Modification of the PWR control system using a gaseous absorber

A modification of the PWR control system is suggested, based on the introduction of a gaseous absorber to the core thimbles. The absorber under consideration is ³He. The advantage of the suggested method is the possibility of controlling the reactor during burnup without affecting the moderator reactivity coefficient, and without distorting the reactor axial power distribution. The suggested method also provides a redundancy of the control system. Initial calculations corresponding to this modified control system are presented, while its advantages and disadvantages are discussed.