Irreversible Circulation of Fluctuation in Coupled-Core Nuclear Reactors

Abstract

The irreversible circulation α of fluctuation a for a coupled-core nuclear reactors is derived. Neutrons in this system are transported from a certain core to another one with a finite time lag and their fluctuations are generally described by a set of non- Markoffian Langevin equations.

This system cannot accept Tomita's original theory based on the Markoffian stochastic process. When the system has the exp(-t/τ)-type memory kernel, we can, however, build up an equivalent Markoffian model—points model—by introducing “transit zones”, and we can evaluate the irreversible circulation of fluctuation α. The α for symmetrically coupled-cores takes null-value, while for an asymmetrical case the α becomes finite and turns out to be a new information from which the coupling parameters between the cores can be extracted.

KEYWORDS:

• asymptotic evaluation
• scaled variable
• normal case
• non-Markoffian Langevin equation
• coupled-core nuclear reactors
• fluctuation-dissipation theorem
• irreversible circulation of fluctuation
• equivalent Markoffian model
• dummy variable
• transit zone
• irreversible filter
• auto and cross power spectral density