Overview of the use of prestressed concrete in U.S. nuclear power plants

Ashar, H.; Naus, D.J.

doi:10.1016/0029-5493(83)90009-2

Cited by 12 publications

(9 citation statements)

References 4 publications

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“…Tendons that have been stored on site for long periods with no protection or that have not been properly protected once installed, but prior to the application of permanent corrosion protection, can have degradation. Ashar et al (1994) also discuss findings of containments with lower than expected prestressing levels. In one case, several hoop tendons' prestressing levels measured at three years after posttensioning were lower than levels predicted to occur after 40 years.…”

Section: Introductionmentioning

confidence: 86%

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Capacity of Prestressed Concrete Containment Vessels with Prestressing Loss

Smith

2001

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Reduced prestressing and degradation of prestressing tendons in concrete containment vessels were investigated using finite element analysis of a typical prestressed containment vessel. The containment was analyzed during a loss of coolant accident (LOCA) with varying levels of prestress loss and with reduced tendon area. It was found that when selected hoop prestressing tendons were completely removed (as if broken) or when the area of selected hoop tendons was reduced, there was a significant impact on the ultimate capacity of the containment vessel. However, when selected hoop prestressing tendons remained, but with complete loss of prestressing, the predicted ultimate capacity was not significantly affected for this specific loss of coolant accident. Concrete cracking occured at much lower levels for all cases. For cases where selected vertical tendons were analyzed with reduced prestressing or degradation of the tendons, there also was not a significant impact on the ultimate load carrying capacity for the specific accident analyzed. For other loading scenarios (such as seismic loading) the loss of hoop prestressing with the tendons remaining could be more significant on the ultimate capacity of the containment vessel than found for the accident analyzed. A combination of loss of prestressing and degradation of the vertical tendons could also be more critical during other loading scenarios. 5 Acknowledgment

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Section: Introductionmentioning

confidence: 86%

“…Also, vertical tendons were found with excessive loss of prestressing during inspections that occurred about 13 years after post-tensioning. Ashar et al (1994) suggested that contributing factors were improper calibration of the jacks during the initial post-tensioning, higher than expected assumed losses, and failures in quality control.…”

Section: Introductionmentioning

confidence: 99%

Capacity of Prestressed Concrete Containment Vessels with Prestressing Loss

Smith

2001

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“…Although continuing the service of a NPP past the initial operating license period is not expected to be limited by the concrete structures, several incidences of age-related degradation have been reported [39][40][41][42][43][44]. Examples of some of these problems include corrosion of steel reinforcement in water intake structures, corrosion of post-tensioning tendon wires, leaching of tendon gallery concrete, low prestressing forces, and leakage of corrosion inhibitors from tendon sheaths.…”

Section: Operating Experiencementioning

confidence: 99%

“…Causes were primarily related either to improper material selection and construction/design deficiencies, or environmental effects. Examples of some of the problems attributed to these deficiencies include low 28-day concrete compressive strengths, voids under the post-tensioning tendon bearing plates resulting from improper concrete placement; cracking of post-tensioning tendon anchor heads due to stress corrosion or embrittlement; and containment dome delaminations due to low quality aggregate materials and absence of radial steel reinforcement or unbalanced prestressing forces [40][41][42]. Other construction-related problems included occurrence of excessive voids or honeycomb in the concrete, contaminated concrete, cold joints, cadweld (steel reinforcement connector) deficiencies, materials out of specification, higher than code allowable concrete temperatures, misplaced steel reinforcement, post-tensioning system button-head deficiencies, and water-contaminated corrosion inhibitors [37].…”

Section: Operating Experiencementioning

confidence: 99%

Overview of activities in the U.S. related to continued service of nuclear power plant concrete structures

Naus

2011

EPJ Web of Conferences

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Abstract. Safety-related nuclear power plant concrete structures are described and commentary on continued service assessments of these structures is provided. In-service inspection and testing requirements in the U.S. are summarized. The license renewal process in the U.S. is outlined and its current status noted. A summary of operating experience related to U.S. nuclear power plant concrete structures is presented. Several candidate areas are identified where additional research would be of benefit to aging management of NPP concrete structures. Finally current ORNL activities related to aging-management of concrete structures are outlined: development of operating experience database, application of structural reliability theory, and compilation of elevated temperature concrete material property data and information.

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“…Pre-stressed concrete pressure vessels contain the reactor coolant fluid at the high operating pressures and temperatures experienced dur-ing operation, while containment vessels are designed to contain any release of radioactive material from the reactor circuit housed within the building in the event of a fault. These passive barriers are essential to a nuclear reactor's safety strategy, so the evolu-tion of their structural integrity has been the focus of decades of continuous monitoring and research (Ashar and Naus, 1983;Park, 2010). As concrete is weak under tension, PCVs can only func-tion effectively if their levels of compressive prestress, supplied by steel prestressing tendons, remains above a minimum design load.…”

Section: Introductionmentioning

confidence: 99%

High stress monitoring of prestressing tendons in nuclear concrete vessels using fibre-optic sensors

Perry

Yan

Sun

et al. 2014

Nuclear Engineering and Design

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Maintaining the structural health of prestressed concrete nuclear containments is a key element in ensuring nuclear reactors are capable of meeting their safety requirements. This paper discusses the attachment, fabrication and characterisation of optical fibre strain sensors suitable for the prestress mon-itoring of irradiated steel prestressing tendons. The all-metal fabrication and welding process allowed the instrumented strand to simultaneously monitor and apply stresses up to 1300 MPa (80% of steel's ulti-mate tensile strength). There were no adverse effects to the strand's mechanical properties or integrity. After sensor relaxation through cyclic stress treatment, strain transfer between the optical fibre sen-sors and the strand remained at 69%. The fibre strain sensors could also withstand the non-axial forces induced as the strand was deflected around a 4.5 m bend radius. Further development of this technology has the potential to augment current prestress monitoring practices, allowing distributed measurements of short-and long-term prestress losses in nuclear prestressed-concrete vessels.

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Overview of the use of prestressed concrete in U.S. nuclear power plants

Cited by 12 publications

References 4 publications

Capacity of Prestressed Concrete Containment Vessels with Prestressing Loss

Capacity of Prestressed Concrete Containment Vessels with Prestressing Loss

Overview of activities in the U.S. related to continued service of nuclear power plant concrete structures

High stress monitoring of prestressing tendons in nuclear concrete vessels using fibre-optic sensors

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