ML17328A186
| ML17328A186 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 09/29/1989 |
| From: | Giitter J Office of Nuclear Reactor Regulation |
| To: | Alexich M INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| References | |
| IEB-88-002, TAC-67301, NUDOCS 8910120014 | |
| Download: ML17328A186 (8) | |
Text
September 29, I
Docket Nos.
50-315/316 Mr. Milton P. Alexich Indiana Michigan Power Company c/o American Electric Power Service Coporation 1 Riverside Plaza
- Columbus, Ohio 43216
Dear Mr. Alexich:
SUBJECT:
RE(UEST FOR ADDITIONAL INFORMATION REGARDING IMPLEMENTATION OF BULLETIN 88-02, "RAPIDLY PROPAGATING FATIGUE CRACKS IN STEAM GENERATOR TUBES" (TAC 67301)
The staff has reviewed the actions taken by American Electric Power (AEP), as discussed in your letter dated March 31, 1988, to resolve issues in NRC Bulletin 88-02.
For Cook Unit 1, the staff finds that it does not have sufficient information to conclude that the issues identified in the bulletin have been resolved.
The enclosed request for additional information identifies the information needed by the staff and, in addition, makes a number of comments regarding your March 31, 1988 submittal.
The requested information should be submitted to the staff no later than January 31, 1990.
Because the repaired Unit 2 steam generators employ stainless steel support
- plates, and the actions of bulletin 88-02 apply only to Westinghouse plants with carbon steel support plates, the staff concludes that Bulletin 88-02 'is resolved for Unit 2.
Should you decide to discontinue the enhanced monitoring program for Unit 2, the staff encourages you to review your leak rate monitoring procedures to ensure the continued effectiveness'of these'rocedures for the timely detection, monitoring, and trending, of rapidly increasing leak rates.
The request in this letter affects fewer than ten respondents; therefore, OMB clearance is not required under P. L. 96-,511.
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Docket Nos. 50-315/316 UNITEDSTATES NUCLEAR REGULATORY COMMISSION IjltASHlNGTON,D. C. 20555 September 29, 1989 Hr. Milton P. Alexich Indiana Michigan Power Company c/o American Electric Power Service Corporation 1 Riverside Plaza
- Columbus, Ohio 43216
Dear Mr. Alexich:
SUBJECT:
RE(VEST FOR ADDITIONAL INFORMATION REGARDING IMPLEMENTATION OF BULLETIN 88-02, "RAPIDLY PROPAGATING FATIGUE CRACKS IN STEAM GENERATOR TUBES" (TAC 67301)
The staff has reviewed the actions taken by American Electric Power (AEP), as discussed in your letter dated March 31, 1988, to resolve issues in NRC Bulletin 88-02.
For Cook Unit I, the staff finds that it does not have sufficient information to conclude that the issues identified in the bulletin have been resolved.
The enclosed request for additional information identifies the information needed by the staff and, in addition, makes a number of comments regarding your Harch 31, 1988 submittal.
The requested information should be submitted to the staff no later than January 31, 1990.
Because the repaired Unit 2 steam generators employ stainless steel support
- plates, and the actions of bulletin 88-02 apply only to Westinghouse plants with carbon steel support plates, the staff concludes that Bulletin 88-02 is resolved for Unit 2.
Should you decide to discontinue the enhanced monitoring program for Unit 2, the staff encourages you to review your leak rate monitoring procedures to ensure the continued effectiveness of these procedures for the timely detection, monitoring, and trending of rapidly increasing leak rates.
The request in this letter affects fewer than ten respondents; therefore, OHB clearance is not required under P.L.96-511.
Sincerely,
Enclosure:
As stated Joseph G. Giitter Project Manager Project Directorate III-I Division of Reactor Projects - III, IV, V 5 Special Projects Office of Nuclear Reactor Regulation cc w/enclosure:
See next page
u
" 'r'. Hilton Alexich Indiana Michigan Power Company Donald C.
Cook Nuclear Plant CC:
Regional Administrator, Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 Attorney General Department of Attorney General 525 West Ottawa Street Lansing, Michigan 48913 Township Supervisor Lake Township Hall Post Office Box 818 Bridgman, Michigan 49106 W.
G. Smith, Jr., Plant Manager Donald C.
Cook Nuclear Plant Post Office Box 458 Bridgman, Michigan 49106 U.S. Nuclear Regulatory Commission Resident Inspectors Office 7700 Red Arrow Highway Stevensville, Michigan 49127 Gerald Charnoff, Esquire
- Shaw, Pittman, Potts and Trowbridge 2300 N Street, N.W.
Washington, DC 20037 Mayor, City of Bridgman Post Office Box 366 Bridgman, Michigan 49106 Special Assistant to the Governor Room 1 - State. Capitol Lansing, Michigan 48909 Nuclear Facilities and Environmental Monitoring Section Office Division of Radiological Health Department of Public Health 3500 N.
Logan Street Post Office Box 30035 Lansing, Michigan 48909 Mr. S.
Brewer American Electric Power Service Corporation 1 Riverside Plaza
- Columbus, Ohio 43216
RE VEST FOR ADDITIONAL INFORMATION INDIANA MICHIGAN POMER COMPANY COOK UNITS 1 AND 2 IMPLEMENTATION OF BULLETIN 88-02 DISCUSSION By letter dated March 31. 1988, Indiana Michigan Power Company (thc licensee) submitted its response to NRC Bulletin 88-02, "Rapfdly Propagating Fatigue Cracks fn Stcam Generator Tubes."
The liccnsec reports that both the Unit 1
and Unit 2 steam generators exhibit 1'imitcd denting at the uppermost tube support plate.
For plants with denting at the uppermost support plate, item C.2 of the bulle-tin requests that a program be fmplcmentcd to minimize the probability of a rapidly propagating fatigue crack.
The bulletin further requests that a
oetailed description of this program be submitted for NRC staff review and approval prior to restart from the next refueling outage.
The Cook Unit 2 steam gcncrators (which are Mcstinghouse Model 51) are scheduled for replace-ment at the next refuelina outage.
The replacement steam operators are Westinghouse Model 51F employing stainless steel support plates.
This replace-ment activity wi 11 constitute resolution of item C.2 of the bulletin for Cook Unit 2.
For Cook Unit 1, however, the staff does not have sufficient informatfon to conclude that thc licensee has adequately resolved ftem C.2.
Thc staff has the following contents:
The Westinghouse design of the Cook steam generators specified antfvibratfon bar (AVB) insertion to and including row 11.
The licensee concludes, therefore, that the only tubes of concern are those extending out to row 10.
The staff does not agree with this conclusion.
The staff notes, for example, that some row 11 and row 12 tubes at Beaver Valley Unit 1 were actually found to be unsuppor-ted by AVBs, even though the design specification called for the AVBs to bc inserted to at least row 11.
The staff concludes that Cubes in row ll and beyond should not bc assumed to be effectively supported by AVBs unless such support has specifically been confirmed by analysis of the eddy current data.
The presence of a detectable AVB signal does not necessarily ensure that a tube fs effectively supported by the AVB.
For an AVB to provide a fully effective support to a given tube, the center line of the AVB should be at or below the ccntcr linc of the Cube at Che apex of thc U-bend.
Criteria for evaluation of the eddy current data must be devclopcd to determine whether this fs, fn fact, the case.
The licensee's submittal indicates that denting fs present fn rows 11 thru 14 of the Unit 1 steam generators.
Thc staff does not agree that it is necessarily conservative to assume that Chc flow peaking factor for a given tube fs equal to that for the tube that ruptured at North Anna.
There fs a significant uncertainty range associated with thc flow peaking factor exhibited by the North Anna tube which failed.
Part of this uncertainty is due to measurement uncertainties fn establishing AVB insertion depths.
For assessing flow peaking factors relative Co that for Che North Anna tube, the staff believes ft approprfate to consider a lower bound peaking factor for thc North Anna tube based on consideration of the relevant uncertainties.
Thc peaking factor for the tube under evaluation should bc an upper bound value reflecting the relevant uncertainties.
Thc licensee stated fn a telecon with the NRC staff that ft plans to inspect all tubes fn the region of interest (hot and cold 'leg} for denting at the uppermost support plate at the next t'cfuelfng outage.
As we understand the licensee's submittal, unsupported tubes in the t egion of interest which, ff dented, would be susceptible to fatigue crack initiation (due to excessive fluid-elastic instability} will be permitted to remafn fn setvfce so long as they remain undented.
Subject to the comments herein, the staff has no objections to this appt oach fn principle.
Assuming that the plant does not operate with unsupporCcd, dented tubes which are potentially susceptible to fatigue, the staff will entertain any licensee proposai to discontinue, subsequent to the next refueling outage, thc enhanced 1eak rate monftot ing program previously coamftted to by thc'icensee fn response to item G.l of the bulletin.
For thc lfcensee's information, wc have enclosed the staff's safety cva1uatfon (non-proprietary version) of the generic methodology dcvclopmcnt by Mestfnghousc to t'csolve.ftem C.2 of thc bulletin.
ke believe this SER may be of fntct'cst to the licensee even though thc licensee may choose to follow an alternative approach.
RE UESTEO INFORMATION The staff requests the following information for Cook Unit 1 so that it can complete its review of the licensee's program prior to the next scheduled refueling:
The licensee's submittal provided information concerning the extent of denting in the Cook steam generators.
The licensee should confirm that its criteria for considering a tube to be dented fs consistent with the definition of denting given in the bulletin.
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4, 6.
The licensee should provide details of its methodology and criteria for assessing AVB insertion depths and for determining whether an AVB indication (as seen by eddy current) is indicative of a fully effective support.
The licensee should submit a listing of all tubes (including tubes beyond row 10) which are dented and unsupported by AVBs. If available.
the staff requests a listing ~o all tubes beyond row 7 which are not supported by AVBs.
For any unsupported tubes which are dented (except tubes in low row numbers where it is reasonably established that such tubes are not subject to significant loadings), stability ratio estimates (including flow peaking effects) and limiting fatigue usage factors should be provided.
Details of the methodology employed should also be provided.
The licensee is requested to provide additional details of the level of inspection sampling which will be performed for denting in the region of interest at each refueling outage.
The staff believes that should future inspections reveal new indications of denting at the uppermost support plate or further progression of previously observed dents, then all unsupported tubes in the region of interest should be inspected at that time for denting.
The licensee should conmit to establish administrative controls as necessary to ensure that these inspections are conducted at future inspections.
The licensee should also coamit to administrative controls to ensure that items C.1 and C.2 of the bulletin are impleoented ff unsupported tubes in the region of interest are found to be dented in the future.
Note that the actions in C.2 of the bulletin should be completed and approved by the NRC prior to restart from the outage during which the dented tubes were found. unless there remain fewer than 90 days prior to scheduled star tup.
In the latter case, the actions must be completed 'and approved prior to restart from the next scheduled refueling.
- However, NRC staff review and approval may not be necessary if the licensees methodology and criteria for implementing item C.2 have previously been reviewed and approved by the NRG staff.
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