Project Details
[Return to Previous Page]REACTOR PRESSURE VESSEL WATER LEVEL MEASUREMENT
Company: GE-Hitachi Nuclear Energy Americas LLC
Major(s):
Primary: ME
Secondary: EE
Optional: EGEE
Non-Disclosure Agreement: YES
Intellectual Property: YES
GEH AND BWRX-300 BACKGROUND GE-Hitachi Nuclear Energy’s (GEH’s) BWRX-300 is a 300 MWe water-cooled, natural circulation Small Modular Reactor (SMR) with passive safety systems that leverages the design and licensing basis of GEH's U.S. NRC-certified ESBWR. Through dramatic and innovative design simplification, the utilization of a licensed and proven fuel design and the incorporation of proven components and supply chain expertise, GEH believes the BWRX-300 can become the lowest-risk, most cost-competitive and quickest to market SMR. As the tenth evolution of the Boiling Water Reactor (BWR), the BWRX-300 represents the simplest, yet most innovative BWR design since GE began developing nuclear reactors in 1955. Advanced nuclear technologies like the BWRX-300 are a key pillar of GE’s energy transition leadership. The BWRX-300 produces no carbon during operation and has been designed to achieve construction and operating costs that are substantially lower than traditional nuclear power generation technologies. The BWRX-300 plant is composed of some major systems as shown in the attached Figure 1, including the primary circuit, or Nuclear Boiler System (NBS). The primary functions of the NBS are to: 1) deliver steam from the Reactor Pressure Vessel (RPV) to the turbine main steam system, 2) deliver feedwater from the condensate and feedwater system to the RPV, 3) provide overpressure protection of the Reactor Coolant Pressure Boundary (RCPB), 4) provide the instrumentation necessary for monitoring RPV pressure, steam flow, core flow, water level, and metal temperature. One key component is RPV, as shown in the attached Figure 2, which has an inside diameter of ~ 4 m, wall thickness of ~136 mm, and height of ~26 m. The bottom of the active fuel location is ~ 5.2 m from the bottom of the vessel and the active core is 3.8 m high. The relatively tall vessel, due to the chimney, permits natural circulation driving forces to produce abundant core coolant flow. WATER LEVEL MONITORING AND PROJECT DESCRIPTION Water level monitoring (WLM) in the RPV is critical during normal operation to maintain the optimum water inventory for core cooling and steam generation. In addition, it is imperative to maintain WLM capability during off-normal events and accident conditions in support of automatic or operator actions to restore normal conditions, or to maintain the plant in a safe condition. The primary WLM method in the industry is differential pressure (dP), which will also be the primary method for the BWRX-300. There are known issues with dP accuracy, especially during accident conditions. This project intends to characterize the conditions that cause inaccuracies and possibly develop correction algorithms to achieve high accuracy in all conditions. Another objective is to support measurement diversity with other methods. Time-domain reflectometry (TDR) and heated-junction thermocouples (HJT) are the likely candidates to supplement dP. Test data will be obtained from these additional methods. This project can include analysis of the data to determine applicability and where improvements can be made. This may involve the addition of filtering, digital signal processing, and enhanced calibration algorithms. The RPV dP level measurement schematic in attached Figure 3 illustrates the region where dP will be used to measure water level. Notice that the dP transducer pairs do not cover lower elevations such as over the core during low level transients. Therefore, other supplemental methods are necessary to extend WLM coverage. TDR and/or HJTs are the likely methods that will supplement dP. A major challenge, and the primary objective for this project, is to understand how well each of the methods perform under abnormal conditions. One example is when a rapid depressurization event occurs and the water inventory flashes resulting in voiding and mixed phase layers or gradients.
