Xenon instability study of large core Monte Carlo calculations

摘要

One of the goals of neutronic calculations of large cores may be self-consistent distribution of equilibrium xenon through the reactor core. In deterministic calculations such self consistency is relatively simply achieved with the help of additional outer iterations by xenon, which can increase several times solution run time. But in stochastic calculation of large cores such increase is utterly undesirable, since even without these outer iterations it demands modeling of billion of histories, which in case of complicated large core may take about a day of 100 processors work. In addition the unavoidable statistical uncertainty here plays role of transient process, which excites xenon oscillations. In this work the rise of such oscillations and the way of their overcoming with the help of hybrid stochastic/deterministic calculation is studied. It is proposed to make at first single static Monte Carlo calculation of given core and to receive multi-group mesh cell characteristics for future use in operative code. This one will evaluate xenon distribution through the core, which will be equilibrium for deterministic solution and substantially close to equilibrium Monte Carlo solution, paid with enormous computing cost.