Building the Technical Case for Long-Term Operation

2015 ◽  
Author(s):  
Richard Tilley ◽  
Robin Dyle
Keyword(s):  
Operating Experience ◽  
Academic Community ◽  
Degradation Mechanisms ◽  
Comprehensive Understanding ◽  
Term Operation ◽  
Societal Benefits ◽  
Actual Operating ◽  
Nuclear Plants ◽  
The Us

United States (US) and International utilities are actively engaged in assessing the economic and societal benefits of operating nuclear plants beyond their initial license periods. Nuclear plant generated electricity is still the largest contributor to non-carbon dioxide emitting generation. In the US, a majority of operating plants has already received approval for an additional 20 years of operation, and soon it is expected that utilities will begin the process to seek a second 20 year renewal. The keys to successful renewal are to maintain safe and reliable operations by building a sound technical case through the following activities: • Develop comprehensive understanding of aging degradation issues for systems, structures and components (SSCs) • Implement specific plant aging management programs to address aging degradation • Confirm behavior of degradation mechanisms for the entire period of operation This paper will step through the above elements to illustrate how a strong technical case may be created for safe and reliable long-term operation. Examples or case studies will be provided to clearly link the fundamental science of materials degradation to the inspection, testing and evaluation efforts implemented at a plant and to the confirmatory data that is provided by both actual operating experience and the extensive research and development projects pursued by industry, governments, and the academic community.

License Renewal and Subsequent License Renewal in the U.S.

2014 ◽  
Author(s):  
Garry G. Young
Keyword(s):  
Nuclear Industry ◽  
Significant Progress ◽  
Safe Operation ◽  
Term Operation ◽  
Nuclear Plants ◽  
The Status ◽  
License Renewal ◽  
The U.S ◽  
Operating Plant

As of February 2014, the NRC has renewed the operating licenses for 73 nuclear units, allowing for up to 60 years of safe operation. In addition, the NRC has license renewal applications under review for 18 units and 9 additional units have announced plans to submit applications over the next few years [1]. This brings the total of renewed licenses and plans for renewal to 100% of the operating nuclear units in the U.S. By the end of 2014, there will be 38 nuclear plants that will have operated for more than 40 years and will be eligible to seek a subsequent license renewal (or almost 40% of the nuclear units expected to be operating at the end of 2014). In 2013, nuclear plant owners of 5 units shutdown operation or announced plans to shutdown by the end of 2014. However, most of the remaining operating plant owners are keeping the option open for long term operation beyond 60 years. NRC and the U.S. nuclear industry have made significant progress in preparing the way for subsequent license renewal applications. This paper presents the status of the U.S. license renewal process and issues being addressed for possible applications for subsequent renewals for up to 80 years of operation.

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.

Application of Metallographic Methods for Thermal Ageing Evaluation on Samples from Primary Piping of NPP

2017 ◽  
Vol 891 ◽  
pp. 60-66
Author(s):  
Jana Petzová ◽  
Martin Březina ◽  
Miloš Baľák ◽  
Mária Dománková ◽  
Ľudovít Kupča
Keyword(s):  
Material Properties ◽  
Nuclear Power ◽  
Power Plants ◽  
Operating Temperature ◽  
Thermal Ageing ◽  
Primary Circuit ◽  
Degradation Mechanisms ◽  
Reliable Operation ◽  
Term Operation

During a long-term operation of nuclear power plants (NPP), the changes of structural material properties occur. To ensure the safe and reliable operation, it is necessary to monitor and evaluate these changes mainly on components from primary circuit of NPPs. One of the dominant ageing mechanisms of NPP components besides the radiation embrittlement and the fatigue loads is the thermal ageing. The thermal ageing is the temperature, material and time dependent degradation mechanisms due to long-term exposure at the operating temperature of 570 K.This paper describes the project for thermal ageing monitoring at primary piping in NPP Bohunice Unit 3. There are summarized the results obtained from evaluation of original primary piping material.

Turbine Blade Tip Clearance Improvement

1991 ◽  
Author(s):  
B. Glezer
Keyword(s):  
Turbine Blade ◽  
Operating Experience ◽  
Engine Performance ◽  
Tip Clearance ◽  
Analytical Prediction ◽  
Term Operation ◽  
Extensive Field ◽  
Blade Tip ◽  
Blade Tip Clearance

A recently developed non-traditional design concept addressing turbine blade tip clearance reduction to provide long-term engine performance improvement and stability is presented. The concept is based on the direct attachment of the diaphragm, which supports Stage 1 integral nozzle and tips shroud segments, to the bearing housing, thus providing a close thermal link between the rotor and the stator. Transient thermal matching between the rotating and stationary structures was based on analytical prediction. Results of the complex turbine hot section study including cooling flow, thermal, stress, and deflection analyses are presented. An advanced tip clearance measurement technique was used in the full scale engine test to verify the analytical predictions. The potential to reduce tip clearance to less than 1% of blade height without blade tip rubs has been demonstrated. Extensive field operating experience with more than 100 Centaur Type ‘H’ engines showed very light or no blade tip rub and corresponding engine performance stability during long-term operation.

Subsequent License Renewal in the U.S.

2015 ◽  
Author(s):  
Garry G. Young ◽  
Jason Remer
Keyword(s):  
New York ◽  
New York Times ◽  
Nuclear Industry ◽  
News Article ◽  
Term Operation ◽  
Nuclear Plants ◽  
The Status ◽  
License Renewal ◽  
The U.S

As of January 2015, the NRC has renewed the operating licenses for 75 nuclear units, allowing for up to 60 years of safe operation. In addition, the NRC has license renewal applications under review for 19 units and 5 additional units have announced plans to submit applications over the next few years. This brings the total of renewed licenses and plans for renewal to almost 100% of the operating nuclear units in the U.S. At the end of 2014 there were 38 nuclear plants that had operated for more than 40 years and are eligible to seek a second license renewal (or 38% of the operating units). [1] Although some nuclear plant owners have shutdown operation recently and others have announced plans to shutdown before reaching 60 years, the majority are keeping the option open for long term operation beyond 60 years. NRC and the U.S. nuclear industry have made significant progress in preparing the way for second license renewal applications. For example, in October 2014, 7 nuclear units were identified as the leading candidates for subsequent license renewal in a New York Times news article. This paper presents the status of the issues being addressed for possible applications for second license renewals for up to 80 years of operation.

scholarly journals Long-term operation of a boiling pressure vessel and its internals

2019 ◽  
Vol 52 (4) ◽  
pp. 200-221
Author(s):  
Otso Cronvall
Keyword(s):  
Power Plant ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Power Plants ◽  
Pilot Project ◽  
Computational Time ◽  
Degradation Mechanisms ◽  
Term Operation ◽  
Reactor Pressure

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 the susceptibility to degradation mechanisms, and computational time limited ageing analyses (TLAAs). The ageing of nuclear power plants (NPPs) emphasizes the need to anticipate the possible degradation mechanisms. The BWR survey on the susceptibility to these mechanisms uses the RPVs and significant internals of the Olkiluoto power plant units OL1 and OL2 as a pilot project. For the components that screened in, the potential to brittle, ductile or other degradation is determined. This was carried out by applying structural mechanics and fracture mechanics procedures. Only some most significant cases and results are presented here.

The Role of Failure Data in Plant Aging Management and Life Extension

2008 ◽  
Author(s):  
Alan D. Chockie ◽  
Frank E. Gregor
Keyword(s):  
Nuclear Regulatory Commission ◽  
The United States ◽  
Nuclear Industry ◽  
Life Extension ◽  
Aging Research ◽  
Failure Data ◽  
Nuclear Plants ◽  
The Us ◽  
Regulatory Commission

The aging management and life extension process for the United States (US) nuclear industry has been refined and improved over the years. It has become an efficient and effective method to ensure that the nuclear plants in the US can be safely operated beyond their original 40-year operating license. The wealth of failure data from Nuclear Regulatory Commission and industry aging research programs in combination with plant specific data has provided a strong technical foundation for the aging management and long-term plant operation. This paper examines the role that generic and plant specific failure data has played in the development, application, and refinement of aging management and life extension efforts at US nuclear plants.

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