Reactor Noise Theory based on System Size Expansion

Abstract When a reactor noise theory is applied to reactor diagnosis or stability analysis, it is necessary to consider non-linear non-stationary reactor noise phenomena. A new approach to the reactor noise theory is developed on the basis of recent studies on the theory of non-linear non-equilibrium statistical physics. This approach brings into relief the importance of making a clear distinction between extensive and intensive variables. A basic equation is derived in a quite general form, which yields a solution of asymptotic character for large systems. In the lowest-order approximation, the formalism yields the conventional equations. This leads to a clear description of the relation between the Langevin and the Kolmogorov methods, and substantiates the assumption of Gaussian distribution of the number of neutrons. A rigorous analysis of the newly derived equation is made with the aid of flow patterns representing the Hamilton-Jacobi equation. A sample application of the formalism is presented for a ...