Fast Reactor Transfer Functions with Special Reference to the Nonlinearities and the Spatial Dependence of the Heat Transfer Process

A computer program for the calculation of reactor transfer functions has been written and tested. The model used for the temperature feedbacks differs from previous models because it accounts not only for heat propagation and heat transport effects but also for effects due to the nonlinearities of thermal parameters, such as the fuel thermal conductivity, the fuel specific heat capacity, and the heat transfer coefficient of the gap between fuel and cladding. Transfer functions are evaluated by making use of analytical methods. Numerical results are also included and show that physical changes in the gap during power oscillations will have an important effect on some particular transfer functions. This result is important if one wants to evaluate the gap heat transfer coefficient from power oscillation experiments.