ML17326A627
| ML17326A627 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 02/25/1980 |
| From: | Schwencer A Office of Nuclear Reactor Regulation |
| To: | Dolan J INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| References | |
| NUDOCS 8004020457 | |
| Download: ML17326A627 (10) | |
Text
Docket Nos.
and 50-316 t1r. John Dolan, Vice President Indiana and f~Iichigan Electric Company Post Office Box 18 Bowling Green Station
Dear Hr. Dolan:
Th'e cracking that was found in the feedwater system piping at your plants, is summarized in Table 1 of the enclosed safety analysis.
r
.The flRC Staff has reviewed the actions you have taken and'finds that the repair program, the nondestructive inspections and leakage testing per-formed following the repairs are adequate to insure that the integrity of the feedwater piping will be maintained until the recommendations of the Owners'roup and the NRC's Pipe Crack Study Group have been evaluated.
Should we determine that further licensing actions are required after these evaluations, you will be notified.,
Sincerely, Original Stgned By A. Schwencer, Chief Operating Reactors Branch 81 Division of Operating Reactors
Enclosure:
Safety Analysis of Interim Actions Taken to Eliminate Feedwater Piping Cracks cc:
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UNITEDSTATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 fENUARY'8 5
]98O Docket Nos. 50-315 and 50-316 Mr-John Dolan, Vice President Indi.ana and Michigan Electric Company Post Office Box 18 Bowling Green Station New York, New York 10004
Dear Mr ~ Dolan:
The cracking that was found in the feedwater system piping at your plants, is summarized in Table 1 of the enclosed safety analysis.
The NRC Staff has reviewed the actions you have taken and finds that the repair program, the nondestructive inspections and leakage testing per-formed following the repairs are adequate to insure that the integrity of the feedwater piping will be maintained until the recomendations of the Owners'roup and the NRC's Pipe Crack Study Group have been evaluated.
Should we determine that further licensing actions are required after these evaluations, you will be notified.
Sincerely,
Enclosure:
Safety Analysis of Interim Actions Taken to Eliminate Feedwater Piping Cracks A. Schwencer, Chief Operating Reactors Branch 41 Division of Operating Reactors cc:
w/enclosure See next page aoo4oso957
Mr. John Dolan
'ndiana and Michigan Electric Company fEBROARY 2 5 198D cc:
Mr. Robert W. Jurgensen Chief Nuclear Engineer American Electric Power Service Corporation 2 Broadway New York, New York 10004 Gerald Charnoff, Esquire Shaw, Pittman, Potts and Trowbridge 1800 M Street, N.W.
Washington, D.
C.
20036 Citizens for a Better Environment 59 East Ij'an Buren Street Chicago, Illinois 60605 Maude Preston Palenske Memorial Library 500 Market, Street St. Joseph, Michigan 49085 Mr. D. Shaller, Plant Manager Donald C.
Cook Nuclear Plant P. 0.
Box 458 Bridgman, Michigan '49106 Mr. Robert Masse Donald C.
Cook Nuclear Plant P. 0.
Box 458 Bridgman, Michigan 49106
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SAFETY ANALYSIS OF. INTERIM ACTIONS TAKEN TO ELIMINATE FEEDMATER PIPING CRACKS On May 20, 1979, Indiana and llichigan Power Company notified the NRC of cracking in two feedwater lines at their D. C. Cook Unit 2 facility.
The cracking was discovered following a shutdown on May 19 to investigate leakage inside contain-
. ment.
Leaking circumferential cracks were identified in the 16-inch diameter feed-water elbows adjacent to two steam generator nozzle to elbow welds.
Subsequent radiogr aphic examinat'ious revealed cracks in all eight steam generator feedwater lines at this location on both units 1 and 2.
On May 25,
- 1979, a letter was sent to all PWR licensees by the Office of Nuclear Reactor Regulation which informed licensees of the D. C.
Cook failures and requested specific inforamtion on feedwater system design, fabrication, inspection and oper-ating histories.
To further explore the generic nature of the cracking probl~,
the Office of Inspection and Enforcement requested licensees of PWR plants in current outages to immediately conduct volumetric examination of certain feedwater piping welds.
As a result of these actions several other licensees reported cracking in the steam gener ator feedwater nozzl -to-piping weld vicinity.
On June 25, 1979, IE Bulletin 79-13 was issued.
The Bulletin required inspection of the steam =ener-ator nozzle-to-pipe welds and adjacent areas within 90 days.
If flaws were found in these welds, the feedwater piping welds to the first support, the feedwater piping to containment penetr ation and the auxiliary feedwater to main feedwater pipi..g connection were required t'o be inspected.
In conformance with the Bulletin, the licensees of the plants listed in the attached Table 1 completed the radiographic examinations and found cr acL;in~ in the feedwater piping systems".
Meetings and/or telephone conference calls were held with the respective lice.-.s~
s to discuss the following items regarding the feeawater piping cracks at their faci 1 ities:
1.
Nature and extent of the cracking.
2.
Metallurgical evaluation of the cracking including identification of the
..o e
of fai lure.
3.
Str ss analyses 4.
Operating history 5.
Feedwater chemistry 6.
Corrective actions 7.
Saf ety Implications The licensees'nterim reports containing the information above were submitte" and reviewed by the staff prior to the units returning to power.
The extent of =.;e cracking at the facilities is summarized in Table 1.
The mode of failure at =',; the facilities discussed in this analysis; with the exception of Yankee Rowe, was
-':-. nti fied as fatigue assisted by corrosion.
'e Yankee Rowe facility had gross, =-. ication defects in its feedwater piping.
No ano".ol ies were found in the Code requir=-
s--'. ess analyses at the faci 1 ities.
Fro;,. the results of instrumentation instal led at several plants which have ev-rienced Teedwater piping cracks and o her modeling and analyses by a utility sponsor=-
Group, significant cyclic stresses have been identified that occur in the feedwater piping in the vicinity of the steam generator nozzle from mixing and stratification of cold auxi.liary feedwater with hot water from the steam generator during low flow conditions.
The Owners Group is expected to complete their investigations and make recommendations for changes in design and operating procedures in February 'lg8O.,
The licensees have repaired and/or replaced the affected piping in most cases with.
improved designs to minimize stress risers.
In addition, the licensees have com-mitted to reinspect the steam generator to feedwater piping weld vicinities at the subsequent refueling outage.
Although the piping has been repaired at the facilities listed in Table 1, the staff feels that cracking could re-occur in the future at these facilities.
The staff and Owners Group both have performed independent analyses and have deter-mined that flawed feedwater piping could withstand challenges from operating and faulted loads including seismic and limited water loads without loss of piping integrity.
Pipe breaks have occurred in the past in feedwater piping as the result of water hanmer loads.
However, design changes such as "J" tubes have been rade and operational changes have occurred to minimize the possibility of water hacker.
In the unlikely event of a feedwater pipe break from a
severe water hamm r, the consequences have been analyzed as a design base accident and acceptable measures to deal with the event have been established.
The NRC has instituted a Pipe Crack Study Group to review this and other pipe crack-ing problems in PWR's.
It is anticipated that the Pipe Crack Study Group will complete its work by June 1980".and provide recommendations for review and im-lemen-tation by licensees.
as new criteria for operating plants.
Me conclude that repairs to the feedwater piping, the nondestructive inspections-performed and scheduled, and the analyses p rfomed for flawed piping ensure that the piping integrity will be maintainea until the recommendations of the Own.s Group and the Pipe Crack Study Group have been evaluated.
Should th staff c termine
.hat further actions are required after evaluation of the Owners Group and P;pe Crack Study Group recommendations, the licensees will be notified at that time.
Table 1 Summary of PHIL Feedwnter Piping Cracks
's'lANT I':KI.'I'.NT OF CRACKING NOZZI.E VICLNITY)
PIPING COHPONRNT Pl>OIIAIILE CAUSE CONTI'.NTS lf>>x.
~no ta I.ocatlon max.
No. of l,l>>en D. C.
Cook J/2 Thru wall TOP Bof 8 elbow Corrosion Assis ted 2 cracks thru wall Fati ue Denver Vn.l.ley 0.400" 9 0'clock 3 of 3 elbow Corrosion Assisted 13 additio>>ul fab. rel I'ati ue i>>dicot lu>>s rc uilrc Knwaonee 0.050" 7 0'clock 2 of 2 Corrosion Assistd Fati ue 3>> dia aux feed near SG inlet Pt.
Brncl) 1/2 0.047" 3 0'clock 2of 2 reducer Corrosion Assisted 3" dia. aux.
feed near FaL'iaue SG i>>let II.II.Hobl>>son 2
0.750" 9 0'clock 3 of 3 red<<cer Corrosion Assisted Fntl ue Shallow cracking in no under thermal sleeve Snlcltl 1 0.235" 4of4 elbbw reducer Corrosio>> Assisted Fati ue San Onofre 1
0.100" lower half of reducer 3of 3 reducer Stress Assisted Corrosio>>
'Multiple branched crar evltle>>ce of some fn Sorry 1/2 0.000" 2and5 0'clock 6of6 reduc'er Corrosion Assisted Fati ue Ginna
- 0. 107'I B:30 0'clock 2of2 elbow Stress Assisted Cracks also'at deep Corrosion/Corrosion machining marks Fati >>e
'Ziu>> 1/2 O,OBB" 4 0'clock 8 of B
c.lbow pl.l)e Corrosion Assisted Fatigue
~
)~nkee Rowe Gross fabrtcatton
'defects ln piping
'I'<<lilc 1 - Si<n<<<inry of PMR Feedwnter P(pinp Crncks 3'I,ANT EXTENT OF CRACKING (NOZZLE VICINITY)
PIPING COHPONENT PROBABLE CAUSE COKIPSXH Hnx.
~l)o )
tlat Location mnx.
No. of I ines Combos l.Ion l'.ngincer.tnt Hillstone 2
0.250" l2 0'clock 2 of 2 pipe Not analyzed P<<I l<<n<l< n
- 0. ] 70" 3 nnd 9 0'clock 2 of 2 pipe Corrosion Assisted Fatigue Cracks found also at wc vicinity of horizontal i in
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