuclear boiling water reactor fuel bundle and measuring the subchannel void fraction in the two-phase region of the emulated fuel bundle by gamma ray attenuation is disclosed. The emulated fuel bundle has individual emulated nuclear fuel rods typically heated by individual electrical currents instead of nuclear reaction and are cylindrically hollow. A gamma-emitting source is placed on a probe and mounted for vertical excursion inside a selected emulated hollow fuel rod. A detector, typically a Geiger-Muller counter, is placed for corresponding vertical excursion inside another and preferably adjacent fuel rod. Gamma radiation from the source to the detector through the walls of the emulated fuel rods is measured. Preferably, both detector and source are collimated so that the detector does not receive gamma ray scattering from the interior of the test assembly.

Abstract: Fission chamber with a wide measuring range and apparatus for measuring the neutron flux density using said fission chamber. The chamber comprises an enclosure (2) filled with a gaseous medium and, in the latter, electrodes (8,10) adjacent the periphery of the enclosure, whereof at least one is covered with a fissile material having a large surface density or mass, as well as other electrodes (10,12) adjacent the center of the enclosure, whereof, at least one is covered with a fissile material having a smaller surface density, chosen so as to optimize (a) the ratio of the electric currents respectively due to the neutrons and to spurious gamma radiation detected by the other electrodes and (b) the linearity of the signal supplied by the latter for a given flux density range.

Abstract: A muon detector system including central and end air-core superconducting toroids and muon detectors enclosing a central calorimeter/detector. Muon detectors are positioned outside of toroids and all muon trajectory measurements are made in a nonmagnetic environment. Internal support for each magnet structure is provided by sheets, located at frequent and regularly spaced azimuthal planes, which interconnect the structural walls of the toroidal magnets. In a preferred embodiment, the shape of the toroidal magnet volume is adjusted to provide constant resolution over a wide range of rapidity.

Abstract: A method of downhole neutron monitoring using an oxygen containing scintillating material to generate scintillator light as a function of electrons and gamma rays emitted from the product of the .sup.16 O (n,p) reaction in a scintillator, converting the generated scintillator light to an electrical signal, and using the electrical signal to record the flux of measured neutrons.

Abstract: A nuclear excitation laser type intra-reactor neutron flux measuring system of this invention is comprised of a laser oscillator filled with a nuclear exciting gas such as .sup.3 He, KrF or XeF, mounted on the tip of a control rod. The nuclear exciting gas is made into a plasma by the neutrons or the fragments of fissioned nuclei when the tip is positioned in the reactor core by raising the control rod. Since the nuclear exciting gas made into a plasma itself generates a laser beam or amplifies a laser beam projected from the outside, the behavior of neutrons can be monitored in detail after guiding this light response to the light processing system located outside, distinguishing the energies of neutrons from the spectrum and calculating the density and the flux of the neutron in each energy. Furthermore, the detecting sensitivity can be enhanced by forming the responsive membrane made of U.sub.3 O.sub.8 and so on, on the laser oscillator.

Abstract: Neutrinos are detected by allowing them to scatter on nuclei contained in a detector and by detecting the recoil of the nuclei. Because the probability of a neutrino being scattered is very low the probability is very high that a neutrino will only cause recoil of a single nucleus. On the other hand background radiation is likely to cause the recoil of a large number of electrons and/or nuclei so that neutrino scattering can be detected by distinguishing between the recoil of a single nucleus and the simultaneous recoil of a plurality of electrons/nuclei. In one form of the detector the nuclei are present as minute superconducting metal grains which are held in the superconducting state. At low temperatures the grains have a very low specific heat and the scattering of a neutrino will cause a single grain to heat up and change from the superconducting to the normal conducting state.

Abstract: A beta ray flux measuring device in an activated member in-core instrumentation system for pressurized water reactors. The device includes collector rings positioned about an axis in the reactor's pressure boundary. Activated members such as hydroballs are positioned within respective ones of the collector rings. A response characteristic such as the current from or charge on a collector ring indicates the beta ray flux from the corresponding hydroball and is therefore a measure of the relative nuclear power level in the region of the reactor core corresponding to the specific exposed hydroball within the collector ring.

Abstract: A method for producing ultralow-mass fissionable deposits for nuclear reactor dosimetry is described, including the steps of holding a radioactive parent until the radioactive parent reaches secular equilibrium with a daughter isotope, chemically separating the daughter from the parent, electroplating the daughter on a suitable substrate, and holding the electroplated daughter until the daughter decays to the fissionable deposit.

Abstract: An alpha recoil ion-implantation method and apparatus are described which use an alpha-emitting source that is a radioactive parent of the daughter isotope of interest to implant into a suitable substrate the recoil daughter ions resulting from alpha decay of the parent. For example, a .sup.241 Am source in thin layer form is placed next to a substrate such as a solid state track recorder in a vacuum which houses an assembly for rotating opposing disks receiving the alpha-emitting source and the substrate, respectively. Each alpha decay of .sup.241 Am results in a .sup.237 Np ion with enough recoil energy to be implanted into the substrate. Fissionable deposits of .sup.239 Pu, .sup.235 U, and .sup.238 U can also be made by this method and apparatus.

Abstract: A beam of neutrino or antineutrino particles is detected with a crystal containing coherent elastic scatterers for the particles. The elastic scatterers respond to the particles of the beam incident thereon by transferring momentum from the particles to mechanical momentum in the crystal. The mechanical momentum transferred to the crystal by the momentum of the particles is detected by a torsion balance carrying the crystal or a transducer on a tuning fork carrying the crystal. The beam incident on the crystal carried by the tuning fork is amplitude modulated by a chopper including several scatterers for the particles in the path of the beam.

Abstract: A high fluence neutron dosimetry method is described, including the steps of: exposing a dosimeter containing an alpha-emitting target isotope to neutron irradiation to form an alpha-emitting product isotope; determining the alpha decay rates of the target nucleus and the product nucleus; and using known alpha decay constants for the target nucleus and the product nucleus and the determined alpha decay rates of the target nucleus and the product nucleus to determine the neutron capture rate of the product nucleus.

Abstract: Ability of ion adsorption apparatus such as a desalting unit, etc. as used in an atomic power plant is continuously monitored, and any deterioration in the ability is detected in advance by a method and an apparatus for monitoring a break in an ion adsorption apparatus by detecting a break point of the ion adsorption apparatus using ion exchange resin, thereby determining a timing for regenerating or exchanging the resin, which comprises making an ion species having a weaker selective adsortability to the ion exchange resin as a sampling ion species than that of a target ion species to be adsorbed and present in water to be treated, and detecting leakage of the sampling ion species at the downstream side of the adsorption apparatus, thereby determining the break point of the ion exchange resin.

Abstract: A dosimeter which incorporates new methods for determining neutron dose. Less than one millirad of dose due to neutrons of all energies down to approximately 10.sup.3 eV can be measured, and the response can be adjusted by design of the dosimeter. The dosimeter utilizes the sputtering of material from a target due to the action of the neutrons and measuring of the amount of sputtered material to determine the dose. The sputtered material may be, for example, a noble gas or an inert solid. Various radiator materials can be included to interact with the neutrons so that the resulting charged particles control the sputtering process and hereby increase the sensitivity of the dosimeter. The target material can be, for example, noble-gas-impregnated polycrystalline or amorphous metals. The sputtered material is analyzed using resonance ionization spectroscopy, sputter-initiated resonance ionization spectroscopy or other methods to determine its quantity and hence the neutron dose.

Abstract: A detector apparatus for differentiating between gamma and neutron radiation is provided. The detector includes a pair of differentially shielded Geiger-Mueller tubes. The first tube is wrapped in silver foil and the second tube is wrapped in lead foil. Both the silver and lead foils allow the passage of gamma rays at a constant rate in a gamma ray only field. When neutrons are present, however, the silver activates and emits beta radiation that is also detected by the silver wrapped Geiger-Mueller tube while the radiation detected by the lead wrapped Geiger-Mueller tube remains constant. The amount of radiation impinging on the separate Geiger-Mueller tubes is then correlated in order to distinguish between the neutron and gamma radiations.

Abstract: A circuit for biasing a solid state crystal used as a radiation detector in hich the passage of the initial gamma ray pulse from the explosion of a nearby tactical nuclear weapon is utilized to temporarily remove the bias from said crystal for a time sufficient to permit the fast neutron pulse from the same explosion to pass by without permanently damaging the counter crystal. The circuit comprises an RC circuit between the bias supply and the crystal with a reverse biased diode across the capacitor.

Abstract: An apparatus for measuring the emissivity and opacity coefficients of a test plasma. The apparatus includes a target comprising a support structure of a carrier material with an asymmetrical sample of a test material disposed thereon, a driver for ionizing the test material into a test plasma and the carrier material into a carrier plasma, and spectrographs for measuring the intensity of photons traversing said test plasma. Embodiments including a separate photon source are also disclosed.

Abstract: An energy beam, particularly a neutrino beam or an optical radiation beam, is detected by irradiating a material with the beam in the presence of electromagnetic fields. The material is such that the beam is coherently scattered thereby, and the coherent scattering of the beam causes coherent stimulated emission of radiant energy fields in the material. Electric or magnetic fields adjust the scatterer energy levels so that energy and momentum are conserved overall, and for detection. The neutrino beam causes derivation of RF photons which are detected by a radio receiver. Alternatively, the neutrino beam irradiates a bulk material having nuclei with non-zero spin and non-zero magnetic moments and with sufficient stiffness to recoil as a single entity after absorbing momentum from each neutrino in the beam.

Abstract: Seismic restraint means are provided for mounting an elongated, generally cylindrical nuclear radiation detector within a tubular thimble. The restraint means permits longitudinal movement of the restraint means and the radiation detector into and out of the thimble. The restraint means includes spring bias means and thimble constant means whereby the contact means engage the thimble with a constant predetermined force which minimizes seismic vibration action on the radiation detector.

Abstract: Simultaneous photon and neutron interrogation of samples for the quantitative determination of total fissile nuclide and total fertile nuclide material present is made possible by the use of an electron accelerator. Prompt and delayed neutrons produced from resulting induced fissions are counted using a single detection system and allow the resolution of the contributions from each interrogating flux leading in turn to the quantitative determination sought. Detection limits for .sup.239 Pu are estimated to be about 3 mg using prompt fission neutrons and about 6 mg using delayed neutrons.