### Skapa referens, olika format (klipp och klistra)

**Harvard**

Pál, L. och Pázsit, I. (2009) *The fast fission factor revisited*.

** BibTeX **

@article{

Pál2009,

author={Pál, Lénárd and Pázsit, Imre},

title={The fast fission factor revisited},

journal={Nuclear Science and Engineering},

issn={0029-5639},

volume={161},

issue={1},

pages={111 - 118 },

abstract={The concept and calculation techniques of multiplicities in
nuclear safeguards are applied to the calculation of the traditional fast fission factor of reactor physics. The concept is the assumption that the original source neutrons from spontaneous or induced fission, and the further neutrons given rise through fast fission in the sample before leakage, are considered as being generated simultaneously with the source neutrons. The number
distribution of the neutrons arising from such a "superfission" process will be different from that of the nuclear fission process. Concerning the mathematical treatment, in safeguards works the master equation approach is used to calculate the moments of such a distribution. Hence, to follow suite, a derivation of the fast fission factor is given here by a backward master equation. This method has the advantages that the derivation of the fast fission factor becomes more transparent than the traditional one, and that it allows also to determine
higher order moments, notably the variance, of the total number of neutrons generated, i.e. when account is taken also of the contribution of fast fission to these moments. The results show that the relative standard deviation increases fast with the increase of the non-leakage probability of neutrons, and hence with the increase of the fast fission factor itself. Also the Diven factor of the superfission process (neutrons from fast fissions included) is significantly larger than that of thermal fission. We argue that the traditional model, in which the Feynman- and Rossi-alpha models are derived, does not account correctly for the extra branching represented by the fast fission
process. Hence the Diven factor traditionally used in those
formulae should be used in a modified form. We show how the effect of fast fission needs to be included into the model to obtain the correct formula, and give explicit expressions. Some quantitative examples are given for illustration. },

year={2009},

keywords={Fast fission factor, master equations, Diven factor, superfission},

}

** RefWorks **

RT Journal Article

SR Electronic

ID 79838

A1 Pál, Lénárd

A1 Pázsit, Imre

T1 The fast fission factor revisited

YR 2009

JF Nuclear Science and Engineering

SN 0029-5639

VO 161

IS 1

SP 111

OP 118

AB The concept and calculation techniques of multiplicities in
nuclear safeguards are applied to the calculation of the traditional fast fission factor of reactor physics. The concept is the assumption that the original source neutrons from spontaneous or induced fission, and the further neutrons given rise through fast fission in the sample before leakage, are considered as being generated simultaneously with the source neutrons. The number
distribution of the neutrons arising from such a "superfission" process will be different from that of the nuclear fission process. Concerning the mathematical treatment, in safeguards works the master equation approach is used to calculate the moments of such a distribution. Hence, to follow suite, a derivation of the fast fission factor is given here by a backward master equation. This method has the advantages that the derivation of the fast fission factor becomes more transparent than the traditional one, and that it allows also to determine
higher order moments, notably the variance, of the total number of neutrons generated, i.e. when account is taken also of the contribution of fast fission to these moments. The results show that the relative standard deviation increases fast with the increase of the non-leakage probability of neutrons, and hence with the increase of the fast fission factor itself. Also the Diven factor of the superfission process (neutrons from fast fissions included) is significantly larger than that of thermal fission. We argue that the traditional model, in which the Feynman- and Rossi-alpha models are derived, does not account correctly for the extra branching represented by the fast fission
process. Hence the Diven factor traditionally used in those
formulae should be used in a modified form. We show how the effect of fast fission needs to be included into the model to obtain the correct formula, and give explicit expressions. Some quantitative examples are given for illustration.

LA eng

LK http://epubs.ans.org/rip/index.cgi?jd=nse-161-1-111-118

OL 30