Fleet Of Nuclear Power Plants Research Articles

Application of a Multi-Stage Testing and Evaluation Approach for a Safety-Related Digital Upgrade at a Nuclear Power Plant

There is an imminent need for existing United States nuclear power plants to reduce their operating and maintenance costs to remain economically viable. Digital technology provides significant opportunity for the existing nuclear power plant fleet to transform that way in which work is accomplished to reduce costs and allow the fleet to remain economically competitive. However, a careful understanding of the human-technology integration is needed to ensure the continued safe and reliable operation of these existing plants with new digital capabilities. This work presents interim findings in applying human factors engineering to a safety-significant digital upgrade for a United States nuclear power plant, following the new Alternative Review Process in the recently revised Digital Instrumentation and Control Interim Staff Guidance Licensing Process, Revision 2. The interim results described in this work provides an industry perspective, based on ongoing work, to support recent work published from Vazquez, Green, and Desaulniers (2022).

Cyber hardening of Nuclear Power Plants with real-time nuclear reactor operation, 1. Preliminary operational testing

Maintaining and extending the lifetime of the domestic Nuclear Power Plant fleet is predicated on digitalization. However, digitalization also gives rise to increasing vulnerabilities. This paper is the first in a body of novel research at the Idaho Falls Center for Higher Education focusing on the cyber hardening of currently operating and aging Nuclear Power Plants that uses the Western Services Corporation Generic Pressurized Water Reactor real-time operational platform. The Western Services Corporation platform was used here natively to collect data during atypical plant events that could be initiated by cyberattacks. The goals of this first phase of work is to identify data ‘fingerprints’ unique to each of the initiating events, determine when or if the reactor trips, and suggest operator actions that could mitigate the cyberattack and possibly avoid a trip and maintain operations. First, a cyber-informed Preliminary Hazards Analysis was conducted to determine plant systems most vulnerable to a cyberattack. Then, the associated malfunction as an analogue to a potential cyberattack on the selected system was executed during operation of the reactor. Relevant data was collected during these events until the reactor tripped. The data was then processed to determine if a fingerprint could be crafted, and mitigating operator actions were formulated. Finally, we demonstrate a proof-of-concept for simulating cyberattacks on the Western Services Corporation platform in real-time during reactor operation. This development will open possibilities for ‘Red Team/Blue Team’ exercises for cyber hardening of the domestic Nuclear Power Plant fleet.

Implementation of in-rod axially heterogeneous thorium-uranium fuel in a typical PWR

Given the potential of the thorium fuel cycle and the predominance of PWRs in today’s commercial fleet of nuclear power plants, further investigations on the introduction of thorium-based fuel in open-cycle reactors such as PWRs are warranted. The benefits of microheterogeneous thoria-urania fuel (e.g. increased burnup / fuel cycle length, reduced radiotoxicity and increased stability of spent fuel, proliferation advantages due, feasibility of converting UO2-based fuel manufacturing plants to ThO2-UO2), are diminished by fuel manufacturing costs, the need to denature thorium sections of the fuel, thermo-hydraulic design requirements, higher fission gas release and cladding temperature gradients.This paper presents results of the neutronic performance of homogeneous and multiple heterogeneous fuel pin cell designs and explores the fundamental reasons and reaction balances between the different fuel models. The work utilises fuel models with variations in the length and composition of thorium and uranium sections. We compare the various urania-thoria fuel models with a reference PWR (North-Anna 1) with similar fissile content. We postulate a number of fuel design criteria, to appraise fuel models in trade-off studies, including improved burnup and cycle length, limitations on fuel enrichment grade and excess reactivity during burnup (typically at beginning of cycle), safety requirements such as limitations on total burnup, power peaking and feedback mechanisms. In addition, criteria are set for proliferation resistance and radiotoxicity.Verification studies were performed on fuel with homogeneous and axially heterogeneous fuel cell pins, followed by initial assembly and full-core analyses, to affirm confidence in the models employed. Our results confirm significant conversion of thorium to 233U, resulting in an improved burnup and fuel cycle length. Shut down margins and neutron economy are improved by significantly reducing beginning of cycle excess reactivity and hence reducing the need for burnable and soluble neutron absorbers. The conversion of thorium to 233U then leads to an increase in reactivity later in the cycle. To address proliferation concerns, fuel models with denatured thorium sections are introduced.We conclude that among the well-performing fuel models, fuel comprising heterogeneous pins repeating 3 cm thorium and 1 cm uranium sections, with the uranium region enriched to 20 at% 235U, and the thorium region denatured to a specific degree, performed best in terms of the fuel criteria considered. The promising results for the fuel pin cell models were confirmed with initial assembly and full core models: Burnup improvement rendered by the 3Th1U fuel models is 25.6% / 22.3% / 17.9% for the pin cell / assembly / full core models respectively, in spite of employing denaturing of thorium sections, while also fulfilling the other stated fuel criteria.

A Passive System Technical Specification for CANDU 6 Generation II Reactor

The Fukushima accident led to concerns about enhancement of safety for the new design nuclear plants and also for the existing fleet of nuclear power plants (NPPs) by introducing passive safety systems. An important objective is to increase the grace time for a plant operator to establish an alternate heat sink in the case of a station blackout (SBO) accident. Efforts made by RATEN (https://www.raten.ro/?lang=en) in the frame of H2020 PIACE projects were to implement a passive safety system in the CANadian Deuterium Uranium 6 (CANDU 6) project. In this project, RATEN was in charge of the engineering design and computational modeling aspects, required to integrate a passive safety system in the existing CANDU 6 project. In order to design a passive safety system, a 3-day SBO accident was credited to occur at the Cernavoda Unit 2 NPP, a CANDU 6–type reactor. An isolation condenser (IC) system capable of transporting the total energy produced in the reactor core due to decay heat was designed and modeled. The engineering design solutions were made by RATEN CITON (http://www.citon.ro/english_index.html), and the thermal-hydraulic analysis was performed by RATEN ICN (https://nuclear.ro/en/) using the RELAP5 computer code (https://relap53d.inl.gov/SitePages/Home.aspx) to confirm natural circulation both in the secondary and the primary circuits during the SBO accident and heat transfer capability of the IC with and without noncondensable gases. The passive safety system design consists of four (4 × 33%) closed loop independent circuits, one for each steam generator. Each loop has an IC design to transport 0.66% of nominal thermal power of the reactor. In order to avoid a rapid transient during reactor cooldown, the system is endowed with four noncondensable gas tanks (one for each IC), connected to the outlet header of each IC, provided for reducing the IC heat flux simultaneously with reactor core residual heat decrease. The design concept was adapted to the CANDU 6 reactor power and the specific layout of the Cernavoda site, starting from the Advanced Lead-cooled Fast Reactor European Demonstrator (ALFRED) patent (the demonstrator of lead fast reactor technology) passive system, to increase the plant operator grace time from 23 h (current situation) to more than 72 h.

Guiding Transformation: The Role of a Design Philosophy

Unlike renewables such as wind and photovoltaics, nuclear power is a carbon-free source of energy that offers reliable, dispatchable baseload energy. This unique characteristic makes nuclear energy an important component of the U.S. mix of carbon-free energy, and thus, a major contributor to achieving the goals laid out in the Paris Agreement. However, the current fleet of nuclear power plants are being outpriced by other energy sources, such as natural gas. One contributor to the high cost of nuclear is the outdated concept of operations. The current fleet of nuclear reactors employs the same concept of operations they started with over half a century ago. Idaho National Laboratory’s (INL’s) Human Factors Engineering (HFE) team under the U.S. Department of Energy’s Light Water Reactor Sustainability Program is engaged in helping the nuclear fleet modernize their control rooms. The goal is to transform nuclear power plant operators’ perceptions to improve efficient and safe plant operation. A major component to successfully transforming an aged control room with advanced technology is to use a design philosophy that guides the modernization effort. This paper discusses design philosophy and the role it plays. Also discussed is the initial approach to design philosophy and adherence to safety and regulatory requirements. Last, a brief discussion of how INL’s HFE team plans to implement a design philosophy that can be used industry wide.

Seismic risk assessment for the CEUS nuclear power plant fleet based on the NGA-East ground motion model

Knowledge of seismic hazard at engineered facilities evolves with the growth in related technical fields. This presents challenges to stability and decision-making concerning safety that require effective assessment tools. Updated mean hazard estimates were developed at nuclear power plant (NPP) sites in Central and Eastern United States (CEUS) using the Next Generation Attenuation (NGA)-East ground motion model (GMM) and the latest available site amplification data. These estimates indicated that seismic hazard increases at several CEUS NPP sites, especially for spectral frequencies below 5 Hz. To assess the safety implications, updated mean seismic core damage frequency (SCDF) estimates were developed for the CEUS NPP fleet using the updated mean hazard estimates and updated plant-level fragilities (PLFs). The PLFs were developed from plant-specific information compiled by the U.S. Nuclear Regulatory Commission (USNRC) and recent seismic probabilistic risk assessments (SPRAs) completed by some NPPs. The SCDF quantification followed a method defined by the USNRC to combine risk contributions from different spectral frequencies. While not intended to provide a precise quantification of risk, such as that provided by a full SPRA, when the results are compared against other estimates using the same approach, this process provides valuable insight into the overall change in risk as the understanding of hazard changes. The assessment indicated no significant change in estimated risk for the majority of the CEUS fleet compared to the 2010 USNRC estimates—about 90% of the fleet risk distribution was lower, equal, or slightly higher. A few NPPs had SCDF estimates significantly larger than the 2010 estimates. The SCDF increases at these few NPPs have larger contributions from updated PLFs than updated hazard estimates. The majority of these NPPs have recently completed detailed SPRAs and have tools to develop more accurate estimates of the updated risk than can be achieved in this fleet-level study.

Enabling Business-Driven Innovation Through Human Factors Engineering In Nuclear Power Plants

For existing United States nuclear power plant fleet to remain economically viable, the nuclear industry needs to fundamentally change the way in which these plants are operated, maintained, and supported. A digital transformation is a key strategy to address this challenge. Though, guidance in this area is a continued effort. One framework to support innovation in the nuclear industry has taken a broader perspective by focusing on how technology can be used to meet specific business needs and work for the people and processes at hand. This work discusses the role and value of human factors engineering within this nuclear innovation framework. Human factors methods are presented here regarding how they address the phases of nuclear innovation. This work seeks to describe how human factors can be applied in nuclear innovation by strengthening the alignment of technology, people, processes, and regulations such that the needs of the business is addressed.

Nuclear Power Plant Instrumentation and Control Cable Prognostics Using Indenter Modulus Measurements

As the fleet of nuclear power plants (NPPs) approach their1 original qualified life (typically 40 years) and operators seek license extensions, regulators require assurance that they can continue to operate safely in the decades to come. Some of the most important, yet often overlooked components, are the cables that provide the signal paths for instrumentation and control (I&C) systems used to ensure safe and efficient operation of NPPs.In response to this, the authors explore the use of expanding indenter modulus (IM), an industry-accepted technique for cable condition monitoring, into a prognostic tool for predicting the remaining useful life (RUL) of I&C cables. Not only is this technique non-destructive, but it can be performed while NPP cables are in service, thus making it practical for adoption into existing cable condition monitoring programs. In this paper, the authors describe an accelerated aging cable test bed used to acquire several types of measurement parameters as cables age. Additionally, practical techniques are described in which simple IM measurements can be leveraged for condition monitoring and RUL estimation.Error analysis indicates the proposed method is superior to conventional RUL estimation techniques, such as simple trending and curve fitting. The authors demonstrate that using IM can potentially provide a non-destructive, in-situ estimation of RUL for I&C cables. As described in this paper, the IM data clearly shows trends as a function of cable age, and shows promising performance for RUL estimation especially compared with conventional techniques.

Prognostic and Health Management of Active Assets in Nuclear Power Plants

This paper presents the development of diagnostic and prognostic capabilities for active assets in nuclear power plants (NPPs). The research was performed under the Advanced Instrumentation, Information, and Control Technologies Pathway of the Light Water Reactor Sustainability Program. Idaho National Laboratory researched, developed, implemented, and demonstrated diagnostic and prognostic models for generator step-up transformers (GSUs). The Fleet-Wide Prognostic and Health Management (FW-PHM) Suite software developed by the Electric Power Research Institute was used to perform diagnosis and prognosis. As part of the research activity, Idaho National Laboratory implemented 22 GSU diagnostic models in the Asset Fault Signature Database and two wellestablished GSU prognostic models for the paper winding insulation in the Remaining Useful Life Database of the FW-PHM Suite. The implemented models along with a simulated fault data stream were used to evaluate the diagnostic and prognostic capabilities of the FW-PHM Suite. Knowledge of the operating condition of plant asset gained from diagnosis and prognosis is critical for the safe, productive, and economical long-term operation of the current fleet of NPPs. This research addresses some of the gaps in the current state of technology development and enables effective application of diagnostics and prognostics to nuclear plant assets.

The governance of nuclear power in China

Abstract China has the third largest fleet of nuclear power plants in the world, totalling more than 45 GWe at the end of 2019. With the current high rate of growth, its capacity will soon overtake that of France. The country’s nuclear power industry has suffered no serious accidents to date. Nevertheless, the poor safety record of some other heavy industries in China, combined with the rapid growth of civil nuclear power capacity, has raised concerns over the industry’s ability to prevent a serious accident. The organization, development and governance of China’s nuclear power industry reflects the high strategic importance that the government has placed on the industry over several decades. At the same time, it has taken steps to address domestic and international concerns over its ability to effectively govern nuclear safety and security. The country has become party to most major treaties and conventions relating to nuclear matters and has frequent interaction with the International Atomic Energy Agency. Despite many significant steps taken by the government, a number of questions remain concerning: the capacity and independence of the National Nuclear Safety Administration; the relatively incoherent nature of the body of laws, regulations and rules that govern nuclear safety and security; the absence of a clear legal basis for managing civil nuclear liability, especially in the context of an accident with transboundary consequences; and the quality of public participation, especially in the case of planned nuclear power plants.

Exploring The Use of Cognitive Models for Nuclear Power Plant Human-System Interface Evaluation

Many of the United States’ commercial fleet of nuclear power plants (NPPs) are approaching the end of their operating licenses. To extend the life of these plants, advanced human-system interface (HSI) technologies are being researched to address aging and reliability concerns with existing legacy systems. Human factors engineering (HFE) a critical role in ensuring these technologies are designed in a way that does not introduce new failure modes and promotes optimal human-system performance. An important focus of HFE in NPP modernization is early involvement to inform design of the HSI. This includes traditional formative evaluations, which are done to collect design feedback. While these evaluations are useful, they are limited in providing convincing quantitative data for efficiency of use. This paper discusses the use of cognitive models to provide quantitative data early in the HSI design process. A comparison is made of three open-source and readily accessible cognitive modeling tools.

The value of the nuclear power plant fleet in the German power market under the expansion of fluctuating renewables

Flexibility of a conventional power plant fleet is becoming an increasingly valuable quality in several electricity markets due to growing solar and wind power supply. Nuclear power plants are not very flexible in terms of output, but their advantage is their low variable cost of generating electricity. Using a short-term techno-economic model which incorporates both the electricity and the balancing market, we examine quantitatively whether costs incurred by nuclear units' lower flexibility outweigh the low generation costs of nuclear power in the German power market, and investigate how this depends on the amount of fluctuating renewables. We show that, due to low negative prices stemming from inflexible baseload plants, balancing costs may increase rapidly with solar and wind power. Higher balancing and start-up costs arising from nuclear units in the fleet are still largely compensated by the nuclear units’ lower generation costs, and it is not cost-efficient to decommission nuclear units in the near future. The results suggest that it would be economically beneficial to harness the full flexibility potential of nuclear plants and curtail excess solar and wind power or include those in the negative balancing reserve.

Time-dependent reliability analysis of overpacks for high-level radioactive waste

In France, nuclear energy is extensively used for electricity production, and consequently high-level radioactive waste are generated by the fleet of nuclear powerplants. This waste is planned to be disposed of in a deep geological repository. Engineers have only a limited feedback from similar disposal facilities, as this project is innovative. This lack of knowledge and the timescales involved induce uncertainties about the disposal environment and about the conditions of operation. Reliability analysis is used here as it provides a suitable framework to deal with such uncertainties. This paper focuses on the overpack, which isolates the waste from the environment during the early stage of disposal (at least 500 years). The failure probability is investigated through a crack propagation criterion using a Monte Carlo analysis performed on two levels. The approach is based on a dedicated stochastic structural model including the corrosion rate, the mechanical loading and initial crack conditions. The robustness of this approach is evaluated through sensitivity analysis, and by considering multiple distributions for the variables elicited from expert’s opinion.

An overview of methodologies for cybersecurity vulnerability assessments conducted in nuclear power plants

Cyber-attacks against critical energy infrastructure have gone from possible to eventual to actual. With electrical generation sources in the United States changing under a wide range of pressures, the current fleet of nuclear power plants in the United States provides a reliable and sustainable source of electrical generation capacity. However, in order to extend the lifetime of the fleet, modernization upgrades to digital instrumentation and control systems are required. While this produces many opportunities for increased efficiency, it introduces a new level of complexity for securing and reliably operating reactors in the presence cyber-threats. The United States Nuclear Regulatory Commission recently began urging stronger cybersecurity efforts at nuclear power plants. As upgrades at nuclear power plants begin, the implementation of digital instrumentation and control systems to monitor and run the power plant introduces new vulnerabilities that must be addressed. This necessitates a more modern discussion of risk. Within this context, we critically review past cyber-vulnerability incidents at nuclear installations and other critical facilities. We then analyze challenges to vulnerabilities within the context of modernization of the current nuclear fleet and propose future research directions needed to resolve these issues.

Major hydropower states, sustainable development, and energy security: Insights from a preliminary cross-comparative assessment

Abstract Hydropower remains, by a wide margin, the largest source of renewable electricity around the world, and hydropower dams supply a greater source of commercial energy than the world's fleet of nuclear power plants. Yet far less attention has been paid to the political, security, and governance elements underlying the continued use and growth of hydropower. Theorists from many disciplines—political geography, security studies, development studies, economics, public policy, and governance—have questioned both the proper role and ostensible benefits from the generation of electricity from large-scale hydroelectric dams, but have tended to approach the problem on a case-by-case basis. In this study, we provide the first systematic, cross-comparative assessment of five hypotheses about global hydropower states, using World Bank data from 1980 to 2010 and a research design which incorporates five reference classes of countries. Based on regression and comparative country analyses, we find tentative statistical evidence that hydropower countries do seem to perform worse on a series of security, economic development, and governance metrics.

Assessment of spent nuclear fuel amounts to be managed based on disposal option in Republic of Korea

The Republic of Korea (ROK) was operating 24 nuclear power plants (NPPs) at the end of 2015 and nearly 30% of electricity was supplied by the fleet of NPPs. Currently, spent nuclear fuel (SNF) from the NPPs is stored in pools attached to each NPP. However, the pools have been gradually filling up and would be saturated within decades. Recently, The Public Engagement Commission on Spent Nuclear Fuel Management (PECOS) submitted its final report to government proposing direct disposal of SNF from the early 2050s. It also suggested construction of an interim storage facility at the same site. In this work, the amount of SNF was quantified based on various nuclear scenarios. National electricity plans address the installed capacity of nuclear to 2035. To extend the period of the scenarios up to 2100, the results of open research were adopted and nine sub-scenarios were derived, considering the prospect for electricity demand (highest, reference and lowest) as well as the lifetime extension of NPPs. The total amount of SNF was estimated at between 60 and 102ktHM at 2100. The required at-reactor (AR) storage capacity was evaluated within a range of 10–12ktHM and an away-from-reactor (AFR) facility would store 14–17ktHM depending on the scenarios.

Going nuclear for climate mitigation: An analysis of the cost effectiveness of preserving existing U.S. nuclear power plants as a carbon avoidance strategy

Nuclear power plants generate over 60% of the carbon-free electricity in the U.S. Due to a decrease in electricity prices as a result of the availability of cheaper natural gas and increased low-cost renewables, many of these plants are at risk of premature retirement. If nuclear power plants retire, CO2 emissions in many U.S. states could increase, even while the states comply with EPA legislation aimed at mitigating emissions of greenhouse gases that contribute to climate change. In this paper, we perform a Monte Carlo-based analysis to determine the breakeven price of electricity these plants must secure in order to avoid financial loses between 2015 and 2040, and find median breakeven electricity prices to range between $35 and $73 per MWh. Based on our estimates of future electricity prices under a low natural gas price scenario from the Energy Information Administration, our analysis suggests that U.S. nuclear plants would require between $8 and $44 per MWh (median results) on top of electric sales revenue in order to breakeven. Assuming natural gas plants would replace retired nuclear power plants, we estimate an equivalent cost of avoided CO2 emissions to be $18-$30 per metric ton of avoided CO2 (median results) for multi-reactor nuclear plants, and $47-$97 per metric ton of avoided CO2 (median results) for single-reactor plants. Preserving the existing nuclear power plant fleet, especially multi-reactor plants, is thus a cost effective carbon-avoidance strategy compared to the social cost of carbon.

Analysis of loss of residual heat removal system for CPR1000 under cold shutdown operation

After Fukushima accident, the safety assessments within the full range of operation conditions for the current fleet of nuclear power plants in China are requested to be performed by the national nuclear safety administration. Accordingly, twelve typical cases were simulated to study the thermal-hydraulic behavior of loss of residual heat removal system for CPR1000 under cold shutdown operation with RELAP5/MOD3.3 code. The transient behaviors of system pressure, coolant temperature, water inventory, coolant boiling and core uncovering time, and other important parameters under 12 different plant configurations are predicted. The results indicate that the system pressure of cases with intact system increases continuously to the set value of 3.8MPa for opening the relief valve in the RHR system without any mitigation action. The starting time of coolant boiling highly depends on the initial water inventory in the RPV as well as its behavior during the initial stage after losing the RHR system, while the starting time of core uncovering highly depends on the plant configurations. The results of the study can provide references for the plant safety improvement and guideline for an operator to strategize a mitigation action.

Handbook of Generation-IV Nuclear Reactors

Handbook of Generation IV Nuclear Reactors presents information on the current fleet of Nuclear Power Plants (NPPs) with water-cooled reactors (Generation III and III+) (96% of 430 power reactors in the world) that have relatively low thermal efficiencies (within the range of 32 36%) compared to those of modern advanced thermal power plants (combined cycle gas-fired power plants ? up to 62% and supercritical pressure coal-fired power plants ? up to 55%). Moreover, thermal efficiency of the current fleet of NPPs with water-cooled reactors cannot be increased significantly without completely different innovative designs, which are Generation IV reactors. Nuclear power is vital for generating electrical energy without carbon emissions. Complete with the latest research, development, and design, and written by an international team of experts, this handbook is completely dedicated to Generation IV reactors.Presents the first comprehensive handbook dedicated entirely to generation IV nuclear reactorsReviews the latest trends and developments Complete with the latest research, development, and design information in generation IV nuclear reactorsWritten by an international team of experts in the field

The future of nuclear power in France: an analysis of the costs of phasing-out

Nuclear power is an important pillar in electricity generation in France. However, the French nuclear power plant fleet is ageing, and the possibility of reducing the technology's share in power generation or even a complete phase-out has been increasingly discussed. This paper focuses on three inter-related questions: First, what are the costs of phasing-out nuclear power in France? Second, who has to bear these costs, i.e., how much of the costs will be passed on to the rest of the European power system? And third, what effect does the uncertainty regarding future nuclear policy in France have on system costs? Applying a stochastic optimization model for the European electricity system, the analysis showed that additional system costs in France of a nuclear phase-out amount up to 76 billion €2010. Additional costs are mostly borne by the French power system. Surprisingly, the analysis found that the costs of uncertainty are rather limited. Based on the results, it can be concluded that a commitment regarding nuclear policy reform is only mildly beneficial in terms of system cost savings.