Reactor process water (PW) piping inspections, 1984--1990
In July 1983, the NRC ordered the shutdown of five boiling water reactors (BWR`s) because of concerns about reliability of ultrasonic examination for detecting intergranular stress corrosion cracking (IGSCC). These concerns arose because of leaking piping at Niagara Mohawk`s Nine Mile Point which was attributed to IGSCC. The leaks were detected shortly after completion of ultrasonic examinations of the piping. At that time, the Dupont plant manager at Savannah River (SR) directed that investigations be performed to determine if similar problems could exist in SR reactors. Investigation determined that all conditions believed necessary for the initiation and propagation of IGSCC in austenitic stainless steel exist in SR reactor process water (PW) systems. Sensitized, high carbon, austenitic stainless steel, a high purity water system with high levels of dissolved oxygen, and the residual stresses associated with welding during construction combine to provide the necessary conditions. A periodic UT inspection program is now in place to monitor the condition of the reactor PW piping systems. The program is patterned after NRC NUREG 0313, i.e., welds are placed in categories based on their history. Welds in upgraded or replacement piping are examined on a standard schedule (at least every five years) while welds with evidence of IGSCC, evaluated as acceptable for service, are inspected at every extended outage (15 to 18 months). This includes all welds in PW systems three inches in diameter and above. Welds are replaced when MSCC exceeds the replacement criteria of more than twenty percent of pipe circumference of fifty percent of through-wall depth. In the future, we intend to perform flow sizing with automated UT techniques in addition to manual sizing to provide more information for comparison with future examinations.
- Research Organization:
- Westinghouse Savannah River Co., Aiken, SC (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC09-89SR18035
- OSTI ID:
- 10133814
- Report Number(s):
- WSRC-MS-90-308; CONF-9011174-4; ON: DE92009855
- Resource Relation:
- Conference: 32. meeting of the Weapons Agencies Nondestructive Testing Organization (WANTO),Aiken, SC (United States),27-29 Nov 1990; Other Information: PBD: [1990]
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
REACTOR COOLING SYSTEMS
ULTRASONIC TESTING
P REACTOR
C REACTOR
K REACTOR
L REACTOR
PIPES
WELDED JOINTS
INTERGRANULAR CORROSION
STRESS CORROSION
HEAT TRANSFER
HYDRAULICS
INSPECTION
AUSTENITIC STEELS
DISSOLVED GASES
220900
220600
360105
REACTOR SAFETY
RESEARCH
TEST
TRAINING
PRODUCTION
IRRADIATION
MATERIALS TESTING REACTORS
CORROSION AND EROSION