Evaluation of treatment of effects of debris in coolant on ECCS and CSS performance in pressurized water reactors and boiling water reactors

Original publisher: Washington, DC : U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation, [2010] OCLC Number: (OCoLC)650088759 Subject: Nuclear power plants -- United States -- Safety measures. Excerpt: ... 4. a prototypic or conservative methodology for estimating the head loss across the suction strainer ( s ) for all possible debris bed characteristics for a given plant 5. a prototypic or conservative methodology for estimating the amount of debris that could pass through the screens or strainers 6. a prototypic or conservative methodology for estimating the effects of debris in the coolant on downstream components, including the vessel and core ( e.g., increased pressure loss, erosion, plugging ) The conservatism of the overall approach for determining NPSH margin depends primarily on developing a sound technical basis for defining the ZOI and the models for debris generation within the ZOI for a given LOCA event. This definition should be equivalent for both types of reactors ( although dependent on jet specifics ), and should be formulated to yield conservative estimates of the amount and specific types of debris generated. The debris generation methodology must be conservative if the overall analysis is to be conservative. The debris transport methodology should be consistent between PWR and BWR systems, since the same type of hydrodynamic forces are involved. Differences should relate only to differences in details of containment configuration, sump or pool dimensions, and structural design of the strainers. Similarly, the methodologies for determining debris bed formation and head loss across the debris bed for the suction strainers should reflect similar hydrodynamic behavior, with differences reflecting differences in strainer geometries and support structures. Table S. 1 lists the specific recommendations developed to provide consistent guidance for analysis of the effects of debris on system performance during a LOCA and subse...