Start-Up of the PHW 600 Reactor with a Reduced Initial Core Loading

Abstract

<p>Savings, in terms of increased first charge burnup and lower fuel inventory costs, are made when a CANDU reactor is started up with a reduced initial core loading. Enough fuel is loaded to make the reactor critical and then progressively added to the outer channels to maintain criticality during operation over the initial transient. As more fuel is loaded, the form factor improves permitting the reactor power to be increased. When the last channel is loaded, full power can be achieved.</p> <p>The trade off between decreased fuel costs and energy loss has been investigated by simulating operation to 300 full power days (FPD) with a two dimensional fuel management program for various initial loadings of the PHW 600 reactor. The results for the reference case (fully loaded initial core producing full power from start-up) were available from a previous study (2). It was found that the optimum trade off occurred for an initial loading of about 95%. A 3% improvement in first charge burnup was obtained which was offset by an energy loss of 8 FPD over the initial transient. The maximum burnup improvement, for 34% initial loading, was about 13% with an energy loss of 73 FPD.</p> <p>It was concluded that the reduced core concept can be used to advantage only by a utility which does not require full power immediately. If, however, the lost energy has to be replaced from another source, utility operating costs are minimized by starting up under normal conditions owing to relatively high replacement energy costs.</p>