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The effect of capture gammas, photofission and photonuclear neutrons to the neutron-gamma Feynman variance-to-mean ratios (neutron, gamma and total)

Dina Chernikova (Institutionen för teknisk fysik, Nukleär teknik) ; Imre Pázsit (Institutionen för teknisk fysik, Nukleär teknik) ; S. Croft ; A. Favalli
Mathematics and Computations, Supercomputing in Nuclear Applications and Monte Carlo International Conference, M and C+SNA+MC 2015, Nashville, United States, 19-23 April 2015 (2015)
[Konferensbidrag, refereegranskat]

Two versions of the neutron-gamma variance-to-mean (Feynman-alpha) formula for separate gamma detection and total neutron-gamma detection were recently derived and evaluated by Chernikova, et. al. [1]. However, the neutrons and gammas emitted in a photofission reaction or the release of gammas in certain thermal neutron capture reactions were not included in the theoretical models of Chernikova, et. al. [1]. In this paper, in order to evaluate the influence of these type of reactions to the values the neutron-gamma Feynman variance-to-mean ratios (neutron, gamma and total), we derive the enhanced Feynman-alpha formulae for separate neutron, gamma detection and total neutron-gamma detections. The theoretical derivation is based on the Chapman-Kolmogorov equation with inclusion of general reactions, photofission and capture gammas. The quantitative evaluation of the effect of capture gammas and photonuclear neutrons to the neutron-gamma Feynman variance-to-mean ratios (neutron, gamma and total) is done by using reaction intensities obtained from MCNPX simulations. The new enhanced formulas and their impact to the final values of different variance-to-mean ratios are the main subject of the discussion in the present paper.

Nyckelord: Feynman-alpha, Gammas, Photofission, Photonuclear, Thermal neutron capture, Totals



Denna post skapades 2016-01-13.
CPL Pubid: 230562

 

Institutioner (Chalmers)

Institutionen för teknisk fysik, Nukleär teknik (2006-2015)

Ämnesområden

Subatomär fysik
Kärnkemi

Chalmers infrastruktur