Seismic design for nuclear power facilities is generally based on a prescribed earthquake response spectrum, which defines the response of a simple oscillator of a given natural frequency to the expected motions. To develop standard designs that may be suitable in a number of possible future locations, it is useful to develop standard spectra that describe typical environments. The adequacy of the standard design for a particular location may then be judged based on comparison of the standard spectrum with a site-specific "uniform hazard spectrum" (UHS). In this paper, UHS results from selected publicly available studies are used to develop a standard spectral shape that describes moderate-seismicity sites in eastern North America, on hard-rock site conditions. Compared with a standard spectrum that has been suggested for future nuclear plants on rock sites (modified Canadian Standards Association CSA/CAN-N289.3), the spectral shape proposed herein has higher amplitudes at high frequencies and lower amplitudes at low frequencies.Résumé : La conception sismique des centrales nucléaires est généralement basée sur un spectre de réponse prévu lors de séismes; ce spectre définit la réponse d'un simple oscillateur aux mouvements escomptés, à une fréquence naturelle donnée. Afin d'établir des conceptions standards qui peuvent convenir à plusieurs emplacements futurs, il serait utile de développer des spectres standards qui décrivent des environnements typiques. L'adéquation de cette conception standard pour un emplacement particulier pourrait ensuite être jugée en comparant le spectre standard à un « spectre de danger uniforme » (« UHS ») spécifique à un site. Cet article montre que les résultats UHS d'études sélectionnées disponibles au grand public sont utilisés pour développer une forme spectrale standard qui décrit les sites à sismicité modérée de l'est de l'Amérique du Nord pour des conditions de roches dures. Par rapport au spectre standard qui a été suggéré pour les futures centrales nucléaires construites sur de la roche (norme CSA/CAN-N289.3 modifiée), la forme spectrale proposée dans cet article possède des amplitudes plus élevées à des hautes fréquences et de plus faibles amplitudes à des basses fréquences.Mots clés : mouvement du sol lors de séisme, spectre de réponse, centrale nucléaire, forme spectrale, mouvement du sol servant à la conception du projet.[Traduit par la Rédaction] Atkinson and Elgohary 18
Atomic Energy of Canada Limited (AECL) has established a successful, internationally recognized line of CANDU® reactors that use heavy water moderator and pressure tubes; in particular the medium-sized CANDU-6 reactor. AECL has consistently adopted an evolutionary approach to the enhancement of CANDU nuclear power plant designs over the last 30 years. This approach has been extended further in the development of the ACR-1000®. The ACR-1000 design has evolved from AECL’s in-depth knowledge of CANDU structures, systems, components and materials, as well as the experience and feedback received from builders, owners and operators of CANDU plants. While retaining the proven strengths and features of CANDU reactors, the ACR design incorporates innovations and state-of-the-art technologies where appropriate. Part of this innovation is to develop an efficient and optimized plant layout that includes diverse features and requirements from many engineering disciplines. The ACR-1000 plant layout satisfies safety requirements and regulations and includes input from construction, operations and maintenance feedback from existing stations/utilities, while maintaining the process functional configuration for the overall layout of the plant, building and systems. This paper discusses a number of key aspects in developing the ACR-1000 plant layout design using representative sketches and 3D CADDS illustrations.
The ACR-700 has been designed with safety, cost and schedule as major drivers. Early in the concept stage it was demonstrated that short construction schedules can be achieved by paralleling activities, using such techniques as extensive modularization, combined with open top construction of the reactor building, as well as using the latest construction techniques available such as climbing formwork, prefabricated rebar, automatic welding, etc. This paper looks at the continued evolution of detailed construction sequences as a planning tool tied to the Primavera schedule. It also looks at examples where cost and schedule become important factors in making engineering decisions associated with the construction method and sequence. Experience on the modularization benefits achieved from the recently completed Qinshan CANDU project is presented. Finally it draws conclusions on the confidence in achieving construction schedules for both the first and nth units of a series.
There is "high confidence" in the ability of structures, systems and components (SSCs) of Nuclear Power Plants (NPPs) to perform as designed during Design Basis Accidents. For Design Extension Conditions (DECs), the SSCs are required to perform as designed with "reasonably high confidence." A deterministic design method is proposed to address DECs' higher demands in new and existing CANDU NPPs. The deterministic method builds on the current requirements of applicable codes and standards and recommends more relaxed acceptance criteria. Nevertheless, a means to probabilistically evaluate built-in margins exceeding demand induced by a DEC would provide a measure of the confidence in a DEC-assigned structure or component performing its function. Therefore, a probabilistic method that estimates the probability of survivability for a structure or component when subjected to the demand induced by a DEC is proposed. The probabilistic method could be used to indicate whether there is a need for applying design modification to existing design features to address demands of seismic DEC. The mean, 5-percentile, and 95-percentile fragility functions of these SSCs are used. These fragility functions are typically developed to determine the High-Confidence-Low-Probability-of-Failure value associated with the contribution of a structure or component to the overall plant seismic risk. Sample cases for design features that were implemented in existing CANDU NPPs to address DECs are presented. Both the deterministic and probabilistic methods are applied to cases of Civil structures, passive Mechanical & Electrical components as well as active Control & Instrumentation components.
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