Abstract: In a nuclear reactor core, a lower tie plate assembly is provided with asymmetric features designed to control or vary a loss coefficient as a function of rotation of the associated fuel assembly. An associated method is provided to control the flow of coolant through the associated fuel assembly via rotation of the fuel assembly relative to the fuel support member. Control of the flow can be used to adjust assembly flow rate, assembly power and flow quality within the fuel assembly, among other assembly operational characteristics. Such flow control will impact the flow through other assemblies as well, since core flow remains generally fixed. On a core-wide basis, such flow control can be used to optimize core wide parameters. Optimization parameters of particular interest are the fuel cycle cost and moisture carryover.

Abstract: A debris exclusion and retention device traps and retains foreign material within the lower tie plate of the fuel assembly utilizing the existing flow paths within the lower tie plate, and without redirecting coolant flow. Flow through the inlet nozzle of the lower tie plate into an enlarged lower tie plate housing creates strong jet impingement against the center of the lower tie plate grid or debris filter, if present, which has a tendency to push debris to the periphery of the lower tie plate. Low flow zones around the periphery of the lower tie plate allow debris to fall back toward the inlet nozzle. The retention device traps and retains debris in these low flow zones without impacting existing flow patterns in the lower tie plate. Thus, the retention device has minimal or no impact on lower tie plate pressure drop.

Abstract: A debris exclusion and retention device traps and retains foreign material within the lower tie plate of the fuel assembly utilizing the existing flow paths within the lower tie plate, and without redirecting coolant flow. Flow through the inlet nozzle of the lower tie plate into an enlarged lower tie plate housing creates strong jet impingement against the center of the lower tie plate grid or debris filter, if present, which has a tendency to push debris to the periphery of the lower tie plate. Low flow zones around the periphery of the lower tie plate allow debris to fall back toward the inlet nozzle. The retention device traps and retains debris in these low flow zones without impacting existing flow patterns in the lower tie plate. Thus, the retention device has minimal or no impact on lower tie plate pressure drop.

Abstract: In a nuclear reactor core, a lower tie plate assembly is provided with asymmetric features designed to control or vary a loss coefficient as a function of rotation of the associated fuel assembly. An associated method is provided to control the flow of coolant through the associated fuel assembly via rotation of the fuel assembly relative to the fuel support member. Control of the flow can be used to adjust assembly flow rate, assembly power and flow quality within the fuel assembly, among other assembly operational characteristics. Such flow control will impact the flow through other assemblies as well, since core flow remains generally fixed. On a core-wide basis, such flow control can be used to optimize core wide parameters. Optimization parameters of particular interest are the fuel cycle cost and moisture carryover.

Abstract: Systems and methods for servicing a fuel assembly in a light water reactor include those for controlling flow through a fuel assembly to maintain debris in the fuel assembly during removal and transportation of the fuel assembly, those for discharging debris from the fuel assembly, and those for isolating and sampling the water chemistry of a fuel assembly. An exemplary system includes a closure device configured to seal a mast to a fuel assembly to surround the upper opening of the fuel assembly and provide a flow control channel between a void in the mast and a lower opening in a lower tie plate.