Leak-Before-Break Under Beyond Design Basis Seismic Loading

Author:

Zhang Tao1,Brust Frederick W.,Wilkowski Gery,Xu Heqin2,Betervide Alfredo A.,Mazzantini Oscar3

Affiliation:

1. e-mail:

2. Engineering Mechanics Corporation of Columbus, 3518 Riverside Dr. - Suite 202, Columbus, OH 43221

3. Nucleoelectrica Argentina S. A., Buenos Aires 2806, Argentina

Abstract

The Atucha II nuclear power plant is a unique pressurized heavy water reactor (PHWR) being constructed in Argentina. The original plant design was by Kraftwerk Union (KWU) in the 1970's using the German methodology of break preclusion. The plant construction was halted for several decades, but a recent need for power was the driver for restarting the construction. The United States Nuclear Regulatory Commission (US NRC) developed leak-before-break (LBB) procedures in standard review plan (SRP) 3.6.3 Revision 1 for the purpose of eliminating the need to design for dynamic effects that allowed the elimination of pipe whip restraints and jet impingement shields. This SRP was originally written in 1987. The US NRC is currently developing a draft Regulatory Guide on what is called the transition break size (TBS). However, modeling crack pipe response in large complex primary piping systems under seismic loading is a difficult analysis challenge due to many factors. The initial published work (Wilkowski et al., “Robust LBB Analysis for Atucha II Nuclear Plant,” 2011 ASME PVP Conference, July 17–21, Baltimore, MD) on the seismic evaluations for the Atucha II plant showed that even with a seismic event with the amplitudes corresponding to the amplitudes for an event with a probability of 1 × 10−6 per year, that a double-ended guillotine break (DEGB) was pragmatically impossible due to the high leakage rates and total loss of make-up water inventory. The critical circumferential through-wall flaw size in that case was 94% of the circumference. This paper discusses further efforts to show how much higher the applied accelerations would have to be to cause a DEGB for an initial circumferential through-wall crack that was 33% around the circumference. This flaw length would also be easily detected by leakage and loss of make-up water inventory. These analyses showed that the applied seismic peak-ground accelerations had to exceed 25 g's for the case of this through-wall-crack to become a DEGB during a single seismic loading event. This is a factor of 80 times higher than the 1 × 10−6 seismic event accelerations, or 240 times higher than the safe shutdown earthquake (SSE) accelerations.

Publisher

ASME International

Subject

Mechanical Engineering,Mechanics of Materials,Safety, Risk, Reliability and Quality

Reference13 articles.

1. Olson, R., Scott, P., and Wilkowski, G., 1992, “Application of a Nonlinear-Spring Element to Analysis of Circumferentially Cracked Pipe Under Dynamic Loading,” ASME Pressure Vessels and Piping Conference, June 21–25, New Orleans, LA.

2. Olson, R., Wolterman, R., Scott, P., Krishnaswamy, P., and Wilkowski, G., 1994, “The Next Generation Analysis Methodology for Cracked Pipe Systems Subjected to Dynamic Loads,” ASME Pressure Vessels and Piping Conference, June 19–23, Minneapolis, MN.

3. Analysis of JNES Seismic Tests on Degraded Piping,2010

4. Numerical Analysis of JNES Seismic Tests on Degraded Combined Piping System;ASME J. Pressure Vessel Technol.,2012

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