External Flooding Research Articles

Fact-finding surveys on role of flood fighting in present-day Japan and future prospects: case studies of Yodo River and Yamato River

AbstractFlood mitigation efforts (flood fighting), including raising awareness among local residents, have been crucial in Japan to reduce damage during flood events. In this study, interviews were conducted with three flood fighting management bodies on the Yodo and Yamato Rivers, which still have strong flood fighting corps, and field investigations were performed focusing on the actual operation of flood fighting warehouses, which serve as infrastructure bases for flood fighting. Targets included the flood fighting affairs associations on the left and right banks for the Yodo River and that on the right bank for the Yamato River. The survey results showed that with the progress of flood control measures and river improvement, opportunities to conduct actual flood fighting work during floods decreased in all cases in recent years, but flood fighting techniques and knowledge were passed on through exercises and drills. In addition, the flood fighting warehouses were well managed and maintained their functions as material and equipment storage places and as waiting and meeting places for flood fighting corps members. Considering the intensification of external flood forces due to future extreme weather changes, it was deemed that the role of the flood fighting corps is expected to increase in importance, and it was judged that preparations were being made to respond to this trend. On the other hand, there were some challenges in terms of securing a sufficient number of members due to the shortage resulting from the aging of the corps members and maintaining warehouses from a budgetary standpoint.

Risk-Informing Nuclear Reactor Safety: The Prediction of the Probability of Core Damage Due to Loss of Power and Cooling

Abstract The modern idea of risk-informed decision-making (RIDM) is here critically examined for all existing, advanced and, generation-IV nuclear reactor systems. Motivated by the predictive difficulties of probabilistic risk assessment (PRA) in regard to occurred accidents, it is evident that the real (not hypothetical) consequences of nuclear core damage accidents that must be considered and quantified are the financial losses, infrastructure damages, societal disruptions, and adverse political policies, and not solely the traditional exceedance of regulated radiation release or public exposure limits. With this perspective, a new dynamic analysis is presented for estimating the probability of core damage due to extended loss of power and cooling in a modern nuclear reactor, giving results different from current standardized PRA/PSA analyses. Using existing data, we approach the multitude of different events in a new way: whatever the initial event in the finite event set {external flood, fire, hurricane, ice storm, typhoon, earthquake, cyber attack…}, the fundamental concerns are the consequent loss and nonrestoration of power, and the inadequate cooling of the core. The present proposed quantitative evaluation uses applicable and fully “exchangeable” severe event data for nuclear and nonnuclear systems, including active and passive emergency back-up systems for a wide range of power losses that lead to widespread damage and societal disruption. While not design-specific, this new independent “order-of-magnitude” estimate for the probability of core damage is some two to two hundred times larger than that shown or reported in recent modern and formal PSA/PRA for licensing submissions using generic failure rate data rather than actual severe event data. This new finding suggests greater uncertainties exist than presently assumed for risk-informed decision-making (RIDM), and points to the need for a major reconsideration and updating of risk assessment and regulatory risk-informed approaches for nuclear plant safety evaluation.

A mechanistic model of a PWR-based nuclear power plant in response to external hazard-induced station blackout accidents

Natural hazard-induced nuclear accidents, such as the Fukushima Daiichi Accident that occurred in Japan in 2011, have significantly increased reactor safety studies in understanding nuclear power plant (NPP) responses to external hazard events such as earthquakes and floods. Natural hazards could cause the loss of offsite power in nuclear power plants, potentially leading to a Station Blackout (SBO) accident that significantly contributes to the overall risk of nuclear power plant accidents. Despite the fact that extensive research has been conducted on the station blackout accident for nuclear power plant, further understanding of these events is needed, particularly in the context of the dynamic nature of external hazards such as external flooding. This paper estimates the progression of station blackout events for a generic pressurized water reactor (PWR) in response to external flooding events. The original RELAP5-3D model of the Westinghouse four-loop design pressurized water reactor was adopted and modified to simulate the external flood-induced station blackout accident, including the short-term and long-term station blackout scenarios. A sensitivity analysis of long-term station blackout, examining reactor operation times and analyzing key parameters over time, was also conducted in this work. The results of the analyses, especially the critical timing parameters of key event sequences, provide useful insights about the time during the external flooding event, which is important for plant operators to make timely decisions to prevent potential core damage. This paper represents significant progress toward developing an integrated risk assessment framework for further identifying and assessing the effects of the critical sources of uncertainties of nuclear power plant under external hazard-induced events.

Perspectives on factors that influence local communities’ vulnerability to coastal floods in Ketu South Municipality of Ghana

Vulnerability studies in relation to coastal floods in Ghana have generally focused on assessing the biophysical vulnerability and flood hazard modelling - rather than exploring the combination of both biophysical and socioeconomic factors that affect the vulnerability of coastal communities to floods. In response, this study aimed to explore the factors that influence the vulnerability of coastal communities in Ketu South Municipality, Ghana, to floods. These communities remain vulnerable to coastal flood events from storm surges, high tidal waves, lagoon overflow and heavy rainfall. However, the local conditions that make these communities vulnerable is poorly understood. The study used data from eight (8) in-depth interviews, nine (9) Focus Group Discussions and 354-household survey to explore local vulnerability factors in the study area. Results show that factors such as low land elevation, inadequate sea defence structures, high flood frequency, large flood extent, long flood duration, flood impacts, are among the exposure factors influencing vulnerability in the study area. It also shows that socioeconomic factors; such as weak demographic groups, low-income levels, low level of education, and some local adaptation measures plus external flood relief supports from National Disaster Management Organization (NADMO) influence the vulnerability of the communities. The result further revealed salt production activities, and relocating to flood prone areas, as well as rise in coastal water table and rapid shoreline erosion are the observable vulnerability factors in the study area whiles gender was a significant social factor influencing flood preparedness. These results can be useful for flood disaster management programs.

Application of external flood probabilistic safety assessment methodology to Prototype Fast Breeder Reactor

ABSTRACT This paper presents the methodology adopted, accident sequence analysis and salient results from the external flood probabilistic safety analysis exercise for Prototype Fast Breeder Reactor. The major steps performed are the probabilistic hazard estimation, fragility computation, system reliability modelling and risk quantification. The hazard analysis has been performed for rainfall, storm surge and tsunami as typically associated with a coastal site, from which correlation function relating flood level to the annual exceedance frequency is estimated. The fragility analysis of different safety systems is estimated by considering submergence mode of failure using step fragility functions. The secondary effects of flood such as debris impact, load falling and flood-induced sodium fires are not considered. The human reliability analysis of manual operations necessary for plant safety is done for the control room as well as onsite actions. The challenges encountered during the analysis, salient results and uncertainties involved are presented with inferences. Abbreviations: AHX: air heat exchanger; CDF: core damage frequency; EFPSA: external flood probabilistic safety assessment; EL: elevation levels; EOP: emergency operation procedure; ET: event tree; FT: fault tree; HRA: human reliability analysis; IE: initiating events; NPP: nuclear power plant; OGDHRS: operation grade decay heat removal system; PFBR: prototype fast breeder reactor; POT: peak over threshold; PSA: probabilistic safety assessment; PTHA: probabilistic tsunami hazard assessment; RY: reactor year; RCB: reactor containment building; RP: return period; SGDHRS: safety grade decay heat removal system; SSC: structures, systems and components

Applying the wellbeing valuation method to value the costs of roadworks and flooding

ABSTRACT This study uses the wellbeing valuation method to monetise the association between water flooding or roadworks incidents and subjective wellbeing for customers served by Anglian Water in the UK. Using this method, we find that the estimated wellbeing cost per incident for flooding is considerably higher than for roadworks, that internal sewer flooding is associated with a higher wellbeing cost per property than external sewer flooding, and that internal water flooding has a lower estimated wellbeing cost per property than internal sewer flooding. The findings were used in Anglian Water’s 2019 Price Review (PR19) business planning. By providing a wellbeing valuation for events that have also been studied through stated preference models, this research also provides a case study for comparing the differences in results between the two valuation methodologies.

Thermal hydraulic and mechanical behaviour of VVER-1000 reactor lower plenum in the late phase of severe accident

One of the most critical issues for determining the life extension of a nuclear power plant is the structural integrity analysis of a reactor pressure vessel (RPV). This work, examines the specifics of thermal-mechanical analysis, for the lower plenum of the reactor pressure vessel of VVER-1000, during the late in-vessel phase of a severe accident. Thermal-hydraulics and structural models of ANSYS FLUENT17.2 are prepared to obtain both the radial, axial temperatures and the stress field across the vessel wall thickness. Boundary conditions obtained from the ASTEC code are applied as input to the ANSYS FLUENT simulation for corium behavior in lower plenum: 2D meshing of vessel lower plenum, two corium layers (oxide layer and metal layer).The variation of stress, strain and damage with time at the critical axial layer are investigated. The analysis identifies the worst crack orientation and location. The results show without external flooding of the vessel, a pure thermal failure (melt-through) is highly probable due to the high thermal loads imposed by the decay power. Applied external flooding of the vessel would help the stability of the vessel and the retention of the molten corium inside the reactor pressure vessel and can prevent the vessel failure.

Development of a pressurized internal cooling milling cutter and its machining performance assessment

In view of the serious problem of milling heat in milling nickel-based superalloys Inconel 718, this paper investigates the heat transfer performance of internal cooling in end milling Inconel 718, and the superiority of internal cooling milling cutter's heat exchange ability during processing is explored. The flow field characteristics of cutting fluid and milling temperature are studied by Computational Fluid Dynamics (CFD) and Finite Element Method (FEM). Compared with external flood cooling, the principle of internal cooling with excellent heat transfer performance is explained and the influence of coolant pressure on lubrication performance is analyzed. Experiments for end milling of Inconel 718 under different cutting speeds and cooling conditions have been carried out. The results indicate that the simulated and measured temperatures showed an acceptable agreement. The internal cooling has better heat transfer performance compared with flood cooling. With the increase of coolant pressure, the heat exchange efficiency is gradually enhanced. When the coolant pressure rises from 2 bar to 10 bar, the milling temperature at the measured point inside the workpiece reduces by 27.55 °C, the surface roughness reduces by 12.0%, the surface residual compressive stress increases by 68.37 MPa and better surface morphology is obtained. Besides, in the experimental range, with the increase of cutting speed, milling temperature increased, the pile-up effect on the sides of scratching was weakened and better machined surface integrity was found.

Probabilistic flood hazard assessment method considering local intense precipitation at NPP sites

In recent years, the flooding risk of major facilities has increased significantly due to heavy rainfall events. These facilities must evaluate both external and internal flooding risk such as from heavy rainfall, flash floods, watershed flooding, river flooding, and coastal flooding. This study first estimates flooding from extreme rainfall with local intense precipitation and analyzes the resulting impacts on buildings and roads at a specific nuclear power plant (NPP) site, with which a roughness coefficient according to the landuse condition is estimated. A two-dimensional external flooding hazard analysis is then carried out with tidal levels as the external boundary conditions, and based on the results, new hazard curves for the inundation depth with frequency and duration are developed for the NPP site to show the relationships among rainfall, flood depth, and annual exceedance probability. To match the proper probability distribution types to the flood hazard curves, the fit was analyzed through Akaike’s information criterion verification. After analyzing the correlation between the flood depths, the mode values were calculated through Monte Carlo simulation with the verified probability distribution types. Finally, probabilistic flood hazard curves for the NPP site were obtained based on the calculated mode values. Representatively, when a 106-year return period rainfall occurs at the nuclear power plant site, the mode flood depth was found to be 1.07 m for power plant 1 and 0.61 m for power plant 2. In this way, the approach of this study is expected to support the waterproof design of critical facilities, flood prevention function design, the advancement of flood prevention measures and procedures, and the evaluation of flood mitigation functions.

Mechanical Resources Available At Middle Tisza District Water Directorate for External Flood Protection and Outsourcing

Abstract After 1998, the flood waves of the Tisza, Zagyva and Hármas-Körös rivers reached record levels in the area of operation of MTDWD requiring significant mechanical resources from the Water Directorate and participating external organizations in order to perform the protection tasks. In this article, the author describes the volume of mechanical resources used in the management of the MTDWD and the volume of those provided by external organizations during the flood control of the Tisza River in 2000, 2006 and 2010. It proves that in the event of flood defenses exceeding the order level, the Directorate’s own machinery resources are not sufficient, and that therefore, external machinery capacities are indispensable to meet future requirements.

Adequacy evaluation of smoothed particle hydrodynamics methods for simulating the external-flooding scenario

In modern nuclear risk analysis for external-flooding scenarios, Computational Fluid Dynamics (CFD) tools are used to simulate the generation, propagation, and interactions of Nuclear Power Plants (NPPs) with the nuclear Systems, Structures, and Components (SSCs). Smoothed Particle Hydrodynamics (SPH), as a Lagrangian and mesh-free method, is one of the particle-based CFD methods. Since SPH methods can effectively handling large-scale fluid simulations with complex interfacial structures, SPH-based software has been used to simulate the impacts of external flood onto nuclear facilities, and the simulation results have been used to support nuclear safety analysis. However, previous risk analysis assumes that SPH methods and the corresponding simulation packages are applicable to the external-hazards risk analysis, and their simulation uncertainties do not affect the confidence of safety decision. Considering the high consequences to nuclear safety induced by simulation errors, a systematic and complete validation process is needed to evaluate the adequacy of SPH simulations in informing related safety decisions.In this study, a scoping-stage assessment is performed for SPH’s adequacy in simulating the real-scale external flooding scenarios, especially in predicting the surface-wave impacts on SSCs at NPP sites. To ensure the completeness and consistency, validation frameworks, Code Scalability Applicability and Uncertainty (CSAU), and its regulatory guide, Evaluation Model Development and Assessment Process (EMDAP) are followed to guide validation activities and to make final code adequacy assessment. First, an external-flooding scenario is designed, and SPH simulations are performed with an SPH-based software named Neutrino. A Phenomenon Identification and Ranking Table (PIRT) is created, and the surface-wave impacts are identified as one of the high-rank phenomena. At the same time, a performance measurement standard is created for measuring the code adequacy in informing safety decisions consistently and transparently. Next, numerical benchmarks are designed for assessing the code adequacy of SPH methods and corresponding software implementations on Neutrino. Next, code accuracy is evaluated by comparing simulation results from Neutrino against experimental measurements in each benchmark. Meanwhile, a scaling analysis is performed to determine a group of dimensionless number for characterizing important physics and to assess the applicability of validation database collected in reduced-scale facility to the prototypic scenario. Finally, results from all activities are brought together to make an adequacy decision. It is found that, based on the current evidence, SPH methods and associated Neutrino software can predict the unbroken surface-wave peak pressure onto stationary rigid with reasonable accuracy if the suggested sizes of particles are used. However, it is suggested by independent reviews that the validity of major assumptions in target applications need to be evaluated with large-scale experiments, and the relevancy of other phenomena like turbulence and air pockets need to be identified with more benchmarks. As for the SPH’s adequacy in predicting the impact forces on dynamic rigid, the available evidence is not sufficient to support the decisions.

An extended method for evaluating assumptions deviations in quantitative risk assessment and its application to external flooding risk assessment of a nuclear power plant

In quantitative risk assessment, assumptions are typically made, based on best judgement, conservative, or (sometimes) optimistic judgments. Best judgment and optimistic assumptions may result in failing to meet the quantitative safety objectives, whereas conservative assumptions may increase the margins which the objectives are met with but result in cost-ineffective design or operation. In the present paper, we develop an extended framework for the analysis of the criticality of assumptions in risk assessment by evaluating the risk that deviations from the assumptions lead to a reduction of the safety margins. The framework aims to support risk-informed decision making by identifying important assumptions and integrating the assessment of their criticality into the quantitative risk assessment (QRA). The framework is, finally applied within the quantitative risk assessment of a Nuclear Power Plant (NPP) exposed to external flooding. Compared to previous works on the subject, we consider also conservative assumptions and introduce decision flow diagrams to support the classification of the criticality of the assumptions. The framework provides a more comprehensive and transparent evaluation of the assumptions deviation risk through the decision flow diagrams that facilitate the standardization of the evaluation of the assumption deviation effects on the risk assessment.

A practical approach for evaluating the strength of knowledge supporting risk assessment models

In this paper, we develop a new quantitative method to assess the Strength of Knowledge (SoK) of a risk assessment. A hierarchical framework is first developed to conceptually represent the SoK in terms of three attributes (assumptions, data, phenomenological understanding), which are further broken down in sub-attributes and “leaf” attributes to facilitate their assessment in practice. The hierarchical framework, is, then, quantified in a top-down, bottom-up fashion for assessing the SoK. In the top-down phase, a reduced-order risk model is constructed to limit the complexity and number of basic elements considered in the SoK assessment. In the bottom-up phase, the SoK of each basic element in the reduced-order risk model is assessed based on predefined scoring guidelines and, then, aggregated using a weighted average of “leaf” attributes, where the weights are determined based on the Analytical Hierarchical Process (AHP). The strength of knowledge of the basic events is in turn, aggregated using a weighted average to obtain the SoK for the whole risk assessment model. The developed methods are applied to a real-world case study, where the SoK of the Probabilistic Risk Assessment (PRA) models of a Nuclear Power Plants (NPP) is assessed for two hazards groups, i.e., external flooding and internal events.

Risk informed validation framework for external flooding scenario

Safety of nuclear plants against external flooding has gained significant attention following the accident at Fukushima Daiichi nuclear power station. In United States, Oyster Creek nuclear plant was safely shutdown when high storm surge during hurricane Sandy caused a potential flooding threat. Subsequently, the nuclear energy industry experienced a significant activity in Probabilistic Risk Assessment (PRA) for external flooding. Increasingly, methods of computational fluid dynamics including advanced simulation codes are being considered to evaluate the sequence of events during different scenarios of flooding at a plant. One of the key limitations in the use of advanced codes for external flooding is related to a lack of credibility of such simulations. The motivation of this study is to develop a formal validation approach that provides a basis to quantify credibility of risk assessments that are based on advanced simulation codes. In this study, we illustrate the application of existing performance based risk-informed validation framework to an external flooding event. However, it is determined that a direct application of this approach to flooding is restricted due to a lack of relevant data to evaluate experimental fragilities for flooding failures. Therefore, we take a simple synthetic example to evaluate the applicability of the proposed framework to validation of flooding PRA scenario and update the proposed framework as needed.

From Response to Recovery: Infection Prevention's Role in a Flood Disaster Event

BACKGROUND Environmental issues are a constant concern in healthcare as facilities and processes can fail when tested during natural and man-made disasters. Water damage can have more of an impact than just the initial cosmetic damage. Soil and silt intrusion from external flooding may bring in harmful bacteria and mold spores. During a recent disastrous flood, water flowed through the basement affecting critical departments including: operating rooms, sterile processing, laboratory, pharmacy, EVS and the kitchen. The Infection Prevention team adapted traditional construction principles to manage and mitigate harm to patients, healthcare workers, and visitors. METHODS Following the flood, response and recovery efforts must prioritize patient, staff and visitor safety. Incident command gathered experts early and developed prioritized response activities. As consultants in the hospital's incident command, the Infection Prevention team developed response and containment pathways to ensure hospital safety and tactics to move the process from response to recovery of critical services. Mitigation efforts were based on assessment of the situation and prioritization to restore essential hospital functions. Additionally, prospective patient surveillance was established to monitor for flood related outcomes including fungal and bacterial infections. RESULTS Innovative restoration of functions and strategic placement of barriers and ante-rooms allowed the facility to remain open and come off of divert status quickly. Due to the severity of the event, services were relocated or modified; food was catered, lab and the gastrointestinal services were moved to pre-op with temporary walls and cooling units. CONCLUSIONS The evidence supporting the purpose and function of the Infection Preventionist in construction and renovation is available but our practices are not well integrated in emergency or large scale disasters due to a lack of resources and functional, concrete tools. Using priority-driven goals, containment, and strategic remediation techniques, we were able to restore facility function while protecting patients and healthcare workers.

Prediction of Tool-Chip Interface Temperature in Cryogenic Machining of Ti–6Al–4V: Analytical Modeling and Sensitivity Analysis

Abstract The goal of this work is to predict the tool-chip interface temperature during cryogenic machining and determine the effectiveness of this cooling strategy. Knowledge of the tool-chip interface temperature is needed to conduct process planning: choosing a tool cooling geometry, cutting speed, and cryogen flow rate as well as predicting tool life and achievable material removal rate. A detailed explanation of the analytical heat transfer model is presented, which is a modified form of Loewen and Shaw's orthogonal cutting model, where a thermal resistance network is applied to represent the heat transfer mechanisms in, and out of, the cutting tool. An in-depth discussion of the temperature rise at the tool-chip interface during orthogonal machining of titanium alloy Ti–6Al–4V is presented. The effect of cutting speed, cryogen flow rate and quality, and cooling strategy are explored. The model is used to compare the effect of internal cryogenic cooling with external flood cooling using a water-based metalworking fluid or liquid nitrogen. A sensitivity analysis of the model is conducted and ranks the relative importance of various design parameters. The thermal conductivity of the cutting insert has the greatest influence on the predicted interface temperature. The low boiling temperature and phase change are what make internal cooling of a cutting insert with liquid nitrogen effective at reducing the tool-chip interface temperature. If the heat flowing into the tool, from the tool-chip interface, does not exceed the available latent heat in the cryogen, then this method is more effective than external flood cooling.

Verification and validation of explicit moving particle simulation method for application to internal flooding analysis in nuclear reactor building

ABSTRACT The Fukushima nuclear accident raised the importance of flooding study in nuclear reactor buildings. It is known that the external flooding can be attributed to natural causes, while the internal flooding is caused by the piping ruptures, tank failure or the actuation of fire suppression systems. The building flooding process can damage the safety-related components and systems, which needs to study carefully. In order to simulate this phenomenon which is accompanied by complex flow with free surface, a particle method based on Lagrangian approach named explicit moving particle simulation (EMPS) method, is employed in this analysis. Verification and validation analyses are carried out. The verification problems are a hydrostatic analysis and a water spreading to investigate the differences of the particle wall and polygon wall boundary models, while the validation studies of two experiments of dam-break induced flooding show good agreements. Afterwards, the internal flooding process in AP1000 is simulated by assuming a break of the in-containment refueling water storage tank as an example. The results achieved so far indicate that the EMPS method is capable to simulate the internal flooding process in the nuclear reactor buildings.

Estimation of initiating event frequency for external flood events by extreme value theorem

External flood is an important common cause initiating event in nuclear power plants (NPPs). It may potentially lead to severe core damage (SCD) by first causing the failure of the systems required for maintaining the heat sinks and then by contributing to failures of engineered systems designed to mitigate such failures. The sample NPP taken here is twin 220 MWe Indian standard pressurized heavy water reactor (PHWR) situated inland. A comprehensive in-house Level-1 internal event PSA for full power had already been performed. External flood assessment was further conducted in area of external hazard risk assessment in response to post-Fukushima measures taken in nuclear industries. The present paper describes the methodology to calculate initiating event (IE) frequency for external flood events for the sample inland Indian NPP. General extreme value (GEV) theory based on maximum likelihood method (MLM) and order statistics approach (OSA) is used to analyse the rainfall data for the site. Thousand-year return level and necessary return periods for extreme rainfall are evaluated. These results along with plant-specific topographical calculations quantitatively establish that external flooding resulting from upstream dam break, river flooding and heavy rainfall (flash flood) would be unlikely for the sample NPP in consideration.

Probabilistic risk assessment framework for structural systems under multiple hazards using Bayesian statistics

Conventional probabilistic risk assessment (PRA) methodologies (USNRC, 1983; IAEA, 1992; EPRI, 1994; Ellingwood, 2001) conduct risk assessment for different external hazards by considering each hazard separately and independent of each other. The risk metric for a specific hazard is evaluated by a convolution of the fragility and the hazard curves. The fragility curve for basic event is obtained by using empirical, experimental, and/or numerical simulation data for a particular hazard. Treating each hazard as an independently can be inappropriate in some cases as certain hazards are statistically correlated or dependent. Examples of such correlated events include but are not limited to flooding induced fire, seismically induced internal or external flooding, or even seismically induced fire. In the current practice, system level risk and consequence sequences are typically calculated using logic trees to express the causative relationship between events. In this paper, we present the results from a study on multi-hazard risk assessment that is conducted using a Bayesian network (BN) with Bayesian inference. The framework can consider statistical dependencies among risks from multiple hazards, allows updating by considering the newly available data/information at any level, and provide a novel way to explore alternative failure scenarios that may exist due to vulnerabilities.

A Methodology to Analyze the Safety of a Coastal Nuclear Power Plant Against Typhoon External Flooding Risks

For the protection of a coastal nuclear power plant (NPP) against external flooding hazard, the risks caused by natural events have to be taken into account. In this article, a methodology is proposed to analyze the risk of the typical natural event in China (Typhoon). It includes the simulation of the storm surge and the strong waves due to its passage in Chinese coastal zones and the quantification of the sequential overtopping flow rate. The simulation is carried out by coupling two modules of the hydraulic modeling system TELEMAC-MASCARET from ElectricitØ de France (EDF), the shallow water module (TELEMAC2D) and the spectral wave module (TOMAWAC). As an open-source modeling system, this methodology could still be enriched by other phenomena in the near future to ameliorate its performance in safety analysis of the coastal NPPs in China.