Universality and aperiodic behavior of nuclear reactors

When a heat transfer coefficient is varied in a lumped-parameter model of a nuclear reactor, the model can undergo period-doubling pitchfork bifurcations leading to aperiodic behavior. Until aperiodicity commences, the model behaves in the universal manner predicted by Feigenbaum, and the Poincare map for the excess neutron population behaves as a typical onedimensional map with a quadratic maximum. In the aperiodic region, though, this Poincare map displays a hysteresis-like folding. At all times, the model's dynamic evolution remains bounded.