NDLI: Study of the Effects of Environment in the Fatigue Analysis on Existing LWR as Proposed in USNRC RG 1.207

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Tom, Eugene Dong, Milton Lee, Hong Ming
Copyright Year	2009
Abstract	US NRC Regulatory Guide 1.207 Rev. 0 provides guidance for use in determining the acceptable fatigue life of ASME pressure boundary components, with consideration of the light-water reactor (LWR) environment. Because of significant conservatism in quantifying other plant-related variables (such as cyclic behavior, including stress and loading rates) involved in cumulative fatigue life calculations, the design of the current fleet of reactors is satisfactory. For new plants under design and current operating plants considering applying for License Renewal, the environment effects may need to be considered in the design. RG 1.207 proposes using an environmental correction factor (Fen) to account for LWR environments by correcting the fatigue usage calculated with the ASME “air” curves. The Fen method is presented in NUREG/CR-6909, “Effect of LWR Coolant Environments on the Fatigue Life of Reactor Materials”. By definition, Fen is the ratio of fatigue life of the component material at room temperature air environments to its fatigue life in LWR coolant at operating temperature. To incorporate environmental effects into the fatigue evaluation, the fatigue usage is calculated using provisions set forth in Section III of the ASME Code, and is adjusted by multiplying a correction factor. The calculated Fen values are then used to incorporate environmental effects into ASME fatigue usage factor evaluation. Once the environmental correction factors have been determined, the previously calculated allowable number of cycles for each load set pair based on the current Code fatigue design curve can be adjusted to determine the new fatigue usage factors for environmental effects. This paper presents a study of the effect of the Regulatory Guide if it is to be implemented on the current fleet of LWR. A quick assessment of the sensitivity of the various environmental parameters is also included in this paper. The comparison of environmental effects between the simplified approach in this paper and the results with detailed computer analyses, such as Unisont’s propriety computer code UPIPENB (Ref. 4), will be our next research project to be presented in the future conference.
Sponsorship	Pressure Vessels and Piping
Starting Page	163
Ending Page	170
Page Count	8
File Format	PDF
ISBN	9780791843666
DOI	10.1115/PVP2009-77915
e-ISBN	9780791838549
Volume Number	Volume 3: Design and Analysis
Conference Proceedings	ASME 2009 Pressure Vessels and Piping Conference
Language	English
Publisher Date	2009-07-26
Publisher Place	Prague, Czech Republic
Access Restriction	Subscribed
Subject Keyword	Computers Fatigue life Cycles Temperature Fatigue design Light water reactors Fatigue Fatigue analysis Licensing Pressure Stress Design Coolants Asme standards Operating temperature
Content Type	Text
Resource Type	Article

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