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Source-jerk analysis using a semi-explicit inverse kinetic technique

Description: A method is proposed for measuring the effective reproduction factor, k, in subcritical systems. The method uses the transient response of a subcritical system to the sudden removal of an extraneous neutron source (i.e., a source jerk). The response is analyzed using an inverse kinetic technique that least-squares fits the exact analytical solution corresponding to a source-jerk transient as derived from the point-reactor model. It has been found that the technique can provide an accurate means… more
Date: January 1, 1985
Creator: Spriggs, G.D. & Pederson, R.A.
Partner: UNT Libraries Government Documents Department
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Criticality alarm system verification at the Los Alamos critical experiments facility: Past experience and present capabilities

Description: The Los Alamos Critical Experiments Facility (LACEF) has been involved in the testing and evaluation of criticality accident alarm systems since 1980. At that time we designed and built the solution critical assembly SHEBA for this purpose. The response of the alarms to neutron pulses was done using the GODIVA-IV Burst Assembly. Currently, SHEBA and a new fast assembly, SKUA, are being modified for burst operation. 8 refs., 7 figs., 2 tabs.
Date: January 1, 1988
Creator: Plassmann, E.A. & Spriggs, G.D.
Partner: UNT Libraries Government Documents Department
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Particle-Size-Distribution of Nevada Test Site Soils

Description: The amount of each size particle in a given soil is called the particle-size distribution (PSD), and the way it feels to the touch is called the soil texture. Sand, silt, and clay are the three particle sizes of mineral material found in soils. Sand is the largest sized particle and it feels gritty; silt is medium sized and it feels floury; and clay is the smallest and if feels sticky. Knowing the particle-size distribution of a soil sample helps to understand many soil properties such as how m… more
Date: September 17, 2007
Creator: Spriggs, G & Ray-Maitra, A
Partner: UNT Libraries Government Documents Department
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TRAC-PF1 analyses of potential pressurized-thermal-shock transients at a Combustion-Engineering PWR. [Overcooling]

Description: Los Alamos is participating in a program to assess the risk of pressurized thermal shock (PTS) to a reactor vessel. Our role is to provide best-estimate thermal-hydraulic analyses of 12 postulated overcooling transients using TRAC-PF1. These transients are hypothetical and include multiple operator/equipment failures. Calvert Cliffs/Unit-1, a Combustion-Engineering plant, is the pressurized water reactor modeled for this study. The utility and the vendor supplied information for the comprehensi… more
Date: January 1, 1984
Creator: Koenig, J. E.; Spriggs, G. D. & Smith, R. C.
Partner: UNT Libraries Government Documents Department
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The shift of prompt critical in reflected reactors and the limitations of the mean prompt-neutron lifetime model

Description: Prompt critical in a bare reactor is defined as the point at which the reactivity {rho} of the reactor is equal to the effective delayed neutron fraction {beta}. In a reflected reactor, however, it is shown that prompt critical will occur at a reactivity of {rho} = {beta}(1-f) where f is the fraction of core neutrons that return to the core region after having leaked into the reflector. Furthermore, it is also shown that the mean prompt-neutron lifetime model that has been traditionally used to… more
Date: August 1, 1994
Creator: Spriggs, G. D. & Busch, R. D.
Partner: UNT Libraries Government Documents Department
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Usefulness of k{sub eff} measurements in validating nuclear cross-section sets

Description: A k{sub eff} measurement is a necessary and vital measurement, but by itself it is not sufficient to validate any cross-section set; to validate all aspects of a cross-section set, numerous integral quantities such as k{sub eff}, neutron lifetime, fission ratios, central reactivity worth, neutron spectra, effective delayed neutron fraction, and others should be measured.
Date: November 1, 1997
Creator: Spriggs, G. D. & Frankle, S. C.
Partner: UNT Libraries Government Documents Department
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On the Rossi-{alpha} measurement of {beta}{sub eff} in reflected reactors

Description: In unreflected reactors, the probability of detecting chain-related counts is given by the well known Rossi-{alpha} expression. Using this the author derives an expression for the effective delayed neutron fraction, {beta}. He demonstrates that this expression for {beta} is equally applicable for a reflected systems in which two alphas are experimentally observed.
Date: March 13, 1997
Creator: Doulin, V.A. & Spriggs, G.D.
Partner: UNT Libraries Government Documents Department
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{beta}{sub eff} measurements in reflected reactors using a Rossi-{alpha} technique

Description: In this report the authors calculate the effective delayed neutron fraction equation for reflected reactors using the Rossi-{alpha} technique. They determine that the equation for the delayed neutron fraction is just as valid for reflected systems as it is for unreflected systems.
Date: January 20, 1998
Creator: Doulin, V.A. & Spriggs, G.D.
Partner: UNT Libraries Government Documents Department
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A few-group delayed neutron model based on a consistent set of decay constants

Description: As part of an international effort, the Los Alamos National Laboratory has been asked to (1) determine if there is a set of dominant precursors that are common to all fissionable isotopes and all incident neutron energies, (2) expand the existing experimentally-measured few-group models commonly used in the nuclear industry into their 8-group equivalent using a consistent set of decay constants corresponding to these dominant precursors, and (3) formulate new group spectra for the equivalent 8-… more
Date: January 22, 1998
Creator: Campbell, J.M. & Spriggs, G.D.
Partner: UNT Libraries Government Documents Department
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Inhour equation in a two-region reactor with multiplication in both regions

Description: In Reference 1 (G.D. Spriggs, R.D. Busch, and John G. Williams, ``Two-Region Kinetic Model for Reflected Reactors,`` Ann. Nucl. Energy, 24, No. 3, 205, (1997)), the authors presented a two-region point kinetic model for reflected reactors based on the Avery-Cohn differential equations. The model was developed for a core region surrounded by a non-multiplying, source-free reflector region. As part of the model development, they also introduced several probability relationships that were essentia… more
Date: January 22, 1998
Creator: Spriggs, G. D. & Busch, R. D.
Partner: UNT Libraries Government Documents Department
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Coupling parameters for partially reflected reactors

Description: For situations in which the standard point kinetic model does not adequately characterize the kinetic behavior of a reflected system, the Avery-Cohn differential equations can be used. However, these equations require that one determine the coupling parameters between the core and the reflector, f{sub cr} and f{sub rc}. The coupling parameter, f{sub cr}, represents the probability that a neutron in the core will leak into the reflector, and the coupling parameter, f{sub rc}, represents the prob… more
Date: July 1, 1995
Creator: Busch, R. D. & Spriggs, G. D.
Partner: UNT Libraries Government Documents Department
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Rossi-{alpha} measurements in the fast critical assembly XIX-2

Description: A Rossi-{alpha} experiment was performed on the zero-power, XIX-2 assembly at the Fast Critical Assembly (FCA) facility operated by the Japan Atomic Energy Research Institute (JAERI), Tokai-mura, Japan. The XIX-2 assembly is a plutonium/natural uranium system comprised of plutonium/natural uranium core surrounded by a depleted uranium dioxide blanket (referred to as the soft blanket). The soft blanket is surrounded by an outer blanket comprised of depleted uranium dioxide blanket (referred to a… more
Date: May 21, 1997
Creator: Spriggs, G.D.; Sakurai, Takeshi & Okajima, Shigeaki
Partner: UNT Libraries Government Documents Department
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KENO lifetimes

Description: When performing k-eigenvalue solutions with KENO-V.a, two different prompt neutron lifetimes are estimated - a system lifetime and a neutron generation time. The meaning of these two lifetimes has been ascertained by comparing values of various neutron lifespans/lifetimes predicted by MCNP and DANTSYS based on the neutron-balance theory. The system lifetime in KENO-Va corresponds to the unweighted removal lifetime calculated by both MCNP and DANTSYS. The unweighted removal lifetime is the avera… more
Date: January 30, 1997
Creator: Petrie, L.; Parsons, D.K. & Spriggs, G.D.
Partner: UNT Libraries Government Documents Department
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Definition of neutron lifespan and neutron lifetime in MCNP4B

Description: MCNP4B was released in early 1997. In this new version, several major changes were made to the underlying theory used to estimate the non-adjoint-weighted removal, fission, capture, and escape prompt-neutron lifetimes. These four lifetimes are now being calculated in accordance to the neutron-balance theory described by Spriggs et al. in which the non-adjoint-weighted lifetime for a particular type of reaction (i.e., fission, capture, escape, removal, etc.) is defined as the total neutron popul… more
Date: January 15, 1997
Creator: Busch, R. D.; Spriggs, G. D. & Hendricks, J. S.
Partner: UNT Libraries Government Documents Department
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Comparison of neutron lifetimes as predicted by MCNP and DANTSYS

Description: The prompt removal lifetime algorithm used in the latest version of MCNP was modified to conform with the neutron-balance definitions described by Spriggs et al. In accordance with the neutron-balance theory, the non-adjoint-weighted removal lifetime is given by where {Phi} is the angular neutron flux, v is the neutron velocity, {Sigma}{sub a} is the macroscopic absorption cross section, E is neutron energy, {Omega} is angle, and r is a spatial vector. The numerator in this expression represent… more
Date: January 22, 1997
Creator: Hendricks, J.S.; Parsons, D.K. & Spriggs, G.D.
Partner: UNT Libraries Government Documents Department
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On the definition of neutron lifetimes in multiplying and non-multiplying systems

Description: Historically, the term neutron lifetime has been used in the literature to describe a wide variety of different time intervals associated with a neutron`s trek through a given system. This duplication of usage of the term neutron lifetime has undoubtedly resulted in some confusion concerning its physical meaning. In hopes of reducing some of this confusion, we suggest in this work that the various time intervals characterizing the life of a neutron be divided into three general categories: (1) … more
Date: June 1, 1997
Creator: Spriggs, G.D.; Adams, K.J. & Parsons, D.K.
Partner: UNT Libraries Government Documents Department
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Measurement of the equivalent fundamental-mode source strength

Description: The steady-state multiplication, M, of a subcritical system that is in equilibrium with an external/intrinsic source is defined as the total neutron-production rate divided by the external/ intrinsic neutron source rate, S. The total neutron-production rate, in this context, is the sum of the fission-production rate plus the source rate. Because the system is in equilibrium, the total neutron-production rate is identically equal to the loss rate from the system due to absorption plus leakage. I… more
Date: January 21, 1997
Creator: Spriggs, G. D.; Busch, R. D.; Sakurai, Takeshi & Okajima, Shigeaki
Partner: UNT Libraries Government Documents Department
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The equivalent fundamental-mode source

Description: In 1960, Hansen analyzed the problem of assembling fissionable material in the presence of a weak neutron source. Using point kinetics, he defined the weak source condition and analyzed the consequences of delayed initiation during ramp reactivity additions. Although not clearly stated in Hansen`s work, the neutron source strength that appears in the weak source condition corresponds to the equivalent fundamental-mode source. In this work, we describe the concept of an equivalent fundamental-mo… more
Date: February 1, 1997
Creator: Spriggs, G. D.; Busch, R. D.; Sakurai, Takeshi & Okajima, Shigeaki
Partner: UNT Libraries Government Documents Department
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The equivalent, fundamental-mode source

Description: In 1960, Hansen analyzed the problem of assembling fissionable material in the presence of a weak neutron source. Using point kinetics, he derived the weak source condition and analyzed the consequences of delayed initiation during ramp reactivity additions. Although not clearly stated in Hansen`s work, the neutron source strength that appears in the weak source condition actually corresponds to the equivalent, fundamental-mode source. In this work, they describe the concept of an equivalent, f… more
Date: December 24, 1996
Creator: Spriggs, G. D.; Busch, R. D.; Sakurai, Takeshi & Okajima, Shigeaki
Partner: UNT Libraries Government Documents Department
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Neutron chain length distributions in subcritical systems

Description: In this paper, the authors present the results of the chain-length distribution as a function of k in subcritical systems. These results were obtained from a point Monte Carlo code and a three-dimensional Monte Carlo code, MC++. Based on these results, they then attempt to explain why several of the common neutron noise techniques, such as the Rossi-{alpha} and Feynman's variance-to-mean techniques, are difficult to perform in highly subcritical systems using low-efficiency detectors.
Date: September 27, 1999
Creator: Nolen, S.D. & Spriggs, G.
Partner: UNT Libraries Government Documents Department
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Preliminary results of a Rossi-alpha experiment in the IPEN/MB-01 research reactor

Description: A preliminary set of Rossi-alpha measurements were performed on the IPEN MB-01 research reactor. The intent of the measurements was to determine if the efficiency of the BF{sub 3} detectors placed in the central region of the core was sufficiently high enough to allow an accurate measurement of the effective delayed neutron fraction, {beta}{sub eff}, and the alpha at delayed critical. In addition, a preliminary measurement of the intrinsic source strength was performed to determine the optimum … more
Date: September 23, 1997
Creator: Spriggs, G.D.; Carneiro, A.L.G.; Abe, A.Y. & Miranda, A.F.
Partner: UNT Libraries Government Documents Department
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Critical experiments in support of the CNPS (Compact Nuclear Power Source) program

Description: Zero-power static and kinetic measurements have been made on a mock-up of the Compact Nuclear Power Source (CNPS), a graphite moderated, graphite reflected, U(19.9% /sup 235/U) fueled reactor design. Critical configurations were tracked from a first clean configuration (184 most central fuel channels filled and all control rod and heat pipe channels empty) to a fully loaded configuration (all 492 fuel channels filled, core-length stainless steel pipe in the twelve heat-pipe channels, and approx… more
Date: January 1, 1988
Creator: Hansen, G. E.; Audas, J. H.; Martin, E. R.; Pederson, R. A.; Spriggs, G. D. & White, R. H.
Partner: UNT Libraries Government Documents Department
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