Ultrasonic defect detection and size approximation using thin annulus probes

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:72573

Light, G M; Fisher, J L; Tennis, R F; Stolte, J S; Hendrix, G J ^[1]

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1. Southwest Research Inst., San Antonio, TX (United States)

Concern has been generated recently about the capabilities of performing nondestructive evaluation (NDE) of the closure head penetrations in nuclear-reactor pressure vessels (PV). These penetrations, primarily for instrumentation and control rod drive mechanisms (CRDMs), are usually thick-walled Inconel tubes, shrink-fitted into the steel closure head. The penetrations are then welded between the outside surface of the penetration and inside surface of the closure head. Stress corrosion cracks initiating at the inner surface of the penetration have been reported at several plants. Through wall cracks in the CRDM penetration or CRDM weld could lead to loss of PV coolant. The penetration presents a complex geometry for conventional NDE techniques. A thermal sleeve, through which pass the mechanical linkages for control-rod operation, is inserted into the penetration so that only a small annulus (nominally 3 mm) exists between the thermal sleeve and inside surface of the penetration. SwRI has developed and evaluated ultrasonic techniques for sizing defects in this area. Long, thin probes were designed to fit into the annulus to carry irrigated ultrasonic transducers into the region of interest. The probes were used to detect cracks in the penetration and to estimate remaining wall thickness.

• OSTI ID: 72573
• Report Number(s): CONF-931061--; ISBN 0-87170-506-0
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
ANNULAR SPACE
CONTROL ROD DRIVES
CRACK PROPAGATION
EVALUATION
GUIDE TUBES
IN CORE INSTRUMENTS
PRESSURE VESSELS
REACTOR CONTROL SYSTEMS
ULTRASONIC TESTING
WELDED JOINTS