Author: Athar NaeemPublisher:
ISBN:
Category :
Languages : en
Pages : 310
Book Description
Energy Measurements of Delayed Neutron Groups from 235U.
Author: Athar NaeemGrande exposition de photographies à l'occasion du 800ème anniversaire de Tramelan
Author: Measurements of Delayed Neutron Parameters for U-235 and Np-237
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 134
Book Description
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.
Delayed Neutrons from U235 After Short Irradiation
Author: Delayed Neutrons
Author: George Robert KeepinPublisher:
ISBN:
Category : Delayed neutrons
Languages : en
Pages : 56
Book Description
A comprehensive review is given of existing measurements as of October 1955 on the properties of delayed neutrons from various fissionable isotopes. The relation of these measurements to current theory and practice is discussed.
Determining 235U Enrichment Using a Dual-energy Approach for Delayed Neutron Measurements
Author: Angela Lynn LousteauPublisher:
ISBN:
Category : Delayed neutrons
Languages : en
Pages : 252
Book Description
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.
Delayed Fission Neutrons
Author: International Atomic Energy AgencyPublisher:
ISBN:
Category : Neutrons
Languages : en
Pages : 268
Book Description
Energies of the Delayed Neutrons from U235 Fission Products
Author: Delayed Neutrons from Fissionable Isotopes of Uranium, Plutonium, and Thorium
Author: George Robert KeepinPublisher:
ISBN:
Category : Delayed neutrons
Languages : en
Pages : 58
Book Description
Measurement of Delayed Neutron Yields in Plutonium, Uranium-233, Uranium-238, and Thorium Relative to Yield in Uranium-235
Author: G. S. BrunsonPublisher:
ISBN:
Category : Delayed neutrons
Languages : en
Pages : 32
Book Description
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.