ML19253C009
| ML19253C009 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 10/11/1972 |
| From: | US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML19253C007 | List: |
| References | |
| NUDOCS 7911040016 | |
| Download: ML19253C009 (2) | |
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TOPICAL REPORT EVALUATION Report Identification: BAW-10047, Revision 1
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A Study of Discontinuities in Control Rod Drive Motor Tube Report
Title:
Extensions Report Date:
August 1972 Originating Organization: Babcock & Wilcox Materials Engineering Branch, Mechanical Engineering Branch Reviewed By:
and Reactor Systems Branch, AEC Directorate of Licensing SUWd1Y OF TOPICAL REPORT Some motor extension tubes exhibited localized variations in wall thick-ness and discontinuities on the inner surface, not detected by ultra-sonic testing techniques certified to be in accordance with ASME Code, The investigation included metallographic and chemical Section III.
examinations, specialized ultrasonic inspection techniques and fracture mechanics analysis.
Tubes meeting the Code-required minimum wall thickness based on the original design temperature of 650*F and having no indicated dis-continuities deeper than 5% of the nominal-finish wall thickness will be accepted and returned to the field for service.
n Where wall thickness permits, discontinuity indications greater than 5%
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of the nominal-finish wall thickness will be reduced by honing the I.D.
surface of the tubes while maintaining the ASEE Code,Section III Tubes required wall thickness based on the original design temperature.
will then be reexamined ultrasonically for discontinuity depth and for proper wall thickness.
The remaining tubes withheld, because of wall thickness, will be re-evaluatcd based on a revised design temperature of 450*F, which is a more realistic but stil. conservative value of the maximum temperature ion tubes will operate. The basis f or this at which the upper exterr revised temperatura has been established by extensive mockup testing at A testing the Alliance Research Center and measurements at Oconee 1.
and surveillance program will also be implemented on one of the first 1505 122 79110400 g
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facilities utilizing the affected motor tube extensions in order to verify that the mockup tests accurately siculated the operating condi-tions of a typical f acility.
SUMMARY
OF REGULATORY EVALUATION Repair of tubes which showed excessive discontinuities has been accom-plished by honing the I.D., which is allouable in accordance with ASME Code,Section III, Class 1 Compohents, paragraph NB-2558.
Some motor tube extensions have localized variations and some repaired
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tubes also had a wall thickness below the Code-allouable thickness for a design condition of 650*F and 2500 psig. These tubes were re-evaluted on the basis of 450*F and 2500 psig, uhich is allowabic by ASME Code,Section III, Class 1 Components, paragraph NB-3112.2 The actual caximum metal te=perature which exists under the specified normal oper-ating condition was determined by mockup testing and measurement at Oconee 1.
Specialized ultrasonic test inspection techniques have been developed to accurately defir_e the depth of discontinuities. Indicated discontinuity depths no greater than 5% of the nominal vall thickness are allowed.
This is in accordance with ASME Code,Section III, Class 1 Compcnents, paragraph NB-2552.1.
A fracture mechanics analysis by Southwest Research Institute h..s con-cluded that a 90 mil notch in the worst case longitudinal direction is acceptable f or the design life of the tube. We concur with the SRI findings.
REGULATORY POSITION We conclude that the motor tube extensions accepted under the criteria proposed by B&W have an adequate margin of safety and that the subj2ct report is acceptable provided the results of the testing and sur-These results veillance program are densistent with the mockup tests.
should be documented by a revision or supplement to this ' Topical Report.
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