Analysis of thermal mixing and boron dilution in a PWR

Technical Report · Mon Feb 01 00:00:00 EST 1993

OSTI ID:6983457

Sun, J G; Sha, W T ^[1]

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1. Argonne National Lab., IL (United States)

Thermal mixing and boron dilution In a pressurized water reactor were analyzed with COMMIX codes. The reactor system was a four-loop Zion reactor that was initially filled with hot boron-rich water. It wasassumed that the reactor coolant pumps are tripped. Following the trip, cold unborated water from seal injection or other sources continuously flows into the reactor coolant system and dilution takes place first in the pump suction line and then in the reactor vessel. The thermal mixing and boron dilution under these conditions were analyzed. For the analysis of thermal mixing, water at room temperature (referred to as cold water) was fed into the cold leg of the reactor system at various flow rates. For the analysis of boron dilution, cold and hot unborated water was fed into the cold leg at a high flow rate. The subsequent transient thermal mixing and boron dilution that would occur in the reactor system were simulated for 1--2 h, depending on the flow rate. A third analysis was performed for the boron dilution after the startof the reactor coolant pump, which forces a slug of cold unborated water from the pump suction line into the reactor vessel. This transient was simulated for 20 sec, by which time the slug has been pushed out of the reactor core. The rates of reactivity insertion were evaluated for these analyses.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (United States). Div. of Safety Programs; Argonne National Lab., IL (United States)
• Sponsoring Organization: USNRC; Nuclear Regulatory Commission, Washington, DC (United States)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6983457
• Report Number(s): NUREG/CR-5822; ANL-91/43; ON: TI93009508
• Country of Publication: United States
• Language: English

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