Research On Life Estimation Method Of Components In Nuclear Power Plants Based On Local Accelerated Aging

Because of the accident in Fukushima Daiichi Nuclear Power Station, the safetystandard and requirement to Nuclear Power Plants(NPPs) has reached a higher level allover the world. ForNPPs especially for those in the late period, component failurecaused by aging would be a great threat to safety and productivity. Measures takenagainst this threat is only some related surveillance and management according tooperating experience feedback from similar NPPs at present. However, localenvironmental conditions in different NPPs vary significantly and some factors in theworking environment may cause accelerated aging to components, which may changethe life of them andleads to failures deviating from operating experience feedback.These failures will worsen the safety of NPPs and bring extra expenses. Therefore theysignificantly influence the NPP operation plan and life cycle management ofcomponents.Usually there exists few failure data of components in NPPs, which leads to theabsence of a high degree confidence in the result through traditional life estimationmethod.While accelerated life tests are carried out in predetermined stresses withoutconsidering environmental factors in an integrated way. Againstaccelerated aging ofNPPs components, a life estimation method of components in NPPs under localaccelerated aging is established. The method takes all the integrated environmentalfactors affecting componentsinto account and analysis performance degradation databesides failure life datain order to quantitatively evaluate the influence of workingenvironment on the life of components. The completed research and correspondingresults are as follows:(1)A research on the aging mechanisms of metal pipeline, polymer and electroniccomponents in NPPs has been accomplished. Related aging mechanisms, acceleratedaging stresses and empirical formulas about performance parameter or failure life areobtained as the basis of accelerated aging models.(2)Based on aging mechanisms, taking all the integrated environmental factors intoaccount, An integrated algorithm of life estimation method of components in NPPsunder local accelerated aging, which is applicable to failure life data and performance degradation data of all components and materials, is established and presented. Throughthis method, an integrated accelerating aging model, accelerated aging factors can becalculated and obtained.All these results can be used to quantitatively evaluate theinfluence of local environment on components life, and they can be used directly inengineering application or reference.(3)A software based on Matlab to implement the calculation process of lifeestimation method of components in NPPs under local accelerated aging is programmed.And the algorithm and software are proven correct by a random sample.On the basis of research and analysis of aging mechanisms of components, thisthesis presents a new life estimation method of components in NPPs under localaccelerated aging in order to better analyze accelerated aging phenomena in NPPs. Themethod provides direct data reference and technical support in the decision-makingprocess of NPPs components life cycle management and improves the safety andproductivity of NPPs.