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Description: Absolute fission rate measurements using modified National Bureau of Standards fission chambers were performed in the Fast Flux Test Facility at two core locations for isotopic deposits of {sup 232}Th, {sup 233}U, {sup 235}U, {sup 238}U, {sup 237}Np, {sup 239}Pu, {sup 240}Pu, and {sup 241}Pu. Monitor chamber results at a third location were analyzed to support other experiments involving passive dosimeter fission rate determinations.
Date: May 1, 1981
Partner: UNT Libraries Government Documents Department

Preparation of fission foils for fission ionization chambers using a painting technique

Description: Fission foils for use in fission ionization chambers were produced by painting metal substrates with coats of fissionable isotopes. Areal densities as large as 2.0 mg/cm/sup 2/ were obtained with excellent adhesion. This painting technique has been successful in depositing isotopes of uranium, plutonium, americium, and curium on metal substrates made of beryllium, aluminum, copper, and nickel. The cost of this painting technique is estimated to be approximately one-tenth the cost of producing foils by evaporation, electrodeposition, or sputtering techniques. In addition, the painting technique is highly efficient, thereby minimizing waste of the available fissionable material. (auth)
Date: November 14, 1973
Creator: Behrens, J.W.
Partner: UNT Libraries Government Documents Department

FFTF (Fast Flux Test Facility) Reactor Characterization Program: Absolute Fission-rate Measurements

Description: Absolute fission rate measurements using modified National Bureau of Standards fission chambers were performed in the Fast Flux Test Facility at two core locations for isotopic deposits of {sup 232}Th, {sup 233}U, {sup 235}U, {sup 238}U, {sup 237}Np, {sup 239}Pu, {sup 240}Pu, and {sup 241}Pu. Monitor chamber results at a third location were analyzed to support other experiments involving passive dosimeter fission rate determinations.
Date: May 1, 1981
Creator: Fuller, J.L.; Gilliam, D.M.; Grundl, J.A.; Rawlins, J.A. & Daughtry, J.W.
Partner: UNT Libraries Government Documents Department

Design of optimized RC-CR filters for current-pulse operation of fission counters and high sensitivity fission counters for high gamma backgrounds

Description: A calculational procedure was developed to design RC-CR filters for processing current pulses from fission counters in a gamma background ranging from 10$sup 5$ to 6 x 10$sup 6$ R/hr. The effects of noise from the gamma background and the input preamplifier and of the time constant of the fission counter and input cable were studied. Analytical results were in close agreement with experimental data. A pole-zero network was examined as a means of compensating for the time constant of the fission counter and input cable, but its improvement was insignificant. The procedure was expanded to design a high sensitivity, gamma-tolerant fission counter (approximately 10 counts sec$sup -1$ NV$sup -1$ at 10$sup 5$ R/hr), and the result was a conceptual design with a performance almost equal to a recently developed high temperature fission counter. (auth)
Date: January 1, 1975
Creator: DeLorenzo, J.T.
Partner: UNT Libraries Government Documents Department

Rejection of radio-frequency noise with a wide-band differential preamplifier and solid-shielded coaxial input cables

Description: Radio-frequency signals simulating electrical interference ranging from 50 Hz to 50 MHz were applied to the shields of the input cable system (two solid- shielded, mineral-insulated cables approximately 6 m long) of a wide-band (approximately 60 MHz) differential preamplifier for use with fission counters as input devices as part of in-vessel, low-level flux monitors in future liquid- metal fast breeder reactors (LMFBRs) to determine the common-mode rejection. Results show that differences in electrical properties and shielding characteristics of the two input coaxial cables along with end effects produced by an unbalanced sensor severely degrade the rejection capability of the differential preamplifier. At 1 MHz, the common-mode rejection without input cables is approximately -70 dB; this is reduced to approximately -10 dB when measured with the rf signal applied to the surface of the input cable shields. Measurements of the shielding characteristics of the input cables showed resonances at test frequencies greater than 2 MHz. A ferrite core was installed in the input assembly to increase the impedance of the shields and to permit termination of the coaxial line consisting of the input cable shields and the protective metal conduit for the input cables. This assembly eliminated all resonances below 20 MHz. The increased impedance also reduced the amplitude of the shield currents, resulting in an increase in the shielding effectiveness of the input cables without affecting the signal transmission of the cables. (auth)
Date: January 1, 1975
Creator: Burns, R.S. & De Lorenzo, J.T.
Partner: UNT Libraries Government Documents Department

Near-Core and In-Core Neutron Radiation Monitors for Real Time Neutron Flux Monitoring and Reactor Power Level Measurements

Description: MPFDs are a new class of detectors that utilize properties from existing radiation detector designs. A majority of these characteristics come from fission chamber designs. These include radiation hardness, gamma-ray background insensitivity, and large signal output.
Date: June 12, 2006
Creator: McGregor, Douglas S.; Adams, Marvin L.; Carron, Igor & Nelson, Paul
Partner: UNT Libraries Government Documents Department

Tritium production by fast neutrons on oxygen : an integral experiment /

Description: This report describes an integral experiment of tritium production in water by neutrons from the LANSCE/WNR spallation neutron source. Neutron energies covered the range from 1 MeV to about 300 MeV. The neutron fluence was determined with a 238U fission chamber. After irradiation, the water samples were analyzed for tritium. The results are compared with calculations and agreement is found to within a factor of 2.
Date: January 1, 2001
Creator: Haight, Robert C.; Wermer, J. R. (Joseph R.) & Fikani, M. M. (Michael M.)
Partner: UNT Libraries Government Documents Department

A Low Dead-Time Neutron-Counting System

Description: A counting system capable of processing input pulses at an average rate in excess of 3 x lO/sup 5/ counts per second with less than 10% counting loss because of instrumental dead time is described. The system is capable of detecting thermal neutrons in the presence of a high gamma background. It consists of a fission counter, a preamplifier, linear amplifier, and integral discriminator. Components of the system are described in detail, and circuit diagrams and layout information are given. Factors governing the design are discussed; testing procedures and the performance are outlined. (auth)
Date: January 1, 1961
Creator: Epstein, R. J. & Thompson, D. C.
Partner: UNT Libraries Government Documents Department


Description: Two spherical versions of earlier cylindrical assemblies were used for a critical study of shape effects for fast reactor cores with volumes of 300 to 400 liters. Assemblies 24 (cylindrical) and 38 (spherical) had a high-density metallic U blanket, whereas the set of assemblies numbered 31 (cylindrical) and 39 (spherical) had a low-density U-fueled core (with steel and Al diluents) with a highdensity blanket of depleted U. The main features of these assemblies are summarized. Reactivity coefficients of a small number of fissile and nonfissile materials were measured in both assemblies (38 and 39). In Assembly 38 the effects of environment, etc., upon fission rates measured with absolute fission chambers were investigated. Radial fission rate traverses in different directions were made in Assembly 39 to reveal any flux asymmetry due to heterogeneity of the core; no such effect was detected.(auth)
Date: July 1, 1962
Creator: Bates, J.C.; Davey, W.G.; Amundson, P.I.; Gasidlo, J.M.; Long, J.K. & Keeney, W.P.
Partner: UNT Libraries Government Documents Department


Description: Two parallel-plate fi ssion counters, utilizing U/sup 235/ foils, amd a parallel-plate alpha counter, utilizing a B/sup 10/ foil, are combined in one chamber for cross-section measurements at low neutron energies. The alpha counter allows a l/V normalization of the neutron beam intensity. (auth)
Date: July 1, 1957
Creator: White, F.A. & Shefield, J.C.
Partner: UNT Libraries Government Documents Department


Description: This report describes progress in the USAEC-sponsored Interlaboratory LMFBR Reaction Rate (ILRR) program. This program has been established by RDT to develop a capability to accurately measure neutron-induced reaction rates for LMFBR fuels and materials development programs. The initial goal for the principal fission reactions, {sup 235}U, {sup 238}U, and {sup 239}Pu, is an accuracy to within {+-} 5 at the 95% confidence level. Accurate measurement of other fission and non-fission reactions will be required, but to a lesser accuracy, between {+-} 5 to 10% at the 95% confidence level. A secondary program objective is improvement in knowledge of the nuclear parameters involved in fuels and materials dosimetry measurements of neutron flux, spectra, fluence, and burnup. The accuracy goals of the ILRR program are severe; measurements of fast-neutron-induced reaction rates have not been rapidly moving toward this level of precision. Using a number of techniques in well established neutron environments of current interest for fast reactor development and critically evaluating the results will help establish existing levels of accuracy and indicate the scale of effort required for improvement. To accomplish the objectives of this program, reliable and accepted experimental values of reaction rates and ratios will be determined for various well established and permanent neutron fields. The Coupled Fast Reactivity Measurement Facility (CFRMF) at Aerojet Nuclear Company (ANC) is the first neutron field being studied because of the similarity of its spectrum to that of a fast reactor and the range and reproducibility of flux levels available for track etch, fission chamber, radiochemistry, and helium mass spectrometric measurements. Results of the CFRMF and other ILRR tests coupled with those of past and present EBR-II dosimetry tests will provide the improved and more precise values of nuclear parameters urgently needed for LMFBR fuels and materials development programs.
Date: September 1, 1971
Creator: WN, MCELROY
Partner: UNT Libraries Government Documents Department

Design considerations for neutron activation and neutron source strength monitors for ITER

Description: The International Thermonuclear Experimental Reactor will require highly accurate measurements of fusion power production in time, space, and energy. Spectrometers in the neutron camera could do it all, but experience has taught us that multiple methods with redundancy and complementary uncertainties are needed. Previously, conceptual designs have been presented for time-integrated neutron activation and time-dependent neutron source strength monitors, both of which will be important parts of the integrated suite of neutron diagnostics for this purpose. The primary goals of the neutron activation system are: to maintain a robust relative measure of fusion energy production with stability and wide dynamic range; to enable an accurate absolute calibration of fusion power using neutronic techniques as successfully demonstrated on JET and TFTR; and to provide a flexible system for materials testing. The greatest difficulty is that the irradiation locations need to be close to plasma with a wide field of view. The routing of the pneumatic system is difficult because of minimum radius of curvature requirements and because of the careful need for containment of the tritium and activated air. The neutron source strength system needs to provide real-time source strength vs. time with {approximately}1 ms resolution and wide dynamic range in a robust and reliable manner with the capability to be absolutely calibrated by in-situ neutron sources as done on TFTR, JT-60U, and JET. In this paper a more detailed look at the expected neutron flux field around ITER is folded into a more complete design of the fission chamber system.
Date: December 31, 1997
Creator: Barnes, C.W.; Jassby, D.L.; LeMunyan, G.; Roquemore, A.L. & Walker, C.
Partner: UNT Libraries Government Documents Department

Calibration issues for neutron diagnostics

Description: In order for ITER to meet its operational and programmatic goals, it will be necessary to measure a wide range of plasma parameters. Some of the required parameters e.g., neutron yield, fusion power and power density, ion temperature profile in the core plasma, and characteristics of confined and escaping alpha particle populations are best measured by fusion product diagnostic techniques. To make these measurements, ITER will have dedicated diagnostic systems, including radial and vertical neutron cameras, neutron and gamma ray spectrometers, internal and external fission chambers, a neutron activation system, and diagnostics for confined and escaping alpha particles. Engineering integration of many of these systems is in progress, and other systems are under investigation. This paper summarizes the present state of design of fusion product diagnostic systems for ITER and discusses expected measurement capability.
Date: October 1997
Creator: Sadler, G. J.; Adams, J. M. & Barnes, C. W.
Partner: UNT Libraries Government Documents Department

Determining Pu-239 content by resonance transmission analysis using a filtered reactor beam.

Description: A novel technique has been developed at Argonne National Laboratory to determine the {sup 239}Pu content in EBR-II blanket elements using resonance transmission analysis (RTA) with a filtered reactor beam. The technique uses cadmium and gadolinium filters along with a {sup 239}Pu fission chamber to isolate the 0.3 eV resonance in {sup 239}Pu. In the energy range from 0.1 to 0.5 eV, the total microscopic cross-section of {sup 239}Pu is significantly larger than the cross-sections of {sup 238}U and {sup 235}U. This large difference in cross-section allows small amounts of {sup 239}Pu to be detected in uranium samples. Tests using a direct beam from a 250 kW TRIGA reactor have been performed with stacks of depleted uranium and {sup 239}Pu foils. Preliminary measurement results are in good agreement with the predicted results up to about two weight percent of {sup 239}Pu in the sample. In addition, measured {sup 239}Pu masses were in agreement with actual sample masses with uncertainties less than 3.8 percent.
Date: November 25, 1998
Creator: Klann, R. T.
Partner: UNT Libraries Government Documents Department

Reconciliation of Measured and TRANSP-calculated Neutron Emission Rates in the National Spherical Torus Experiment: Circa 2002-2005

Description: A change in the response of the neutron detectors on the National Spherical Torus Experiment occurred between the 2002-2003 and 2004 experimental run periods. An analysis of this behavior by investigating the neutron diagnostic operating conditions and comparing measured and TRANSP-calculated neutron rates is presented. Also a revised procedure for cross calibration of the neutron scintillator detectors with the fission chamber detectors was implemented that delivers good agreement amongst the measured neutron rates for all neutron detectors and all run periods. For L-mode discharges, the measured and TRANSP-calculated neutron rates now match closely for all run years. For H-mode discharges over the entire 2002-2004 period, the 2FG scintillator and fission chamber measurements match each other but imply a neutron deficit of 11.5% relative to the TRANSP-calculated neutron. The results of this report impose a modification on all of the previously used calibration factors for the entire neutron detector suite over the 2002-2004 period. A tabular summary of the new calibration factors is provided including certified calibration factors for the 2005 run.
Date: June 15, 2005
Creator: Medley, S. S.; Darrow, D. S. & Roquemore, A. L.
Partner: UNT Libraries Government Documents Department