Figure 39 - uploaded by Annie Kammerer
Content may be subject to copyright.
Finite-element model for the SSI analysis of the representative nuclear power plant structure (oblique view).
Source publication
Although the US regulatory framework has continued to evolve over time, the tools, methods and data available to the US nuclear industry to meet the changing requirements have not kept pace. Notably, there is significant room for improvement in the tools and methods available for external event probabilistic risk assessment (PRA), which is the prin...
Similar publications
Stable isotopes of mammoths and mastodons have the potential to illuminate patterns in late Glacial landscapes and megafaunal population dynamics as these species approached extinction. The ecological factors at play in this extinction remain unresolved. Stable isotopes of bone collagen (δ13C, δ15N) and tooth enamel carbonate (δ13C, δ18O, 87Sr/86Sr...
In 2008 a rich accumulation of vertebrate bones and teeth was discovered in a small tributary drainage to Big Cypress Creek near the town of Hockley in Harris County, Texas. The fossils were recovered from sandy sediments of fluvial origin, interspersed with contemporaneous spring boil deposits, attributed to the Deweyville Formation and the recove...
The reassignment of a mandible fragment bearing an m3 and also a left upper tusk previously described as “Mastodon (Tetralophodon) grandicissivum” to Choerolophodon cf. anatolicus is the leading goal of the paper. The records were collected from Khersonian rocks which crop out on the interfluve between Ulucilor/Ulucelor and Topu valleys (Tanacu vil...
Proboscidean limb bones discovered in Yukon during the 1960s and 1970s exhibit fracture patterns, notches, and bone flakes that are characteristic of percussion. Because of the unique properties of thick cortical proboscidean bone (probably woolly mammoth Mammuthus primigenius or less likely American mastodon Mammut americanum), some researchers hy...
Citations
... SPRA was first applied to NPPs in the US in the 1970s and is now widely used [1]. The PRA has recently evolved to advanced PRA [2][3][4][5][6][7][8], which aims to remove excessive conservatism from the current PRA practice. However, it requires tremendous computational resource to assess the SPRA using highfidelity models. ...
... The likelihood function L is the occurrence probability of the NLTHA result ε when A m and β assume certain values; the value of L can be calculated using equation (8) or (9). Based on the assumed prior joint probability density function f 0 (A m , β) and likelihood function L, the posterior joint probability density function f 1 (A m , β) can be obtained using equation (3). Subsequently, using the obtained value of f 1 (A m , β) in equations (4) and (5) below, values of the marginal probability density functions -f 1Am (A m ) and f 1β (β) for A m and β, respectively -can be obtained. ...
This paper presents a Bayesian-estimation-based seismic fragility assessment method that can significantly reduce the computational burden. The likelihood function and prior distribution used in the Bayesian estimation were enhanced. A probability density function of the seismic capacity was adopted as the likelihood function, although previous studies have generally used the fragility curve. Further, the prior distribution was assumed based on the seismic capacity obtained by incremental dynamic analysis. A sophisticated parametric study was additionally conducted, and we obtained information on the unknown parameters of the prior distribution to establish the initial values. Preliminary investigations show that these enhancements reduced the required number of seismic simulations to approximately 1/5 of that of the conventional Bayesian method. Then, the method was applied to a reinforced-concrete water intake system, which is a critical component of the core-cooling system in nuclear power plants (NPPs). The results revealed that the fragility curves determined using the proposed method with 12 repetitions of the simulations were comparable to those using a detailed method developed by the Atomic Energy Society of Japan with 500 repeated simulations. Therefore, we concluded that the proposed method could be applied to high-fidelity structures to substantially reduce the computational burden.
... Notwithstanding IAEA, the U.S. Department of Energy (USDOE) likewise featured the significance of multi-hazard evaluation for NPP facilities [6,7]. The progressing venture of the Korea Atomic Energy Research Institute (KAERI), called the "Development of multi natural hazard risk assessment," likewise upholds various multi-hazard research themes, including different multi-hazard combinations (e.g., earthquake mainshock-aftershock, typhoon-earthquake, earthquake-landslide, and earthquake-tsunami) to work with the multi-hazard risk measurement for NPPs [8][9][10]. ...
... 2 Internal Flooding Simulations 2.1 Recent Studies. In recent years, flooding risk assessments studies have been conducted by simulating various flooding scenarios in the plant using modern tools [16][17][18]. Such simulations model the plant's external and internal three-dimensional layouts including various openings and drainage systems. ...
... A key challenge in this process lies in identification of flooding sources as well as the rate of flooding from each such source particularly in case of internal flooding resulting from leakages in pipes and tanks. A simple approach used in Coleman et al. [16] starts with the fragilities of piping systems at different locations. For a given value of intensity measure such as peak ground acceleration (PGA), the fragility curves are used to sample the locations at which leakages could occur, i.e., any location for which the probability of failure (fragility) value at the given PGA is zero or nearly zero will not leak, whereas all locations that have nonzero fragility values will have some likelihood of leakage. ...
... For each sample set, a flooding simulation is used to determine the potential flooding related consequences and the corresponding risks. While the details of sampling the potential flooding locations and the degree of leakage at each location are not described explicitly in Coleman et al. [16], it appears that a simple sampling scheme as described below is used: ...
Internal flooding due to pipe breaks can interfere with a plant's ability to safely shut down or maintain the decay heat removal. Flooding simulation tools require information on location of pipe breaks and the degree of damage at each location as input for assessing the flooding risk. This can be especially challenging as the number of potential leakage locations are quite large and the state-of-the-art simulation tools cannot determine the degree of damage at a location. This paper presents a novel simulation-based framework that can be used to determine seismically induced flooding scenarios including the potential locations of leakage and the degree of leakage at each location. The proposed framework builds upon a few recent experimental and simulation-based studies on piping fragilities. This research identifies that a direct use of piping fragility information by flooding simulation tools is not appropriate. This paper presents a new approach that creates mutually exclusive and collectively exhaustive events to characterize the complete sample space at each location and employs the total probability theorem to characterize the probabilities for each event in this space. This paper also identifies the importance of including the temporal effects in the piping fragilities in order to allow a more realistic simulation of internal flooding scenarios.
... That is, variability of the seismic input ground motions, soil behavior, and structure behavior should be modeled probabilistically. One method is described in Coleman et al. (2016a). ...
This report provides guidance on conducting nonlinear soil-structure-interaction (NLSSI) analysis of safety-related nuclear facilities. Analysis is performed in the time domain. The guidance provided in this report addresses both design and seismic probabilistic risk assessment, and has been written to address significant limitations in the guidance currently available to designers, owners, and regulators of nuclear facilities in the United States.
This report discusses technical elements involved in NLSSI analysis in an integrated presentation. Both hazard evaluation and site-response analysis (SRA) are discussed, as they provide inputs to NLSSI analysis.
The motivation for development of the guidance in this document includes the following issues and benefits:
The tools currently used for nuclear power plant (NPP) design are not well-suited for highly nonlinear conditions, such as gapping and sliding between the soil and structure or NPP configurations using seismic isolation.
NLSSI analysis can more accurately assess seismic response of structures for the full range of ground motions considered in seismic probabilistic risk assessment (SPRA), particularly for beyond-design-basis earthquake ground motions that may trigger significant inelastic response in soil and structure.
The legacy methods of soil-structure-interaction (SSI) analysis are not well-suited for accommodating nonvertically propagating shear waves or cases where the generation and dissipation of excess pore-water pressure are important.
Nearly all of the available guidance on SSI is targeted at design. This document provides guidance on both seismic design and SPRA, and includes perspective and insights on how the two activities and their SSI analysis needs can differ.
... The cost of constructing safety-related nuclear facilities is driven in significant part by considerations of the effects of earthquake shaking, especially in commercial nuclear power plants. Capital cost can likely be reduced by the use of advanced numerical tools such as those for nonlinear site-response (e.g., Bolisetti et al. 2014), soil-structure interaction analysis (e.g., Coleman et al., 2015), and advanced probabilistic risk assessment (e.g., Huang et al., 2008aHuang et al., , 2011aHuang et al., , 2011bBolisetti et al., 2015;Coleman et al., 2016). Another strategy to decrease capital costs is to substantially reduce seismic demands required for seismic qualification of systems and components, which can be accomplished using seismic isolation and damping systems. ...
The implementation of seismic base isolation can substantially reduce horizontal seismic demands on structures, systems, and components (SSCs) in a nuclear facility, potentially providing significant benefits in terms of increased safety (smaller seismic risk) and reduced capital construction cost. Although increased safety of SSCs has been demonstrated previously, the possible reduction in their capital cost has not been explored. To quantify the reduction in risk enabled by isolation, nonlinear response-history analysis of a conventionally founded and a base-isolated model of a generic nuclear facility (GNF) is performed at the sites of the Idaho National Laboratory and the Los Alamos National Laboratory: sites of moderate and high seismic hazard, respectively. Seismic probabilistic risk assessment is performed to compute the mean annual frequency of unacceptable performance. The seismic risk is reduced by 7 to 8 orders of magnitude by the implementation of isolation. The costs of addressing seismic loadings are estimated for the GNF in both the conventionally founded and base-isolated GNF. The possible reductions in the required seismic ruggedness and in the cost of SSCs in the isolated GNF are quantified at both sites. A reduction in cost enabled by isolation is possible at nearly all sites of nuclear facilities in the United States, with the greatest benefit at sites of high seismic hazard, such as LANL. Two risk-calculation procedures are used in the assessment: a simplified method based on Boolean mathematics and a rigorous method based on Monte Carlo analysis. The simplified procedure, which is suitable for implementation with preliminary design calculations, produces accurate estimates of risk unless the mean annual frequencies of unacceptable performance are very small, measured here as smaller than 10-10. The sensitivity of the calculated risk in the conventionally founded GNF, to the choice of anchor period for the seismic hazard curve, is investigated and found to be insignificant over the range considered: 0 to 0.10 second.
... To identify and address limitations in the initial guidance, Idaho National Laboratory (INL) has initiated several projects focused on further developing the technical and licensing underpinnings for facilities using SI technology. These efforts include a 2014 workshop focused on SI (Coleman and Sabharwall, 2014), development of new structural analysis tools and methodologies appropriate for SI (Coleman et al., 2016), were updated or revised in the latter report as a result of peer review and feedback from experts and industry stakeholders. However, the latter report was intended to supplement, and not replace, the earlier report. ...
Because Seismic Isolation (SI) is being considered for nuclear power plants (NPPs) in the United States (US), the Nuclear Regulatory Commission (NRC) initiated research activities on SI in 2009. That work, which focused around a risk-informed regulatory approach, resulted in a forthcoming draft NUREG/CR report that discusses considerations for the implementation of SI technology in NPPs. The draft NUREG/CR report provides a set of recommended performance objectives and criteria that could serve as the foundation for a broader set of guidance on the use of SI and related technology. Methods of analysis and design for NPPs using SI, have also been implemented in the recently published American Society of Civil Engineers Standard ASCE/SEI 4-16. While these foundational documents provide a good starting point, they were, necessarily limited in scope. The focus of the guidance is the horizontal base isolation of surface-founded light water reactors (LWRs). To identify and address the limitations in the guidance, Idaho National Laboratory (INL) initiated several projects focused on further developing the technical and licensing underpinnings for facilities using SI technology, including non-LWR NPPs. As part of the INL effort, the Advanced Nuclear Technology group recently sponsored work to identify regulatory gaps and challenges related to the use of SI technology in advanced reactors. This work resulted in two 2016 INL reports, INL/EXT-15-36945 and INL/EXT-16 40668 (Kammerer, Whittaker and Coleman 2016a and 2016b), which builds upon the guidance available to industry and the NRC. The report discusses gaps and challenges identified in several areas, including: (1) tools and methodologies, (2) the certified design process, (3) configurations and applications not addressed in the current guidance, (4) seismic qualification of the isolator units, and (5) construction and operations. This paper summarizes the outcomes of the INL projects and discusses ongoing efforts to address the issues in support of efforts to effectively license facilities incorporating SI in the US.
... A nonlinear time-domain code for performing NLSSI simulations, Mastodon, 8 is being developed using the NQA-1 (ASME 2015) certified INL Multi-Physics Object-Oriented Simulation Environment (MOOSE) framework (see Coleman et al. 2016b). INL efforts focus on commercially-supported codes that meet NQA-1 requirements and have formal version control, both of which are generally required for applications in the nuclear industry in the U.S. ...
Over the last decade, particularly since implementation of the certified design regulatory approaches outlined in 10 CFR 52, “Licenses, Certifications, and Approvals for Nuclear Power Plants,” interest has been increasing in the use of seismic isolation (SI) technology to support seismic safety in nuclear facilities. In 2009, the United States (U.S.) Nuclear Regulatory Commission (NRC) initiated research activities to develop new guidance targeted at facilities incorporating isolation technology because SI is being considered for nuclear power plants in the U.S. One product of that research, which has been developed around a risk-informed regulatory approach, is a draft Nuclear Regulatory Commission (NUREG) series report that investigates and discusses considerations for use of SI in otherwise traditionally-founded large light water reactors (LWRs). A coordinated effort led to new provisions for SI of LWRs in the American Society of Civil Engineers standard American Society of Civil Engineers/Structural Engineering Institute (ASCE/SEI) 4 16, “Seismic Analysis of Safety Related Nuclear Structures.” The risk-informed design philosophy that underpinned development of the technical basis for these documents led to a set of proposed performance objectives and acceptance criteria intended to serve as the foundation for future NRC guidance on the use of SI and related technology.
Although the guidance provided or expected to be provided in the draft SI NUREG/CR report and ASCE/SEI 4 16 provides a sound basis for further development of nuclear power plant (NPP) designs incorporating SI, these initial documents focused on surface-founded or near-surface-founded LWRs and were, necessarily, limited in scope. For example, there is limited information in both the draft NUREG/CR report and ASCE/SEI 4-16 related to nonlinear analysis of soil-structure systems for deeply-embedded reactors, isolation of components, and use of vertical isolation systems. Also not included in the draft report are special considerations for licensing of isolated facilities using the certified design approach in 10 CFR 52 or a detailed discussion of seismic probabilistic risk assessments for isolated facilities.
To identify and address limitations in the initial guidance, Idaho National Laboratory (INL) has initiated several projects focused on further developing the technical and licensing underpinnings for facilities using SI technology. These efforts include a 2014 workshop focused on SI (Coleman and Sabharwall 2014), development of new structural analysis tools and methodologies appropriate for SI, and development of INL report INL/EXT-15-36945, “Regulatory Gaps and Challenges for Licensing Advanced Reactors Using Seismic Isolation,” (Kammerer, Whittaker, and Coleman 2016) that identified and described regulatory guidance gaps and challenges related to licensing of advanced reactors using SI. Nearly all of the gaps and challenges identified in INL/EXT-15-36945 fall outside the scope of current research and development efforts (including those at INL). This report builds on information in INL/EXT 15 36945 by providing additional actionable details related to the scope and possible schedule of activities to address the gaps and challenges identified. Although some discussions and issues have been updated or revised in this report as a result of peer review and feedback from industry stakeholders, this report is intended to supplement, and not replace, the earlier report.
Because efforts to date related to regulatory guidance development (e.g., the draft NRC SI NUREG/CR report) have principally considered designs similar to the light water reactor technologies currently being licensed, the existing literature (as discussed in INL/EXT 15 36945) is reflective of traditional LWR designs. All of the regulatory guidance gaps and challenges that apply to large surface-founded LWRs also apply to advanced reactors; and the LWR case often provides a simplified example as compared to the range of cases found in advanced reactors. Advanced reactor designs also lead to new gaps and challenges not faced in LWR design. Although both this report and INL/EXT 15 36945 discuss advanced reactors broadly , the exact set of challenges and potential solutions for any particular reactor design is technology-specific. The activities detailed in this report necessarily require some level of specificity. However, significant effort is made to develop the activities to be as technology neutral as possible.
Advanced reactors will likely be designed and constructed very differently from LWRs, regardless of whether they employ SI and damping devices. Key technical advances in civil and structural engineering needed to deploy advanced reactors are:
1. Development of performance-based seismic design and assessment procedures for non-LWR reactors
2. Development and deployment of analysis methodologies suitable for computing the response of deeply-embedded power reactors, including nonlinear time domain, soil-structure-interaction analysis
3. Development, prototyping, and deployment of two dimensional and three-dimensional isolation systems suitable for components ranging in size and complexity from diesel generators to reactor vessels.
Advances in Items 1 and 2, above, are needed for deeply-founded NPPs, regardless of whether seismic protective measures (i.e., such as those noted in Item 3) are deployed. A focus on developing additional guidance for isolation of major components is enhanced in this report (as compared to the discussion in INL/EXT 15 36945) due to input provided during the technical peer review process. Not covered in this report are other important technical advances in civil and structural engineering needed for economical deployment of advanced reactors (e.g., development and deployment of modular construction strategies used to minimize “one-off” fieldwork, schedule delays, and construction cost).
In addition to improving safety, SI offers potentially significant economic benefits for advanced reactors because the isolation system can reduce site-dependent seismic demands below pre-qualified levels in certified design. Their protective isolation systems would be site-specific and based on site-specific ground motions. Although design optimization and commercial aspects related to the use of SI have been identified in Coleman and Sabharwall (2014) and elsewhere as possible issues or areas of opportunity, only topics that may impact efficient licensing are addressed in this report.
INL/EXT 15 36945 identifies gaps and challenges that are discussed throughout that report and summarized in Section 7. INL/EXT-15-36945 also identifies critical and high-impact/high value topics that should be addressed in the short term and that must be satisfactorily completed before substantial progress on other tasks can be made. This report builds upon INL/EXT-15-36945 by providing a more detailed roadmap that prioritizes and organizes activities. The prioritization considers the following elements:
• The potential level of regulatory risk
• The potential for the work to provide high-impact and high-value in terms of supporting efficient licensing activities
• The sequencing of the issue to resolving other gaps and challenges identified.
The gaps and challenges identified are summarized in Table 2. The 19 unique gaps and challenges identified and evaluated have each been assigned a Topic number; and tasks needed to address an issue are numbered using the associated Topic numbers. Table 2 provides a summary roadmap of identified tasks, including possible timelines. Based on the roadmap provided, it is recommended that four Topics should be prioritized for funding:
• Development of NLSSI tools and guidance, including verification and validation activities. (Topic 1)
• Development of SPRA methodologies for seismically isolated facilities, with an emphasis on advancement of methods applicable when linear scaling assumptions do not apply. (Topic 6)
• Clarification of the approaches to licensing of facilities using seismic isolation technology within the certified design process and the associated clarification of the intent of the term “foundation” in existing requirements and guidance (Topics 12 and 14)
• Development of approaches and guidance for isolation of large equipment (Topic 4)
One DOE goal specified in the draft document entitled, “Vision and Strategy for the Development and Deployment of Advanced Reactors,” is:
“By the early 2030s, at least two non-light water advanced reactor concepts would have reached technical maturity, demonstrated safety and economic benefits, and completed licensing reviews by the U.S. Nuclear Regulatory Commission (NRC) sufficient to allow construction to go forward.”
SI has been identified as an important technology that both facilitates the siting of advanced reactors in a wider range of locations and improves seismic safety. SI can also minimize the need for “one-off” advanced reactor designs that would need to be changed to meet site-specific seismic hazard curves. Minimization of one-off designs would improve economics of advanced reactors. Several of the topics and tasks identified in this report support the design and licensing of advanced reactors, regardless of whether SI technology is used, particularly if the NPPs are deeply embedded. Additionally, current advanced reactor venders, in collaboration with INL, are interested in initiating sensitivity studies for seismic isolation of their specific technologies. This report provides a 10-year timeline for completing activities to address the issues identified. Not starting the four near term activities in a timely way would limit the impact of the collaborative work with advanced reactor venders due to the regulatory uncertainty. A delayed start, as well as a lengthened timeline due to insufficient funding, would also make achieving the goals laid out in the DOE vision document less likely.
... The cost of constructing safety-related nuclear structures is driven in significant part by considerations of the effects of earthquake shaking, especially in nuclear power plants. Capital cost can be reduced by the use of advanced numerical tools such as those for nonlinear site-response (e.g., Bolisetti et al., 2014), soil-structure interaction analysis (e.g., Coleman et al. 2015), and advanced probabilistic risk assessment (e.g., Huang et al. 2008bHuang et al. , 2011aHuang et al. , 2011bBolisetti et al. 2015;Coleman et al. 2016). Another strategy to decrease capital costs is the reduction in seismic demands, which can be accomplished using seismic isolation and/or supplemental damping systems. ...
A simulation based framework is proposed to determine seismically induced flooding scenarios including the potential locations of leakage and the degree of leakage at each location. Internal flooding due to pipe breaks can interfere with a plant's ability to safely shut down or maintain the decay heat removal. Flooding simulation tools require information on location of pipe breaks and the degree of damage at each location as input for assessing the flooding risk. This can be especially challenging as the number of potential leakage locations are quite large and the state-of-the-art simulation tools cannot determine the degree of damage at a location. The proposed framework identifies that a direct use of piping fragility information by flooding simulation tools is not appropriate. A new approach is presented in which mutually exclusive and collectively exhaustive events are created to characterize the complete sample space at each location and employs the total probability theorem to characterize the probabilities for each event in this space. Evaluation of seismic fragility requires an appropriate limit-state or performance function that characterizes the failure in a structural system or a component. The accuracy of the fragilities and the corresponding risk estimates are highly dependent on the definition of an appropriate performance function. A new limit state is proposed which considers the cyclic behavior of a T-joint and quantifies the number of cycles to failure. The component level simulation models of T-joints developed utilizing the experimental study cannot be extended directly for other pipe wall thicknesses and pipe diameters. Conducting multiple experiments for different pipe properties can be quite costly and impractical. A new approach to characterize the T-joint behavior through a closed-form solution is presented. The simulation of T-joint behavior using the closed-form solution is validated by comparison with the corresponding experimental results.
