Monitoring With Good Cause — Basic Principles and Current Status

2013 ◽  
Author(s):  
Horst Rothenhöfer ◽  
Andreas Manke
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Holistic Approach ◽  
Economic Benefits ◽  
Current Status ◽  
Special Importance ◽  
Basic Principles ◽  
Term Operation ◽  
Fatigue Monitoring

With the interest in long term operation of nuclear power plants there is a growing interest in monitoring the degradation of a component. The intention is to prevent failures, leakages and incidents and thus enhance safety and reliability of a plant. While researchers are developing new sensors and technologies, there is a long tradition in fatigue monitoring in Germany and a growing number of plants in other countries is implementing that well-proven methodology. This paper summarizes the current status and long-term experience of fatigue monitoring and explains the basic principles and benefits. It declares why fatigue has a special importance among other degradation mechanisms in a holistic approach. Fatigue monitoring is a combination of load monitoring and fatigue assessment methods. More than 30 years of monitoring have revealed that unspecified loads and unexpected load cycles do occur in service that could violate the integrity of safety relevant components. The knowledge of real load histories not only results in realistic usage factors but empowers operators to optimize operation modes for preventing failures and reducing the annual increments of fatigue usage. Numerous examples — such as leaking valves, unintended valve switching, fluctuating thermal stratification or water hammer — demonstrate that unintended or unexpected loads occur every now and then at different locations with different causes. To discover these loads immediately after occurrence means a direct feedback about root causes for degradation which is a valuable decision support for appropriate corrective or preventive actions. Fatigue monitoring has proved to enhance safety and to generate significant economic benefits. Now it is time to make it an international standard.

Guided Waves as an Online Monitoring Technology for Long-Term Operation in Nuclear Power Plants: Experimental Results on a Steam Discharge Pipe

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Mauro Cappelli ◽  
Francesco Cordella ◽  
Francesco Bertoncini ◽  
Marco Raugi
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Guided Waves ◽  
Complex Structure ◽  
Theoretical Background ◽  
Guided Wave ◽  
Experimental Results ◽  
Term Operation

Guided wave (GW) testing is regularly used for finding defect locations through long-range screening using low-frequency waves (from 5 to 250 kHz). By using magnetostrictive sensors, some issues, which usually limit the application to nuclear power plants (NPPs), can be fixed. The authors have already shown the basic theoretical background and simulation results concerning a real steel pipe, used for steam discharge, with a complex structure. On the basis of such theoretical framework, a new campaign has been designed and developed on the same pipe, and the obtained experimental results are now here presented as a useful benchmark for the application of GWs as nondestructive techniques. Experimental measures using a symmetrical probe and a local probe in different configurations (pulse-echo and pitch-catch) indicate that GW testing with magnetostrictive sensors can be reliably applied to long-term monitoring of NPPs components.

Research Activities in the European Union on Ageing Management for Long Term Operation of Nuclear Power Plants

2010 ◽  
Author(s):  
Oliver Martin ◽  
Antonio Ballesteros ◽  
Christiane Bruynooghe ◽  
Michel Bie`th
Keyword(s):  
Energy Supply ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Age Distribution ◽  
Term Operation ◽  
Research Activities ◽  
Ageing Management ◽  
The Eu

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.

Long-Term Operation of BWR RPV and its Internals

2018 ◽  
Author(s):  
Otso Cronvall
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Pilot Project ◽  
Computational Time ◽  
Degradation Mechanisms ◽  
Irradiation Embrittlement ◽  
Screening Process ◽  
Term Operation ◽  
Operational Lifetime

This study concerns the long-term operation (LTO) of a boiling water reactor (BWR) reactor pressure vessel (RPV) and its internals. The main parts of this study are: survey on susceptibility to degradation mechanisms, and computational time limited ageing analyses (TLAAs). The ageing of nuclear power plants (NPPs) emphasises the need to anticipate the possible degradation mechanisms. The BWR survey on susceptibility to these uses the OL1/OL2 RPVs and significant internals as a pilot project. It is not necessary to carry out the TLAAs for all components. Some components were excluded from the TLAAs with a screening process. To do this, it was necessary to determine the component specific load induced stresses, strains and temperature distributions as well as cumulative usage factor (CUF) values. For the screened-in components, the TLAAs covered all significant time dependent degradation mechanisms. These include (but are not limited to): • irradiation embrittlement, • fatigue, • stress corrosion cracking (SCC), and • irradiation accelerated SCC (IASCC). For the components that were screened-in, the potential to brittle, ductile or other degradation was determined. Only some of the most significant cases and results are presented. According to the analysis results, the operational lifetime of the OL1/OL2 RPVs and internals can safely be extended from 40 to 60 years.

Fracture Toughness Predictive Models Within the SOTERIA EU Project

2018 ◽  
Author(s):  
P. M. James ◽  
M. Berveiller
Keyword(s):  
Cleavage Fracture ◽  
Nuclear Power ◽  
Power Plants ◽  
Radiation Effects ◽  
Austenitic Stainless Steels ◽  
Irradiation Damage ◽  
Tensile Behaviour ◽  
Horizon 2020 ◽  
Term Operation

SOTERIA is focused on the ‘safe long term operation of light water reactors’. This will be achieved through an improved understanding of radiation effects in nuclear structural materials. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under agreement No 661913. The overall aim of the SOTERIA project is to improve the understanding of the ageing phenomena occurring in ferritic reactor pressure vessel steels and in the austenitic internals in order to provide crucial information to regulators and operators to ensure safe long-term operation (LTO) of existing European nuclear power plants (NPPs). SOTERIA has set up a collaborative research consortium which gathers the main European research centers and industrial partners who will combine advanced modelling tools with the exploitation of experimental data to focus on two major objectives: i) to identify ageing mechanisms when materials face environmental degradation (such as e.g. irradiation and corrosion) and ii) to provide a single platform containing data and tools for reassessment of structural components during NPPs lifetime. This paper provides an overview of the ongoing activities within the SOTERIA Project that are contained within the analytical work-package (WP5.3). These fracture aspects are focused on the estimates of fracture in both ferritic steels and irradiation assisted stress corrosion cracking (IASCC) in austenitic stainless steels, under irradiated conditions. This analytical development is supported by analytical estimates of irradiation damage and the resulting changes in tensile behaviour of the steels elsewhere in SOTERIA, as well as a wider number of experimental programmes. Cleavage fracture estimates are being considered by a range of modelling estimates including the Beremin, Microstructurally Informed Brittle Fracture Model (MIBF), JFJ and Bordet Models with efforts being made to understand the influence of heterogeneity on the predicted toughness’s. Efforts are also being considered to better understand ductile void evolution and the effect of plasticity on the cleavage fracture predictions. IASCC is being modelled through the INITEAC code previously developed within the predecessor project Perform 60 which is being updated to incorporate recent developments from within SOTERIA and elsewhere.

Fatigue Monitoring in the Context of Long-Term Operation of the Goesgen Nuclear Power Plant Using AREVA’s FAMOSi

2015 ◽  
Author(s):  
Thomas Wermelinger ◽  
Florian Bruckmüller ◽  
Benedikt Heinz
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Primary Circuit ◽  
Feed Water ◽  
Term Operation ◽  
Operation Modes ◽  
Fatigue Monitoring ◽  
Load Evaluation

In the context of long-term operation or lifetime extension most regulatory bodies demand from utilities and operators of nuclear power plants to monitor and evaluate the fatigue of system, structures and components systematically. As does the Swiss Federal Nuclear Safety Inspectorate ENSI. The nuclear power plant Goesgen started its commercial operation in 1979 and will go into long-term operation in 2019. The increased demand for monitoring and evaluating fatigue due to the pending long-term operation led the Goesgen nuclear power plant to expand the scope of their surveillance and therefore to install AREVA’s fatigue monitoring system FAMOSi in the 2014 outage. The system consists of 39 measurement sections positioned at the primary circuit and the feed-water nozzles of the steam generators. The locations were chosen due to their sensitivity for fatigue. The installed FAMOSi system consists of a total of 173 thermocouples which were mounted in order to get the necessary input data for load evaluation. The advantage of FAMOSi is the possibility to obtain real data of transients near places with highest fatigue usage factors. Examples of steam generator feed-in during heating-up and cooling-down will be given. In addition, spray events before and after the installation of closed loop controlled spray valves will be compared. The measurements and the results of the load evaluation are not only of interest for internal use e.g. in regard to optimization of operation modes (e.g. load-following), but must also be reported to ENSI annually. In addition, by evaluation of stresses and determination of usage factors combined with an optimization of operation modes an early exchange of components can be avoided.

Regulatory Perspectives on Fitness for Service Assessments of CANDU Pressure Boundary Components

2017 ◽  
Author(s):  
John C. Jin ◽  
Blair Carroll
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Management Program ◽  
Steam Generators ◽  
Operating Life ◽  
Term Operation ◽  
Pressure Tubes ◽  
Extended Operation ◽  
Condition Assessments

Major pressure boundary components such as pressure tubes, feeder pipes and steam generators at some Canadian CANDU nuclear power plants are entering periods of extended operation beyond their initially assumed operating life. The Canadian Nuclear Safety Commission (CNSC) has approved their long term operations based on the assurance of fitness for service of those components which was composed of condition assessments and aging management programs carried out and implemented by the Canadian licensees. The condition assessments were conducted to demonstrate that components would be within their design basis for the period of intended long term operation and the aging management program was implemented to ensure that the conditions of the components would be maintained as evaluated in the condition assessments and to monitor if new degradation mechanisms would become active. This paper presents the CNSC regulatory practice adopted in the course of technical reviews of fitness for service assessments of major pressure boundary components conducted by Canadian nuclear licensees to demonstrate the safe long term operation of major components can be achieved.

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