Transient Behavior of the HWOCR with a Positive Power Coefficient

The positive coolant coefficient of reactivity characteristic of a large, economic, heavy-water-moderated, organic-cooled reactor (HWOCR) may make the power coefficient slightly positive. Therefore, the inherent reactor response characteristic of a positive power coefficient was studied dynamically to determine if a practical controller and shutdown system could be designed. Reactivity, coolant flow, and coolant inlet temperature perturbations were studied in controlled and uncontrolled situations. It is concluded that with a small positive power coefficient this reactor can be stably controlled with a simple on-off dead band controller and that a relatively unsophisticated shutdown system will prevent damage under severe transient conditions even in the case of a failure of the automatic controller.