Multiplicities of Fission Neutrons

Diven, B.C.; Martin, H. C.; Taschek, R. F.; Terrell, J.

doi:10.1103/physrev.101.1012

Cited by 241 publications

(41 citation statements)

References 12 publications

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“…Figure 1 compares our preliminary results with the 1956 thermal neutron data of Diven et al [4]. The agreement of FREYA with the data is rather good although the average multiplicity from FREYA (m = 2.37) is somewhat smaller than that of the data (m = 2.47).…”

Section: Preliminary Resultssupporting

confidence: 53%

Event-by-Event Simulation of Induced Fission

Vogt¹,

Randrup²,

Escher³

et al. 2008

AIP Conference Proceedings

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Abstract. We are developing a novel code that treats induced fission by statistical (or Monte-Carlo) simulation of individual decay chains. After its initial excitation, the fissionable compound nucleus may either deexcite by evaporation or undergo binary fission into a large number of fission channels each with different energetics involving both energy dissipation and deformed scission prefragments. After separation and Coulomb acceleration, each fission fragment undergoes a succession of individual (neutron) evaporations, leading to two bound but still excited fission products (that may further decay electromagnetically and, ultimately, weakly), as well as typically several neutrons. (The inclusion of other possible ejectiles is planned.) This kind of approach makes it possible to study more detailed observables than could be addressed with previous treatments which have tended to focus on average quantities. In particular, any type of correlation observable can readily be extracted from a generated set of events. With a view towards making the code practically useful in a variety of applications, emphasis is being put on making it numerically efficient so that large event samples can be generated quickly. In its present form, the code can generate one million full events in about 12 seconds on a MacBook laptop computer. The development of this qualitatively new tool is still at an early stage and quantitative reproduction of existing data should not be expected until a number of detailed refinement have been implemented.

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Section: Preliminary Resultssupporting

confidence: 53%

Event-by-Event Simulation of Induced Fission

Vogt¹,

Randrup²,

Escher³

et al. 2008

AIP Conference Proceedings

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“…where C 0 was a correlation amplitude including detection efficiencies of two neutron counters, the Diven factor [27], neutron number per pulse and α 0 . From least-squares fit of Equation (6) to correlated reactornoise component of measured cross-power spectral density, the fundamental prompt-neutron decay constant α 0 could be determined.…”

Section: Cross-power Spectral Analysismentioning

confidence: 99%

Measurement of large negative reactivity of an accelerator-driven system in the Kyoto University Critical Assembly

Sakon

Hashimoto

Maarof

et al. 2013

Journal of Nuclear Science and Technology

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Large negative reactivity of a subcritical system driven by a pulsed 14 MeV neutron source has been measured in the Kyoto University Critical Assembly. The subcriticality of the accelerator-driven system (ADS) ranged in effective multiplication factor roughly from 0.98 to 0.92, which corresponded to an operational range of an actual ADS proposed by Japan Atomic Energy Agency. As the measurement technique, pulsed neutron method, power spectral analysis for pulsed neutron source, accelerator-beam trip method were employed. From neutron count decay data obtained by the pulsed neutron experiment, not only the promptneutron decay constant of fundamental mode but also a higher spatial mode could be derived. The subcriticality was also determined from the fundamental decay constant. The measured cross-power spectral density consisted of a familiar correlated reactor-noise component and many uncorrelated delta-functionlike peaks at the integral multiple of pulse repetition frequency. The fundamental prompt-neutron decay constant, i.e., the subcriticality determined from the latter uncorrelated peaks was consistent with that obtained by the above pulsed neutron experiment. However, the magnitude of the former correlated component was reduced with an increase in the subcriticality and eventually this component became almost white at deeply subcritical state ranging in the multiplication factor under 0.95. Consequently, the determination of the decay constant from the correlated component was impossible under such a subcritical state. As data analysis method for the beam trip experiment, both the conventional integral count method and the least-squares inverse kinetics method (LSIKM) were employed. The LSIKM analysis led to the consistent subcriticality with that obtained by the pulsed neutron experiment, while the integral count method significantly underestimated the subcriticality. This underestimation originated from a residual background count, which was maintained after the beam trip. The LSIKM was mostly not influenced by such a slight count rate.

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“…and 1 1 From above equations, the total fission rate can be expressed by Number of total fission or (4) P: Power in W*.…”

Section: Principle Of Measurementmentioning

confidence: 99%

A Method for Measuring Absolute Reactor Power through Neutron Fluctuation

Suzuki

1966

J. Nucl. Sci. Technol.

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A new principle is presented for obtaining absolute reactor power by processing the random fluctuation of neutron flux based on the stochastic nature of nuclear reactions. The required combination of instruments to carry out experiments is described, and experimental results o!Jtained in a swimming pool reactor are reported. The power spectral density of the output current of an ion chamber located near the reactor core is determined by reactor kinetic parameters such as delayed neutron yield, life time, iJ (mean number of neutrons generated per fission) and counter efficiency as well as by the total number of neutrons in the core, which is a measure of absolute power.Using either logarithmic amplifier or reactivity meter, absolute reactor power can be measured without any inlormation about detector efficiency. This method has such merits as easiness and simplicity in operation, ability to measure absolute power in the range 0.01~100 W where other methods are inapplicable, and negligible effect of changes in core configuration or in detector position.The results of actual reactor experiments with this method proved to agree fairly well with those of absolute measurement hy gold foil activation.

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Multiplicities of Fission Neutrons

Cited by 241 publications

References 12 publications

Event-by-Event Simulation of Induced Fission

Event-by-Event Simulation of Induced Fission

Measurement of large negative reactivity of an accelerator-driven system in the Kyoto University Critical Assembly

A Method for Measuring Absolute Reactor Power through Neutron Fluctuation

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