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Measurements Of Delayed Neutron Parameters For U 235 And Np 237
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Book Synopsis Measurements of Delayed Neutron Parameters for U-235 and Np-237 by :
Download or read book Measurements of Delayed Neutron Parameters for U-235 and Np-237 written by and published by . This book was released on 1997 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Delayed neutrons are emitted by excited nuclei formed in beta decay of fission products called delayed neutron precursors. About 1% of the total neutrons released in fission are delayed neutrons; however, this small fraction plays an important role in nuclear reactor control. The delayed neutrons determine the time-dependent behavior of reactors, and knowledge of parameters used to predict neutron emission rate is essential for establishing reactivity worths. The delayed neutron yields, decay constants, and the absolute yield for the six-group delayed neutrons have been measured for U-235 and Np-237. This experiment has been called for in the forecast of experiments needed to support operations in the US. The bare U-235 metal assembly Godiva IV at the Los Alamos Critical Experiment Facility (LACEF) provided the source of neutrons. Godiva IV generated about 107 total fissions in the samples for the infinite and instantaneous irradiation needed to accentuate the shorter and longer-lived groups of delayed neutrons. The detection system used in the experiment consisted of 20 He-3 tubes embedded in a polyethylene cylinder. The delayed neutron activity resulting from the fast neutron-induced fission has been measured. The measured absolute yield for U-235 was determined to be 0.0163 " 0.009 neutrons/fission. This value compares very well with the well-established Keepin absolute yield of 0.0165 " 0.0005. The newly measured absolute yield value for Np-237 was 0.0126 " 0.0007, which compares well to the recently reported value of 0.0129 " 0.0004 by Saleh and Parish. The measured values for U-235 are corroborated with period (e-folding time) versus reactivity calculations.
Book Synopsis Grande exposition de photographies à l'occasion du 800ème anniversaire de Tramelan by :
Download or read book Grande exposition de photographies à l'occasion du 800ème anniversaire de Tramelan written by and published by . This book was released on 1978 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Measured Delayed Neutron Spectra from the Fission of U-235 and Np-237 by :
Download or read book Measured Delayed Neutron Spectra from the Fission of U-235 and Np-237 written by and published by . This book was released on 1998 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: Texas A & M University, in collaboration with Oak Ridge National Laboratory / the Japan Atomic Energy Research Institute, have been actively studying the delayed neutron emission characteristics of the higher actinide isotopes for several years. 1-3 Recently, a proton recoil detector system was designed, built, and characterized for use in measuring delayed neutron energy spectra following neutron induced fission. The system has been used to measure aggregate delayed neutron energy spectra from neutron induced fission of U-235 and Np-237. These spectra have also been compared to that calculated using individual precursor P, values, yields, and spectra from the ENDF/B-VI file. A proton recoil detector array consisting of three LND Model 28305 high- -pressure proton recoil detectors has been constructed at the Texas A & M University Nuclear Science Center. The array was characterized using several neutron and gamma- ray sources to check for efficiency, gamma-ray response, and reliability of the unfolding techniques. Resultant measured proton recoil distributions were unfolded using a modified version of the spectrum unfolding code PSNS (the new code was renamed SAC). SAC used response functions calculated using MCNP 4A. This feature allowed the inclusion of several inches of lead between the detector and the source to decrease the detector's sensitivity to gamma-rays, while appropriately accounting for the effect on the transmitted neutron spectrum. Following proper calibration of the array, highly-purified sources of U-235 were irradiated in the Nuclear Science Center Reactor (NSCR) at a power of 1 MW for 200.
Book Synopsis Measurements of Delayed Neutron Emission from Np-237, Am-241, and Am-243 by : Habeeb H. Saleh
Download or read book Measurements of Delayed Neutron Emission from Np-237, Am-241, and Am-243 written by Habeeb H. Saleh and published by . This book was released on 199? with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Measurements of Delayed Neutrons Parameters for 235U and 237Np by : David Loaiza
Download or read book Measurements of Delayed Neutrons Parameters for 235U and 237Np written by David Loaiza and published by . This book was released on 1997 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Measurements of Delayed Neutron Emission from Np-237, Am-241, and Am-243 by :
Download or read book Measurements of Delayed Neutron Emission from Np-237, Am-241, and Am-243 written by and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Delayed Neutrons from Fissionable Isotopes of Uranium, Plutonium, and Thorium by : George Robert Keepin
Download or read book Delayed Neutrons from Fissionable Isotopes of Uranium, Plutonium, and Thorium written by George Robert Keepin and published by . This book was released on 1957 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Delayed Neutron Emission Measurements for U-235 and Pu-239 by : Yong Chen
Download or read book Delayed Neutron Emission Measurements for U-235 and Pu-239 written by Yong Chen and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The delayed neutron emission rates of U-235 and Pu-239 samples were measured accurately from a thermal fission reaction. A Monte Carlo calculation using the Geant4 code was used to demonstrate the neutron energy independence of the detector used in the counting station. A set of highly purified actinide samples (U-235 and Pu-239) was irradiated in these experiments by using the Texas A & M University Nuclear Science Center Reactor. A fast pneumatic transfer system, an integrated computer control system, and a graphite-moderated counting system were constructed to perform all these experiments. The calculated values for the five-group U-235 delayed neutron parameters and the six-group Pu-239 delayed neutron parameters were compared with the values recommended by Keepin et al. (1957) and Waldo et al. (1981). These new values differ slightly from literature values. The graphite-moderated counting station and the computerized pneumatic system are now operational for further delayed neutron measurement.
Book Synopsis Delayed Neutron Measurements for Th-232, Np-237, Pu-239, Pu-241 and Depleted Uranium by : Joseph C. Stone
Download or read book Delayed Neutron Measurements for Th-232, Np-237, Pu-239, Pu-241 and Depleted Uranium written by Joseph C. Stone and published by . This book was released on 2001 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Measurement of Delayed Neutron Yields in Plutonium, Uranium-233, Uranium-238, and Thorium Relative to Yield in Uranium-235 by : G. S. Brunson
Download or read book Measurement of Delayed Neutron Yields in Plutonium, Uranium-233, Uranium-238, and Thorium Relative to Yield in Uranium-235 written by G. S. Brunson and published by . This book was released on 1955 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: Delayed neutron studies have been made in the Experimental Breeder Reactor (EBR), using a conventional sample transfer system and a neutron counter comprised of BF3 tubes in a graphite geometry. Samples of U-235, U-233, U-238, Pu, and Th were irradiated in a fast flux; samples of U-235, U-233, and Pu were irradiated in a thermal flux.
Book Synopsis Measurements of Delayed Neutron Yields from Thermal Neutron Induced Fission of 235U, 233U, 239Pu, and 237Np by : S. B. Borzakov
Download or read book Measurements of Delayed Neutron Yields from Thermal Neutron Induced Fission of 235U, 233U, 239Pu, and 237Np written by S. B. Borzakov and published by . This book was released on 1998 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Uncertainty Evaluation of Delayed Neutron Decay Parameters by : Jinkai Wang
Download or read book Uncertainty Evaluation of Delayed Neutron Decay Parameters written by Jinkai Wang and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In a nuclear reactor, delayed neutrons play a critical role in sustaining a controllable chain reaction. Delayed neutron's relative yields and decay constants are very important for modeling reactivity control and have been studied for decades. Researchers have tried different experimental and numerical methods to assess these delayed neutron parameters. The reported parameter values vary widely, much more than the small statistical errors reported with these parameters. Interestingly, the reported parameters fit their individual measurement data well in spite of these differences. This dissertation focuses on evaluation of the errors and methods of delayed neutron relative yields and decay constants for thermal fission of U-235. Various numerical methods used to extract the delayed neutron parameter from the measured data, including Matrix Inverse, Levenberg-Marquardt, and Quasi-Newton methods, were studied extensively using simulated delayed neutron data. This simulated data was Poisson distributed around Keepin's theoretical data. The extraction methods produced totally different results for the same data set, and some of the above numerical methods could not even find solutions for some data sets. Further investigation found that ill-conditioned matrices in the objective function were the reason for the inconsistent results. To find a reasonable solution with small variation, a regularization parameter was introduced using a numerical method called Ridge Regression. The results from the Ridge Regression method, in terms of goodness of fit to the data, were good and often better than the other methods. Due to the introduction of a regularization number in the algorithm, the fitted result contains a small additional bias, but this method can guarantee convergence no matter how large the coefficient matrix condition number. Both saturation and pulse modes were simulated to focus on different groups. Some of the factors that affect the solution stability were investigated including initial count rate, sample flight time, initial guess values. Finally, because comparing reported delayed neutron parameters among different experiments is useless to determine if their data actually differs, methods are proposed that can be used to compare the delayed neutron data sets.
Book Synopsis Seven Surrogate Precursors for Modeling Delayed Neutron Decay and Predicting Reactivity by :
Download or read book Seven Surrogate Precursors for Modeling Delayed Neutron Decay and Predicting Reactivity written by and published by . This book was released on 1997 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of a different set of group decay constants for each fissionable nuclide complicates analysis of the dynamic behavior of fast reactors. A fast reactor containing six principal fissioning nuclides of uranium and plutonium must, in effect, be described by 36 delayed neutron groups. Additionally, the use of group decay constants that depend on the neutron energy spectrum makes it difficult to select values that describe the dynamic response of epithermal systems because virtually all delayed neutron activity measurements have been performed for fast or thermal-neutron-induced fission. Clearly, it would be desirable to have a single set of group decay constants that could be applied to all fissionable nuclides. A set of seven fixed decay constants is proposed herein. Each of the proposed decay constants is associated with a specific, dominant delayed neutron precursor. In effect, each group is represented by a single surrogate precursor. Using recently measured delayed neutron activities for U-235 and Np-237, the proposed set of decay constants actually improved the goodness of fit to the data. For other fissionable nuclides lacking experimental data, a method has been devised to obtain yields consistent with the proposed set of decay constants from the traditional six-group parameters. This transformation is accomplished without altering the traditional inferred reactivity scale.
Book Synopsis Determining 235U Enrichment Using a Dual-energy Approach for Delayed Neutron Measurements by : Angela Lynn Lousteau
Download or read book Determining 235U Enrichment Using a Dual-energy Approach for Delayed Neutron Measurements written by Angela Lynn Lousteau and published by . This book was released on 2017 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bulk uranium items are often measured using active neutron interrogation systems to take advantage of the relatively high penetrability of neutrons, providing the ability to quickly and accurately measure uranium masses in large, dense configurations. Active techniques employ an external neutron source to induce fission in the uranium and subsequently measure emitted prompt fission or delayed neutrons. Unfortunately, the emitted neutrons from 235U [uranium-235] and 238U [uranium-238] are, for all practical purposes, indistinguishable; therefore, commonly used systems such as the Active Well Coincidence Counter, the 252Cf [californium-252] Shuffler, and other systems based on measurement of prompt or delayed fission neutrons require many representative calibration standards and/or well-known isotopic information to interpret the results (i.e., extract an isotopic mass from the effective fissionable mass), thus limiting these techniques for safeguards applications. The primary objective of this research was to develop and demonstrate a dual-energy neutron interrogation technique using a 252Cf Shuffler measurement chamber for determination of uranium enrichment, thus eliminating the need for a (traditionally separate) gamma isotopic measurement. This new technique exploits the change in fission rates as a function of interrogating neutron energy to independently determine the 235U and 238U content in the measurement item. Dual neutron interrogation energies were achieved by adding a deuterium- tritium (D-T) neutron generator into the measurement chamber of the Oak Ridge National Laboratory 252Cf Shuffler. Results from traditional 252Cf measurements and the new D-T measurements were then used to develop a relationship between uranium enrichment and the ratio of the two delayed neutron count rates. Parameter studies were performed to optimize the measurements for each source using a combination of modeling/simulation and experimental measurements. This dissertation presents the detailed development of this novel dual-energy neutron interrogation technique. The results are promising and with engineering refinements could be deployed for routine assay of certain types of materials.
Book Synopsis Preliminary Pulsing Experiments to Measure Delayed Neutron Emission Parameters by :
Download or read book Preliminary Pulsing Experiments to Measure Delayed Neutron Emission Parameters written by and published by . This book was released on 1998 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent interest in delayed neutron parameters including comparisons between macroscopic (experimental) and microscopic (calculated) results have prompted a set of experiments using the 1MW Triga Reactor at the Texas A and M University (TAMU) Nuclear Science Center (NSC) designed to measure the complete set of seven-group delayed neutron parameters for several higher actinides. Operating the Nuclear Science Center Reactor (NSCR) in a pulsed mode, a complete set of delayed neutron parameters were measured for Np-237 and Am-243. The total delayed neutron yield per 100 fissions for Np-237 and Am-243 was found to be 1.14 " 0.07 and 0.85 " 0.05, respectively. Comparisons to previous measurements are made where such measurements are available.
Book Synopsis Energy Measurements of Delayed Neutron Groups from 235U. by : Athar Naeem
Download or read book Energy Measurements of Delayed Neutron Groups from 235U. written by Athar Naeem and published by . This book was released on 1971 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Delayed neutron parameters for thermal neutron induced fission of [superscript 235]U by : S. Synetos
Download or read book Delayed neutron parameters for thermal neutron induced fission of [superscript 235]U written by S. Synetos and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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