ML20211L248
| ML20211L248 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 06/27/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20211L254 | List: |
| References | |
| NUDOCS 8607020034 | |
| Download: ML20211L248 (3) | |
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ENCLOSURE g
SAFETY EVALUATION REPORT ON REQUEST FOR RELIEF FROM INSERVICE INSPECTION REQUIREMENTS VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 DOCKET NOS. 50-280 & 50-281 BACKGROUND By letter dated April 24, 1986, Virginia Electric and Power Company (the licensee) requested relief from certain inservice examination requirements of the 1980 Edition through Winter 1980 Addenda of Section XI of the ASME Code at Surry Power Station Units 1 and 2.
This report provides an evaluation of the licensee's inservice inspection (ISI) relief request, supporting information, and alternative examinations or tests, as well as the staff's bases for granting or denying the request pursuant to 10 CFR 50.55a(g). The relief granted remains in effect for the second ten-year inspection interval. Tl.a relief is not " permanent" because the staff requires a licensee to submit new ISI programs for every ten-year inspection interval. Furthermore, new Code editions with different requirements will be incorporated by reference in future issues of 10 CFR 50.55a(b), and the ISI technology advances will improve the examination capabilities of future inspections. The relief request is evaluated below.
EVALUATION OF RELIEF REQUEST Inside Radius Sections of Category B-D & C-B Nozzles on Steam Generators and Pressurizer i
Code Requirement The Code requires that the nozzle inside radius section of Category B-D and C-B nozzles on the steam generator and pressurizer must be examined volumetrically in accordance with subsections IWB-2500 and IWC-2500 during each inspection interval. Categories B-D and C-B include nozzles with full penetration welds to the vessel shell (or head) and integrally cast nozzles, but exclude manways and handholes either welded to or integrally cast in the vessel.
If the examinations are conducted from inside the component and the nozzle weld is examined by straight beam ultrasonic method from the nozzle bore, the remaining examinations required to be conducted from the shell may be perfonned at or near the end of each inspection interval.
Code Relief Request Relief is requested from the volumetric examination requirements of the nozzle inner radii for the steam generator and pressurizer nozzles.
Licensee Basis for Relief Relief from examining the Code required volume is requested based upon the following criteria:
8607020034 860627 PDR ADOCK 05000280 0
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(1) Nozzles in the pressurizer and steam generators contain inherent geometric constraints and clad inner surfaces which limit the ability to perform meaningful volumetric (UT) examinations of the inner radii areas.
The pressurizer surge line nozzle I.D. is physically restricted by the sparger, the thermal sleeve, and heater bank interferences. The steam
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generator main steam nozzles are physically restricted by the flow limiting devices.
1 (2) Presently, there is no comprehensive inspection technique, or guidance for such in the ASME Code, which would provide a conclusive assessment of the Code required volumetric inspections of these inner radii, particularly since no preservice results are available for review.
(3) Radiography (RT) is not a viable inspection technique due to the same i
inherent geometric constraints and accessibility limitations that restrict the effectiveness of the ultrasonic inspection method.
In addition, high radiation levels on primary system nozzles would expose radiographic film, causing it to " fog" beyond acceptable standards.
Licensee Proposed Alternative Test (1) All five (5) pressurizer upper head nozzles shall be visually examined 2
from the I.D. using direct or remote techniques when accessible prior to the end of the inspection interval. Two nozzles are scheduled for such inspection this refueling outage.
(2) The lower pressurizer nozzle shall be visually examined from the 0.D.
after this refueling when the unit has restarted and reached normal operaHng pressure and temperature.
(3) Category B-D, primary inlet and outlet nozzles on one steam generator shall be visually examined from the I.D., using manual or remote techniques during this outage. The other two steam generators will be examined sequentially during upcoming inspection periods, prior to the end of the inspection interval.
i (4) The steam generator feedwater nozzle thermal sleeve restricts access to the inside radius area of the nozzle. A visual inspection of the accessible areas of the inside radius will be performed during this outage for one steam generator and prior to the end of the inspection interval for the other two steam generators.
(5) The flow limiting device installed in the steam generator main steam nozzle restricts access to the nozzle inside radius area. One main steam nozzle shall be visually inspected from the 0.D. after this refueling when the unit has restarted and reaches normal operating pressure and temperature. The remaining two main steam nozzles will be inspected as above prior to the end of the inspection interval.
r Staff Evaluation and Conclusions Volumetric examination of the nozzle inside radius sections from the internal surface is difficult because of geometric constraints. Also, the radiation exposure to the inspector is a factor.
Meaningful volumetric examination of the nozzle inside radius sections from the external surface is difficult with existing inspection equipment. Typical nozzle configurations involve different radii of curvature on the inside and outside surfaces in the transition region where the inside radius section is to be examined. Changes in section thickness are also typical in this region.
These geometric factors result in unreliable interpretation of examination data. Current radiographic methods are also of little use in detecting fine surface cracks on the inside radius of nozzles.
The licensee proposes a combination of visual examinations from the I.D. and 0.D. of the nozzles.
Furthermore, the Code-required system leakage and hydrostatic tests will provide assurance of the integrity of the nozzles.
Based on the staff's evaluation and the licensee's discussion above, Code requirements are impractical.
It is further concluded that the alternative examinations discussed above will provide necessary added assurance of the nozzles' structural reliability. Therefore, relief from the volumetric examination requirements of the nozzle inner radii for the steam generator and pressurizer nozzles may be granted as requested.
Principal Contributor S. Lee l
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