ML20045D971
| ML20045D971 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 06/23/1993 |
| From: | Mcmeekin T DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20045D972 | List: |
| References | |
| NUDOCS 9306300268 | |
| Download: ML20045D971 (8) | |
Text
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Duke Ibwer Company (704)8774000 McGuire Nuclear Station 12700 Hagers Ferry Road Huntersville, NC28078 8985 DUKEPOWER l
l L
June 23, 1993 1
U.S. Nuclear Regulatory Commission Washington, DC 20555 Attention:
Document Control Desk
Subject:
McGuire Nuclear Station, Units 1 and 2 Docket Nos. 50-369 and 50-370 Proposed Technical Specification Change Gentlemen:
Pursuant to 10 CFR 50.4 and 50.90, attached is a proposed license amendment to Appendix A, Technical Specifications, of Facility Operating Licenses, NPF-9 AND NPF-17 for McGuire Nuclear Station Units 1 and 2,
respectively.
This proposed i
change would only effect Unit 1
but is included herein administratively because both units Technical Specifications are included in one document.
The proposed change would be a-one time change to make the allowable combined bypass leakage rate given in Technical Specifications 3.6.1.2 a value of 0.104 L from the current value of 0.07 L.
This change would be,in the ' form of a footnote which wo,uld be applicable only for Unit 1 Cycle 9.
It is requested that this proposed amendment receive timely review and approval.
Attachment I contains the background and justification for the proposed change. contains the proposed Technical Specification change.
Attachment
.3 contains' the analysis-performed in accordance with the standards contained-in 10 CFR 50.92, which concludes that.the amendment does not involve a significant Hazards Consideration.
The proposed amendment has been reviewed and has been determined to have no adverse safety" or environmental impact.
Duke Power is forwarding a copy of this amendment request application and No Significant Hazards Consideration analysis to the appropriate North Carolina state officials.
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i 9306300268 930623 PDR ADOCK 05000369
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L Document Control Desk Page 2 June 23, 1993 Should there be any. questions concerning this proposed amendment or if additional information is required, please ' call
'R.
O.
Sharpe at (704) 875-4447.
Very truly you MJf L T.
C. McMeekin Attachments xc:
(W/ Attachments)
Mr.
S. D.
Ebneter, Regional Administrator U.S.
Nuclear Regulatory Commission, Region II Mr. Dayne Brown, Chief Radiation Protection Branch Division of Facility Services Department of Human Services, State of NC Mr. Victor Nerses, Project Manager Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mr.
P.K. VanDoorn NRC Resident Inspector McGuire Nuclear Station American Nuclear Insurers M & M Nuclear Consultants INPO Records Center I*
Document Control Desk Page 3 June 23, 1993 T.C.
- McMeekin, being duly sworn, states that he is Vice-President of Duke Power Company; that he is authorized on the part of said Company to sign and file with the Nuclear Regulatory Commission this revision to the McGuire Nuclear i
Station License Nos. NPF-9 and NPF-17 and that all statements-
'l and matters set forth therein are true and correct to the best of his knowledge.
tdf L.
T. C'.
McMeekin, Vice President Subscribed and sworn to before me this
.23 xri day of aune,-
1993.
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$9/1 Nogary ublic [
My Commission expires:
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ATTACHMENT 1 BACKGROUND / JUSTIFICATION During the McGuire Unit 1 end-of-cycle 8 (EOC8) refueling outage, a Type A, Integrated Leak Rate Test (ILRT) was conducted as required by McGuire Technical Specification 4.6.1.2.a,
" Surveillance Requirements for Primary Contairment/ Containment Integrity".
After successful completion.of this ILRT, testing wu performed on all dual ply bellows assemblies as specified by McGuire Technical Specification 4.6.1.2.h.
The bellows assembly on penetration M-441 (Steam Generator 10 Main Steam Line) exhibited large leakage in comparison to other similar penetrations and in compe'-ison to previous test results for this penetration which showec only minor leakage.
The bellows assembly for penetration M-441 is a 54" diameter dual ply design constructed of four separate dual ply bellows.
The outer ply serves as a pressure test boundary for verifying 3
integrity of the inner ply which is considered containment boundary.
Failure of the as-designed test method (pressurizing between the two plys and measuring air makeup required to maintain a designated pressure) prompted the development of an alternate:
testing method.
This alternate testing method simulates actual penetration challenge and consists of installing a temporary test boundary between the guard pipe and inner ply boundaries inside containment, pressurizing and measuring air makeup required to maintain the test pressure.
The alternate testing method has been used following previous ILRTs on this penetration since 1986.
Penetration M-441 was again tested during the current 1EOC8 outage using the alternate testing method.
The test failed which indicated leakage past the inner ply.
Additional pressure tests were performed to. further quantify the magnitude of leakage at each of the four bellows, including how much leakage represented " bypass leakage" around the Annulus and Annulus Ventilation System.
These tests revealed that about one third of the: penetration leakage represented bypass leakage subject to Technical Specification 4.6.1.2.f, and that most of that bypass leakage was associated with one of the two bellows located outside of the Annulus.
Visual inspections were performed on the outer ply of this bellow using soap bubble solution while. the penetration was.
f pressurized.
Formation of bubbles verified leakage through he inner and outer plys on this bellows.
Root Cause Determination Inspection methods available to characterize the bellows flaws are limited.
For the outer two bellows sections (test connection number one and two), visual inspection of the inner (1)
4 i
i ply is impossible.
Visual inspection of the outer ply' is difficult
~due to the space limitations between the outer ply and the containment sleeve.
Using the inspection techniques available (compact video camera equipment, boroscope),
potentially damaged areas were discovered.
Discoloration was noted on the outermost convolution (inspected from doghouse side) of the. test connection number two bellows section.
This discoloration is speculated to have been caused by a welding arc strike.
This further supports the possibility of damage during fabrication or installation.
The remaining three penetration assemblies have been inspected visually (outer plys of test connection sections one and two) and no significant damage was found.
A definite root cause determination cannot be made without removal of the bellows sections and use of destructive inspection techniques.
Test Results y
A special test was conducted to assess the amount of leakage which was routed back to the Annulus through the between ply test connection and tubing.
(This tubing and the second ply of the two ply bellows have been qualified for containment integrity.)
This test was conducted by-first measuring total makeup flow required to pressurize to 14.8 psig with bellows #3 and #4 vented between plies to the Annulus.
This makeup-number (which also represents penetration leakage under' this configuration) was 12,780 sccm.
Shortly after this makeup number was determined, flow exiting the between-ply. connections from #3 and #4 into the Annulus (through tubing) was measured at 8790 sccm, while the penetration remained pressurized to 14.8 psig.
The difference between makeup flow and measured flow to the Annulus (non-bypass) has been conservatively assessed as bypass flow and was calculated as follows:
12,780 +/- 200 scem Total penetration leakage
=
Bellows #3 and #4 between-ply 8,790 +/- 200 sccm-t flow to Annulus
=
3,990 +/- 282 sccm Bypass leakage =
=
This bypass leakage number was used in the Unit.1 Containment Leakage procedure as the bypass leakage of Penetration M-441 at cold conditions.
Because the leakage through this penetration represented a significant step change in bellows performance, a baseline assessment of bellows leakage at hot conditions and monthly monitoring during operation was determined to be prudent and necessary; particularly because thermal expansion during startup (2) l 7
could increase the leakage rate..The most reasonable monitoring was determined to be between-ply pressurization to 4 psig (limit set by manufacturer).
This monitoring is conducted with the exterior of each bellows assembly at ambient pressure, so that i'
measured. leakage can be a combination of inward leakage through the inner ply and outward leakage through the outer ply.
This measured leakage, when extrapolated to a 14.8 psig condition (square root of 14.8/4), conservatively bounds the' potential outward leakage through both plies (in series) in an accident condition.
To provide a method to conservatively bound total bypass leakage, any increases in the between-ply measured leakages, relative to a baseline value obtained at cold conditions, are to be added to total bypass leakage measured at cold conditions, including the 3,990 +/- 282 sccm bypass leakage for penetration i
M-441 determined as described earlier.
'In addition,- any unexpected changes or adverse trends will be evaluated to determine if immediate corrective actions are needed.
- Finally, if the unit is brought to cold shutdown (Modes 5 or 6).during the remainder of Cycle 9 the special 14.8 psig test of.the full penetration will be repeated as described above.
The cold, between ply baseline for bellows #3 was conducted and makeup flow (leakage out the inner and outer plies _ combined) measured at 6,660 +/- 200 sccm at 4 psig.
Bellows #4 required makeup flow of 48 +/- 2 scem at 4 psig.
These tests were conducted with the penetration at 90 degrees F.
Another test was conducted at hot conditions with the Main Steam line at 542 degrees F; within several degrees of operating temperature during power operations.
As anticipated, the thermally induced movement of the main steam line (about 1 inch) had stretched the #3 bellows and caused its leakage to increase slightly.
The hot, between-ply baseline for bellows #3 was conducted and makeup flow was measured at 8,340 +/- 200 scem at 4 psig, an increase of 1,680 +/- 282 sccm over cold conditions.
Bellows #4 makeup flow was measured at 53.2 +/- 2 sccm, an increase of 5.2
+/- 2.8 secm.
This resulted in an extrapolated (to 14.8 psig) leakage increase of 3,232 +/- 282-sccm for bellows #3 and 10.0 +/- 2.8 sccm for bellows #4.
This assumed total leakage increase of 3,242 sccm, added to the 3,990 sccm previously established for penetration M441 and to all other measured bypass leakages, results in a total measured bypass leakage of 9,359 scem (instrument error included).
Currently, the Technical Specification limit of.07 X La bypass leakage is 9,427 scem for McGuire Unit 1.
Future monthly between-ply hot tests will likely show some~ small (3)
variability in leakage.
In addition, other on-line penetration
- testing, namely the Containment Purge Isolation
- valves, j
typically show some increase in leakage.
i Repair Options Three repair options have been considered to date. Descriptions of the repair processes and estimated schedules are as follows:
Weld Repair of Damaged Areas Weld ' repair of the damaged areas would require access through an opening of approximately six inches to a depth of approximately sixty inches.
The bellows plys are fabricated from thin gauge sheet material (wall thickness
.035 inches).
Based on the materials used for
=
construction and the access requirements, manual weld repair is impractical.
Automated weld repair would require development of remote welding heads / controls, surface preparation, and video inspection equipment.
This process is currently not available from the industry.
The unknowns associated with flaw detection, removal, and repair on thin gauge material makes scheduling estimates difficult.
Development of this process could require months for completion.
Replace Bellows Assembly with Same Design The option would require severing the forty inch guard pipe, the thirty one inch steam process piping and removal of the bellows guards (doghouse and annulus side) at each end of the bellows assembly to - allow removal of the assembly.
Another section of process / guard piping would have be removed to provide a space for bellows assembly and installation.
The assembly could then be further dismantled to facilitate transport out of the reactor building.
Installation would require removal of all interferences in the transport path-for the four foot by 10 foot replacement bellows assembly. Even though adequate space exists in the fan room for removal of the _ piping section, no known transport path exists for an assembly this large.
The only other removal / installation path would be from the doghouse side of the penetration.
Removal of concrete structures would be required for this path.
No spare bellows assemblies are available.
Using the time -
estimates provided for the auxiliary _ bellows _ option,- a minimum six week delivery time would be required for (4)
fabrication.
Due to the complexity of transport of the bellows assembly, an eight week schedule may be required for piping / concrete structure interference removal and replacement.
This would result in a total repair estimate of 14 weeks.
Auxiliary Bellows Installation This is the most desirable repair option available.. This method requires installation of a'
two piece bellows assembly that is attached to the guard pipo - and the containment sleeve.
The difficulty of installation with this method is the welding of the bellows halves on the inner and outer plys.
A single ply test bellows of a similar size was installed on penetration number 1M393 and 2M154.
Surface preparation, materials transport,- and installation required approximately two weeks. Since a two ply bellows would be required for permanent installation, another week would be required for installation of the second bellows.
Bellows manufacturers have been contacted and estimate-approximately six weeks for procurement of materials and fabrication.
Installation estimates from the manufacturer range from one to four weeks.
In summary, preliminary scheduling estimates indicate seven to ten weeks for job completion.
Qualified Epoxy Coating Investigations are being conducted as to whether an epoxy coating repair method can be qualified for use on the outer bellows. If. a suitable epoxy can be identified, qualified, and demonstrated to be compatible with the material and functional requirements of the. bellows, then an epoxy repair could be made during operation. Investigation of this possibility is expected to take several weeks.
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