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Maintenance Strategies implemented in the research:<\/p>\n\n\n\n
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We have chosen a service life of 80 years for the four critical systems studied<\/strong>. This choice is based on real industrial practices, where extending the operational life of nuclear plants has become increasingly common. For example, the Oconee Nuclear Station in the United States was recently authorized to operate for 80 years<\/strong>, showing that this service life is realistic for major nuclear infrastructures. It also corresponds to the expected lifetime of the parking garage, shuttle tunnel, and containment building, which are designed to remain functional for several decades with regular maintenance.<\/p>\n\n\n\n For the pedestrian passage, the usual service life of urban sidewalks is around 40 years, but they experience much higher traffic than the passage in our plant. In this case, the pedestrian passage will see limited use and will be regularly maintained, allowing its service life to align with the 80 years of the other infrastructures.<\/p>\n\n\n\n Although there are generally three types of maintenance (preventive, corrective, and predictive), in nuclear plants predictive maintenance is continuously performed 24\/7 and is considered an integral part of normal system operation. As a result, it is not included in our optimization study, since it is always in effect.<\/p>\n\n\n\n For the four critical systems considered in this study, there are two types of maintenance: one preventive maintenance and two corrective maintenance strategies with different intervention frequencies.<\/p>\n\n\n\n In this study, the four infrastructures (parking garage, pedestrian passage, shuttle tunnel, and nuclear containment building) are considered as an integrated system whose purpose is to ensure safe plant operation and continuous accessibility for qualified personnel. The overall system is defined as functional only when all four subsystems are operational simultaneously. This is necessary for safety reasons: the nuclear plant cannot operate without the containment building, and personnel such as operators, engineers, and technicians, who perform daily monitoring and supervision tasks, require access via the parking garage, pedestrian passage, and shuttle tunnel, as explained at the beginning of this report. If any one of these subsystems is unavailable due to maintenance, the integrated system is considered to be in a degraded state and plant operation must be suspended. The service level objective adopted in this work is therefore to maximize the long-term availability of the integrated system, which is quantified by minimizing the total number of plant shutdown days over the 80-year service life. Since the maintenance interventions of the different subsystems are independent and of different types, it is possible to bundle multiple interventions together in the same outage, allowing all necessary tasks to be performed simultaneously and improving the overall efficiency of maintenance planning.<\/p>\n\n\n\n For each of the subsystem in our current system the types of interventions shown is the following: <\/p>\n\n\n\n VI- Visual Inspection\/Routine Examination<\/strong><\/p>\n\n\n\n This is the representation of the lowest level of intervention and it’s quite logically sound for any maintenance. It consists of systemic visual surveys to identify early signs of deterioration through non-destructive tests or checks. For different systems the checks are different. For concrete which is the check for all of the systems in the current scope of the study, early signs of deterioration such as cracking, surface degradation, moisture ingress, leakage. VI does not include restoration of structural capacity, but it is rather a condition assessment and decision making for higher-level maintenance actions (OECD\/NEA; International Atomic Energy Agency, 2007). Similarly asset management for tunnels or sidewalks, infrastructure in general include and describe inspection activities as frequent low-impact actions intended to maintain acceptable service and safety levels (International Tunnelling and Underground Space Association, 2011; Federal Highway Administration, 2017). As the requirements for this maintenance is minimal the relative repair interventions are quite short regardless of the subsystem.<\/p>\n\n\n\n SR- Surface Repair \/ Surface Protection (SR)<\/strong><\/p>\n\n\n\n Surface repair interventions focus on the localized durability related damage that will accelerate deterioration if it is untreated and will eventually affect the structural performance. The actions that are typical for this maintenance action are patch repairs, treatment of spalling, delamination, crack sealing and localized damage repair (American Concrete Institute, 2013; International Atomic Energy Agency, 2007). The technical workflow of surface repair is common across civil infrastructure sectors therefore this maintenance action is considered across all of the systems. As it is a well defined and widely applied durability intervention action. <\/p>\n\n\n\n In nuclear containment structures, aging management frameworks identify explicitly the localized surface degradation and loss of protective function as conditions which require timely repair to prevent long-term structural and functional impairment (International Atomic Energy Agency, 2007; OECD\/NEA). Parking structures are quite vulnerable to the spalling and corrosion caused by water and salt exposure as the current project is near surface water and lakes. Therefore it is quite necessary for recurrent repairs of such nature (American Concrete Institute, 2013). Tunnel linings commonly experience cracking, leakage and localized lining defects which are managed through the surface level repairs to maintain safety and the durability of the tunnel (PIARC, 2016). For sidewalks, partial and surface level repairs are the standard practice according to the federal highway administration (Federal Highway Administration, 2014; 2017). The duration of the intervention is governed by the repair scope and the concrete curing requirements. <\/p>\n\n\n\n DR- Deep Repair \/ Rehabilitation \/ Replacement (DR)<\/strong><\/p>\n\n\n\n Deep repair, rehabilitation or replacement refers to a high severity maintenance type of intervention that restores or replaces the structural component due to the structural integrity of the system being compromised. These interventions typically involve removal of degraded concrete and then replacement of the reinforcement or reconstruction of the structural concrete elements. In contrast to surface repair, DR interventions are solely made to address the structural capacity and long term safety aspects of the structural element (American Concrete Institute, 2013). <\/p>\n\n\n\n Across the systems considered in the study, DR interventions are due to long term exposure to environmental actions, loading and material ageing and these conditions that cannot be mitigated by repairing localized issues alone. In nuclear containment structures the maintenance management guides explicitly state and identify the major rehabilitation of the reinforced concrete as necessary as stated in (International Atomic Energy Agency, 2007; OECD\/NEA). For parking structures, deep repairs take shape in the form of structural replacement when corrosion-induced damage compromises slabs or load bearing elements, as described in the concrete repair and rehabilitation standards outlined in the American Concrete Institute (American Concrete Institute, 2013). Tunnel maintenance guidelines outline a similar repair strategy which includes major rehabilitations as deep interventions (International Tunnelling and Underground Space Association, 2011; PIARC, 2016). For sidewalks, full deck replacement is considered when partial repairs are no longer effective as reflected in the pedestrian infrastructure asset-management guide. The durations associated with the DR interventions are based on the curing activity and the quality control requirements. <\/p>\n\n\n\n As shown in the table above the interruption time required for any of the visual inspections is one day. This is considered enough for any of the maintenance engineers or inspectors to visually inspect all of the systems as it was previously discussed that those inspections are not considered to require a high amount of effort or machinery therefore, it seems prudent to have them at a day each. <\/p>\n\n\n\n Nuclear Containment Building<\/strong><\/p>\n\n\n\n For the nuclear containment building the interventions were considered based on the International Atomic Energy Agency. (2007). Ageing management of concrete structures in nuclear power plants (IAEA Nuclear Energy Series No. NP-T-3.5). IAEA. They consider the average for surface protection, spalling and delamination repairs to average about 2 weeks for each intervention, therefore an assigned interruption duration of 12 days, which is consistent with the guidance as the current nuclear containment building is not as big as usual nuclear containment buildings and therefore a decrease was warranted (International Atomic Energy Agency, 2007). Rehabilitation or repair of the reinforced concrete elements (DR.n) was assigned a longer interruption of duration of 28 days, the averages are from several weeks to a few months, as mentioned before the size of the building is on the smaller range, 4 weeks is appropriate for the partial replacement (U.S. Nuclear Regulatory Commission, 2011). <\/p>\n\n\n\n Parking Garage Structure<\/strong><\/p>\n\n\n\n For the parking structure, surface protection, spalling repair and delamination repair they were assigned an interruption duration of 7 days. Although concrete repair will reach early strength within a few days, the guidance for the parking structures guides emphasize that adequate curing and strength development are essential due to repetitive vehicle loading and high live loads (American Concrete Institute, 2013). One week of interruption aligns with common practice as mentioned in the American Concrete Institute. While partial replacement interventions are assigned 15 days, which reflect the need for concrete placement and curing times. For large areas curing times are better for 14 days and load verification prior to reinstating service where structural capacity is affected (ACI, 2013; Silva et al., 2018).<\/p>\n\n\n\n Shuttle Tunnel<\/strong><\/p>\n\n\n\n The tunnel’s second maintenance is for localized damage repair, which was assigned an interruption duration of 10 days. Due to the safety coordination that is typical of tunnel maintenance operations (International Tunnelling and Underground Space Association, 2011), it is appropriate to choose 10 days for this interruption. Limited repairs to tunnel linings and drainage systems often required staged execution and extended closure periods to ensure worker safety and system integrity. Large-scale replacement is assigned a 21 day interruption, this is for major system upgrades, which typically take from 3 weeks to a couple of months, while the tunnel is only 700 meters therefore it is expected that the range of interruption is on the minimum range. <\/p>\n\n\n\n Sidewalk System<\/strong><\/p>\n\n\n\n For the sidewalk system, partial repair interventions (SR.s) were assigned a 5-day interruption, consistent with guidance on partial-depth concrete pavement repairs that require saw-cutting, removal of deteriorated concrete, placement of repair material, and curing before reopening to pedestrian use (Federal Highway Administration, 2014). Deck replacement interventions (DR.s) were assigned a 10-day interruption, which is considered appropriate given the assumed lower pedestrian demand compared to dense urban environments. Reduced usage allows for longer closure durations without significant service disruption, while still accommodating demolition, replacement, curing, and safety checks (Federal Highway Administration, 2017; Zhang et al., 2019).<\/p>\n\n\n\n Main <\/a>| Introduction <\/a>| Integration Context<\/a> | Maintenance Strategies<\/a> | Life-Cycle Analysis<\/a> | Multi-Objective Optimization<\/a> | Conclusion<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" Maintenance Strategies implemented in the research: We have chosen a service life of 80 years for the four critical systems studied. This choice is based on real industrial practices, where extending the operational life ofContinue reading<\/a><\/p>\n","protected":false},"author":280,"featured_media":0,"parent":26284,"menu_order":3,"comment_status":"closed","ping_status":"closed","template":"page-templates\/page_fullwidth.php","meta":{"footnotes":""},"class_list":["post-26439","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"http:\/\/141.23.68.248\/wp\/index.php?rest_route=\/wp\/v2\/pages\/26439","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/141.23.68.248\/wp\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/141.23.68.248\/wp\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/141.23.68.248\/wp\/index.php?rest_route=\/wp\/v2\/users\/280"}],"replies":[{"embeddable":true,"href":"http:\/\/141.23.68.248\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=26439"}],"version-history":[{"count":15,"href":"http:\/\/141.23.68.248\/wp\/index.php?rest_route=\/wp\/v2\/pages\/26439\/revisions"}],"predecessor-version":[{"id":26836,"href":"http:\/\/141.23.68.248\/wp\/index.php?rest_route=\/wp\/v2\/pages\/26439\/revisions\/26836"}],"up":[{"embeddable":true,"href":"http:\/\/141.23.68.248\/wp\/index.php?rest_route=\/wp\/v2\/pages\/26284"}],"wp:attachment":[{"href":"http:\/\/141.23.68.248\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=26439"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Sub-Systems, Interventions and Intervals <\/h2>\n\n\n\n
Subsystem<\/strong><\/td> Intervention<\/strong><\/td> Acronym<\/strong><\/td> Interval (years)<\/strong><\/td><\/tr> Nuclear Containment Building<\/td> Detailed Examination and visual inspection<\/td> VI.n<\/td> 4<\/td><\/tr> Surface protection, spalling repair and delamination repair<\/td> SR.n<\/td> 11<\/td><\/tr> Rehabilitation\/Repair of reinforced concrete<\/td> DR.n<\/td> 26<\/td><\/tr> Parking Garage Structure<\/td> Routine Maintenance and visual inspection<\/td> VI.p<\/td> 6<\/td><\/tr> Surface protection, spalling repair and delamination repair<\/td> SR.p<\/td> 12<\/td><\/tr> Partial Replacement<\/td> DR.p<\/td> 20<\/td><\/tr> Shuttle Tunnel<\/td> Routine Maintenance and visual inspection<\/td> VI.t<\/td> 5<\/td><\/tr> Localized damage repair<\/td> SR.t<\/td> 10<\/td><\/tr> Large-scale Replacement<\/td> DR.t<\/td> 25<\/td><\/tr> Urban Sidewalk<\/td> Visual inspection and minor maintenance<\/td> VI.s<\/td> 3<\/td><\/tr> Partial Repair<\/td> SR.s<\/td> 10<\/td><\/tr> Deck Replacement<\/td> DR.s<\/td> 20<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n Interventions and their respective Interruption <\/h2>\n\n\n\n
Subsystem<\/strong><\/td> Intervention<\/strong><\/td> Acronym<\/strong><\/td> Interruption (days)<\/strong><\/td><\/tr> Nuclear Containment Building<\/td> Detailed Examination and visual inspection<\/td> VI.n<\/td> 1<\/td><\/tr> Surface protection, spalling repair and delamination repair<\/td> SR.n<\/td> 12<\/td><\/tr> Rehabilitation\/Repair of reinforced concrete<\/td> DR.n<\/td> 28<\/td><\/tr> Parking Garage Structure<\/td> Routine Maintenance and visual inspection<\/td> VI.p<\/td> 1<\/td><\/tr> Surface protection, spalling repair and delamination repair<\/td> SR.p<\/td> 7<\/td><\/tr> Partial Replacement<\/td> DR.p<\/td> 15<\/td><\/tr> Shuttle Tunnel<\/td> Routine Maintenance and visual inspection<\/td> VI.t<\/td> 1<\/td><\/tr> Localized damage repair<\/td> SR.t<\/td> 10<\/td><\/tr> Large-scale Replacement<\/td> DR.t<\/td> 21<\/td><\/tr> Sidewalk<\/td> Visual inspection and minor maintenance<\/td> VI.s<\/td> 1<\/td><\/tr> Partial Repair<\/td> SR.s<\/td> 5<\/td><\/tr> Deck Replacement<\/td> DR.s<\/td> 10<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
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