[en] The subject of life extension of nuclear power plants has drawn considerable attention during the last few years. Interest in life extension initiated because of both safety and economic reasons. A number of evaluations have been performed. The main thrust of earlier work was directed toward evaluating the factors causing aging, and defining degradation sites, degradation mechanism and failure modes. At present, attention is directed toward establishing the appropriate inspection programs suitable for each of the defined aging sites. Some components and aging sites are already subjected to routine inspection programs such as the surveillance of post-tensioning system and the integrated leak rate test (ILRT) of prestressed concrete and reinforced concrete containments. The aging process affects mechanical, electrical and structural components in all types of containments. This paper addresses the structural components of PWR containments only and presents examples of inspection approaches and describes methods to prevent further degradation of select sites

[en] This report presents an assessment of the aging (time-dependent degradation) of selected major light water reactor components and structures. The stressors, possible degradation sites and mechanisms, potential failure modes and currently used nondestructive examinations, in-service inspection (ISI) and life assessment methods are discussed for seven major light water reactor components: pressurized water reactor (PWR) and boiling water reactor (BWR) pressure vessels, PWR containment structures, PWR reactor coolant piping, PWR steam generators, BWR recirculation piping, and reactor pressure vessel supports. Unresolved technical issues related to life extension of these components, including requirements for advanced ISI and life assessment methods, are also discussed

[en] Nuclear power plant owners and regulatory commissions have recently turned their attention to evaluating the aging characteristics of such plants. The purpose of the evaluation is two-fold, safety and economy. The major safety consideration of a containment structure is it be capable of preventing the leakage of radioactive material to the outside environment. Early identification of possible degradation areas and implemantation of protective measures is far less expensive than allowing deterioration to progress to the point major repairs become necessary. In order to assess aging effects, an evaluation has been performed to identify the degradation factors, degradation sites, and degradation mechanisms for prestressed concrete containment structures and postulate possible occurrences. (orig.)

[en] The main function of the post-tensioning system is to provide the primary concrete containment with the capability to resist the tension forces caused by internal accident pressure. This function is accomplished by introducing permanent, counteracting compression forces. The post-tensioning system consists of high strength wire or strand tendons placed inside ducts formed within the containment walls and dome. Each tendon end is attached to an anchorhead which transfers the highly stressed tendon tension load to steel bearing plates embedded in concrete. The exposed ends of of the tendons are sealed with steel caps and the entire system is protected against corrosion by filling the void area in the ducts and caps with a specially formulated petroleum grease. (orig.)

[en] A simplified method for prediction of creep in concrete is presented. Predicted values are compared with actual test results and with values computed using the ACI recommended method. In addition, a study of the effect of load history on the volume change characteristics of structural concrete is presented and qualitatively compared to actual structural behavior. (orig./HP)

[en] The material presented herein summarizes the progress that has been made in the analysis, design, and testing of concrete structures

[en] The material presented in this paper summarizes the progress that has been made in the analysis, design, and testing of concrete structures. The material is summarized in the following documents: Part I: Containment Design Criteria and Loading Combinations; Part II: Reinforced and Prestressed Concrete Behavior; Part III: Concrete Containment Analysis, Design and Related Testing; Part IV: Impact and Impulse Loading and Response Prediction; Part V: Metal Containments and Liner Plate Systems; Part VI: Prestressed Reactor Vessel Design, Testing and Analysis. (orig.)