Probability and consequences of rapid boron dilution in a PWR: A scoping study

Technical Report · Mon Jun 01 04:00:00 EDT 1992

OSTI ID:5176498

Diamond, D J; Kohut, P; Nourbakhsh, H ^[1]; Valtonen, K ^[2]; Secker, P ^[3]

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1. Brookhaven National Lab., Upton, NY (United States)
2. Finnish Centre for Radiation and Nuclear Safety (STUK), Helsinki (Finland)
3. Arizona Univ., Tucson, AZ (United States)

This report documents the results of a scoping study of rapid dilution events in pressurized water reactors. It reviews the subject in broad terms and focuses on one event of most interest. This event could occur during a restart if there is a loss-of-offsite power when the reactor is being deborated. If the volume control tank is filled with water at a low boron concentration then a slug of this water could accumulate in the lower plenum. This would be the result of the trip of the reactor coolant pumps leading to relatively low flow conditions and the restart of the charging pumps on emergency power. The concern is that this diluted slug will rapidly enter the core after a reactor coolant pump is restarted and this could cause a power excursion leading to fuel damage. This problem was studied probabilistically for three plants and the important design features that affect the core damage frequency were identified. This analysis was augmented by an analysis of the mixing of the diluted water with the borated water already present in the vessel. The mixing was found to be significant so that neglect of this mechanism in probabilistic analysis leads to very conservative results. Neutronic calculations for one plant were carried out to understand the effect of nuclear design on the consequences of the event.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (United States). Div. of Systems Technology; Brookhaven National Lab., Upton, NY (United States)
• Sponsoring Organization: NRC; Nuclear Regulatory Commission, Washington, DC (United States)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5176498
• Report Number(s): NUREG/CR-5819; BNL-NUREG--52313; ON: TI92016531
• Country of Publication: United States
• Language: English

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ACCIDENTS
ALLOYS
BLACKOUTS
BORIC ACID
BORON ADDITIONS
BORON ALLOYS
BORON COMPOUNDS
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INORGANIC ACIDS
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NEUTRAL-PARTICLE TRANSPORT
NEUTRON TRANSPORT
OPERATION
OXYGEN COMPOUNDS
POWER REACTORS
PROBABILITY
PWR TYPE REACTORS
RADIATION TRANSPORT
REACTOR ACCIDENTS
REACTOR COMPONENTS
REACTOR COOLING SYSTEMS
REACTOR CORES
REACTOR FUELING
REACTOR OPERATION
REACTOR SAFETY
REACTOR SHUTDOWN
REACTOR START-UP
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SAFETY
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THERMAL REACTORS
WATER CHEMISTRY
WATER COOLED REACTORS
WATER MODERATED REACTORS