An algorithm of higher-order perturbation variables satisfying the additivity for system operators

If the variations of reactor-system operators are linearly summable for all perturbation types of parametric perturbation (PP), its higher-order perturbation (HOP) variables including neutron-flux distribution can be simply composed of the perturbation variables caused only by an individual type of perturbation. In order to lay a numerical foundation of utilizing HOP variables, based on the nodal Greenʹs function method, an algorithm of HOP variables satisfying the additivity for operators is developed in this paper. The additivity for reactor-system operators will be extensively ensured by way of introducing the reference Greenʹs function and defining the generalized flux reasonably. While the numerical realization is making full use of the existing computer code, a so-called recursive-increment method is developed to avoid the difficulty of solving the mathematical-adjoint equations. Some checking computations have shown that the algorithm is stable.