Derivation of BWR Core Dynamics Models and Analysis of JPDR Core Transient Tests

Abstract

The purpose of the present work is to establish a core dynamics model for the JPDR plant (natural circulation boiling water reactor plant). First, upon surveying the analytical model with the so-called distributed parameters in reference to the experimental results obtained during the JPDR initial power-up test, it was decided to develop the core dynamics model with lumped rather than distributed parameters, and to further modify it to obtain the highest possible accuracy. Three equations for mass, energy and momentum balances were used, and particular care was taken in the determination of the core void fraction and recirculation flow, the development of the thermo-hydrodynamic equation in the saturated region, and the choice of void sweep time as well various numerical constants. The derived dynamics model was then applied to the analysis of the JPDR transient test involving Bypass Regulator and Initial Pressure Regulator operations, as well as to that of the Bypass Regulator oscillation test. The calculated results by this model agreed well with data from experiment. A comparison was then made between the model and other core dynamics models. It was concluded that this model intrinsically has good accuracy and is easy to handle; it should prove very useful for core dynamics analysis of any BWR, in their relation to the out-of-core controlling system.