Temperature Dynamic Analysis of Fuel Elements for Boiling Water Reactors

Normally a boiling water reactor operates in the nucleate region at a quiescent point on the boiling curve. Considering small variations which occur about the quiescent operating point, the fuel element temperature dynamics can be properly described by a transfer function relating incremental variation in the fuel element surface temperature and heat rate generated within. In this work transfer functions are derived to represent the heat transfer dynamics for plate and cylindrical fuel elements under boiling conditions. The heat rate generation is taken to be nonuniform and the special case of uniform heat is deduced. Computational results are presented for typical BWR fuel elements under different operating conditions.