Acceptable Seismic-Induced Risks per U.S. Department of Energy Standards at Nuclear Facilities

Abstract

This paper investigates the potential impacts of the transition to the U.S. Department of Energy (DOE) Order 420.1B requirements and the criteria promulgated by the new DOE-STD-1189 on the current practice for seismic design of structures, systems, and components (SSCs). Addressed in the review is the modification of the prescribed methodology provided in ANSI/ANS-2.6-2004 by the new DOE standard. The new ANSI/ANS standards provide criteria and guidance in selecting the seismic design category (SDC) and the limit state (LS) for the SSCs that are important to safety. An unmitigated consequence analysis considering the uncertainties in estimating failure and the safety consequences of the failure may be performed to determine the SDC and the LS, which then are used to establish the level of peak ground acceleration and design response spectra. The new DOE-STD-1189 modifies the prescribed methodology provided in ANSI/ANS-2.6-2004 for calculation of unmitigated radiological dose consequence. Unmitigated consequence analysis is a procedure that has been used by the DOE for the purpose of incorporating safety in the design and operation of its nuclear facilities and is also used in 10 CFR 70, the U.S. Nuclear Regulatory Commission regulation applicable to fuel cycle facilities, and the associated Standard Review Plan (NUREG-1520). This paper identifies the iterative DOE double-pronged approach to seismic design, and a simplified example demonstrates the unmitigated seismic hazard consequence analysis.