Combination of Two Spectral Shift Control Methods for Pressurized Water Reactors with Improved Power Utilization

Two methods for spectral shift control have been proposed for pressurized water reactors. The first method is a mechanical spectral shift where the moderator-to-fuel volume is changed. The second method is a chemical one in which the D₂O/H₂O ratio is changed. Utilization of a combination of the two methods has been suggested and analyzed. It was found that the advantage of the combined method is better than the sum of the advantages of the two methods separately. Emphasis was on using the spectral shift controls for one-batch reloads in order to increase the fuel cycle’s length and thus the electricity production. It was found that it is possible to increase electricity production during the plant’s lifetime by ∼6 to 9% compared to three and four batches using a regular control.