Potential for boron dilution during small-break LOCAs in PWRs
This paper documents the results of a scoping study of boron dilution and mixing phenomena during small break loss of coolant accidents (LOCAs) in pressurized water reactors (PWRs). Boron free condensate can accumulate in the cold leg loop seals when the reactor is operating in a reflux/boiler condenser mode. A problem may occur when the subsequent change in flow conditions such as loop seal clearing or re-establishment of natural circulation flow drive the diluted water in the loop seals into the reactor core without sufficient mixing with the highly borated water in the reactor downcomer and lower plenum. The resulting low boron concentration coolant entering the core may cause a power excursion leading to fuel failure. The mixing processes associated with a slow moving stream of diluted water through the loop seal to the core were examined in this report. A bounding evaluation of the range of boron concentration entering the core during a small break LOCA in a typical Westinghouse-designed, four-loop plant is also presented in this report.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- Nuclear Regulatory Commission, Washington, DC (United States)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 119434
- Report Number(s):
- BNL-NUREG-62261; CONF-9510225-1; ON: TI96002007; TRN: 95:024502
- Resource Relation:
- Conference: OECD/Committee on Safety of Nuclear Installations (CSNI) specialist meeting on boron dilution reactivity transients, State College, PA (United States), 18-20 Oct 1995; Other Information: PBD: [1995]
- Country of Publication:
- United States
- Language:
- English
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