Plant Asset Management Today and Tomorrow

Nuclear power plants (NPP) are subject to stiff requirements as to the cost effectiveness of their operation. However, since the NPP operation may be associated with the occurrence of severe environmental, social, political, material and other consequences as the result of nuclear and radiological accidents at NPPs, ensuring the specified level of the NPP safety is an operational task of the utmost importance. The current practice of the NPP design and operation suggests that the objectives involved in improving the efficiency of operation and those of ensuring the NPP safety level required by federal standards and regulations (NP-001) are achieved in isolation: no issues of ensuring high efficiency of the NPP operation are taken into account when addressing the issues involved in ensuring the safety of the NPP and, vice versa, it is a priori assumed that the required level of safety is ensured at any time when high efficiency of operation is achieved. The reason for this is the absence of procedures that make it possible to assess, in an integrated manner, the interdependence of economic and technological factors. The paper describes some of the methods to raise the efficiency of the NPP operation by selecting the best possible NPP maintenance and repair (M&R) strategies leading to high utilization and capacity factor values. A distinctive feature of the proposed techniques is that the efficiency of the NPP operation is proposed to be improved while ensuring at the same time the required level of the NPP safety with any NPP configuration.

Further increase of the reliability and efficiency of the operation of nuclear power plants depends on the comprehensive solution of many problems, of which the problem of optimization and increase of the informativeness of chemicotechnological monitoring is gaining in importance. There is a clear rift between the level of scientific ideas and technical solutions on which nuclear power plants are based and the existing approach to the organization of chemical monitoring. Everyone understands the necessity of chemical monitoring, but many people do not regard it as a necessary element for ensuring normal operation of a nuclear power plant. The lack of standard requirements and a standard methodical base markedly lowers the reliability of the results of analyses, and behind this lies possible breakdowns of the water-chemical conditions. How can this situation be explained? The consequences of deviations of water-chemical conditions from regulation standards are by no means manifested immediately. Apparent wellbeing at any given time creates the impression that the requirements of the chemical laws can be ignored with impunity. But there is also another reason for the disdainful attitude toward chemical monitoring. Chemical-technological monitoring at a nuclear power plant reduces to the determination of ~20 water-quality indicators for the basic and auxiliary systems. Considering the number of existing points at which samples are extracted in each block of a nuclear power plant and the frequency with which the analyses are performed, it is not difficult to imagine the impressive number of the overall volume of data obtained. Thus the total number of analyses per month for one block of a nuclear power plant with RBMK-1000 approaches 15,000 [i]. In addition, as a rule, these are single measurements, whose error it is virtually impossible to estimate exactly. Moreover, regardless of how conscientious the chemists-analysts at the technological laboratories are, in the monotony of repeating values it is difficult to escape big blunders in the case of unforeseen deviations of the parameters in the water-chemical conditions. Under these conditions there is no hope of obtaining reliable information for each of the measurements, making sense of the observational results, and drawing correct conclusions. We arrive at a p~r~dox, By increasing the number of parameters monitored and the number of points at which samples are extracted we strive to increase the information content of chemical monitoring, but we actually achieve the opposite result. At the present time, when nuclear power has transformed from a unique source of energy to one of the most important elements of the power production in the country, it is essential to reexamine the concepts forming the basis for the implementation of chemical-analytical monitoring at nuclear power plants. At the first nuclear power plants the research and technological functions of analytical monitoring were balanced, and preference was often given to obtaining research information. For serially produced nuclear power plants research programs are a rare episode. It is evident that the main reason for this situation is hidden in the existing standards and requirements imposed on the chemical monitoring system at nuclear power plants. At the first stages of development of nuclear power the striving toward performing as much analysis as possible and over the entire technolgocial loop was justified, whereas at the present time, as experience in operating nuclear power plants in this country and abroad shows, the time has come to search for new approaches to the problem of analytical monitoring of the quality of water heat carriers. The successful solution of the problem of analytical monitoring is often linked primarily with the instrumentation. But the number of methodical and instrumentation developments continues to increase, and the chemical-technological monitoring remains as before one of the laborious and unreliable elements in the overall chain of operational monitoring of nuclear power plants. Fundamental restructuring of the overall scheme of such monitoring is possible only based on automatic or, at least, automated means of chemical analysis.

With the development of civilization and the growth of the world’s population, the need for electricity also increases. Today, the main electricity sources are nuclear power plants (NPPs) and hydroelectric power plants (HPPs) that run on hydrocarbon fuels such as coal, peat, gas, and fuel oil. But these generating electricity methods have serious drawbacks, for example, the depletion of hydrocarbon natural resources, which leads to their shortage and rise in price. Nuclear and hydroelectric power plants cannot fully cover the need for electricity. In addition, the tragic events in the history of nuclear energy, e.g., the accident at the Chernobyl nuclear power plant, the nuclear power plant disaster in the city of Fukushima, etc., show great risks associated with the operation of nuclear power plants. Thus, solar energy engineering is the most efficient type of alternative, safe energy in the foreseeable future of mankind. This review is an effort to highlight the major progress and future challenges of using renewable energy sources.

With growing concerns about global warming, building more nuclear power plants is becoming one of the inevitable options to provide the world’s electricity. This is mainly because nuclear power is considered as the major source of “carbon-free” energy. Currently, extensive preventive maintenance, inspection, andmonitoring programs are developed to ensure safe and reliable operation of nuclear power plants. These programs involve safety analysis codes, equipment health monitoring, degradation-specific inspections, and plant lifecycle management (PLM). Although extensive effort has been invested to develop such programs, nuclear power plants continue to experience problems and therefore more accurate analysis and related researchwork still receive a great attention. This is mainly because the unresolved safety problems or lack in systems monitoring often causes significant safety-related events at nuclear power plants. Therefore, the demand for applied research work continues to grow in order tomitigate such events, increase the plant capacity factor, and gain public support for nuclear power as an alternative power source. This special issue identifies and analyzes major practical problems in nuclear energy and it contains 7 articles out of 14 articles that were initially received for publication. Even with the limited number of articles presented in this special issue, a wide range of topics are covered to present different experiences from several nuclear power plants and research institutions around the world. These topics are gathered in this issue to present the best engineering analyses, research effort, and practice with as little prejudice as possible. The issue starts by the novel method for optimization of the maintenance activities presented by A. Volkanovski and L. Cizelj in the nuclear power plant in order to improve plant safety. The authors consider different constraints on the optimization of the maintenance activities in the nuclear power plants. Three severe accident sequences of nuclear plants are discussed by G. Shao et al. to show that the natural circulation phenomenon results in heat transfer from the core to the pipes in RCS and consequently may cause the creep rupture of pipes in RCS and delay the severe accident progression. Also, S. Liu et al. were able to show that thermal stress failure caused by alternating operational loads is one of the important damage mechanisms in the nuclear power plants. Furthermore, R. K. Ur et al. discuss the impact of instrumentation and control components on the architecture of reactor protection systems. On the numerical and statistical analysis side, the article of S. U.-D. Khan et al. presents a modification to the neutron kinetics code, which originally works for the cylindrical type fuel elements, to plate type fuel nuclear reactor. Moreover, the study performed by M. El Nakla et al. has stressed the importance of the local scale observation leading to better understanding of the CHF phenomena in large pipe. They were able to predict the occurrence of critical heat flux in horizontal tubes using an extra correction factor to account for flow stratification. Finally, T. H. Woo contributed to this special issue with a paper on the nuclear power plant security. He presented dynamical assessment, which helps operator to find the dangerous situation in the site and avoid possible incidents that could be a catastrophe for theNPPs.We believe that this special issue provides interesting information on the recent progress in nuclear power research.

To the Editor: I read with great interest the recent article (1) and subsequent debate (2, 3) regarding the cohort study on cancer risks among those residing near nuclear power plants. Since the issue of health effects among populations living near nuclear facilities is an important topic within public health discourse, further scientific communication would contribute to a more complete understanding of radiation exposure and health. In this light, I would like to add a few comments on this issue. First, the study objective of the original investigation is indeed a fundamental issue which cannot be dismissed as a 'silly question'. If the study purpose is to identify the cancer risk due to radiation exposure from nuclear power plants, then it is difficult to justify why the original study did not include radiation-sensitive subpopulations such as fetuses or children from the beginning of the study. Also, considering that accurate exposure assessment is a vital component of environmental epidemiology, the simple application of a crude exposure index (i.e., distance from nuclear power plant) in this study raises questions related to the study purpose. I would judge that the main purpose of the original study was to build a prospective cohort of adults for cancer and other diseases rather than one focused on radiation exposure and cancer. Therefore, we need to acknowledge that while this is in fact a well-designed general cohort study, the cohort includes certain limitations for drawing causality with radiation exposure and cancer. Therefore, the results must be analyzed with caution. In my opinion, the results of this study should not be misleadingly interpreted as solid null findings rather than as inconclusive. Second, I am convinced that conducting a re-analysis of the existing dataset would be a worthwhile undertaking in order to investigate the association in greater depth. This is not a case of right versus wrong, but a natural process of investigating the truth. Existing and future findings together will contribute to a better understanding of the full scope of the radiation effect. A re-analysis study may provide us with valuable distinct approaches and considerations. Continued monitoring of health outcomes, refinement of exposure assessment, and corresponding updates of analysis are fundamental elements and advantages of cohort studies. Since the government and a number of researchers have dedicated considerable time, effort and funds to this cohort, I believe the existing data, as a national asset, need to be actively applied in support of the public interest. However, we must at the same time acknowledge the limitations of the original cohort which may continue to hinder the investigation of the association between radiation exposure and cancer risk even after applying more sophisticated statistical analyses. Therefore, additional efforts to compensate for the limitations of this study, in particular improving exposure assessment, minimizing exposure misclassification, and conducting new epidemiologic studies focusing on children, are warranted in order to better shed light on the association between radiation exposure from nuclear power plants and the development of cancer. Third, I would like to point out that there remain certain uncertainties in estimating cancer risk associated with exposure to ionizing radiation. Even the Life Span Study of Japanese atomic bomb survivors, which serves as a quantitative basis for radiation risk estimation worldwide, featured drawbacks including selection bias, immortal bias, and missing information (4). It is difficult to state that a low level of measured radiation can on its own completely guarantee no increased cancer risk for those living near nuclear power plant sites. The discrepancy between measured radiation doses and cancer risk remains mainly unexplained, and a possible hypothesis has been suggested (5). Although the majority of previous studies on cancer risks in populations near nuclear facilities have reported null findings except in the case of childhood leukemia (6), it is the role of epidemiology to clarify this issue of whether or not the observed cancer risk is related with radiation. Therefore, I would like to emphasize the importance of epidemiologic study in combination with surveillance data on radiation doses in populations near nuclear power plants. I believe that constructive discussions focusing on research itself can further advance radiation epidemiology in Korea and I hope this journal can serve as a means to accomplish this in its basic role as a scientific journal.

The energy supply of the future in the EU will be a mix of renewable, fossil and nuclear. There are 145 nuclear power reactors in operation in 15 out of the 27 EU countries, with installed power ∼132 GWe. The age distribution of current nuclear power plants in EU is such that in 2010 most of them will have passed 20-years and approximately 25% of them 30 years of age. The decrease of energy supply from nuclear generated electricity can not always be compensated in a reliable and economical way within a short time span. For this situation utilities may be keen to upgrade the reactor output and /or to ask their regulatory bodies for longer term operation. Under the research financed in the Euratom part of the Research Directorate (RTD) of the European Commission several projects explicitly address the safe long term operation of nuclear power plants (NULIFE, LONGLIFE) and the topics proposed in the 2010 call explicitly address issues concerning component ageing, in particular non metallic components, i.e. instrumentation and cables (I&C) and concrete ageing. This paper presents an overview of the plans for long term operation (LTO) of nuclear power plants in the EU. Special emphasis is given on research activities on component ageing management and long term operation issues related to safety.

The monetary value of the man-mSv for operators of Korean nuclear power plants (NPPs) was calculated using a radiation aversion factor based on a survey of NPP workers. Initially, the life expectancy in the population is 79.4 y, the average age of cancer occurrence is 60 y, the average annual wage for an electric worker is 56 000 $ y(-1) and the nominal risk coefficient induced by radiation is 4.2E(-5) mSv were used to evaluate the basic monetary value (α(base)) resulting in 45.6 $ mSv(-1). To investigate the degree of radiation aversion, the subject of the investigation was selected as the working radiation workers in 10 NPPs in Korea (Kori 1-2, Yeonggwang 1-3, Ulchin 1-3 and Wolseong 1-2). In August 2010, with the cooperation of KHNP and partner companies, a total of 2500 survey questionnaires to 10 NPPs (or 250 surveys to each NPP) were distributed to currently employed radiation workers. From these, 2157 responses were obtained between August and October 2010. The assessed radiation aversion factor and the monetary value of the man-mSv from the calculated radiation aversion factor were 1.26 and ∼50 $ in the 0-1 mSv range, 1.38 and ∼200 $ in the 1-5 mSv range, 1.52 and ∼1000 $ in the 5-10 mSv range, 1.65 and ∼4000 $ in the 10-20 mSv range and 1.74 and ∼8500 $ >20 mSv.

Power transformer is one of the most important electrical equipment for safe and reliable operation of Nuclear Power Plant. For trouble free operation of transformer, it is necessary to monitor its health during the lifecycle. There are clear needs for the development of prognostics and health management techniques so that smooth operation of transformer as well as safe operation of nuclear power plant can be ensured. This paper focuses on transformer asset management using Health Index approach. According to actual available data from a nuclear power plant, this paper revises the referenced HI model (Kinectrics Inc.) to consider actual test results of transformer performed in the field, dissolved gas analysis and other test of oil, maintenance work orders on various components of transformer, health of tap changer etc. The final value of health index is associated with the predicted life and condition of transformer according to pre-defined limits. Revised health index model studied is tested by the actual test data collected from a real nuclear power plant. It shows that the improved method is practically feasible for nuclear power plant. Introduction, revised health index model, results, discussion and recommendations are described in detail in following sections.

A nuclear power plant is a complex technological facility. The introduction of new standards and experience gained in the operation of domestic and foreign nuclear power plants requires the introduction of changes in the operating organization of existing nuclear power plants and improvements in their equipment. A general survey of the modernization of existing nuclear power plants with RBMK-1000 type reactors is presented. Measures for modernization of the power-generating units of nuclear power plants carried out following the accident at the Chernobyl nuclear power plant and at the present time are discussed. Because of modernization, the safety, reliability and economic efficiency of nuclear power plants have improved. The principal focus is on modernization of the reactor plant.

ABSTRACTOperational radioactive waste is generated during routine operation of nuclear power plants (NPP). This waste must be solidified in order to ensure safe conditions of storage and disposal. Vitrification of NPP operational waste is a relative new solidification option being developed for last years. The vitrification technology comprises a few stages, starting with evaporation of excess water from liquid radioactive waste, followed by batch preparation, glass melting, and ending with vitrified waste blocks and some relative small amounts of secondary waste. Application of induction high frequency cold crucible type melters facilitates the melting process and significantly reduces the generation of secondary waste. Two types of glasses were designed in order to vitrify operational waste depending on the reactor type at the NPP. For the NPP with RBMK-type reactors the glass 16.2Na2O 0.5K2O 15.5CaO 2.5 Al2O3 1.7Fe2O3 7.5B2O3 48.2SiO2 1.1 Na2SO4 1.2NaCl (5.7 others) was produced. For NPP with WWER reactors the glass 24.0Na2O 1.9K2O 6.2CaO 4.3Al2O3 1.8Fe2O3 9.0B2O3 46.8SiO2 0.8Na2SO4 0.9NaCl (4.3 others) was produced. The melting temperatures of both glass formulations were 1200–1250 C, specific power consumption was 5.2 ± 0.8 kW h/kg, 137Cs loss was within the range 3 - 4 %. The specific radioactivity of glass reached 7.0 MBq/kg. Glass blocks obtained were studied both in laboratory and field conditions. Long-term studies revealed that vitrified NPP operational waste has the minimal impact onto environment. Since the glass has excellent resistance to corrosion it gives the basic possibility of maximal simplification of engineered barrier systems in a disposal facility. The simplest disposal option for vitrified NPP waste is to locate the packages directly into earthen trenches provided the host rock has the necessary sorption and confinement properties.

VERLIFE – “Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs during Operation” was initiated and co-ordinated by the Czech and was developed within the 5th Framework Program of the European Union in 2003 and later upgraded within the 6th Framework Program “COVERS – Safety of WWER NPPs” of the European Union in 2008. This Procedure had to fill the gap in original Soviet/Russian Codes and Rules for Nuclear Power Plants (NPPs) with WWER (Water-Water-Energetic-Reactor = PWR type) type reactors, as those codes were developed only for design and manufacture and were not changed since their second edition in 1989. VERLIFE Procedure is based on these Russian codes but incorporates also new developments in research, mainly in fracture mechanics, and also some principal approaches used in PWR codes. Last upgrading and principal extending of this VERLIFE Procedure was realized within the 3-years IAEA project (in close co-operation with another project of the 6th Framework Program of the European Union “NULIFE – Plant Life Management of NPPs”) that started in 2009 with final approval and editing in 2013. As all versions of the VERLIFE procedure were coordinated by the Czech and first version was based on the Czech version of the NTD ASI, there have been simultaneously incorporated into the Czech NTD ASI (Normative Technical Documentation of the Czech Association of Mechanical Engineers) guidelines that are accepted by the Czech State Office for Nuclear Safety for the use in evaluation of Czech NPPs. This document has several parts: Section IV – “Evaluation of Residual Lifetime of Components and Piping in WWER type NPPs” deals with the evaluation during NPP operation. Main part of the document is divided into four main parts: - Evaluation of resistance of components and piping against non-ductile failure - Evaluation of resistance of component and piping against fatigue damage, - Evaluation of resistance of components and piping against corrosion-mechanical damage - Evaluation of residual lifetime of components and piping with defects found during in-service inspections Additionally, several appendices are included for detailed description of individual parts of evaluation, e.g. - Determination of neutron fluences in reactor pressure vessel and internals - Determination of degradation of materials during operation - Requirements for evaluation of pressurized thermal shock regimes - Evaluation of corrosion-errosion effects in piping - Environmental fatigue evaluation - Evaluation of reactor pressure vessel failure probability Finally, the following appendices dealing with components integrity have been included: - Lifetime of reactor pressure vessel internals - Leak-before-break concept for WWER piping - No-break-zone for WWER piping The paper will describe structure and main principles of this Section IV.

Low-voltage cable as an important power equipment for the safe operation of nuclear power plants, mainly used for the transmission of power and signals, its safe and reliable service is directly related to the safe and stable operation of the power plant, as soon as possible to carry out low-voltage cable aging management and life assessment research on the safe operation of nuclear power plants and the continuation of the operation license are of great significance. In this paper, the research process and method of low-voltage cable aging management and life assessment in nuclear power plants are introduced in detail, and the construction and development of low-voltage cable aging management are put forward.

Modeling interconnections of safety and financial performance of nuclear power plants, part 3: Spatiotemporal probabilistic physics-of-failure analysis and its connection to safety and financial performance

Multi external event probabilistic safety assessment framework

Derivation of dose constraint for the general public around nuclear power plants with operational data of radioactive effluent releases