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Author: U.S. Atomic Energy Commission Publisher: ISBN: Category : Nuclear reactors Languages : en Pages : 6
Book Description
The events described in this report illustrate different malfunctions that have occurred at pressurized water reactors involving control rods or control rod drives. All malfunctions were detected during testing periods; none compromised safety of the plant. In one instance, deposits of epoxy-like material on the faces of the clutches in control rod drive mechanisms (CRDM's) caused failures of single control rods to drop on signal. In a second case, CRDM's were damaged when they were dropped with the hydraulic dashpots either empty or only partially filled because of inadequate venting through housing seals. Third, intermittent response to withdraw and insert signals on one control rod was traced to a dragging motor brake on the CRDM. Finally, loose dowel pins used to position the stationary brake discs were found to be the cause of mis-positioned control rods.
Author: U.S. Atomic Energy Commission Publisher: ISBN: Category : Nuclear reactors Languages : en Pages : 6
Book Description
The events described in this report illustrate different malfunctions that have occurred at pressurized water reactors involving control rods or control rod drives. All malfunctions were detected during testing periods; none compromised safety of the plant. In one instance, deposits of epoxy-like material on the faces of the clutches in control rod drive mechanisms (CRDM's) caused failures of single control rods to drop on signal. In a second case, CRDM's were damaged when they were dropped with the hydraulic dashpots either empty or only partially filled because of inadequate venting through housing seals. Third, intermittent response to withdraw and insert signals on one control rod was traced to a dragging motor brake on the CRDM. Finally, loose dowel pins used to position the stationary brake discs were found to be the cause of mis-positioned control rods.
Author: U.S. Atomic Energy Commission. Division of Operational Safety Publisher: ISBN: Category : Nuclear reactors Languages : en Pages : 2
Book Description
A manual control rod drive switch failure during operation of a research reactor caused the withdrawl of one of the control rods. The reactor power level had increased almost 15% above the planned steady state level when the operator manually shut the reactor down. There were no personnel radiation exposures and no damage occurred as a result of the power increase.
Author: Publisher: ISBN: Category : Languages : en Pages : 13
Book Description
An aging assessment of PWR control rod drive (CRD) systems has been completed as part of the US NRC Nuclear Plant Aging Research (NPAR) Program. The design, construction, maintenance, and operation of the Babcock & Wilcox (B & W), Combustion Engineering (CE), and Westinghouse (W) systems were evaluated to determine the potential for degradation as each system ages. Operating experience data were evaluated to identify the predominant failure modes, causes, and effects. This, coupled with an assessment of the materials of construction and operating environment, demonstrate that each design is subject to degradation, which if left unchecked, could affect its safety function as the plant ages. An industry survey, conducted with the assistance of EPRI and NUMARC, identified current CRD system maintenance and inspection practices. The results of this survey indicate that some plants have performed system modifications, replaced components, or augmented existing preventive maintenance practices in response to system aging. The survey results also supported the operating experience data, which concluded that the timely replacement of degraded components, prior to failure, was not always possible using existing condition monitoring techniques. The recommendations presented in this study also include a discussion of more advanced monitoring techniques, which provide trendable results capable of detecting aging.
Author: Publisher: ISBN: Category : Languages : en Pages : 5
Book Description
An aging assessment of the Westinghouse Pressurized Water Reactor (PWR) Control Rod System (CRD) has been completed as part of the US NRC's Nuclear Plant Aging Research, (NPAR) Program. This study examined the design, construction, maintenance, and operation of the system to determine its potential for degradation as the plant ages. Selected results from this study are presented in this paper. The operating experience data were evaluated to identify the predominant failure modes, causes, and effects. From our evaluation of the data, coupled with an assessment of the materials of construction and the operating environment, we conclude that the Westinghouse CRD system is subject to degradation which, if unchecked, could affect its safety function as a plant ages. Ways to detect and mitigate the effects of aging are included in this paper. The current maintenance for the control rod drive system at fifteen Westinghouse PWRs was obtained through a survey conducted in cooperation with EPRI and NUMARC. The results of the survey indicate that some plants have modified the system, replaced components, or expanded preventive maintenance. Several of these activities have effectively addressed the aging issue. 2 refs., 2 figs., 2 tabs.
Author: U.S. Atomic Energy Commission. Reactor Engineering Division. Chicago Operations Office Publisher: ISBN: Category : Electric power-plants Languages : en Pages : 284
Author: U.S. Atomic Energy Commission
Author: U.S. Atomic Energy Commission
Author: U.S. Atomic Energy Commission. Division of Operational Safety
Author: Warren H. Hubble
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Author: U.S. Atomic Energy Commission. Reactor Engineering Division. Chicago Operations Office
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Author: United States. Congress. Senate. Governmental Operations Committee