Thermal stratification in lines connected to a reactor coolant system

Conference · Fri Dec 01 04:00:00 EST 1995

OSTI ID:136764

Lubin, B T ^[1]; Brown, J ^[2]

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1. ABB Combustion Engineering, Windsor, CT (United States). Nuclear Operations
2. Arizona Public Service, Phoenix, AZ (United States)

NRC Bulletins 88-08 and 88-11 identified thermal stratification as a cause of potentially large stresses in primary pressure boundary lines connected to reactor coolant systems. Bulletin 88-11 was specific to surge lines and treated thermal stratification as a new design basis transient. Though Bulletin 88-08 was concerned mainly with unisolable sections of Class 1 lines, where stratification could result from in-or out-leakage of cooler fluid, it directed that all lines be identified in which thermal stratification could result in top-to-bottom differences in wall temperature greater than 50 F. To address these concerns a program was established to identify Class 1 lines where thermal stratification could be present, and for the lines in which thermal stratification was found, to update, as necessary, related plant specific design basis documentation. Data on Class 1 lines were obtained at a number of operating Combustion Engineering plants. Lines in which wall temperatures higher than 50 F were measured included the Safety Injection (SI), Power Operated Relief Valve (PORV), and Shutdown Cooling (SDC) lines. In each of these lines the cause of the thermal stratification was found to be different: natural convection in SI lines, two-phase flow in PORV lines and a combination of turbulent penetration and natural convection in SDC lines. This paper presents representative data for each of these lines and includes discussion on line arrangements, evaluation of the data and predictive methods used to predict wall temperatures for other plants.

• OSTI ID: 136764
• Report Number(s): CONF-950740--; ISBN 0-7918-1344-4
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
22 GENERAL STUDIES OF NUCLEAR REACTORS
CE STANDARD REACTOR
DESIGN BASIS ACCIDENTS
ENGINEERED SAFETY SYSTEMS
PIPES
REACTOR COOLING SYSTEMS
RELIEF VALVES
SAFETY INJECTION
STRATIFICATION
TEMPERATURE DISTRIBUTION