Parametric stochastic stability and decay ratio for a stochastic nonlinearBWR model below the Hopf bifurcation

We have studied the effects of the reactivity noise p(1)(t) (a coloured par ametric noise) upon the neutron fluctuation with the use of a nonlinear BWR model below the Hopf bifurcation. It is clarified that there appears tempo ral variation of a local stability in the neutron field under the influence of pl(t). It is also clarified that pl(t) works to change a global stabili ty of the neutron field. The feature of global variations in the decay rati o (DR) for an exponentially correlated noise < P-1(t)p(1)(t')> = (p(1)(2)) exp(-gamma \ t - t'\) in the 2D (gamma, < p(1)(2)>) parameter space is show n in conjunction with physical interpretation of the correlation function o f the neutron fluctuation. (C) 1999 Elsevier Science Ltd. All rights reserv ed.