Abstract: A method and apparatus for measuring uranium isotope enrichment in a sample uranium solution. In the invention, the concentration of uranium in the uranium solution is determined by K-edge densitometry. The quantity of uranium-235 in the uranium solution is then measured by detecting the gamma rays emitted from the uranium-235 by using a high-purity germanium detector. A value of the uranium isotope enrichment is obtained from the ratio of the quantity of uranium-235 in the uranium solution to the uranium concentration. The invention is designed to provide the improved construction of a radiation source suitable for the K-edge densitometry and to provide the accurate measurements by correcting any error in the measured quantity of uranium-235 in the uranium solution due to the self-absorption of the gamma rays emitted from the uranium-235.

Abstract: A method is described for non-destructively assaying the radionuclide content of solid waste in a sealed container by analysis of the waste's gamma-ray spectrum and neutron emissions. Some radionuclides are measured by characteristic photopeaks in the gamma-ray spectrum; transuranic nuclides are measured by neutron emission rate; other radionuclides are measured by correlation with those already measured.

Abstract: The approach to criticality of a nuclear reactor provided with an artificial neutron source is monitored by two neutron detectors, one which measures the neutron flux in a localized region around the artificial neutron source, and the other located simlarly with respect to the core geometry but removed from the localized region. When the reactor is subcritical, the artificial source dominates and the outputs of the two detectors are noticeably different. As the reactor approaches criticality, the critical mode distribution of neutrons, which is symmetrical with respect to the two detectors, becomes dominant and the detector outputs approach each other in magnitude. The ratio of the output signals therefore, provides an indication of the reactor reactivity state. Either linear or logarithmic ratio signals can be generated, and if desired, either can be compared with an appropriately scaled reference signal representative of a selected reactivity state, such as a multiplication factor of 0.

Abstract: An apparatus (10, 110, 210) including a containment capsule (12, 112, 212) a support member (16, 116, 216) removably disposed within the capsule and carrying therein a solid state track recorder material (20, 120, 220) and a layer of fissile material (20, 120, 220), and means (52) on the exterior of the capsule adapted to be remotely grasped for positioning the capsule adjacent to the fuel. The capsule is lowered into close proximity to the fuel, and positioned at a predetermined location for a period of time between about one hour and one day. The capsule is withdrawn from the fuel, the support member and recording member are withdrawn from the capsule, and the recording member is processed to reveal the fission track density, which is readily correlated to fuel burnup.

Abstract: A method and system for quality control of nuclear fuel materials, said system including amplifier/integrator circuitry, signal processors, and drift control feedback circuitry. The invention permits the qualitative and quantitative measurement of paramagnetic additives such as gadolinium for example in a paramagnetic base nuclear fuel material including ferromagnetic impurities. Drift problems relating to temperature and other effects are solved electrically and mechanically. Analysis can be conducted irrespective of the form or composition of the nuclear fuel.

Abstract: A method and apparatus for determining the subcriticality of masses of uranium by directing epithermal neutrons toward said mass, isolating said material from external thermal neutrons, and measuring the ratio of thermal and epithermal neutrons to epithermal neutrons which enables the establishment of a subcriticality value representative of the mass of uranium.

Abstract: A detector head for in situ inspection of irradiated nuclear fuel assemblies submerged in a water-filled nuclear fuel storage pond. The detector head includes two parallel arms which extend from a housing and which are spaced apart so as to be positionable on opposite sides of a submerged fuel assembly. Each arm includes an ionization chamber and two fission chambers. One fission chamber in each arm is enclosed in a cadmium shield and the other fission chamber is unshielded. The ratio of the outputs of the shielded and unshielded fission chambers is used to determine the boron content of the pond water. Correcting for the boron content, the neutron flux and gamma ray intensity are then used to verify the declared exposure, cooling time and fissile material content of the irradiated fuel assembly.

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: 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.

Abstract: Given are a method and apparatus for measuring nondestructively and non-invasively (i.e., using no internal probing) the burnup, reactivity, or fissile content of any material which emits neutrons and which has fissionable components. No external neutron-emitting interrogation source or fissile material is used and no scanning is required, although if a profile is desired scanning can be used. As in active assays, here both reactivity and content of fissionable material can be measured. The assay is accomplished by altering the return flux of neutrons into the fuel assembly. The return flux is altered by changing the reflecting material. The existing passive neutron emissions in the material being assayed are used as the source of interrogating neutrons.

Abstract: A method and apparatus for analyzing combined secondary and primary materials by directing primary radiation onto said material whereby secondary radiation is generated. A detector senses the secondary radiation as a transport carries the materials into the vicinity of primary radiation and produces signals to be resolved into secondary and primary material source components, establishing a secondary to primary material ratio and indicating the composition of the material.

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: Typical nuclear fuel material contains tramp ferromagnetic particles of random size and distribution. Also, selected amounts of paramagnetic or ferromagnetic material can be added at random or at known positions in the fuel material. The fuel material in its nonmagnetic container can be scanned by magnetic susceptibility change detecting apparatus to provide a unique signal waveform of the container of fuel material as a signature thereof. At subsequent times in its life, the container similarly can be scanned to provide subsequent signatures. Comparison of the signatures reveals any alteration or tampering with the fuel material.

Abstract: A new apparatus is used to substantially instantaneously obtain a profile of an object, for example a spent fuel assembly, which profile (when normalized) has unexpectedly been found to be substantially identical to the normalized profile of the burnup monitor Cs-137 obtained with a germanium detector. That profile can be used without normalization in a new method of identifying and monitoring in order to determine for example whether any of the fuel has been removed. Alternatively, two other new methods involve calibrating that profile so as to obtain a determination of fuel burnup (which is important for complying with safeguards requirements, for utilizing fuel to an optimal extent, and for storing spent fuel in a minimal amount of space). Using either of these two methods of determining burnup, one can reduce the required measurement time significantly (by more than an order of magnitude) over existing methods, yet retain equal or only slightly reduced accuracy.

Abstract: An accurate determination of whether the reactivity of individual spent fuel assemblies exceeds a threshold value is made while each assembly is being transferred from the reactor core to the fuel storage rack. The reactivity of each spent assembly is compared with that of a standard assembly by comparing the subcritical multiplication resulting from insertion of a neutron source into the assemblies. The measuring apparatus preferably exteriorly resembles a control element assembly wherein one control element finger containing the neutron source is yoked to another finger containing a neutron detector. The fingers are simultaneously inserted into a standard assembly having a known reactivity and subcritical multiplication, and the resulting flux signal is recorded. Thereafter spent assemblies are sequentially measured to assure that no assembly having a subcritical multiplication greater than that of the standard is ever placed into the storage rack.