Westinghouse Electric Corporation

Westinghouse Electric Company LLC

David H Roarty

Sam S Palusamy

David E Boyle

George E Rudd

John C Schmertz

Ian L Wilson

David A Eden

Charles B Bond

John C Matarazzo

A high strength bolt fastens a baffle plate and a former plate of a pressurized water nuclear reactor pressure vessel together. The bolt has a head portion and an integral locking member extending from the head portion for engaging one of the structural members to lock the bolt with the structural member. The integral locking member portion has a lower yield stress than the yield stress of the shank. A lower yield stress may be obtained by selective annealing. The locking member is less susceptible to stress corrosion cracking in high temperature, high pressure water of commercial nuclear power reactors.

Bolt with integral locking member

Stress-corrosion damage is monitored in penetrations traversing the wall of a vessel containing an electrolyte, such as a nuclear reactor pressure vessel containing a coolant. The vessel wall has tubular penetrations for coupling external devices to internal structures of the vessel while maintaining a pressure barrier, such as control rod guides and sensor signal cables. The penetrations are subject to stress-corrosion damage, especially adjacent welds affixing the tubes to the vessel head. One or more of the penetrations is provided with a probe forming with the tube an electrochemical sensor cell, including an electrode exposed to the electrolyte together with the surface of the penetration. The electrode and the surface are otherwise insulated, and a plurality of electrodes can be arrayed for monitoring distinct localized areas. The electrodes are wired to a detector circuit developing signals as a function of electrochemical activity due to stress and corrosion, indicative of corrosion of all the penetrations. Electrochemical potential, impedance, current, and particularly noise levels in these signals are detected and read out for assessing deterioration of the penetration surface as a function of the electrochemical activity.

Electrochemical monitoring of vessel penetrations

Temperature transducers are mounted on the outside surface of a containment system such as a pipe to detect thermal stratification and fluctuations thereof. The transducers are mounted in an arc lying in a plane perpendicular to the flow direction in the system at each of several positions separated along the flow direction. The data obtained by the temperature transducers is supplied to a computer for calculation of stress using transfer functions summing changes in both temperature and position over time. The stress due to abnormal thermal loads is combined with other stress on the system so that fatigue usage and fatigue crack growth can be calculated.

Abnormal thermal loading effects monitoring system

A system for analyzing containment integrity of a containment system includes data storage for inspection data and characteristic data and a data evaluation processor for evaluating the inspection data. A data acquisition system is used for periodically obtaining wall thicknesses of selected components in the containment system. After data validation, the actual wall thicknesses are stored as the inspection data in the data storage. The data evaluation processor analyzes the present pipe wall integrity in light of stress calculated from the characteristic data including operational conditions and material properties. In addition, the data evaluation processor analyzes the trend in change of wall thickness to forecast future wall thicknesses.

Corrosion-erosion trend monitoring and diagnostic system

A multi-point wall thickness gage (10) comprises a pad (16) of flexible magnetic material that includes an array of ultrasonic transducers (13) and a multi-point ultrasonic transmitter and receiver (25) to which each transducer (13) is attached. The magnetic pad (16) is attachable to the wall of a ferro-magnetic object (19), and serves to hold the array or matrix of ultrasonic transducers (13) against the wall of the object. The specific region of the object wall being inspected is marked off (17), and the magnetic pad (16) is periodically applied over this region (17). The output of the transducers (13) is used to detect whether any wall thinning is occurring over the particular area of the object covered by the magnetic pad (16), and if so, the particular pattern of thinning within the area. Trend monitoring is simplified since exact relocation of the transducers (13) for periodic measurements is more readily accomplished.

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Murrysville, PA, United States of America

David H Roarty