Nuclear Power Plant Maintenance Research Articles

Application of Laser Ablation Processing in Electric Power System Industries.

The present status of laser ablation processing applied in electric power system industries is reviewed. High average power LD-pumped Nd:YAG lasers with Q-switch have been developed and currently introduced into various applications. Optical fiber based laser beam delivery systems for Q-switched pulse laser are also being developed these years. Based on such laser and beam delivery technology, laser ablation processes are gradually introduced in maintenance of nuclear power plant, thermal power plant and electrical power distribution system. Cost effectiveness, robustness and reliability of the process is highly required for wide utilization in these fields.

Optimization of operation and maintenance of nuclear power plant by probabilistic fracture mechanics

Maintenance activity including inspection, repair and replacement is regarded as the most important key factor for the safety, reliability and economy of a nuclear power plant. The decision making—what kind of and to what extent maintenance should be performed—has to be done based on the evaluation of contribution to not only safety and reliability but also economy during long life time, taking such issues as aging and life extension into consideration. More economical operation of nuclear power plants can be attained not only by reducing the above mentioned costs but by increasing generation of electricity for which increase of total amount of thermal output and improvement of conversion ratio from thermal output to electricity may play important role. Increasing the flow rate of coolant or shifting higher the operational temperature and pressure may serve as candidates for a measure to increase thermal output. It is generally recognized that increasing of power generation may accelerate degradation of components. This means that increasing of power generation can be attained by performing better maintenance which may cost more, as the acceleration of degradation may increase the probability of accident. Following evaluations are performed in this study. Expectation value of cost of countermeasure for accident, expectation value of cost to repair the weld where defects are detected through ISI and cost for inspection are calculated as function of inspection frequency. The optimization of inspection frequency can be attained by finding the frequency where sum of these three costs takes minimum value. By selecting profit as object function, trial calculation for optimization of operation and maintenance of nuclear power plant was performed through calculation of costs for maintenance and electricity generation as function of inspection frequency and operational temperature following the probabilistic fracture mechanics principle. Through the calculation, several problems including identification of degradation for each material are revealed which may serve to make such calculation more realistic and useful when used in nuclear power plant.

An overview of PSA importance measures

The present paper deals with the use of probabilistic safety assessment (PSA) importance measures to optimise the performance of a nuclear power plant. This article is intended to give an overview on the subject for PSA practitioners. The most frequently used importance measures are shortly addressed. It is shown that two importance measures are sufficient to describe the character of the coredamage-equation. The most often used are the risk achievement and Fussell–Vesely importance, in combination with each other. In the field of nuclear power plant test and maintenance activities the Birnbaum importance is advocated.

Surface oxide removal by a XeCl laser for decontamination

The laser ablation performed with an automated excimer XeCl laser unit is used for large surface cleaning. The study focuses on metal surfaces that are oxidised and are representative of contaminated surfaces with radionuclides in a context of nuclear power plant maintenance. The unit contains an XeCl laser, the beam delivery system, the particle collection cell, and the system for real-time control of cleaning processes. The interaction of laser radiation with a surface is considered, in particular, the surface damage caused by cleaning radiation. The beam delivery system consists of an optical fibre bundle of 5 m long and allows delivering 150 W at 308 nm for laser surface cleaning. The cleaning process is controlled by analysing in real time the plasma electric field evolution. The system permits the cleaning of 2 to 6 m2 h-1 of oxides with only slight substrate modifications.

3213 リスクインフォームド ISI の日本における適用可能性と今後の方向性

Risk Informed-ISI utilizes PSA for streamlining the maintenance of nuclear power plants. In RI-ISI, maintenance requirements focus on high-safety-significant components and are relieved for low safety significant ones. This is expected to reduce plant cost as well as maintain safety. Quantitative and qualitative RI-ISI methods have been developed by ASME/Westinghouse Owners Group and EPRI, respectively. These methods have been incorporated in the ASME Sec. XI Code Cases and endorsed by the U.S. NRC. The quantitative method evaluates component segment risks in terms of pipe failure probability calculated with probabilistic failure mechanics (PFM) models and core damage frequency (CDF) calculated with PSA. The qualitative method uses pipe failure potential categorization derived from the plant service experiences and pipe failure impact on CDF derived from the PSA insight. The PFM models do not cover all the significant failure mechanisms, and the qualitative method is based on the U.S. service experiences. Therefore appropriate categorization rules must be developed on the Japanese service experiences. For this purpose, we have devised a framework of computer-aided system for the selection of risk significant elements.

Advantages of intelligent field modules for nuclear power plant operation and maintenance

Advantages of intelligent field modules for nuclear power plant operation and maintenance

Climbing, walking and intervention robots

Explains how the Automatic Control Department of the Instituto de Automatica Industrial (CSIC) in Madrid, Spain has been developing robots for over 15 years. This activity began in the 1980s with the realization of industrial robots and then the department focused its attention on the area of robots for hostile/hazardous environments. Describes several achievements in this field including a complex tele‐operated system for steam generator inspection and maintenance in nuclear power plants; a tele‐manipulator for servicing a new concept of urban infrastructures; a self‐propelling climbing robot with magnetic feet; and a four‐legged walking robot for hazardous environments.

Optimizing nuclear power plant refueling with mixed-integer programming

The problem addressed here is scheduling the shutdown for refueling and maintenance of nuclear power plants. The models have up to four reactors requiring of the order of five shutdowns each over a five-year time horizon. The resulting mixed-integer program is large and complex with interesting structure. We show good results using a mixed-integer optimizer taking advantage of a strong linear programming formulation.

Statistical analysis of the Ft. Calhoun reactor coolant pump system

In engineering science, statistical quality control techniques have traditionally been applied to control manufacturing processes. An application to commercial nuclear power plant maintenance and control is presented that can greatly improve plant safety. As a demonstration of such an approach, a specific system is analyzed: the reactor coolant pumps (RCPs) of the Ft. Calhoun nuclear power plant. This research uses capability analysis, Shewhart X-bar, R charts, canonical correlation methods, and design of experiments to analyze the process for the state of statistical control. The results obtained show that six out of ten parameters are under control specification limits and four parameters are not in the state of statistical control. The analysis shows that statistical process control methods can be applied as an early warning system capable of identifying significant equipment problems well in advance of traditional control room alarm indicators. Such a system would provide operators with ample time to respond to possible emergency situations and thus improve plant safety and reliability.

Economic and Regulatory Factors Affecting the Maintenance of Nuclear Power Plants

This paper examines the factors causing the escalation in the 1980s and' subsequent leveling off of nuclear power plant non-fuel Operating and Maintenance (O&M) costs. Over the period 1974-93, real (inflation-adjusted) non-fuel O&M costs escalated from about $23 to about $97 per kilowatt of installed capacity (kW). However, much of the escalation in costs occurred in the 1980s. Over the period 1975-87, real O&M costs escalated at an annual rate of about 11 percent. Since then, the annual growth rate in real O&M costs fell to about I percent. The research found that the escalation in O&M costs was primarily due to increased regulatory activity by the Nuclear Regulatory, Commission. More important, there is little evidence that the moderation in the growth in O&M costs was regulatory induced, but instead was due to changes in the economic incentives to improve plant performance.

96/01533 The advantages of intelligent field modules for nuclear power plant operation and maintenance

96/01533 The advantages of intelligent field modules for nuclear power plant operation and maintenance

An intelligent human-machine system based on an ecological interface design concept

It seems both necessary and promising to develop an intelligent human-machine system, considering the objective of the human-machine system and the recent advance in cognitive engineering and artificial intelligence together with the ever-increasing importance of human factor issues in nuclear power plant operation and maintenance. It should support human operators in their knowledge-based behaviour and allow them to cope with unanticipated abnormal events, including recovery from erroneous human actions. A top-down design approach has been adopted based on cognitive work analysis, and (1) an ecological interface, (2) a cognitive model-based advisor and (3) a robust automatic sequence controller have been established. These functions have been integrated into an experimental control room. A validation test was carried out by the participation of experienced operators and engineers. The results showed the usefulness of this system in supporting the operator's supervisory plant control tasks.

The development of a functional fail-safe control for advanced robots

Advanced robots for nuclear power plant maintenance are complex compared with industrial robots, and are subjected to severe conditions during use. The importance of their safety and reliability is...

An analysis of nuclear incidents resulting from cognitive error : Gall, W. In: Operating reliability and maintenance of nuclear power plant. Institution of Mechanical Engineers, London, 1990, pp 61–71, 9 refs

An analysis of nuclear incidents resulting from cognitive error : Gall, W. In: Operating reliability and maintenance of nuclear power plant. Institution of Mechanical Engineers, London, 1990, pp 61–71, 9 refs

The application of human factors to the assessment of VDU screen displays in a nuclear chemical plant : Reed, J., Penington, J. and Kirwan, B. In: Operating Reliability and Maintenance of Nuclear Power Plant. Institution of Mechanical Engineers, London 1990, pp 45–59, 5 refs

The application of human factors to the assessment of VDU screen displays in a nuclear chemical plant : Reed, J., Penington, J. and Kirwan, B. In: Operating Reliability and Maintenance of Nuclear Power Plant. Institution of Mechanical Engineers, London 1990, pp 45–59, 5 refs

Human reliability assessment in the development of maintenance procedures : Whittingham, R.B. In: Operating Reliability and Maintenance of Nuclear Power Plant. Institution of Mechanical Engineers, London, 1990, pp 37–43, 10 refs

Human reliability assessment in the development of maintenance procedures : Whittingham, R.B. In: Operating Reliability and Maintenance of Nuclear Power Plant. Institution of Mechanical Engineers, London, 1990, pp 37–43, 10 refs

A Computerized Diagnostic System for Nuclear Plant Control Rooms Based on Statistical Quality Control

In engineering science, statistical quality control techniques have traditionally been applied to control manufacturing processes. An application to commercial nuclear power plant maintenance and control is presented that can greatly improve safety. As a demonstration of such an approach to plant maintenance and control, a specific system is analyzed: the reactor coolant pumps of the St. Lucie Unit 2 nuclear power plant located in Florida. A 30-day history of the four pumps prior to a plant shutdown caused by pump failure and a related fire within the containment was analyzed. Statistical quality control charts of recorded variables were constructed for each pump, which were shown to go out of statistical control many days before the plant trip. The analysis shows that statistical process control methods can be applied as an early warning system capable of identifying significant equipment problems well in advance of traditional control room alarm indicators.

The Role of Human Information Processing Models in System Development

Humans are complicated devices. Thus, systems in which people are embedded necessarily are complex. In order to better develop such systems, a means to organize and understand human complexity is required. Theoretical models of human information processing are one cognitive-engineering tool to help system development. This paper discusses the kinds of models that might be effective in solving practical problems. Suggestions are given for selecting a useful model from the plethora of available theoretical models. These issues are illustrated in the context of current research aimed at providing a general model of human cognition and action for application to the development, operation, and maintenance of nuclear power plants in Japan.

Robotics and teleoperator-controlled devices.

This paper presents a rationale for and a summary of tasks and missions to which mobile and stationary robots and other teleoperator-controlled devices could be assigned in response to the accidental release of radioactive and other hazardous/toxic materials to the environment. Many of these vehicles and devices currently support operation and maintenance of nuclear power plants and other nuclear industry facilities. This paper also discusses specific missions for these devices at the Three Mile Island and Chernobyl nuclear power plant sites at the time of the accidents. Also discussed is the status of devices under development for future applications, as well as research on robotics.

Reactor noise standards in the U.S.A.

The American Society of Mechanical Engineers (ASME) has fostered the development of codes and standards to be used by all facets of the general industry. The ASME Committee on Operation and Maintenance of Nuclear Power Plant (O&M Committee) currently has responsibility of 20 ASME nuclear power standards addressing areas such as “Requirements for Inservice Performance Testing of Pressure Relief Devices” (OM-01) to “Inservice Testing of Diesel Drives in Nuclear Power Stations” (OM-16). The Subcommittee on Vibration Monitoring (SCVM) is responsible for several O&M Committee standards, two of which utilize reactor noise techniques: OM-05, “Inservice Monitoring of Core Support Axial Preload in Pressurized Water Reactors”, and OM-12, “Vibration Monitoring and Diagnostics of Light Water Reactor Loose Parts”. This paper presents an outline of the O&M Committee standards and briefly describes the highlights of the two SCVM standards which utilize Reactor Noise techniques.