Risk-Informed Assessment Methodology Development and Application

Author(s):  
Sung Goo Chi ◽  
Seok Jeong Park ◽  
Chul Jin Choi ◽  
S. E. Ritterbusch ◽  
M. C. Jacob

Westinghouse Electric Company (WEC) has been working with Korea Power Engineering Company (KOPEC) on a US Department of Energy (DOE) sponsored Nuclear Energy Research Initiative (NERI) project through a collaborative agreement established for the domestic NERI program. The project deals with Risk-Informed Assessment (RIA) of regulatory and design requirements of future nuclear power plants. An objective of the RIA project is to develop a risk-informed design process, which focuses on identifying and incorporating advanced features into future nuclear power plants (NPPs) that would meet risk goals in a cost-effective manner. The RIA design methodology is proposed to accomplish this objective. This paper discusses the development of this methodology and demonstrates its application in the design of plant systems for future NPPs. Advanced conceptual plant systems consisting of an advanced Emergency Core Cooling System (ECCS) and Emergency Feedwater System (EFWS) for a NPP were developed and the risk-informed design process was exercised to demonstrate the viability and feasibility of the RIA design methodology. Best estimate Loss-of-Coolant Accident (LOCA) analyses were performed to validate the PSA success criteria for the NPP. The results of the analyses show that the PSA success criteria can be met using the advanced conceptual systems and that the RIA design methodology is a viable and appropriate means of designing key features of risk-significant NPP systems.

1983 ◽  
Vol 105 (2) ◽  
pp. 171-177
Author(s):  
J. M. Thomas ◽  
P. R. Bosinoff

This paper presents a methodology for identifying cost-effective failure prevention strategies for components or systems in nuclear power plants. Two strategies identified are the improvement of component reliability and the addition of redundant components. These two strategies are evaluated within the context of both repairable and nonrepairable systems. Capacity/demand and continuous time models are used to analyze the two strategies and systems. An example problem is developed for a continuous time, repairable system. It is clearly shown that large expenditures are justified to improve the reliability of some major systems in nuclear power plants and that these expenditures, exceeding the original capital cost of the system, could save tens of millions of dollars.


Author(s):  
E. J. Butcher ◽  
J. W. Roe

The September 11, 2001 terrorist attack on the World Trade Center and subsequent events has effected perceptions of the terrorist threat to the U.S. in general, and nuclear power plants in particular. These concerns have given rise to calls by government and private orga nizations for reevaluations of both the nature of the threat and protection against it. This paper suggests a general framework for a balanced approach to these reevaluations and highlights some practical and cost effective approaches for improving nuclear power plant safeguards protection.


Author(s):  
Matteo Vagnoli ◽  
Francesco Di Maio ◽  
Enrico Zio

Climate change affects technical systems, structures and infrastructures, changing the environmental context for which systems, structures and infrastructure were originally designed. In order to prevent any risk growth beyond acceptable levels, the climate change effects must be accounted for into risk assessment models. Climate models can provide future climate data, such as air temperature and pressure. However, the reliability of climate models is a major concern due to the uncertainty in the temperature and pressure future projections. In this work, we consider five climate change models (individually unable to accurately provide historical recorded temperatures and, thus, also future projections) and ensemble their projections for integration in a probabilistic safety assessment, conditional on climate projections. As case study, we consider the passive containment cooling system of two AP1000 nuclear power plants. Results provided by the different ensembles are compared. Finally, a risk-based classification approach is performed to identify critical future temperatures, which may lead to passive containment cooling system risks beyond acceptable levels.


Author(s):  
Alex H. Hashemian ◽  
Hash M. Hashemian ◽  
Tommy C. Thomasson ◽  
Jeffrey R. Kapernick

Small Modular Reactors (SMRs) under design and development today are working to crystallize the measurements that must be made to control the reactor and monitor its safety. Traditionally, temperature, pressure, level, flow, and neutron flux are measured in conventional nuclear reactors for operation and control and to protect against equipment and process deviations that can affect safety. In most current SMR designs, essentially the same process variables may have to be measured; especially primary coolant flow depending on whether the core cooling and heat transfer results from natural circulation or forced flow. The flow can be measured directly or inferred from other measurements or estimated through empirical or physical modeling. The conventional sensors that are qualified for nuclear services and are currently used in nuclear power plants may or may not be suitable for SMRs. It all depends on the size and qualification requirements, installation details, static and dynamic performance specifications, wiring details, and sensor life expectancy. This paper will explore the possibilities that exist for SMRs to use today’s sensors and any need for new sensor designs. In addition, the paper will identify new means for automated monitoring of instrumentation and control (I&C) sensor performance in SMRs. In particular, the existing array of online calibration monitoring techniques and in-situ response time measurement methods will be evaluated for implementation in SMRs. This is important at this early stage as SMRs can easily build provisions in their mechanical, electrical, and I&C designs to accommodate online and automated I&C maintenance. For example, it is envisioned that SMRs will not be performing periodic sensor calibrations using classical hands-on procedures. Rather, SMRs are expected to be equipped with new technologies to verify the I&C performance automatically and flag the sensors and systems to be calibrated, response time tested, repaired, or replaced. The paper will explore these possibilities and will report on a current R&D project that is underway at AMS with funding from the U.S. Department of Energy (DOE) with the goal to adapt the existing online monitoring (OLM) technologies for implementation in SMRs. The existing OLM technologies have been used by AMS in commercial nuclear power plants and research reactors for monitoring of I&C equipment performance including calibration, response time, detection of sensing line blockages, and to distinguish whether a signal anomaly is due to cables/connectors, electromagnetic interference, an end device being a sensor or a pump, other rotating equipment, etc.


2003 ◽  
Author(s):  
F. G. Abatt ◽  
Quazi Hossain ◽  
Milon Meyer

Evaluation of life safety risks to facility occupants, public, and the environment that may result from earthquake events involves both building structures and equipment supported from these structures. But, it is the seismic design of building structures that typically receive the bulk of the attention from the code committees of the national professional organizations and the regulatory authorities. For safety related equipment in nuclear facilities (e.g., Seismic Category I equipment in nuclear power plants and Seismic Performance Category 3 and 4 equipment in the Department of Energy facilities), the seismic design and analysis guidelines and acceptance criteria are well established. But, for Nonseismic Category equipment in nuclear power plants and Seismic Performance Category 1 and 2 equipment in Department of Energy facilities, these have not yet been developed to the same level of completeness and rigor. The code provisions and guidelines available today for these lower class/categories of equipment are briefly, but critically discussed here, along with a comparison of the results of the application of these code provisions.


Author(s):  
Ping K. Wan ◽  
Desmond W. Chan ◽  
Alice C. Carson

Nuclear power generation has become an increasingly attractive alternative in the United States (U.S.) power market due to several factors: growing demand for electric power, increasing global competition for fossil fuels, concern over greenhouse gas emissions and their potential impact on climate change, and the desire for energy independence. Assuring the protection of people and the environment are of paramount concern to nuclear power generators and regulators as we move towards a possible nuclear renaissance. Thus, sound engineering design is of utmost important and potential environmental and safety concerns must be carefully evaluated and disposition during permitting of the new nuclear power plants. Areas to be considered in order to alleviate these concerns include the following: • Site meteorology and dispersion conditions of the area; • Evaluation of radiological consequence during normal plant operation and emergency conditions; • Water availability for plant cooling system; • Evaluation of potential land use, water use, ecological and socioeconomic impacts of the proposed action. This paper focuses on site suitability evaluation for greenfield sites through site characterization, examination of challenges/constraints in deployment of available technology/plant systems, and mapping of permitting compliance strategy. Case studies related to selection of plant systems based on the environmental site conditions, preferred compliance plan, and public acceptance, are included.


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