ML18081B291
| ML18081B291 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 02/25/1980 |
| From: | Schwencer A Office of Nuclear Reactor Regulation |
| To: | Librizzi F Public Service Enterprise Group |
| References | |
| NUDOCS 8004020460 | |
| Download: ML18081B291 (6) | |
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UNITED STATES NUCLEAR. REGULATORY COMMISSION WASHINGTON, D. C. 20555 Docket No. 50-272 Mr. F.
- P *. Librizzi, General Manager *
- Electric Production Production Department Public Service Electric and'Gas Company 80 Park Pl ace, Room 7221 Newark, New Jersey 07101
Dear Mr. Librizzi:
The cracking that was found in the feedwater system piping at your plant, 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 recommendations of the Owners 1 Group and the NRC' s Pipe Crack Study Group.have been evaluated.
Shaul d we determine that furthe~ licensing actions are required: after- ** -* **-** ---.. _ *-- **-
these evaluations, you will be notified *.
o, A. Schwencer, Chief Operating Reactors Branch #1
. Division of Operating Reactors
Enclosure:
Safety Analysis of Interim Actions Taken to Eliminate Feedwater..
Piping Crac~s cc:
w/encl osure See next page
Mr. F. P. Librizzi Public Service Electric and Gas Company cc:
Mark* J. Wetterhahn, Esquire Conner, Moore and Corber Suite 1050 1747 Pennsylvania Avenue, NW Washington, D. C.
20006
. Richard Fryling, Jr., Esquire*
Assistant General Solicitor Public Service Electric and Gas Company 80 Park-Place Newark, New Jersey 07101 Gene Fisher, Bureau of Chief Bureau of Radiation Protection 380 Scotch Road Trenton, New Jersey 08628 Mr. Hank Midura, Manager.
Salem Nuclear Generating Statio~*
Public Service Electric and Gas Company 80 Park Place Newark, New Jersey 07101
. Mr. R. L. Mi ttl -~ General Manager Licensing and E_nvi ronment Public Service Electric and Gas Company 80 Park Place Newark, New Jersey
- 07101 Salem Free Library 112 West Broadway Salem, New Jersey 08079 Leif J. Norrholm
- U. S. Nuclear Regulatory Commission Drawer I Hancocks Sri dge, New Jersey 08038
- n.BRUARY 2 5 1980.
- , :*-~ *.
1"'°1.
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SAFETY ANALYSIS O~ INTERIM ACTIONS TAKEN
. TO ELIMINATE FEEDWATER PIPING CRACKS On May 20, 1979, Indiana and Michigan Power Company notifi.ed 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 radiographic examinaticms 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 Regul at'ion which infonned 1 icensees of the D. C.* Cook failures and requested *.
sp~cific inforamtion on feedwater system design, fabrication, inspection and oper-ating histories. To further explore the generic nature of the cracking problem, the Office of Inspection and Enforcement requested licensees of PWR plants in current outages to irranediately conduct volumetric examination of certain feedwater piping welds.
As a result of these actions several other licensees reported cracking in the steam generator feedwater nozzle-te-piping weld vicinity. On June 25, 1979,
- IE Bulletin 79-13 was issued. The Bulletin required inspection of the steam oener-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 penetration_ and the auxiliary feedwater to main feedwater piping connection were required to be inspected.
In conformance with the Bulletin, the licensees of the plants listed in the-*-.. ---------*
attach~d Table 1 comrleted th~ radio~raphic examinations an~ found cr~c~in~ in
. the feedwater piping systems..
Meetings and/or telephone conference calls were held with the respective license.es to discuss the following items regarding the feedwater piping cracks at their fac-ilities:
- 1.
~ature and extent of the cracking.
- 2.
Metallurgical evaluation of the cracking including identification of the ~ode of failure.
- 3.
Stress analyses
- 4. Operating history
- 5. Feedwater chemistry
- 6. Corrective actions
- 7. Safety Implications The 1; censees 1 interim reports containing the information above were submitted and reviewed by the staff prior to the units returning to power.
The extent of the cracking at the facilities is summarized in Table 1.
The mode of failure ~t a11 the facilities discussed in this analysis; with the exception of Yankee Rowe, was foenti*
- fie: as fatigue assisted by corrosion. The Yankee Rowe facility had gross fa:rication
- defec~s in its feedwater piping.* No anomalies were found in the Code require: stress analyses at the facilities.
Fro::-. the results of instrumentation installed at. several plants which have ex:*e'!"'ienced
. feedwater piping cracks and other modeling_ and analyses by a utility sponsore: Owners
... **--r-
-~~
~2-Group9 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 auxiliary feedwater with hot water from the steam generator during low flow.conditions. The Owners Group is expected to complete their investigations and make recorrmendations for changes in design and operating procedures in February 1980.
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 l,
- 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 harrmer loads. However, design changes such as "J" tubes have been made and operati ona 1 changes have occurred to minimize the possibi1 i ty of water hanrner.
In the unlikely event of a feedwater pipe break from a *severe water hammer, the consequences have been analyzed as a design base accident and acceptable measures to deal with the event have been establ ish.ed.
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 implemen-tation by licensee~ as new criteria for operating plants.
We conclude that repairs to the feedwater piping, the nondestructive inspections*
performed and scheduled, and the analyses performed for flawed piping ensure that -
the* piping integrity will be maintained until the recommendations of the Owners Group and the Pipe Crack Study Group have been evaluated. Should the staff determine that further actions are required after evaluation of the Owners Group and Pipe Crack Study Group recommendations, the licensees will be notified at that time.
Table l - Summary. of PWR Fee<lwater Piping Cracks I' I.ANT EXTENT OF CRACKING (NOZZI.E VlClNI'll)
Westinghouse Mnx.
IJcplh D. C. Cook 1/2 Thru wa'il Denver Vnllei 0.1100" Knwnunce 0.050 11 Pt. Beach 1/2 0.047" II. 8. Roh ins on 2 0.750" Snleh1 1 0.235 11 Son Onofre 1 0.100 11 Surry 1/2 0.080" Ginn a 0.107 11 "Zion 1./2 0.088 11 V:lnkee Rowe Lo-cntion max.
Depth Crock TOP 9 O'clock 1* O'clock 3 O'clock 9 O'clock lower half of reducer 2 end 5*
O'clock 8:30 O'clock 4 O'clock No. *of I.lnce Cruckcd 8 of.8 3 of J 2 of 2 2 of 2 3 of 3 4 of 1, 3 of 3 6 of 6 2 of 2 8 of 8 I
I i
elbow elbow
- pipe reducer reducer elbow reducer reducer reducer elbow e.lbow pipe PRODADLE *cAUSE Corroelon Assisted Fati ue Corrosion Assisted Pnti llC Corrosion Assietd Fatigue Corrosion Assisted Fatigue Corrosion.Assisted Fatigue Corrosion Assisted Fatigue Streee Assisted Corrouiun Corrosion Assisted l~atigue st*ress Assisted Corrosion/Corrosion J~ati ue Corrosion Assis_ted Fatigue COMMENTS I
~-
Shallow cracking in no under thermal sleeve *
- Multiple branched croc cvl<lcrice 1
Cracks nlso*at deep machining liiorko Gross fabr1cat1on.
defects 1ri p1p1ng **.:I I
L Tah 1 e l -
S11n1111ary of PWR Feeclwater P.t.ptnp, Cracks Pl.ANT Mzix.
~)cpth Comh1m t I on En11 I nee r.lncr
- --***- _ ****--------.. _u ______ o_
Millston<~ 2 0.250" Palisades 0.170" J.,ocntion max.
Depth Crock 12 O'clock No. of 1.tneR Cracked 2 of 2 3 and 9 O'clock 2 of.2 I
. l I
I I I*
i 2
PIPING COMPONENT pipe pipe PROHADLE CAUSE Not analyzed Corrosion Assisted Fatigue
.r COMMENTS Cracks found also at w1:
vicinity of horizontal i in