ML20134F086

Forwards Review of Plant Operability Assessment 96-01283, Structural Integrity of CE SG Welded Sleeves

ML20134F086
Person / Time
Site:	Zion File:ZionSolutions icon.png
Issue date:	10/31/1996
From:	Shiraki C NRC (Affiliation Not Assigned)
To:	Johnson I COMMONWEALTH EDISON CO.
References
TAC-M95183, TAC-M95184, NUDOCS 9611040273
Download: ML20134F086 (5)

Text

,

October 31,19%

Ms. Irene Johnson, Acting Manager Nuclear Regulatory Services Commonwealth Edison Company Executive Towers West III 1400 Opus Place, Suite 500 Downers Grove, IL 60515

SUBJECT:

REVIEW 0F ZION, UNIT 2, OPERABILITY ASSESSMENT #96-01283, STRUCTURAL INTEGRITY OF COMBUSTION ENGINEERING STEAM GENERATOR WELDED SLEEVES (TAC NOS, M95183 AND M95184)

Dear Ms. Johnson:

In a letter dated March 25, 1996, Commonwealth Edison Company (Comed) submitted its initial and final operability assessments and a technical report, " Verification of the Structural Integrity of the ABB CEN0 Steam Generator Welded Sleeve," Combustion Engineering, Inc., CEN-628-P, Revision 00-P, March 1996. These documents dealt with the weld zone indications that have been detected in Combustion Engineering's steam generator welded sleeves. The results of the staff's review of the operability assessments and technical report are enclosed.

Sincerely, ORIGINAL SIGFED BY:

Clyde Y. Shiraki, Project Manager Project Directorate III-2 9611040273 961031 Division of Reactor Projects - III/IV DR ADOCK 0500 4 Office of Nuclear Reactor Regulation Docket No. 50-304

Enclosure:

As stated cc w/ enc 1: see next page gg Distribution:

(DocketFile. T PUBLIC PDIII-2 r/f i J. Roe, JWR C. Moore E. Adensam, EGAl C. Shiraki R. Capra 0GC, 015B18 Q' :Ol i ACRS, T2E26 M. Dapas, RIII E. Sullivan, 07D4 DOCUMENT NAME: ZI95183.LTR

• Input provided by memo dated 10/23/96; no major changes Ta receive a copy of this document, indicate p4he box:,

C' - Copy without enclosures *E* = Copy with enclosures *N' = No copy l0FFICE PM:PDIII-2,le lA: P'D AI P-2 l 6 EMCB l D:PDIII-2 lC- l lNAME CSHIRAKI & Ch00RE'i ESULLIVAN* RCAPRA t w lDATE 10/3r /96 10/$/96 10/23/96 10/31/96 0FFICIAL RECORD COPY 040075

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, e, 60 Mc t UNITED STATES jo

,j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2066dM001

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October 31, 1996 l

1 l Ms. Irene Johnson, Acting Manager

! Nuclear Regulatory Services Commonwealth Edison Company i Executive Towers West III

1400 Opus Place, Suite 500 l Downers Grove, IL 60515 t

SUBJECT:

REVIEW OF ZION, UNIT 2, OPERABILITY ASSESSMENT #96-01203, STRUCTURAL INTEGRITY OF COMBUSTION ENGINEERING STEAM GENERATOR WELDED SLEEVES 4

(TAC NOS. M95183 AND M95184) l

Dear Ms. Johnson:

j In a letter dated March 25, 1996, Commonwealth Edison Company (Comed) l submitted its initial and final operability assessments and a technical l

report, "Verificat...) of the Structural Integrity of the ABB CENO Steam Generator Welded Sleeve," Combustion Engineering, Inc., CEN-628-P, l l Revision 00-P, March 1996. These documents dealt with the weld zone ,

indications that have been detected in Combustion Engineering's steam a generator welded sleeves. The results of the staff's review of the

operability assessments and technical report are enclosed.

i Sincerely, Clyde Y. Shiraki, Project Manager Project Directorate III-2 Division of Reactor Projects - III/IV Office of Nuclear Reactor Regulation Docket No. 50-304

Enclosure:

As stated cc w/ enc 1: see next page

I. Johnson Zion Nuclear Power Station Commonwealth Edison Company Unit Nos. I and 2 cc:

Michael I. Miller, Esquire Sidley and Austin One First National Plaza Chicago, Illinois 60603 Dr. Cecil Lue-Hing Director of Research and Development Metropolitan Sanitary District of Greater Chicago 100 East Erie Street Chicago, Illinois 60611 Phillip Steptoe, Esquire Sidley and Austin One First National Plaza Chicago, Illinois 60603 Mayor of Zion Zion, Illinois 60099 Illinois Department of Nuclear Safety Office of Nuclear Facility Safety 1035 Outer Park Drive j Springfield, Illinois 62704 U.S. Nuclear Regulatory Commission )

Zion Resident Inspectors Office '

105 Shiloh Blvd.

Zion, Illinois 60099 Regional Administrator U.S. NRC, Region III 801 Warrenville Road Lisle, Illinois 60532-4351 Station Manager l Zion Nuclear Power Station 101 Shiloh Blvd.

Zion, Illinois 60099-2797 Document Control Desk-Licensing Commonwealth Edison Company ,

1400 Opus Place, Suite 400 i Downers Grove, Illinois 60515  !

j .

RESULTS OF STAFF REVIEW OF OPERABILITY ASSESSMENTS l l AND TECHNICAL REPORT FOR ZION NUCLEAR POWER STATION. UNIT 2 1

Background

i Zion Nuclear Power Station, Unit 2, examined 100 percent of steam generator j (SG) tube sleeves designed by ABB/ Combustion Engineering (ABB/CE) using a plus

point probe in its February 1995 refueling outage. Twenty nine tubes with

weld zone indications (WZI) in the upper weld of the sleeve were reported.

! Twenty six of these tubes were returned to service and the other three were q plugged.

4

! Prairie Island, Unit 1, pulled five sleeve / tube assemblies with similar WZIs i during its Spring 1996 refueling outage for metallurgical examination by l ABB/CE. Because the preliminary results indicated possible issues with structural and leakage integrity, Zion, Unit 2, performed the subject operability assessment to document that the 26 sleeved tubes with.WZIs were i acceptable for service for the remainder of the fuel cycle. The initial

{ operability assessment was performed on March 7, 1996. The final operability assessment was performed on March 25, 1996, to incorporate the results from, i

" Verification of the Structural Integrity of the ABB CEN0 Steam Generator

Welded Sleeve," Combustion Engineering, Inc., CEN-628-P, Revision 00-P,

! March 1996 (final ABB/CE report). Both the initial and final operability j assessments were submitted to the staff in the licensee's letter dated March 25, 1996.

Evaluation i

The NRC staff reviewed the licensee's operability assessment dated March 25, 1996, to assess (1) the evaluation of the structural and leakage integrity of

, the defective sleeves, (2) plans regarding ultrasonic testing (UT) reanalysis

of the defective sleeves, and (3) plans regarding disposition of the sleeved i tubes with WZIs.

l l Zion, Unit 2, cited preliminary results from the ABB/CE evaluation of the

pulled Prairie Island, Unit 1, sleeve / tube assemblies that found the pulled

! assemblies satisfied the requirements of draft Regulatory Guide 1.121, " Bases i for Plugging Degraded PWR Steam Generator Tubes." The licensee then reviewed i the eddy current test (EC) data for the 26 sleeves with WZIs, stated that the i Prairie Island, Unit 1, indications bound the Zion, Unit 2, indications and,

! thus, concluded that the Zion, Unit 2, sleeve / tube assemblies also had l adequate structural integrity. Since the EC method was not qualified for detection or sizing these defect types, additional data were needed for a j final Zion, Unit 2, operability assessment. However, the final ABB/CE report found that the structural integrity of many similarly flawed sleeve / tube

< assemblies with a wide range of EC indications remained intact thus providing i evidence that the Zion, Unit 2, WZIs were indeed similar to the Prairie j

Island, Unit 1, defects.

I Zion, Unit 2, cited preliminary results from ABB/CE that indicated a sleeved tube with 360 degrees of lack of fusion (LOF) could have a maximum leakage i rate of 1.4 gallons per minute (gpm) under main steam line break (MSLB) conditions. The licensee applied this leakage rate to the 18 sleeves in

ENCLOSURE 3

~

one SG to reach a 25.2 gpm leakage rate. Zion, Unit 2, had a 10 CFR Part 100 limit of 5.31 gpm based on a reactor coolant system (RCS) activity of 1 microcurie per gram dose equivalent of I-131. The licensee stated that the 5.31 gpa leakage rate, however, is actually within a small fraction of 10 CFR Part 100 dose limits, but did not provide actual dose rate calculations in the operability assessment. To provide added margin, the licensee reduced the RCS activity to 0.2 microcuries per gram, but again did not provide actual dose rate calculations. ABB/ Combustion Engineering presented results in the final AB8/CE report that supported a maximum leakage rate of 0.016 gpa at MSLB conditions. In the final operability assessment, the licensee showed that applying this leakage rate to all its sleeved tubes with WZIs would result in a total leakage rate well below the 5.31 gpa 10 CFR Part 100 dose limit. The licensee raised the administrative RCS activity limit back to its original level.

l Included in the final operability assessment, were the Zion, Unit 2, plans to i reinspect all sleeved tubes with WZIs using the enhanced UT acquisition and I analysis technique described in " Repair of Westinghouse Series 44 and 51 Steam Generator Tubes Using Leak Tight Sleeves," Combustion Engineering, Inc.,

CEN-629-P, Revision 00, July 1996, (new ABB/CE sleeve topical report). Recent i discussions between the licensee and the staff revealed changes in the plans for Zion, Unit 2, regarding the inspection of ABB/CE sleeves. The licensee now plans to perform a 100 percent inspection of ABB/CE sleeves using the plus point probe using enhanced EC analysis guidelines. All tubes with WZIs, i regardless of position of the indication with respect to the weld centerline,  ;

will be plugged. The licensee no longer intends to reinspect any in service '

sleeved tube using the enhanced UT acquisition and analysis technique.

Conclusion The NRC staff reviewed the licensee's operability assessments and determined that the initial operability assessment dated March 7,1996, relied heavily on preliminary information from the Prairie Island, Unit 1, sleeve / tube pull results and engineering judgement. Much of this information was subsequently revised. The final operability assessment dated March 25, 1996, which was based on the final CE report, was adequate and substantiated the initial operability assessment.