The effect of capture gammas, photofission and photonuclear neutrons to the neutron-gamma Feynman variance-to-mean ratios (neutron, gamma and total)
Paper i proceeding, 2015

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.

Photofission

Gammas

Totals

Feynman-alpha

Thermal neutron capture

Photonuclear

Författare

Dina Chernikova

Chalmers, Teknisk fysik, Nukleär teknik

Imre Pazsit

Chalmers, Teknisk fysik, Nukleär teknik

S. Croft

Oak Ridge National Laboratory

A. Favalli

Los Alamos National Laboratory

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

1040-1051

Ämneskategorier

Subatomär fysik

ISBN

978-151080804-1