ML20245F506

Safety Evaluation Re Request for Relief from Section XI Re Hydrostatic Test Requirement

ML20245F506
Person / Time
Site:	Summer
Issue date:	06/22/1989
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20245F444	List: ML20245F440 ML20245F506
References
NUDOCS 8906280157
Download: ML20245F506 (3)

Text

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, SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION' REGARDING A REQUEST FOR RELIEF:FROM SECTION XI-HYDROSTATIC TEST REQUIREMENT-SOUTH CAROLINA ELECTRIC & GAS-CONPANY-

' SOUTH CAROLINA PUBLIC SERVICE AUTHORITY VIRGIL C. SUP9tER NUCLEAR STATION. UNIT NO. 1 DOCKET'NO 50-395 I.- BACKGROUND INFORMATION The. Virgil C.. Summer Nuclear Station Operating License was. issued on August 6, 1982. Paragraph 10 CFR 50.55a(g)(4) requires that throughout

.the service life of.a boiling or pressurized water-cooled nuclear power facility, components, including supports, which are classified as ASME

. Code Class 1: . Class 2 and Class 3 shall meet the requirements set forth in

the applicable'Section XI Editions and Addenda of the ASME Boiler and Pressure Vessel Code.to the extent practical within the limitations of-l design,' geometry and materials of construction of the components. By.

letter dated March 30, 1988, South Carolina' Electric & Gas Company

(licensee) requested: relief'from the hydrostatic test requirements of the 1977. Edition through Summer 1978 Addenda of Section XI of the.ASME Code following: replacement of valves by welding in the steam generator blowdown lines:at Virgil.C. Summer Nuclear Station. The relief request contained information in support of the licensee's determination that the requirement is impractical to perform at Virgil C. Summer Nuclear Station.

II. . REQUEST, REQUIREMENT, AND SUPPORTING INFORMATION A. Relief Request Relief is requested from performing the hydrostatic test of the welds made during replacement of steam generator blowdown isolation valves XVG-503A-BD, XVS-5038-BD, and XVG-503C-BD.

4 B. Blowdown System Function L The blowdown system function is to assist in controlling the chemistry of the secondary side of the steam generator by reducing the soluble and particulate chemical impurities concentrated, by evaporation of secondary water, in the steam generator (SG). By removing a small  !

fraction of the water from the steam generator on a continuous basis, l j.

control of chemical impurities can be achieved.

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, 2 C. System Modification-p The current design of the blowdown isolation valves (XVG-503A, B, and C).is one that is susceptible to thermal binding.- SCE&G intends to

h. replace'these valves with a design that is less susceptible to thermal binding during the next refueling outage scheduled for April 1990. . Design ~and installation will be.in accordance with the ASME, 1 Code,Section XI,'1977 Edition through and. including Summer,'1978

~ Addenda.

D.Section XI Code Requirements The ASME Section XI.' Code requires that, subsequent.to repairs or modifica-

- tions by welding which penev Les the pressure boundary on piping

. greater than one inch diameter, conduct of a hydrostatic test on such piping be performed.

Pursuant to ASME Code,Section XI, 1977 Edition through and including

< Summer 1978 Addenda, hydrostatic test pressure is 1.25 Psv or 1470 PSI where Psv is the lowest pressure setting among the main steam safety valves.

E. Basis for Relief The licenst indicated that performing the required hydrostatic test on the. blowdown piping. subsequent to the modification would be extremely difficult, impractical, and expensive due to the following:

1. Due to the location of the valves to be replaced, a hydrostatic test, as required by the Code, would impact the secondary side of the Steam Generators and portions of the main feedwater, main steam, and blowdown systems.

2. The inability to maintain pressure due to potential leakage through the feedwater isolation valves, main steam isolation valves, and other valves connected to the-system.

3. Additional time and. effort to pin or block main steam constant i support and variable spring hangers.  !

4. Additional time and effort to remove the main steam safety valves and blank the inlet piping.

5. Potential for placing excess stress on the steam generator shells.

6. Potential for damage to system instrumentation and considerable time to isolate or remove instrumentation.

7. Potential for damage to main steam system and its hangers due to static loads caused by water solid condition.

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8. Potential for damage to steam generator tube bundles.

9. Isolation and preparation of this-system would result in -

additional' radiation exposure.to personnel.-

m , - 10. Inadditiontotheabove~nine-(9) reasons,.thealternate examinations specified will provide a . level of confidence and quality equal to or better than' the" required testing per the ASME Code.

~ F .~ Proposed Alternate Examinations Far Steam Generator Blowdown System Piping Welds The licensee has. committed to performing the following examinations on the affected blowdown system piping welds. prior to declaring the blowdown system operable, except for, Item 4, which will.be completed at the end of the first inspection interval:

l'. Magnetic particle testing examination on the root pass and the final weld surface pursuant to ASME Code Section.V, Article 7.

2.  : Visual examination.

3. Perform inservice leak test at nominal operating pressure.

4. Perform hydrostatic test at the'end of the 10 Year interval.

III. STAFF EVALUATION AND CONCLUSION The staff has reviewed the licensee's justification'for the. request.for relief from performing the Section XI testing ~on the steam generator blowdown valves.: The staff has. determined.that it is impractical to perform the' Code-required hydrostatic test on the welds made during replace-ment of valves XVG-503A-BD, XVG-502B-BD, and XVG-503C-BD.because the valves cannot be isolated from the secondary side of the' steam generators, the-main steam,. and main feedwater systems. To accomplish the hydrostatic test. requirements would cause-the steam generators to be subjected to 1470  !

psig also, .a pressure cycle not. warranted or accounted for in their design. {

'The licensee's proposed alternate examinations (magnetic particle _ testing, I visual examination and an inservice leak test) will provide assurance i that the welds'made during the replacement of the~ steam generator blowdown 1 isolation, valves are structurally sound. The staff, therefore,. concludes that )

relief from the hydrostatic test requirements of the 1977 Edition through- l Summer 1978 Addenda of Section XI of the ASME Code for the subject welds may be granted under 10 CFR 50.55a(g)(5)and(6).

Principal Contributor: G. Johnson Dated: June 22, 1989 -

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