AP1000® Plant Application of Defense in Depth

Author(s):  
Terry L. Schulz ◽  
Julie Gorgemans

The AP1000 plant is an 1100-MWe pressurized water reactor (PWR) with passive safety features and extensive plant simplifications that enhance construction, operation, maintenance and safety. One of the key design approaches in the AP1000 plant design is to use passive features to mitigate design basis accidents. Active defense-in-depth (DiD) features provide investment protection, reduce the demands on the passive features and support the Probabilistic Risk Assessment (PRA). The passive features are classified as safety-related in the United States. The active DiD features are classified as nonsafety-related (with supplemental requirements) in the United States. The AP1000 plant design has also incorporated a standardization approach, which together with the level of safety achieved by the passive safety features, results in a plant design that can be applied to different geographical regions with varying regulatory standards and utility expectations without major changes. This paper will discuss the approach taken to defining DiD in the AP1000 plant and the effectiveness of that approach. It will also address the capability of the AP1000 plant to meet deterministic DiD guidelines such as the ones in application in the UK or described in the Western European Nuclear Regulators’ Association (WENRA) safety objectives for new plants.

Author(s):  
Kathyrn J. Demetri ◽  
Terry L. Schulz ◽  
Bryan N. Friedman

The AP1000® plant is an 1100-MWe pressurized water reactor (PWR) with passive safety features and extensive plant simplifications that enhance construction, operation, maintenance and safety. One of the key design approaches in the AP1000 plant is to use passive features to mitigate design basis accidents. Active defense-in-depth (DiD) features provide investment protection, reduce the demands on the passive features and support the PRA. The passive features are classified as safety-related in the US. The active defense-in-depth features are classified as non-safety (with supplemental requirements) in the US. The AP1000 design has incorporated a standardization approach, which together with the level of safety achieved by the passive safety features, results in a plant design that can be applied to different geographical regions with varying regulatory standards and utility expectations without major changes. While the first deployments of the AP1000 plant are ongoing in China and the United States, Westinghouse has remained active in also pursuing European opportunities for the AP1000 plant. In particular, Westinghouse has cooperated for almost two decades with European utilities to ensure adaptation of the AP1000 plant to the European market. This cooperation has resulted in progress towards AP1000 plant deployment in European countries. The AP1000 plant is recognized worldwide and has been reviewed by regulators around the world, including China, the United Kingdom (UK), Canada as well as the US. The AP1000 PWR is the only Generation III+ reactor design to obtain final design approval from the United States Nuclear Regulatory Commission (US NRC) and interim approval from UK regulatory authorities as part of the Generic Design Assessment (GDA) process. It is the only technology to be licensed for construction in the United States in more than 30 years, and the only Generation III+ technology worldwide to receive an operating license, as well as construction approval in China. The AP1000 plant has been independently assessed and confirmed to meet the requirements of the European Utilities Requirements (EUR) document and the Electric Power Research Institute (EPRI) Advanced Light Water Reactor Utility Requirements Document (URD). The AP1000 plant has also been successfully assessed against multiple European industry guidelines such as the WENRA safety objectives, the IAEA safety standards, the ENSREG stress tests and the UK Weightman Report. In support of multiple ongoing request for proposal (RFP) and pre-RFP activities in European countries, Westinghouse has focused design effort and customer interactions in several European countries to adapt the AP1000 plant to European requirements. Review of the AP1000 plant design with regulators around the world, European Standards compliance activities, and continued cooperation and interaction with European Utilities provide confidence that the AP1000 plant can be successfully licensed and deployed in Europe. The AP1000 50Hz standard plant design (also referred to as European Passive Standard or EPS) is the resulting adaptation of the AP1000 60 Hz US standard plant design to European market needs and requirements, addressing both customer input from such programs as the European Passive Plant (EPP) program in addition to regulatory and Utility needs identified though RFP and pre-RFP activities. The AP1000 50Hz standard plant design retains the overall AP1000 plant design (safe, simple, standard), the use of proven components and its cost, safety and operability advantages, while incorporating some changes to adapt to the European environment. This paper will discuss some of the key changes that have been incorporated into the AP1000 50Hz plant design as necessary to adapt to the European market and demonstrate that the vast majority of the standard AP1000 plant design being built in China and the US is not impacted.


Author(s):  
Yuichi Hayashi ◽  
Gianfranco Saiu ◽  
Richard F. Wright

The AP1000 is two-loop 1100 MWe advanced pressurized water reactor (PWR) that uses passive safety features to enhance plant safety and to provide significant and measurable improvements in plant simplification, reliability, investment protection and plant costs. The AP1000 uses proven technology, which builds on over 30 years of operating PWR experience. The AP1000 final design certification was approved by the NRC in December, 2005. A total of 34 Emergency Operating Procedures (EOPs) for operation of the AP1000 simulator have been prepared based on the AP1000 Emergency Response Guidelines (ERGs), background information documents and detailed plant information. These include 28 EOPs at power and 6 EOPs during shutdown. The AP1000 ERGs were developed by using the generic ERGs for the low pressure reference PWR plant as a basis. The AP1000 design differences from the reference plant were reviewed and reflected in the process of developing operational steps in each ERG. The provisions of the AP1000 PRA were also reviewed and incorporated into the ERGs. Although the AP1000 design does not require operator actions for the first 72 hours after accidents, the operator actions with both safety-related and nonsafety-related equipment have an important role to mitigate the consequence of accidents. In the event of a steam generator tube rupture (SGTR), although the AP1000 is designed so that no operator actions are required to recover from the event, there are actions that can be taken by the operator to limit the release of radioactive effluents from the ruptured SG. These actions include isolation of the ruptured SG and depressurization of the reactor coolant system (RCS) to terminate primary-to-secondary leakage, restoring reactor coolant inventory to ensure adequate core cooling and plant pressure control. It is expected that these operator actions should be incorporated into the ERG to reduce the fission product release. To support the development of the AP1000 ERGs, several transient and accident analyses were performed. These include analyses for LOCA, post-LOCA cooldown and depressurization, passive safety system termination, SGTR and faulted SG isolation. These analyses results were incorporated into the ERG background information documents. In the event of SGTR, several cases were analyzed, including consideration of operator recovery actions. These cases were modeled using the best-estimate state-of-art RELAP5 code. The analyses results show that operator recovery actions are effective for SGTR to be placed under operator control.


Author(s):  
Julie Gorgemans ◽  
Michael M. Corletti ◽  
Richard A. DeLong ◽  
Terry L. Schulz

The AP1000® plant is an 1100-MWe pressurized water reactor (PWR) with passive safety features and extensive plant simplifications that enhance construction, operation, maintenance, safety, and costs. Four AP1000 units are currently under construction on coastal sites of Sanmen and Haiyang, China. Additionally, the United States (US) Nuclear Regulatory Commission (NRC) issued combined licenses (COLs) to allow Southern Nuclear Operating Company (SNC) & South Carolina Electric & Gas Company (SCE&G) to construct and operate AP1000 plants at the existing Vogtle & VC Summer sites in Georgia and South Carolina, respectively. Although construction at both US sites is underway, the first four China AP1000 plants will become operational ahead of the U.S. Domestic AP1000 plants. Westinghouse is also actively engaged in deploying the AP1000 plant design in other regions throughout the world such as Europe. For example, the AP1000 plant design was evaluated by the UK Office for Nuclear Regulation as part of the UK Generic Design Assessment and received a statement of interim Design Acceptance in late 2011. This paper reviews the past and on-going AP1000 plant licensing activities and discusses how the significant lessons learned gathered through the AP1000 plant worldwide deployment increase licensing certainty for any new AP1000 project.


2021 ◽  
Vol 12 (2) ◽  
pp. 101637
Author(s):  
Aine Lehane ◽  
Sarah E. Maes ◽  
Christine B. Graham ◽  
Emma Jones ◽  
Mark Delorey ◽  
...  

Author(s):  
Muchlinski Peter T

This chapter investigates the legal basis for exercising extraterritorial jurisdiction over multinational enterprises (MNEs). The state’s exercise of extraterritorial jurisdiction rests on the international law rules relating to state jurisdiction. A state’s legal jurisdiction can be divided between the jurisdiction to prescribe laws, to adjudicate disputes and to enforce legal orders and judgments. This classification follows the traditional division of governmental authority between legislative, judicial and executive powers, though each branch of government can engage in any of the three. The chapter evaluates the three heads of jurisdiction in turn, relying to a large extent on US practice, which is the most developed in this field. In more recent years, not only the United States, but other global economic powers, have sought to avoid extraterritoriality conflicts though harmonization of regulatory standards and the development of cooperative regulatory structures.


Author(s):  
Kyle Dylan Dickson-Smith

Key lessons can be made from analysing a unique and recent BIT, the Canada–China Foreign Investment Protection Agreement (FIPA), in order better to predict and identify the opportunities and challenges for potential BIT counterparties of China (such as the United States, the European Union (EU), India, the Gulf Cooperation Council, and Columbia). The Canada–China FIPA and the anticipated US–China BIT (and EU–China BIT) collectively fall into a unique class of investment agreements, in that they represent a convergence of diverse ideologies of international investment norms/protections with two distinct (East/West) underlying domestic legal and economic systems. The purpose of this chapter is to appreciate and utilize the legal content of the Canada–China FIPA in order to isolate the opportunities and challenges for investment agreements currently under negotiation (focusing on the US–China BIT). This analysis is conducted from the perspective of China’s traditional BIT practice and political–economic goals, relative to that of its counterparty. This chapter briefly addresses the economic and broader diplomatic relationship between China and Canada, comparing that with the United States. It then analyses a broad selection of key substantive and procedural obligations of the Canada–China FIPA, addressing their impact, individually and cumulatively, to extract what lessons can be learned for the United States (US) and other negotiating parties. This analysis identifies the degree of investment liberalization and legal protection that Canada and China have achieved, and whether these standards are reciprocally applied. The analysis is not divorced from the relevant political economy and negotiating position between China and the counterparty and the perceived economic benefits of each party, as well as any diplomatic sensitive obstacles between the parties. While this chapter does not exhaustively analyse each substantive and procedural right, it provides enough of a comprehensive basis to reveal those challenges that remain for future bilateral negotiations with China.


Author(s):  
Terry L. Dickson ◽  
Shah N. Malik ◽  
Mark T. Kirk ◽  
Deborah A. Jackson

The current federal regulations to ensure that nuclear reactor pressure vessels (RPVs) maintain their structural integrity when subjected to transients such as pressurized thermal shock (PTS) events were derived from computational models that were developed in the early to mid 1980s. Since that time, there have been advancements in relevant technologies associated with the physics of PTS events that impact RPV integrity assessment. Preliminary studies performed in 1999 suggested that application of the improved technology could reduce the conservatism in the current regulations while continuing to provide reasonable assurance of adequate protection to public health and safety. A relaxation of PTS regulations could have profound implications for plant license extension considerations. Based on the above, in 1999, the United States Nuclear Regulatory Commission (USNRC) initiated a comprehensive project, with the nuclear power industry as a participant, to re-evaluate the current PTS regulations within the framework established by modern probabilistic risk assessment (PRA) techniques. During the last three years, improved computational models have evolved through interactions between experts in the relevant disciplines of thermal hydraulics, PRA, human reliability analysis (HRA), materials embrittlement effects on fracture toughness (crack initiation and arrest), fracture mechanics methodology, and fabrication-induced flaw characterization. These experts were from the NRC staff, their contractors, and representatives from the nuclear industry. These improved models have now been implemented into the FAVOR (Fracture Analysis of Vessels: Oak Ridge) computer code, which is an applications tool for performing risk-informed structural integrity evaluations of embrittled RPVs subjected to transient thermal-hydraulic loading conditions. The baseline version of FAVOR (version 1.0) was released in October 2001. The updated risk-informed computational methodology in the FAVOR code is currently being applied to selected domestic commercial pressurized water reactors to evaluate the adequacy of the current regulations and to determine whether a technical basis can be established to support a relaxation of the current regulations. This paper provides a status report on the application of the updated computational methodology to a commercial pressurized water reactor (PWR) and discusses the results and interpretation of those results. It is anticipated that this re-evaluation effort will be completed in 2002.


1997 ◽  
Vol 60 (5) ◽  
pp. 462-465 ◽  
Author(s):  
DALE D. HANCOCK ◽  
DANIEL H. RICE ◽  
LEE ANN THOMAS ◽  
DAVID A. DARGATZ ◽  
THOMAS E. BESSER

Fecal samples from cattle in 100 feedlots in 13 states were bacteriologically cultured for Escherichia coli O157 that did not ferment sorbitol, lacked beta-glucuronidase, and possessed genes coding for Shiga-like toxin. In each feedlot 30 fresh fecal-pat samples were collected from each of four pens: with the cattle shortest on feed, with cattle longest on feed, and with cattle in two randomly selected pens. E. coli O157 was isolated from 210 (1.8%) of 11,881 fecal samples. One or more samples were positive for E. coli O157 in 63 of the 100 feedlots tested. E. coli O157 was found at roughly equal prevalence in all the geographical regions sampled. The prevalence of E. coli O157 in the pens with cattle shortest on feed was approximately threefold higher than for randomly selected and longest on feed pens. Of the E. coli O157 isolates found in this study, 89.52% expressed the H7 flagellar antigen. E. coli O157 was found to be widely distributed among feedlot cattle, but at a low prevalence, in the United States.


Author(s):  
Padmanabha J. Prabhu ◽  
Damian A. Testa

The Steam Generator Asset Management Program (SGAMP) is a long term program designed to maximize the performance and reliability of the steam generators. The SGAMP focuses on plant specific conditions and hence is applicable to the original or the replacement steam generators. It is recommended that the utility and the vendor form a joint steam generator management team (SGMT) to develop, monitor and implement a long-term plan to address steam generator operation, maintenance and life extension goals. The SGMT will consist of representatives from operations, chemistry, maintenance and engineering functions and will be responsible for making decisions related to the steam generators. The charter of the SGMT is to develop a steam generator strategic plan that will cost-effectively manage steam generator options. The strategic plan is consistent with the Steam Generator Program Guidelines (NEI 97-06 in the United States). The strategic plan is a living document and is revised periodically to incorporate inspection results, new technology developments, lessons learned and industry experience. Cost-benefit analyses of strategies may be performed to prolong steam generator operability through steam generator performance modeling (tube degradation, fouling, etc.), diagnostic tools, regulatory strategy, condition monitoring and operational assessment strategy, and maintenance strategy. The SGMT will provide input regarding potential maintenance of the steam generators with schedule and cost impacts for each outage. It will also recommend engineering evaluations to be performed in support of program goals and will develop short- and long-term recommendations. These recommendations will address action plans, performance measures and results. Secondary side inspection and cleaning strategy should be developed (techniques and frequency) to maximize performance cost-effectively. This paper is based on Westinghouse experience gained by working with several pressurized water reactor (PWR) plant operators in the United States (US).


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