Abstract: A pulse discrimination method for discriminating between pulses having a short decay period and a long decay period, may comprise: Detecting the pulse; integrating a rise portion of the pulse; integrating a decay portion of the pulse; and comparing the integrated rise portion of the pulse with the integrated decay portion of the pulse to distinguish between a pulse having a long decay period and a pulse having a short decay period.

Abstract: The present invention relates to a method for determining crystallization in a very small amount of a material of interest (eg a chemical or biological material of interest).

Abstract: A method is disclosed for measuring neutron interaction properties of an earth formation. The method includes irradiating the formation with bursts of high energy neutrons. The bursts have a duration selected to enable detection of short duration burst related phenomena. After at least one of the bursts, short duration burst related phenomena are measured. After a selected number of the bursts, long duration neutron burst-related phenomena are detected. In some embodiments, the short duration burst related phenomena include at least one of inelastic gamma ray related phenomena, neutron slowing down related phenomena and short capture cross section related phenomena.

Abstract: A method of monitoring a nuclear reactor includes monitoring the nuclear reactor with a plurality of radiation sensors having spaced apart attachments to a radiation hard cable; providing signal processing equipment at each end of the cable for processing signals from the radiation sensors; establishing signal time intervals based upon differences in time of arrival of signals from the radiation sensors to the signal processing equipment at each end of the cable; producing a plurality of output signals each of which has an amplitude proportional to a difference in time of arrival of a signal to the signal processing equipment at each end of the cable; and rejecting output signals which have a difference in time of arrival outside of the signal time intervals.

Abstract: A neutron flux measuring apparatus, adapted to a boiling-water reactor (BWR) of a nuclear power plant and an advanced boiling-water reactor (ABWR) of a nuclear power plant, for measuring a neutron flux in a reactor pressure vessel, comprises a neutron flux detector assembly incorporating a local power range monitor detector assembly and a start-up range neutron monitor detector, a preamplifier amplifying a detector signal obtained from said start-up range neutron monitor detector, a start-up range neutron monitor operation unit operating, indicating and monitoring the amplified signal of the start-up range neutron monitor detector, and a local power range monitor operation unit operating, indicating and monitoring a signal obtained from the local power range monitor detector.

Abstract: A method and apparatus for non-invasively determining the internal composition of objects are disclosed. The object of interest is probed with low energy, monoenergetic narrow beams of fast neutrons. The object is generally placed on a conveyor belt which is positioned between the accelerator and the detectors. Detectors, positioned at radial angles corresponding to the resonance energy levels of certain preselected elements, measure the neutrons that are not absorbed or scattered by the elements in the object and thus pass straight through the object. The information obtained from the detectors can then be used for subsequent tomographic reconstruction.

Abstract: The present invention is directed to an analytic method for detecting trace elements in fluid solution. A cation exchange resin is packed with a radiolabelled exchange material having certain characteristics and replaces the trace element ions in the fluid which becomes labelled. The label is subsequently detected using sensitive and well known radiation detection methods.

Abstract: An apparatus and method for non-destructively detecting and identifying narcotics, explosives, and other forms of contraband concealed within a container or otherwise hidden from view. A radioactive source is used in conjunction with both neutron and gamma ray detector arrays. Depending upon the desired accuracy as well as the accessibility to all sides of the container, both back scattered and forward scattered radiation can be measured. Multiple detection systems mounted along different axes allow pseudo three dimensional images of the container in question as well as its contents to be produced.

Abstract: This technique for detecting underground contamination by organic fluids employs a plurality of spaced-apart boreholes adjacent a region to be tested for contamination. A neutron backscatter gauge is introduced into each of the boreholes for measuring the concentration of hydrogen in the soil surrounding the borehole. Such measurements are made at a plurality of spaced elevations along such a borehole and the distribution of hydrogen concentration as a function of elevation is compared with the expected distribution of hydrogen from underground sources of hydrogen, for distinguishing organic fluid contamination from other sources of hydrogen. For example, one can distinguish buried concrete or underground water from organic contamination. Measurements can also be made using chemical analysis methods. In another embodiment, the invention is used to profile and affect biodegradation. A plurality of spaced apart boreholes are provided in the buried material (for example, dump site).

Abstract: A neutron gauge is described for determining the moisture content of a moisture containing material. Samples of the moisture containing material are confined in a sample pan and a sample cover with sufficient neutron moderating activity is pressed against the sample. The cover, sample, and sample pan are placed in the same location in the gauge with respect to the neutron source and detector for each measurement to compensate for volume variations in the sample. The sample can be weighed to compensate for density variations. The sample pan cover can include a cadmium sheet for direct contact with the sample to shield the sample from neutrons thermalized by the cover.

Abstract: An ion implanter for implanting ions into a semiconductor wafer comprises means for generating an ion beam, means for receiving charged particles ejected from the ion beam, first means for rejecting those of the received charged particles below a first predetermined energy, second means for rejecting those of the received charged particles above a second predetermined energy, the first predetermined energy being lower than the second predetermined energy. The ion implanter further comprises means to count the number of received charged particles between the first and second predetermined energies, and scanning means for scanning the first and second predetermined energies to determine the energy at which the number of received charged particles between the first and second predetermined energies is a maximum.

Abstract: A non-invasive inspection system employs the isotropic, resonant scattering of neutrons from an object to determine the presence of at least one preselected element therein. A monoenergetic neutron beam is impinged onto the object and a first detector is disposed to detect neutrons resonantly scattered by the preselected element. A second detector is disposed to detect non-resonantly scattered neutrons. Comparison of the signals from the two detectors is indicative of resonant scattering and hence presence of the preselected element.

Abstract: A process measurement system that utilizes fast neutron backscattering for measuring density, level, and interfaces of substantially non-hydrogenous materials. The present invention substantially expands the use of backscattering technology, by expanding measurement to materials other than those containing hydrogen, and allowing measurement of materials in thicker walled vessels than previously possible. The system contains a fast neutron source for emitting neutrons into the material to be measured. The detection system is mounted near the neutron source to receive the backscattered neutrons. An energy degradation system is also incorporated to reduce the energy level of the fast neutrons down to a desired range.

Abstract: A source of neutrons is pulsed. A resultant flow of pulsed neutrons is detected and initiates a time delay. During the time delay, more quickly moving sources of radiation, such as fast and epithermal neutrons as well as gamma rays pass by an imaging device which is not turned on. Accordingly, these sources of noise are not detected. At the end of the time delay, the detecting imaging device is turned on; and during a resulting window interval, the pulsed thermal neutrons are detected and imaged after passage through an intermediately positioned object.

Abstract: The present invention is a system which determines nuclear reactor control rod axial position using a deviation signature database generated from a current or reference signal pattern produced by one or more strings of axially dispersed fixed incore detector sections in the reactor core. The deviation signature database is produced by assuming deviant axial positions for the control rods in the core, calculating expected detector signals for the assumed positions and storing the deviation of expected signals from a calibration reference along with corresponding assumed rod positions. The signature database is periodically updated to take into account changed core conditions. When a change in detector responses is detected the system performs a signature analysis of the deviations in the signature database using the current deviation from the reference to search for the closest match.

Abstract: An apparatus and method utilize a neutron sensitive medium in which initially existing atoms of the medium are divided into particles, reaction energy and neutron energy. The medium undergoes polarization in response to the reaction energy and the neutron energy. This produces an electrical charge gradient which is proportional to the energies and which can be sensed and analyzed to indicate just the neutron energy.

Abstract: A neutron detector includes a constituent or added sensitizer which enhances the detector's response to neutrons, of a preselected energy. Also disclosed are analytical techniques employing the detector, including a double resonance technique.

Abstract: Paper notes used as a monetary currency are deuterated. The level of deuteration while not complete, is high. For U.S. currency the level of deuteration is at least 0.1 mg of deuterium for each one dollar in value of the currency note, and preferably at least 0.3 mg. Use of X-ray or gamma ray interrogation with a beam energy above 2 MeV produces a nuclear reaction releasing a neutron from the deuterium nucleus. If the currency is in large concentrations, e.g. $100,000 or more, the neutrons emitted by this reaction are reliably detectable. The deuteration occurs in the cellulose fibers forming the currency. To resist an exchange of hydrogen atoms for deterium atoms, the deuterium atoms can be used in the formation of synthetic cellulose where the deuterium is more deeply buried within the cellulose molecule than in naturally occurring cellulose. The deuterated synthetic fibers are blended with natural, non-deuterated fibers to form the paper.

Abstract: A neutron radiography system having a high energy neutron generator (100) of the type comprising an ion accelerator (106) and a tritium target (110) located downstream of the accelerator. The generator is disclosed in a housing (22) containing a moderator medium (140) adapted to absorb part of the energy of the neutrons, thereby creating thermal neutrons. A neutron flux booster (130) comprised of a high neutron cross section material, such as depleted uranium, is disposed between the target and the moderator medium such that collisions of high energy neutrons produced at the target will collide with the uranium to release additional high energy neutrons from the booster into the moderator medium. A collimator (40) is disposed in communication with the moderator material for discharging thermal neutrons from the moderator medium.

Abstract: The temperature of an object (10) is measured by monitoring the thermal Doppler broadening of resonances in its neutron transmission characteristics, as neutrons (11) pass through it from a source (12) to a detector (14). Various surfaces (18, 20, 24) of the object are each plated with a different element, such as platinum, iridium and rhenium respectively. By monitoring the Doppler broadening of resonances due to platinum, the temperature of the platinum surface (18) can be determined; and the temperatures of the iridium surface (20) and the rhenium surface (24) are determined likewise.

Abstract: A system and method for the inspection and/or search for concealed objects impinges a monoenergetic neutron beam upon an object, notes the energy distribution of the neutrons scattered from the object and correlates the energy/intensity distribution of the scattered neutrons with the presence or absence of particular elements. The invention may be utilized to obtain qualitative or quantitative data regarding the composition of the object under interrogation.

Abstract: The range of a neutron backscatter fluid level detector is extended to provide essentially continuous level indication by interpolating neutron backscatter counts of neutrons supplied from a plurality of sources at various heights.

Abstract: A neutron range spectrometer and method for determining the neutron energy spectrum of a neutron emitting source are disclosed. Neutrons from the source are collimnated along a collimation axis and a position sensitive neutron counter is disposed in the path of the collimated neutron beam. The counter determines positions along the collimation axis of interactions between the neutrons in the neutron beam and a neutron-absorbing material in the counter. From the interaction positions, a computer analyzes the data and determines the neutron energy spectrum of the neutron beam. The counter is preferably shielded and a suitable neutron-absorbing material is He-3. The computer solves the following equation in the analysis: ##EQU1## where: N(x).DELTA.x=the number of neutron interactions measured between a position x and x+.DELTA.x,A.sub.i (E.sub.i).DELTA.E.sub.i =the number of incident neutrons with energy between E.sub.i and E.sub.i +.DELTA.E.sub.i, andC=C(E.sub.i)=N .sigma.(E.sub.

Abstract: The nuclear moisture-density gauge of the present invention employs a low activity neutron radiation source and a low activity gamma radiation source. In order to achieve more accurate density measurements at the relatively low count rates which results from the use of a low activity gamma source, the present invention is provided with means for generating a correction signal which is a function of the moisture content of the test material and which represents the amount of gamma radiation emitted from the test material resulting from the neutron capture reaction due to the presence of neutron capture elements, such as hydrogen, present in the test material. This correction signal is applied to the uncorrected density signal obtained from the gauge to thereby obtain a corrected density measurement which is unaffected by background gamma radiation caused by the presence of neutron capture elements in the test material.

Abstract: A non-destructive and non-invasive method of detecting underground tank leaks using three phase testing. A plurality of boreholes are drilled around the tank with the boreholes preferably extending below the tank. In the first phase of testing gas vapor analyzer is used to determine which borehole contains volatile organic material. In the second phase, a neutron back scatter gauge is lowered into those boreholes indicating presence of volatile organic material, and readings are taken at intervals along the length of the borehole. All of the readings are correlated. A sharp increase in reading, over a base reading, detects a probable "leaking" organic material beyond that present in the ambient soil. The third phase of the testing is to identify the probably "leaking" organic material and confirm if it is the same as that contained in the underground tank.

Abstract: A method is described for detecting and correcting for isotope burn-in during-long term neutron dosimetry exposure. In one embodiment, duplicate pairs of solid state track recorder fissionable deposits are used, including a first, fissionable deposit of lower mass to quantify the number of fissions occuring during the exposure, and a second deposit of higher mass to quantify the number of atoms of for instance .sup.239 Pu by alpha counting. In a second embodiment, only one solid state track recorder fissionable deposit is used and the resulting higher track densities are counted with a scanning electron microscope. This method is also applicable to other burn-in interferences, e.g., .sup.233 U in .sup.232 Th or .sup.238 Pu in .sup.237 Np.

Abstract: The thermal neutron absorption cross-section of a sample is measured by placing the sample in a sample container which surrounds a cavity within which a neutron source is positioned. A detector is positioned along a line parallel to an axis passing through the cavity. The source and detector are immersed in a moderator within a tank.

Abstract: A direct dosimeter for measuring gamma radiation flux having dose rates in excess of 0.1 megarad/hr. The dosimeter includes a gamma heating material such as aluminum or lead positioned in an evacuated housing. A thermocouple measures the temperature of the material when subjected to high levels of gamma radiation. From the time rate of change of the temperature measurements, the absolute value of gamma radiation flux may be determined before the temperature of the material has reached a steady state value.

Abstract: Apparatus and method for the direct, nondestructive evaluation of the .sup.235 U nuclide content of samples containing UF.sub.6, UF.sub.4, or UO.sub.2 utilizing the passive neutron self-interrogation of the sample resulting from the intrinsic production of neutrons therein. The ratio of the emitted neutron coincidence count rate to the total emitted neutron count rate is determined and yields a measure of the bulk fissile mass. The accuracy of the method is 6.8% (1.sigma.) for cylinders containing UF.sub.6 with enrichments ranging from 6% to 98% with measurement times varying from 3-6 min. The samples contained from below 1 kg to greater than 16 kg. Since the subject invention relies on fast neutron self-interrogation, complete sampling of the UF.sub.6 takes place, reducing difficulties arising from inhomogeneity of the sample which adversely affects other assay procedures.

Abstract: A method of measuring the density of a first material containing a moderator of fast neutrons comprising the steps of: emitting fast neutrons into a sample having a predetermined volume confined in a predetermined shape and sensing the rate of slow neutrons emerging from the sample for each of a plurality of samples of a second material, each of the plurality of samples of the second material having a different known density and neutron moderating and absorbing characteristics that are substantially the same as the neutron moderating and absorbing characteristics of the first material; emitting fast neutrons into a sample of the first material having a predetermined volume confined in a predetermined shape; sensing the rate of slow neutrons emerging from the sample of first material; and comparing the rate sensed in the sensing of the sample of the first material with the rates sensed in the sensing of the plurality of samples of the second material to determine the density of the first material.

Abstract: Measurement of the amount of a constituent such as glass in a composite structure, by passing neutrons or gamma rays through the structure and measuring the degree to which the neutrons or gamma rays are absorbed.

Abstract: A portable instrument for measuring induced Cerenkov radiation associated with irradiated nuclear fuel assemblies in a water-filled storage pond is disclosed. The instrument includes a photomultiplier tube and an image intensifier which are operable in parallel and simultaneously by means of a field lens assembly and an associated beam splitter. The image intensifier permits an operator to aim and focus the apparatus on a submerged fuel assembly. Once the instrument is aimed and focused, an illumination reading can be obtained with the photomultiplier tube. The instrument includes a lens cap with a carbon-14/phosphor light source for calibrating the apparatus in the field.

Abstract: A self-calibrated neutron radiation monitor includes a flux responsive element comprised of intrinsic silicon neutron detectors and self-calibration resistors in a single structure. As the resistance of the flux responsive element increases to the value of successive calibration resistors, known increments of flux have been encountered.

Abstract: A neutron detector is disclosed which uses the moderating material as the structural support for the neutron detector element. A thin metal liner is affixed to the inside of the plastic moderating material encasement for containing a neutron detecting gas. A high voltage supply is connected to an electrical conductor which extends between the ends of the encasement and serves to furnish output pulses to a pulse counter upon the occurrence of ionization of the counting gas in response to neutron flux through the volume of the detector.

Abstract: A solid-state neutron detector for detecting both fast and slow neutrons comprises two layers, one of which contains a neutron-sensitive first material and the other of which contains a semiconducting second material containing hydrogen, the first and second materials meeting to form a rectifying junction therebetween. The neutrons are detected by detecting electron-hole pairs migrating in opposite directions relative to the junction. The electron-hole pairs are created by energetic free protons produced by the fast neutrons travelling through the second material and by energetic reaction particles produced by the slow neutrons travelling through the first material. Stacking several of these detectors next to each other enhances overall sensitivity for detecting both fast and slow neutrons.

Abstract: A method is provided for monitoring irradiated nuclear fuel inventories located in a water-filled storage pond wherein the intensity of the Cerenkov radiation emitted from the water in the vicinity of the nuclear fuel is measured. This intensity is then compared with the expected intensity for nuclear fuel having a corresponding degree of irradiation exposure and time period after removal from a reactor core. Where the nuclear fuel inventory is located in an assembly having fuel pins or rods with intervening voids, the Cerenkov light intensity measurement is taken at selected bright spots corresponding to the water-filled interstices of the assembly in the water storage, the water-filled interstices acting as Cerenkov light channels so as to reduce cross-talk. On-line digital analysis of an analog video signal is possible, or video tapes may be used for later measurement using a video editor and an electrometer.

Abstract: The invention relates to a process for measuring a continuous neutron flux, and to an measuring apparatus for carrying out this process. According to the invention, a probe is disposed in the neutron flux, comprising a first part defining an enclosure and a second part disposed inside the enclosure and separated therefrom by a medium whose heat conductance is known, one of said parts being made at least partially of fissile material, and the difference in temperatures between the two parts is measured at equilibrium, to deduce therefrom the power released by the fissile material, then the neutron flux. The invention is more particularly applicable to measuring the neutron flux, particularly in the core of nuclear reactors.

Abstract: A method is disclosed for rapidly and accurately generating an output signal corresponding to the power of a nuclear reactor core. The method comprises generating out of core neutron flux signals at different time intervals and utilizing predetermined relationships therebetween to adjust a more accurate thermal power signal which has a slow response to transient power conditions.

Abstract: The ability to measure the ratio of vapor versus liquid in a nuclear steam generating system is highly desirable, particularly since, during transient events such as rapid depressurization, the vapor may not be in thermal equilibrium with its liquid and its distribution in the liquid may be highly non-uniform. By using a relatively mono-energetic neutron source such as Californium 252, exposing the medium under investigation to the radiation and using a proton recoil detector as an energy discriminating counter one can estimate the ratio of vapor to liquid by measuring the reduction of flux loss due to scattering when the medium includes vapor as well as liquid.

Abstract: According to the invention, the radioactivation method for simultaneous determination of the nitrogen, phosphorus and potassium content in plants and fertilizers consists in exposing samples to be analyzed and standard samples to neutron irradiation and recording the spectra of the gamma radiation induced in said samples, whereupon the samples are laid aside for a period of time determined by the half-life of the interfering isotope. This is followed by again recording the spectra of the samples being analyzed and of the standard samples and superposing the first and second spectra of the samples being analyzed and of the standard samples. These spectra are then shifted relative to each other along the energy axis, and the contents of the elements being analyzed are determined by thus comparing the spectra of the samples being analyzed and of the standard samples.

Abstract: An optical apparatus is disclosed which monitors the thickness of a thin film carried by a reflecting substrate. In order to minimize light detection problems caused by inadvertent displacement of the substrate, the light source and detector are located on the same "side" of the optical apparatus, and retro-reflector means are located at the other "side" of the optical apparatus, so that the light is reflected from the substrate to the retro-reflector means, back to the substrate, and thence back to the detector. In the preferred embodiment, the retro-reflector means comprises an array of small retro-reflectors.

Abstract: Direct fast-neutron-induced recoil and alpha particle tracks in polycarbonate films may be enlarged for direct visual observation and automated counting procedures employing electrochemical etching techniques. Electrochemical etching is, for example, carried out in a 28% KOH solution at room temperature by applying a 2000 V peak-to-peak voltage at 1 kHz frequency. Such recoil particle amplification can be used for the detection of wide neutron dose ranges from 1 mrad. to 1000 rads. or higher, if desired.

Abstract: Cold neutron radiation of energy less that 0.025 eV having a flux greater than 1.times.10.sup.3 neutrons/square centimeter/second is used to diagnose temporal information about the spatial distribution of hydrocarbon fuel and lubrication oils in internal combustion engines, gas turbine engines and fuel systems.Images of the movement of fuel or oil are recorded by directing a beam of neutrons through an engine and using an image intensifier responsive to low light levels to intensify an image formed by neutrons which have been directed through the engine onto a fluorescent screen. The output image from the intensifier is recorded by a video or cine camera.

Abstract: The present invention relates to a refractory materials used in processing molten metals comprising combining at least one of the refractory materials selected from the group consisting of SiO.sub.2, Al.sub.2 O.sub.3, MgO, ZrO.sub.2 with an activatable element for labeling which has an activation cross section of over 1 barnand apparatus made from a plurality of differently labeled refractory components.

Abstract: A method and apparatus for monitoring the output of an ion chamber type in-core neutron detector is disclosed. Neutron detectors of this type are known to produce both alternating current and direct current signals which are used as measures of the neutron flux in the chamber. The monitor employs a ratio of the alternating current and direct current signals to detect ion chamber leaks, to correct the output of the detector after a leak, to predict the end-of-life of the detector and to determine the non-linearity of the detector at different power levels.

Abstract: A method for measuring the dose-equivalent for exposure to an unknown and/or time varing neutron flux which comprises simultaneously exposing a plurality of neutron detecting elements of different types to a neutron flux and combining the measured responses of the various detecting elements by means of a function, whose value is an approximate measure of the dose-equivalent, which is substantially independent of the energy spectra of the flux. Also, a personnel neutron dosimeter, which is useful in carrying out the above method, comprising a plurality of various neutron detecting elements in a single housing suitable for personnel to wear while working in a radiation area.

Abstract: N samples are irradiated simultaneously for a period which is N times longer than the period of subsequent measurement of a sample, by means of a device constituted by a transfer circuit in which stations are provided successively for introduction, irradiation, separation, measurement and discharge of samples. A portion of the circuit serves to transfer a sample-holder for N samples, means for positioning the sample-holder and extracting samples therefrom being provided at the separating station.

Abstract: A method of determining a depth of an accumulation of snow in which the water-equivalent depth of an accumulation of snow is determined from the count of survival neutrons of cosmic rays after passing through an accumulation of snow.

Abstract: The sensitivity of a gage using a nuclear source for measuring the water content of bulk materials, such as plastic concrete, is increased by use of a lithium or fluorine neutron nuclear source.

Abstract: Method and apparatus for determining the position of the interface between a liquid and its vapor or between two liquids by exposing the liquid(s) to fast neutrons and monitoring the resultant emergent slow neutrons from the vessel containing the liquid(s).