NRC ATWS-I Stability Tests with Downskew Axial Power Profile: KATHY Test Series STS123 (NUREG/CR-7272)

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Publication Information

Manuscript Completed: September 2020
Date Published: September 2020

Prepared by:
D. Tinkler¹, K. Greene¹, K. Quick¹
J. Kronenberg², R. Velton², F. Wehle²
A. Beisiegel³, T. Berger³, F. El Rharbaoui³
P. Yarsky⁴

¹Framatome Inc.
Richland, WA 99354, USA

²Framatome GmbH
91001 Erlangen, Germany

³Framatome GmbH
63787 Karlstein, Germany

⁴U.S. Nuclear Regulatory Commission
Washington DC, 20555

Tarek Zaki, NRC Project Manager

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington DC 20555-0001

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Abstract

Natural circulation instability tests were performed in the Multifunction Thermal Hydraulic Test Facility KATHY in Karlstein, Germany. One type of test involved stepping up test assembly power in oscillating flow until failure to rewet occurs based on temperature observation. A second type of test introduced a simulated neutronic feedback to dynamically change the power, again with flow oscillations up to the point of failure to rewet. Two tests featured a transient inlet temperature. The largest flow oscillations in the test program ranged from ~ −7 kilograms per second (kg/s) to 13 kg/s. The tests varied system pressure (7 and 8 megapascals), water level in the steam-water separator (0.4 and 1.1 meters), and inlet subcooling (20 Kelvin and 35 Kelvin). A full-scale boiling-water reactor rod bundle was simulated in these tests. Before the dynamic instability tests, the rod bundle was characterized with single-phase- and two-phase pressure drop tests. Steady-state critical power tests were also performed to characterize the conditions under which steady-state dryout occurs. This report describes the tests performed as part of this program. This research effort supported the continued development and benchmarking of the U.S. Nuclear Regulatory Commission (NRC) reactor systems analysis computer code with state-of-the-art, realistic modeling capabilities thereby enabling more effective use of confirmatory calculations in licensing reviews.