ML20126B761

Forwards Safety Analysis of Interim Actions Taken to Eliminate Feedwater Piping Cracks. Replacement & Repair Adequate.Ack Certain Util Commitments

ML20126B761
Person / Time
Site:	Yankee Rowe
Issue date:	02/26/1980
From:	Ziemann D Office of Nuclear Reactor Regulation
To:	Kay J YANKEE ATOMIC ELECTRIC CO.
References
NUDOCS 8003190911
Download: ML20126B761 (6)

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8 UNITED STATES

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NUCLEAR REGULATORY COMMISSION E

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j,g WASHINGTON, D. C. 20565

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February 26, 1930

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Occket No. 50-29 Mr. James A. Kay Senior Engineer-Licensing Yankee Atomic Electric Company 25 Research Drive Westborough, Massachusetts 01531

Dear Mr. Kay:

The !!RC Staff has reviewed the actions you have taken to correct the welding

. discontinuities that were found in the feedwater system piping at Yankee-Rowe.

These discontinuities were determined to be gross fabrication defects and not fatigue cracks assisted by corrosion found at other facilities as summarized in Table 1 of the enclosed safety analysis.

We find that the replacement and repair of the defective welds and radiography of all replaced and repaired welds are adequate to ensure the integrity of the feedwater piping.

We acknowledge your coraitments:

(1) to perform volumetric inspections of the elbow to feedwater nozzle welds during the next refueling outage and (2) to maintain cognizance of the activities of the Owners Group working on feedwater piping problec:s.

You will be advised of any required further actions if warranted by the results of your volumetric inspections or our review of the Owners Group evaluation.

Sincerely,

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Dennis L. Ziemann hief Operating Reactors Branch #2 Division of Operating Reactors

Enclosure:

Safe y Analysis of Interim Actions to Eliminate Feeen'a:er Piping Cracking cc w/enciosure:

See next page 8003190911

Mr. James A. Xay February 26, 1980 cc Mr. James E. Tribble, P resident Yankee Atomic Electric Corpany 25 Research Drive Westborough, Massachusetts 01581 Greenfield Con 1 unity College 1 College Drive Greenfield, Massachusetts 01301 Chai rra n Board of Sel ectren Town of Rowe Rowe, Massachtsetts 01257 Energy Facilities Siting Council 14th Floor One Ashburton Pl ace Boston, Massachusetts 02108 j

Director, Technical Assessment Division Office of Radiation Programs (AW 459)

U. S. Environcental Protection Agen:y Crystal. Mall #2 Ar' ' ;t:n, Y' r;' M 3 20450 U. 5. Envirenrertal Protection Agen:y Regi on I Office ANN : EIS C0:3.C:MTOR JFr. Federal Stii d'ng Boston, Massacnesetts C2233 l

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4 SA E Y ANALYSIS OF, INTERIM ACTIONS TAKEN TO ELIMINATE FEEDW'ATER PIPING CRACV3 On May 20, 1979, Indiana ar.d Michigan Power Cc pany 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-Cent.

Leaking circumferential cracks were identified in the 16.inen dieneter feed-water elbows adjacent to two steam generator nozzle to elben welds.

Subsequent radiog achic examinations revealed cracks in all eight steac generator feedwater lines at this location on both units 1 and 2.

On May 25, 1979, a letter was sent to all P'iR licensees by the Office of Nuclear Reactor Regulation which informed licensees of the D. C. Cook f ailures and requested specific infora: tion on feedwater system design, fabricatien, inspection and oper-ating histories.

To further explore the generic nature of the cracking problem,

ne Cffi:e of Inspection ar.d Enforcement re:uested licensees of PWR plants in curren; outages to immediately concuct volune:ric examination cf certain feedwater

iping welds.

As a result of tnese actions severai otner iicensees reported cracking in :ne s ean generator fee: water no:zie.co.: icing weld vicinity.

On June 25, 1979, was issued.

t he m,ulietir. re:Dired inspe::1or. ci the steam :ener-Lile in 7_

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r a:Or nc::le.to-sice weios anc adj acen: areas withir. 90 days.

.aws were found in these welcs, the teeawa er piping welc.s to :ne first su:ocr, One f eedwater p.ipinc

containmen: cenetra-ion and the auxili ary feedwa er to r.ain fee: water pipino

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conne::i:n were re:uire: :: be inspecte:.

'n confo 7.an:e with the Bulletin, the licensees of :ne plan s liste: in the a: a:ned Table i com,nie ed :ne radionranhic axaminations ene foiand crackin; in

ne feecsater ciain; system:.

Meetings and/or teie:ntne ::nference cliis were held with ne resse: ive licer.se.es

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2-Group, significant cyclic stresses have :een identified that occur in the feedwater piping in the vicinity of the stear, generater no::le fr::n =ixing and stratification of cold auxiliary feedwater with hot wner fro = the s etn generator during low ficw conditions. The Owners Group is expected to c=:siste tneir investigatiens and take reces:endations for changes in desi;r. and operatin; pre:edures in February 1980.

The licensees have repaired and/or replaced the affected piping in most cases with improved designs to minimize stress ristes. In additior., the licensees have com-mitted to reinspect the stea:n generater.c feedwater piping weld vicinities at tne subsequent refueling outage.

Although the piping has been repaired at tne facili:ie_s listed in Table 1 the sta#f feels that cracking could re-c:=:fr in the ft::: e a: these f acilities.

The staff and Owners Group both nave pedemed ince:er. cent analyses and have deter-mined that flawed feeuwater piping c ul: #.::stan :nalienges from operating and

1. aulted loads including seismic and li=ite:. eater 1:ars vitn ut loss of piping integ-ity.

Pipe breaks have o::urred it tne past it feeawater piping as the result Of water harmer loa s.

However, cesig :r.inges su:n as "C tubes have been tace and Ocerttional changes have o::gr-e: :: --it'.mi e : a

ssibility of water he:rer.

In tr.e unlikely even of a feecwiter ;i:e :reak fr=

1 severe water harrner, :ne conse:uences nave been analy:ed as a cesi n :a.se a::icent an: at:eptable mea:ures-ceal witt, One even; have been establis ned.

Tne N?C nas institute a Pipe Crau 1:::. ~ rcu: :: *eview tr.is and other pipe Ora:k-in; cr: biers in PWP,'s.

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=lete its work ey June 1950 an: : evi:e rec:=er.:ari:ns for review an: i=iemen-tition :y licensees as new :riteria fer ::ert:in; :iar.1.

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