United States Nuclear Regulatory Commission - Protecting People and the Environment

In-Tube Steam Condensation in the Presence of Air Under Transient Conditions (NUREG/IA-0210)

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Publication Information

Date Published: May 2007

Prepared by:
A. Tanrikut
Turkish Atomic Energy Authority
Eskisehir Yolu 06530 Ankara Turkey

O. Yesin
Mechanical Engineering Department
Middle East Technical University
06531 Ankara Turkey

M.B. Rubin, NRC Project Manager

Prepared as Part of:
The Agreement on Research Participation and Technical Exchange
Under the International Code Assessment and Maintenance Program (CAMP)

Published by:
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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The experimental investigation of condensation of pure vapor and air/vapor mixture in case of loss of coolant (feed-water) to the secondary side of a condenser imposes a special case since boil-off rate at the secondary side directly affects condensation process inside a condenser tube. The motivation for this special case comes from the experiment performed at the UMCP 2X4 integral test loop at the University of Maryland, which is a 1/500 scaled test facility of a PWR with once-through type steam generators, concerning loss of residual heat removal system during operation with reduced coolant inventory. The first phase of this type the experiment performed at the UMCP 2X4 test facility comprises the boiler-condenser mode (BCM) of operation during which one steam generator is active. However when the steam generator becomes inactive due to loss of feed-water (LOFW) to the secondary side (second phase), heat transfer from primary to secondary side that is mainly by condensation degrades and system pressure escalates. To address the issue outlined here, two experiments were performed at the METU-CTF, including the first phase (BCM) and second phase (LOFW) of the scenario: pure steam and air/steam mixture. These transients showed that the system pressurization is almost linear by time at constant vaporization rate inside the boiler. Similar observation was made for the results of UMCP 2X4 experiment. Besides this, the METU-CTF results show that vapor suction rate, effective condensation length and overall heat transfer rate are the function of boil-off rate of coolant and air mass fraction, as expected.

In this report, the results of experiments performed at the METU-CTF concerning in-tube steam condensation at BCM steady state condition and transient (LOFW) are presented, for both pure steam and air/steam mixture cases. The results of RELAP5 simulation are also discussed. Although given in NUREG/IA-0184, the report on in-tube steam condensation in the presence of air at steady-state condition, a brief description of the METU-CTF test facility is also given in this report. Then the experimental results of the UMCP 2X4 test facility are presented with emphasize given to RELAP5 simulations. The recent version of the RELAP5 code (RELAP5/mod3.3 (beta)) was used in calculations performed for this technical report.

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