ML20147E248

Requests Addl Info Re SG Tube Leak Test & Eddy Current Exam Results Obtained During Current Unit 2 Outage & Including Tubes Previously Repaired Using F* Tube Repair Criteria

ML20147E248
Person / Time
Site:	Prairie Island
Issue date:	02/13/1997
From:	Wetzel B NRC (Affiliation Not Assigned)
To:	Patricia Anderson NORTHERN STATES POWER CO.
References
TAC-M96654, TAC-M96655, NUDOCS 9702180246
Download: ML20147E248 (5)

Text

. . _ _ . - . - - .

Mr. Rog:r 0. Anders:n, Director February 13, 1997 Licensing and Management Issues Northern States Power Company 414 Nicollet Mall Minneapolis, MN._55'401 ,

SUBJECT:

R'EQdEST'FOR AD'ITIONAL D INFORMATION (RAI) REGARDING APPLICATION OF F* AND EF* STEAM GENERATOR TUBE REPAIR CRITERIA: PRAIRIE ISLAND NUCLEAR GENERATING PLANT UNIT.NOS. 1 AND 2 (TAC NOS. M96654

,AND M96655) m .

Dear Mr. Anderson:

The Nuclear Regulatory Commission staff is reviewing steam generator tube leak test and eddy current examination results obtained during the current Unit 2 outage, including tubes previously repaired using the F* tube repair criteria.

- Additionally, the staff is continuing its review of your technical specification amendment request dated September 24, 1996, " Incorporation of Elevated F* Steam Generator Tube Repair Criteria," as supplemented by your submittals dated October 17, 1996, January 3, January 20, and February 3, 1997. In order to verify that the structural and leakage integrity of tubes repaired by the rerolling process is consistent with the assumptions and conclusions in the F* assessment and to complete its review of the pending elevated F* amendment request, the NRC staff requires the additional information identified in the enclosure. Information identified under Item I is necessary for the staff to determine, prior to startup of Unit 2, the acceptability for continued service tubes previously repaired by rerolling.

Information identified under Item 2 is necessary for the staff to complete its review of your technical specification amendment request concerning the use of the elevated F* tube repair criteria.

If you have any questions, please contact me at (301) 415-1355.

Sincerely, Original signed by Beth A. Wetzel Beth A. Wetzel, Project Manager Project Directorate III-l Division of Reactor Projects - III/IV Office of Nuclear Reactor Regulation Docket Nos 50-282 and 50-306 gg cc w/ encl: See next page <

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• • • • • ,$ February 13, 1997 Mr. Roger 0. Anderson, Director Licensing and Management Issues Northern States Power Company ,

414 Nicollet Mall i Minneapolis, MN 55401

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING AP?LICATION OF F* AND EF* STEAM GENERATOR TUBE REPAIR CRITERIA: PRAIRIE ISLAND l

NUCLEAR GENERATING PLANT UNIT NOS. 1 AND 2 (TAC NOS. M96654 AND M96655) l l

l

Dear Mr. Anderson:

The Nuclear Regulatory Commission staff is reviewing steam generator tube leak test and eddy current examination results obtained during the current Unit 2 outage, including tubes previously repaired using the F* tube repair criteria.

Additionally, the staff is continuing its review of your technical specification amendment request dated September 24, 1996, " Incorporation of .

Elevated F* Steam Generator Tube Repair Criteria," as supplemented by your submittals dated October 17, 1996, January 3, January 70, and February 3, 1997. In order to verify that the structural and leakage integrity of tubes ,

repaired by the rerolling process is consistent with the assumptions and conclusions in the F* assessment and to complete its review of the pending elevated F* amendment request, the NRC staff requires the additional information identified in the enclosure. Information identified under Item 1 is necessary for the staff to determine, prior to startup of Unit 2, the acceptability for continued service tubes previously repaired by rerolling.

Information identified under Item 2 is necessary for the staff to complete its review of your technical specification amendment request concerning the use of the elevated F* tube repair criteria.

If you have any questions, please contact me at (301) 415-1355.

Sincerely, hv $

Beth A. Wetzel, oject Manager Project Directorate 111-1 Division of Reactor Projects - III/IV Office of Nuclear Reactor Regulation Docket Nos. 50-282 and 50-306 cc w/ enc 1: See next page i

l .

j l

REQUEST FOR ADDITIONAL INFORMATION l l

ON THE USE OF F* and EF* STEAM GENERATOR TUBE PLUGGING CRITERIA l

1. F* Pluaaine Criteria - Information for NRC Staff Review Prior to Unit 2 Startup

a. Provide an assessment of the rerolled F* tubes that experienced leakage during the secondary-side hydrostatic testing completed during the 1997 Unit 2 refueling outage. The assessment should address the issues identified in the action plan. included in the document " Prairie Island Unit 2 9701 S/G Inspection Results,"

dated February 3, 1997. Also summarize the scope and results of the planned in-situ pressure testing. Demonstrate that the measured leakage is bounded by the leakage assessments in the F= license amendment request. Discuss the changes, if any, made to the reroll acceptance criteria to identify F* tubes that are rerolled into hard packed crevices.

l b. Estimate the total steam line break leak rate in the limiting l steam generator due to bypass leakage around rerolled F* tubes.

i Discuss the assumptions made regarding the number of tubes

! rerolled into hard packed crevices with through-wall flaws and the l bypass leakage per leaking steam generator tube.

c. The ABB/CE report " Series 44 & 51 Design Steam Generator Tube Repair Using A Tube Rerolling Technique," dated December 1996  ;

(proprietary) states that tubes rerolled into hard packed crevices l may have much lower than expected average wall thinning for the rerolled joint. Combustion Engineering Report CEN-620-P

demonstrated that tubes rerolled into hard sludge did not move

! during push testing. However, the assessment does not address the

potential strengthening of the tube-to-tubesheet joint cause by l the application of a compressive load along the axial direction of the tube. Assess the reduction in the pullout load resistance for F* tubes. If a reduction in the calculated pullout load is greater than that assumed in the F* analysis, discuss the basis .

l for returning tubes to service that are rerolled into hard packed '

crevices.

2. EF* Plueeina Criteria - Information for NRC staff review of amendment request permitting the use of EF* tube plugging criteria.

a. Provide an assessment of the rerolled F* tubes that experienced leakage during the secondary-side hydrostatic testing completed l during the 1997 Unit 2 refueling outage. The assessment should L

address the issues identified in the action plan included in the i docueent " Prairie Island Unit 2 9701 S/G Inspection Results,"  :

dated February 3, 1997. Also summarize the scope and results of t

ENCLOSURE L

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the planned in-situ pressure testing. Demonstrate that the measured leakage is bounded by the leakage assessments in the

! EF* license amendment request. Discuss the changes, if any, made i to the reroll acceptance criteria to identify EF* tubes that are j rerolled into hard packed crevices.

i b. Estimate the total steam line break leak rate in the limiting

! steam generator due to bypass leakage around elevated F* tubes.

i

!- c. The ABB/CE report " Series 44 & 51 Design Steam Generator Tube i Repair Using A Tube. Rerolling Technique," dated December 1996, 4

(proprietary) states that tubes rerolled into hard packed crevices

may have much lower than expected average wall thinning for the

! rerolled joint. Combustion Engineering Report CEN-620-P

! demonstrated that tubes rerolled into hard sludge did not move

during push testing. However, the assessment does not address the potential strengthening of the tube-to-tubesheet joint cause by the application of a compressive load along the axial direction of i the tube. Assess the reduction in the pullout load resistance for

EF* tubes. If a reduction in the calculated pullout load is l greater than that assumed in the analysis, discuss the basis for i

returning tubes to service that are rerolled into hard packed crevices.

d. The AB8/CE report dated December 1996, stated that rerolling tubes

into hard sludge is considered off-design, and the decision to 1 return to service tubes rerolled into hard packed crevices will be

+

based on operational concerns. Provide the basis for returning to

service tubes that have been rerolled into hard sludge.

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1 Mr. Roger 0. Anderson, Director Prairie Island Nuclear Generating Northern States Power Company Plant i l

cc:

J. E. Silberg, Esquire Tribal Council Shaw, Pittman, Potts and Trowbridge Prairie Island Indian Community 2300 N Street, N. W. ATTN: Environmental Department Washington DC 20037 5636 Sturgeon Lake Road Welch, Minnesota 55089 Plant Manager Prairie Island Nuclear Generating Plant Northern States Power Company 1717 Wakonade Drive East Welch, Minnesota 55089 Adonis A. Neblett Assistant Attorney General Office of the Attorney General 455 Minnesota Street Suite 900 St. Paul, Minnesota 55101-2127 U.S. Nuclear Regulatory Comission l Resident Inspector's Office 1719 Wakonade Drive East Welch, Minnesota 55089-9642 Regional Administrator, Region III U.S. Nuclear Regulatory Comission 801 Warrenville Road Lisle, Illinois 60532-4351 '

Mr. Jeff Cole, Auditor / Treasurer I Goodhue County Courthouse Box 408 Red Wing, Minnesota 55066-0408 Kris Sanda, Commissioner Department of Public Service 121 Seventh Place East Suite 200 St. Paul, Minnesota 55101-2145 <

Site Licensing Prairie Island Nuclear Generating Plant Northern States Power Company 1717 Wakonade Drive East Welch, Minnesota 55089 November 1996