Dependability Enhancement of Reactor Containment in Safety Critical Nuclear Power Plants Chi-Shiang Cho, Wei-Ho Chung 1 , Deyun Gao 2 , Hongke Zhang 2 , and Sy-Yen Kuo. Department of Electrical Engineering, National Taiwan University Taipei 106, Taiwan sykuo@cc.ee.ntu.edu.tw 1 Research Center for Information Technology Innovation Academia Sinica, Taipei 115, Taiwan 2 College of Electronics and Information Engineering Beijing Jiaotong University, Beijing 100044, P. R. China Abstract—The use of nuclear energy to generate electric power is crucial in meeting the high energy demand of modern economy. The dependability of nuclear power plants has been a critical issue and the reactor containment is the most important safety structure acting as a barrier against the release of radioactive material to the environment. In this paper, we propose a practical framework for design, implementation, and V&V to enhance the dependability of reactor containment through an integrated leakage rate test. Keywords- containment; leakage rate; ILRT; V&V. I. INTRODUCTION Reactor containment is a critically engineered safety feature (ESF) in nuclear power plants (NPPs). The main function of containment is a leak-tight barrier against the release of radioactivity to the environment. The reactor confines the mass of radioactive materials inside the containment, which plays an important role in the recent nuclear crisis of Fukushima I Nuclear Power Plant in Japan. The study of the reactor containment dependability in this paper is crucial in addressing the safety concerns raised by the recent incident. A typical containment is illustrated in Fig. 1. The typical containment is consisting of a structure enclosing the reactor pressure vessel (RPV), electrical and mechanical penetrations, equipment access hatches, air lock doors and hatches, and seals and isolation valves. In the current Nuclear Reactor Commission (NRC) regulation, the Title 10 (10CFR50 Appendix J) specifies the integrated leakage rate test (ILRT) for pre- operational and periodic verification of the leak-tight integrity of the reactor containment [1]. ILRT adopts the Absolute Test Method using Ideal Gas Law to compute dry air masses in the containment. The Absolute Method assumes that the free air volume of containment is constant, i.e., changes of temperature and pressure are not significant enough to affect the containment structure. Several methods are proposed to compute leakage rate based on the Absolute Method. We adopt the standard Mass Point Method jointly with Total Time Method [2], [3], [4]. Table I [5] shows the historical data of leakage rate and calculated leakage areas. Table I demonstrates that the ILRT is effective and the calculated lower bound of leakage area by which this test passes. This paper mainly discusses the design and implementation of the ILRT. We conduct software verification and validation (V&V) on the procedure. We also present the practical operational NPP test cases to validate the correctness of the procedure. Figure 1. Overview of Reactor Containment TABLE I. ILRT LEAKAGE AREA DATA Reactor Name Containment Volume ft.3 Leakage Rate wt%/24h Area sq. in. Brunswick-2 2.9E+05 1.25 0.0092 Fitzpatrick 2.9E+05 0.545 0.0040 LaCrosse 2.6E+05 0.11 0.0007 Surry-2 1.8E+06 0.3 0.014 2011 17th IEEE Pacific Rim International Symposium on Dependable Computing 978-0-7695-4590-5/11 $26.00 © 2011 IEEE DOI 10.1109/PRDC.2011.24 129