This thesis presents the analysis of flow and heat transfer for the SPND (Self-Powered Neutron Detector) system used within the nuclear reactor core in the U.S. Evolutionary Power Reactor developed by AREVA. The SPND system is composed of six individual detectors which are used for in-core measurement of thermal neutron flux. The study of the SPND system is important since this system provides information and signals necessary for safe reactor operation and control. The main goal of the project was to determine the maximum temperature for the SPND detectors under three different operating scenarios. The maximum temperature of the detectors is of special interest, since if it exceeds a limiting temperature of 622 K then the accuracy of the information provided by the system is reduced. All of the flow and heat transfer simulations were performed using the commercial software Fluent.
The first scenario that was studied was for the system under normal operating conditions. For this case, the maximum temperature for a detector was determined to be 603.4 K, which is within the proper range of operation. It was also important to determine the maximum temperature of the fluid within the SPND assembly in order to ascertain that boiling does not occur within the system during normal operation. The maximum fluid temperature was found to be 613.7 K, which is below the boiling temperature of water (618.05 K) at an operating pressure of 2250 psi.
The second scenario involved an increase in the power of the reactor’s core by a factor of 17% in a 30 second period. The results of the unsteady calculation indicated that the maximum temperature for a detector was 608.5 K. The results also indicate that no boiling occurs inside of the SPND system.
The third scenario involved a loss of coolant flow in the SPND system. This reduction in flow rate caused the maximum temperature of the detectors to reach 619.6 K. For this case, boiling occurs within the guide tube and protection tube.
