Operation During the PEO: Difference between revisions
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Revision as of 19:12, 4 October 2024
There are aspects of operation during the period of extended operation (PEO) that are in addition to the long-term operation (LTO) activities for pre-PEO and post-PEO implementation.
Plant Modifications[edit]
- Installation of new systems or components is performed under the plant’s processes for modifications, design changes, and construction or installation.
- There are no requirements for consideration of license renewal aging management for newly installed equipment. This is based on the remaining life of the plant being less than 40 years. However, the existing plant processes for modifications, design changes, etc. do require consideration of preventive maintenance practices, inspections, surveillance, and other design considerations for the expected remaining life of the plant. This includes potential impact to existing aging management programs that are applicable to the modification or design change (e.g., EQ program, ISI program, water chemistry program, etc.).
- An example would be replacement of a diesel driven fire pump with a completely new assembly (pump, diesel engine, gear box, etc.) because of operational problems with the diesel engine. From a license renewal perspective, the diesel engine is an active component and not subject to aging management, but the lube oil cooler for the gear box is a long lived, passive component subject to aging management for reduction of heat transfer. Also, from a license renewal perspective, the remaining lifetime of the new assembly is less than 40 years, so it is not subject to aging management under 10 CFR 54. However, the heat exchanger should still be regularly cleaned and inspected to make sure it will function when needed. This is part of regular operational maintenance which should be performed even though it is not required for license renewal 10 CFR 54. Similar maintenance would be performed on the diesel engine and the fire water pump.
- There may be consideration of impacts on the aging of components that are in the scope of license renewal due to a plant modification.
- An example would be the installation of a stainless steel valve in a water filled system that has all carbon steel piping, valves, and other components. The stainless steel valve was installed because the original carbon steel valve had failed, could not be repaired (e.g. the valve stem had broken), and there were no carbon steel valves available to install in place of the original valve. The stainless steel could set up a situation where galvanic corrosion could result in loss of material in the carbon steel piping attached to the new stainless steel valve. The carbon steel piping should be periodically inspected to determine if galvanic corrosion was occurring.
Obsolescence[edit]
The response to equipment which becomes obsolete and can no longer be maintained or repaired is no different during the PEO than during the original term of the operating license. Obsolescence occurs when the manufacturer no longer makes the necessary parts to repair or replace plant equipment. This has frequently occurred for control systems and components. One example is the analog recorders and indicators in the main control room which have been replaced with digital devices due to obsolescence. When equipment is replaced because of obsolescence, during the PEO, no license renewal considerations are needed because there are less than 20 years of operation remaining, unless the plant plans to renew the license for a second time and operates the plant for 80 years. See the section on Subsequent License Renewal for information on how the newly installed equipment is treated in the subsequent license renewal application.
Supply Chain[edit]
Despite the aging of nuclear power plants (NPPs), global indicators show steady improvement in performance due to replacements, technological advances, enhanced aging management, and safety measures implemented in a timely manner. As long as investments and improvements are continued, performance levels should not decline and may actually improve with LTO.
LTO of nuclear power plants is only possible if countries can ensure its success, which also requires access to a robust supply chain that provides high quality components at a reasonable cost. System, Structure and Component (SSC) obsolescence and supply chain issues have nevertheless become an emerging source of concern over recent years because of policy uncertainties and degraded market perspectives, combined with high qualification needs. These trends vary from country to country depending on the size and standardization of domestic nuclear programs. Thus far, the nuclear industry has been able to manage these risks with the introduction of commercial grade dedication, and higher collaboration and harmonization levels.
According to IAEA-TECDOC-2034, “Suitability Evaluation of Commercial Grade Products for Use in Nuclear Power Plant Safety Systems”, nuclear grade products are designed, manufactured, tested, or inspected specifically for nuclear facilities. However, commercial grade products are those which were not designed, manufactured, tested, or inspected according to regulation, codes, or standards specific to the nuclear industry.
Both prior to and during the LTO period, NPPs must identify when and how commercial-grade products can be used to avoid the issues mentioned above. This analysis can be conducted based on factors such as the importance of safety, risk, and technological complexity. It is also important to consider supply chain factors, taking into account that commercial-grade products tend to have a larger installed base and, consequently, are manufactured on a larger scale. This may mean that commercial-grade products may have advantages or disadvantages over nuclear-grade products from the perspective of an operating organization's supply chain management function.
A procurement engineering function has originated in some countries due to these concerns. The main functions of procurement engineering are to identify item technical, quality, and commercial requirements, and to perform item equivalency evaluations and commercial grade dedication in timely manner.
To conclude, NPPs must ensure that their supply chain is in place, and it will remain available during the period of LTO. For that purpose, the following references provide information on the proper supply chain management and procurement:
- NP-T-3.21, “Procurement Engineering and Supply Chain Guidelines in Support of Operation and Maintenance of Nuclear Facilities”, IAEA
- TECDOC-2034 “Suitability Evaluation of Commercial Grade Products for Use in Nuclear Power Plant Safety Systems”, IAEA
- TECDOC-1740, “Use of graded approach is the application of the management system requirements for facilities and activities”, IAEA
- NP-6629, “Guidelines for the Procurement and Receipt of Items for Nuclear Power Plants”, EPRI
- TR-1008256, “Guidelines for the Technical Evaluation of Replacement Items in Nuclear Power Plants”, EPRI
Knowledge Management[edit]
An essential challenge for ensuring the safety, reliability, and efficiency of the operating and construction of nuclear power plants (NPP) lies in the competence of its personnel. The capability of NPP operating organizations to make safe decisions and undertake appropriate actions can be compromised by knowledge gaps or loss over time. In addition, countries with existing nuclear programs or those expanding their nuclear power programs must ensure they possess the requisite capacities and human resources to maintain the safe operation of existing installations. This includes the challenges associated with the LTO period, decommissioning and with spent fuel and waste programs.
Therefore, it is crucial to create suitable and efficient techniques for knowledge management, while also utilizing relevant technology. This is essential for nuclear knowledge retention, ensuring its availability throughout the entire life cycle of a nuclear power plant, including Long-Term Operation (LTO).
Recognizing the importance of nuclear knowledge management, the IAEA has developed NG-G-6.1 , “Guide to Knowledge Management Strategies and Approaches in Nuclear Energy Organizations and Facilities”. This reference provides useful information on issues related to various aspects such as the benefits of knowledge management for a facility, its integration into the existing organizational structure, and the associated time and effort. Moreover, it offers guidance for implementing a strategic knowledge management program that can provide both financial and security benefits, in addition to reducing the risk of knowledge loss.
A knowledge management program is more likely to be successful when it is built upon a clear strategy and a set of underpinning objectives of benefit that align with the organization's objectives. The first step of crafting a knowledge management strategy is to define the specific challenges to be addressed. This involves conducting an assessment of the organization’s current nuclear knowledge and comparing it with the knowledge necessary for achieving safe, efficient and sustainable organizational performance.
To support the establishment of that strategy, TECDOC-1880 , “Planning and Execution of Knowledge Management Assist Visits for Nuclear Organizations” describes a model approach for conducting a quantitative self‑assessment of knowledge management maturity in nuclear organizations.
IAEA references useful to develop and maintain an effective knowledge management are the following:
- NG-G-6.1, “Guide to Knowledge Management Strategies Approaches in Nuclear Energy Organizations and Facilities”.
- NG-T-6.10. “Knowledge Management and Its Implementation in Nuclear Organizations”, IAEA.
- NG-T-6.11 . “Knowledge Loss Risk Management in Nuclear Organizations”.
- TECDOC-1880, “Planning and Execution of Knowledge Management Assist Visits for Nuclear Organizations”.
- TECDOC-1999, “Mentoring and Coaching for Knowledge Management in Nuclear Organizations”.
Subsequent License Renewal[edit]
The U.S. NRC process to extend plant licenses under 10 CFR 54 allows multiple 20-year extensions. The process to renew a plant’s license the second time is the same as for the first license renewal. The second license renewal application will be based on the plant’s current licensing basis, which includes the first license renewal application and the commitments made to manage the effects of aging. One of the major considerations in a subsequent license renewal application is the effectiveness of the aging management programs at managing aging, and any changes that were needed.
One consideration that a plant must make when operating with a license that has been renewed once, either during the initial 40 years or during the PEO, is the decision making process for maintaining the entire plant so it operates safely, economically and efficiently. The license renewal process focuses on the plant operating safely but does not consider the impact on operation of plant systems and equipment that are not relied upon to maintain the plant safely.
One example is the main turbine electrical generator. The main turbine electrical generator typically can operate for 40 years with normal routine maintenance but does not require major overhauls or replacement. However, for operations beyond 40 years, additional maintenance may be needed. The main generator may need to be rewound to operate for 80 years but could operate for 60 years with a major cleaning of the windings. When the decision is made for the major cleaning the remaining life of the plant should be considered. If the plan is to operate only for 60 years and then decommission the plant, a major cleaning of the generator rotor would be the economically smart decision, but if the plans were to renew the license a second time and operate for 80 years, then the smart decision would be to rewind the main generator rather than the less expensive major cleaning. If the main generator rotor was only cleaned between 40 and 60 years, it would have to be rewound between 60 and 80 years, so the economical choice would be to rewind the generator between 40 and 60 years.
When a second license renewal application is prepared, any systems or components that were installed in the plant after the first renewed license was issued will now be in the scope of the second application. This equipment, because it was installed after the first renewed license was issued, was not subject to aging management even though it would have been in the scope of license renewal if in the plant when the first application was prepared. Because this equipment will be in scope of a second license renewal application, the plant should consider beginning to manage aging of this equipment during the first 60 years of operation and then continuing to manage aging during the second period of operation from 60 to 80 years.
Record of Revisions[edit]
| Number | Date | Description of Changes |
|---|---|---|
| 0 | 6/11/2024 | Initial version |