Effect of void distribution parameter and axial power profile on boiling water reactor bifurcation characteristics

Bifurcation analyses of the impact of the void distribution parameter C-0 a nd the axial power profile on the stability of boiling water reactors (BWRs ) are reported. Bifurcation characteristics of heated channels (without nuc lear feedback) appear to be very sensitive to the axial power profile. A tu rning point bifurcation was detected for a (symmetrically) peaked axial pow er profile. This kind of bifurcation does not occur for a uniformly heated channel. Both supercritical and subcritical Hopf bifurcations were encountered in a (nuclear-coupled) reactor system, depending on the strength of the void rea ctivity feedback. Subcritical bifurcations become less likely to occur as C -0 is significantly larger than unity. In BWRs with a strong nuclear feedba ck, the oscillation amplitude of limit cycles caused by a supercritical bif urcation is very sensitive to both C-0 and the axial power profile.