United States Nuclear Regulatory Commission - Protecting People and the Environment

TRACE Simulation of SBO Accident and Mitigation Strategy in Maanshan PWR (NUREG/IA-0430)

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Publication Information

Manuscript Completed: March 2013
Date Published: September 2013

Prepared by:
Jong-Rong Wang, Kai-Chun Huang*, Hao-Tzu Lin, Chunkuan Shih*

Institute of Nuclear Energy Research, Atomic Energy Council, R.O.C. 1000, Wenhua Rd., Chiaan Village, Lungtan, Taoyuan, 325, TAIWAN

*Institute of Nuclear Engineering and Science, National Tsing Hua University, 101 Section 2, Kuang Fu Rd., Hsinchu, TAIWAN

K. Tien, NRC Project Manager

Division of Systems Analysis
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Prepared as part of:
The Agreement on Research Participation and Technical Exchange
Under the Thermal-Hydraulic Code Applications and Maintenance Program (CAMP)

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

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Abstract

Maanshan Nuclear Power Station is a two-unit Westinghouse three-loop PWR power station. This research studies the simulation of Maanshan SBO accident happened on 18th March, 2001, and thermal-hydraulic phenomena of the plant during station blackout with and without mitigation strategies. The modeling and simulation works were done by using TRACE code, which is a best-estimate thermal-hydraulic system code developed by US NRC. The purpose of using the mitigation strategy during SBO is to cool down NSSS as soon as possible, to keep the fuel covered by water, and not to let peak cladding temperature (PCT) higher than 1088K (1500°F), which is the temperature that metal-water reaction can self-sustain. Actions that considered such as operation of auxiliary feedwater system, depressurization of steam generators (SG), and line-up the alternate water sources such as sea water when regular systems aren't available.

The simulations of mitigation strategies start from normal operation at 100% power then an earthquake is assumed to happen, tsunami strike the site 20 minutes later, and failure of turbine driven auxiliary feedwater is assumed in base cases. Two different basic mitigation strategies were simulated, include (1) SG controlled-depressurization at the time that SBO happen and SG alternate injection after 1 hour of SBO, (2) SG depressurization at the time after 1 hour of SBO that injection is ready. In addition, alternate injection preparation time is further extended to find the longest acceptable value. Reactor coolant pump shaft seal leakage is also considered in all cases.

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