HNP-98-161, Requests Relief from 1989 Edition of ASME Code Section XI,IWA-4120 Requirements for Repair of Control Rod Drive Mechanism Housing Seal Weld.Supporting Calculation,Encl
| ML18016A708 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 11/04/1998 |
| From: | Scarola J CAROLINA POWER & LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML18016A709 | List: |
| References | |
| HNP-98-161, NUDOCS 9811120029 | |
| Download: ML18016A708 (8) | |
Text
CATEGORY 1 REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)
A+>7CFilSSION NBR 9 8 1 1 1 2 0 02 9 DOC ~ DATE 9 8/ 1 1/04 NOTARIZED NO FACXL:50-<00, Shearon Harris Nuclear Power Plant, Unit 1, Carolina AUTH.NPQ4a AUTHOR AFFILXATION NCAROLA,J.
Carolina Power 8 Light Co.
RECIP. NAME RECIPIENT AFFILIATION Records Management Branch (Document Control Desk)
DOCKET OS000400
SUBJECT:
Requests relief from 1989 Edition of ASME Code Section XI,IW A-4120 requirements for repair of control rod drive mechanism housing seal weld. Supporting calculation, encl.
DIsTRIBUTICN coDE:
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TXTLE: OR Submittal: Inservice/Testing/Relief from ASME Code - GL-89-04 NOTES:Application for permit renewal filed.
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Carolina Power &Light Company PO Box 165 New Hill NC 27562 James Scarola Vice President Harris Nuclear Plant NO'lt - 4 1998 SERIAL: HNP-98-161 10 CFR 50.55a United States Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, DC 20555 SHEARON HARRIS NUCLEARPOWER PLANT DOCKET NO. 50-400/LICENSE NO. NPF-63 INSERVICE INSPECTION PROGRAM RELIEF REQUEST NO. 2R1-012 ALTERNATIVETO ASME CODE SECTION XI,IWA-4000 REQUIREMENTS
Dear Sir or Madam:
In accordance with 10 CFR 50.55a(a)(3)(ii), Carolina Power &LightCompany (CP&L) requests telief from the 1989 Edition of the American Society of Mechanical Engineers (ASME) Code Section XI,IWA-4120 requirements for repair of a Control Rod Drive Mechanism (CRDM) housing seal weld. Specifically, NRC approval of an alternative to the surface (liquid penetrant) examination requirement for a repair of a leaking CRDM housing lower canopy seal weld is requested.
Section XIof the Code requires that repairs be performed in accordance with the Owner's original Construction Code of the component or system, or later editions and addenda of the Construction Code. The Harris Nuclear Plant's (HNP) CRDM housing canopy seal welds were designed and fabricated in accordance with the 1974 Edition including Winter 1976 Addenda of Section IIIof the ASME Code (Construction Code). Both this edition and the 1989 edition of Section III(NB-5271, Welds of Specially Designed Seals) require a suiface examination for CRDM housing seal welds. A repair of a CRDM housing lower canopy seal weld willbe petfotmed in accordance with the 1989 Edition ofASME Section III.
As patt of the HNP Refueling Outage 8 (RFO 8) activities, during CRDM area inspection for boric acid leakage, indication ofboric acid was found under the insulation around the top of the t~actor vessel head.
The boric acid was detetmined to be coming from the CRDM housing lower canopy seal weld. The CRDM housing canopy seal weld requires repair prior to the reactor vessel head being placed back on the HNP reactor vessel as part of the activities to complete RFO
- 8. A weld buildup willbe used to repair the weld. Even though the canopy seal does not provide structural strength for the joint, the weld buildup over the canopy seal is considered a repair under the rules ofASME Code Section XI, IWA-4000, because the welding is peiformed on pressure retaining components.
In addition, in order to facilitate the weld buildup repair, a portion of the associated Reactor Vessel Level Instrument System (RVLIS) piping requires removal and subseauent replacement.
This RVLIS work is considered a replacement activity under the rules 98iii20029 98ii04 PDR ADOCK 05000400 8
PDR o4ta anearonnarr s ~oaa new roll, NC Tel 919362-2502 Fax 919362-2095
Document Control Desk SERIAL: HNP-98-161 Page 2 7
of ACMECode Section XI. The RVLIS line is 1-inch diameter, Class 2 ASME piping. As such, this replacement activity is exempt from the ASME Section XIrequirements.
An alternative to the liquid penetrant examination is proposed in the Enclosed Relief Request Number 2R1-012. Peiforming the required liquid penetrant examination on the CRDM housing canopy seal weld would result in hardship or unusual difficultywithout a compensating increase in the level ofquality and safety. Itis requested that the NRC review this relief request by November 6, 1998 to avoid delay of plant restart from RFO 8.
Please refer any question regarding this submittal to Mr. J. H. Eads at (919) 362-2646.
Sincerely, Enclosure c:
Mr. J. B. Brady (NRC Senior Resident Inspector, HNP)
Mr. L. A. Reyes (NRC Re'gional Administrator, Region II)
Mr. S. C. Flanders ( NRR Project Manager, HNP)
Enclosure to SERIAL: HNP-98-161 Page 1 of 3 SHEARON HARRIS NUCLEARPOWER PLANT DOCKET NO. 50-400/LICENSE NO. NPF-63 INSERVICE INSPECTION PROGRAM RELIEF REQUEST NO. 2R1-012 ALTERNATIVETO ASME CODE SECTION XI, IWA-4000 REQUIREMENTS SYSTEM/COMPONENT(S) FOR WHICHRELIEF< IS REQUESTED:
Control Rod Drive Mechanism (CRDM) housing canopy seal weld.
CODE< REQUIREMENT(S):
The 1989 Edition of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI,IWA-4120(a) requires that repairs shall be performed in accordance with the Owner's Design Specification and the original Construction Code of the component or system, or later editions and addenda of the Constiwction Code. Harris Nuclear Plant's (HNP)
CRDM housing canopy seal welds were designed and fabricated in accordance with the 1974 Edition including Winter 1976 Addenda of Section IIIof the ASME Code (Construction Code).
Both this edition and the 1989 edition of Section III(NB-5271, Welds of Specially Designed Seals) require a surface examination for CRDM housing seal welds.
CODE< RE<QUIREMENT FROM WHICHRELIEF IS REQUESTED:
A weld buildup willbe used to repair a CRDM housing lower canopy seal weld. Relief is requested from perfoiming the suiface examination of the weld buildup area. An alternative examination is proposed.
BASIS FOR RELIEF:
Pursuant to 10 CFR 50.55a(a)(3)(ii), relief is requested on the basis that compliance with the oiiginal examination requirements would result in hardship or unusual difficultywithout a compensating increase in the level ofquality and safety. Access to the canopy seal being repaired does not provide adequate clearance to gain complete access to the inner rod travel housing to perform the liquid penetrant examination of the weld repair. Additionally, the canopy seal being repaired is located in a high radiation area.
A liquid penetrant examination would provide a more stiingent verification of the final weld surface condition and, therefore, would afford an added measure of the quality and safety of the completed weld buildup. However, the liquid penetrant examination does not provide a substantial increase in quality and safety above what is provided by the measures (controlled process, observation of the weld process using 8x camera, final 8x visual inspection, and system leakage test) that willbe taken in lieu of the liquid penetrant examination.
These measures are described below.
Enclosure to SERIAL: HN 161 Page 2 of 3 ALTERNATEEXAMINATION(S):
While the liquid penetrant examination specified by the Construction Code and HNP's Design Specification would provide indication of surface cracks, the processes used to perform the weld buildup and the visual examination of the weld provides the best measure of the lower canopy seal weld buildup acceptability due to the limited accessibility and high radiation fields. The surface to be repaired willbe examined with an 8x camera during weld surface preparation.
The weld buildup willbe deposited using a fullyautomatic Gas Tungsten Arc Welding process. Allwelding parameters willbe controlled within the qualified range from a remote panel. The weld puddle/deposit willbe observed via a 8x camera during every phase of the welding. Afinal visual examination of the weld surface willbe completed using the same 8x camera.
In addition, the post outage system leakage test of the reactor coolant system willinclude a VT-2 inspection of the lower canopy seal weld area for leakage.
In summary HNP proposes the following alternative:
l.
2.
3.
4.
Use of a controlled automatic welding process.
Observation of the weld puddle/deposit via a 8x camera during the welding process.
A final visual examination of the weld surface using the same 8x camera.
Performance of a VT-2 inspection of the canopy seal weld area for leakage during the post outage system leakage test.
Authoi~zed Nuclear Inservice Inspector approval of alternative testing and NIS-2 acceptance.
JUSTIFICATION FOR REQUESTING RELIEF:
Performing the required liquid penetrant examination of the canopy seal weld buildup would result in hardship or unusual difficultywithout a compensating increase in the level ofquality and safety. Access to the canopy seal being repaired is difficultdue to the limited clearance between the adjacent control rod drive housings.
The separation between the outer rod travel housing is approximately 8 inches. This is not adequate clearance to gain complete access to the inner rod travel housing to perform the liquid penetrant examination of the weld repair. Additionally, the canopy seal being repaired is located in a high radiation area, with radiation fields of approximately 500 - 800 mrem/hr (1 - 1 /z rem/hr on contact). Final weld surface preparation (giinding), the liquid penetrant examination and the subsequent cleanup would be difficultand time consuming due to the limited access, and personnel performing these operations would incur substantial radiation exposure.
The repair options were evaluated and it was determined that the most appropriate repair was the use of a weld buildup rather than removing the defect and performing a weld repair. A limited liquid penetrant inspection of the leakage area was conducted, after boron removal, to determine the extent of the defect. The coverage of this inspection was limited to the leakage area only.
Two rounded indications, 1/16 - inch in diameter, were identified on the top toe of the canopy seal weld, separated by 1 inch. A faint linear indication was seen that appeared to connect the two rounded indications. The inspection showed no evidence of an axial (longitudinally oriented) flaw. Weld buildup is an acceptable repair technique because the canopy seal weld does not
Enclosure to SERIAL: HNP-98-161 Page3of 3
provide the structural strength or the pressure boundary for the joint. A fracture mechanics analysis was peiformed to justify not removing the existing defect.
An analysis was performed by Stivctural Integrity Associates to demonstrate that a through-wall flaw could be detected by visual examination which has a flaw size which is sufficiently smaller than the ci~tical flaw size, thus assuring sufficient safety margins. The analysis demonstrated
- that, under a variety of conservative assumptions, the critical flaw size predicted for the repair geometry is in all cases ofsignificant length. It is likely that a much smaller flaw could be credibly detected by visual examination under 8x magnification. The analysis results are summarized in Attachment l. Also included in Attachment 1 are the results of the fracture mechanics analysis performed to justify not removing the existing defect.
In order to confirm the detectable flaw size, tests were perfoimed by Welding Services IncoiIiorated to evaluate the capabilities of the camera system used in the peiformance of the weld repair. This testing confirmed that the critical flaw sizes resulting from the Structural Integrity analysis are detectable with margin by the visual inspection technique. A summary of the tests performed and the test results are provided as Attachment 2.
In summary, performing the Code required liquid penetrant examination of the CRDM housing lower canopy seal weld repair would result in hardship or unusual difficultywithout a compensating increase in the level ofquality and safety over that provided by the proposed alternative.
IMPLEMENTATIONSCHEDULE:
This Relief Request is applicable to the HNP Second 10-year Inservice Inspection Interval.
Attachment 1 to SERIAL: HNP-98-161 SHEARON HARRIS NUCLEARPOWER PLANT DOCKET NO. 50-400/LICENSE NO. NPF-63 EVALUATIONOF LIMITINGFLAWS FOR STRUCTURALINTEGRITY IN CANOPY SEAL REPAIRS ATHARRIS NUCLEARPLANT STRUCTURALINTEGRITYASSOCIATES, INC.