ML20062H682

Discusses Differing Prof Opinion of Adequacy of Weld Drawbead Repair of Pressurizer Relief pipe.Third-party Insp Desirable & Should Be Implemented Re Acceptance of Repair

ML20062H682
Person / Time
Site:	Sequoyah
Issue date:	06/16/1980
From:	Halapatz J Office of Nuclear Reactor Regulation
To:	Pawlicki S Office of Nuclear Reactor Regulation
Shared Package
ML20062H675	List: IR 05000327/1980012 ML20062H670 ML20062H676 ML20062H682 ML20062H690 ML20062H693 ML20062H695 ML20062H700 ML20062H704 ML20062H707 ML20062H710 ML20062H713 ML20062H719
References
NUDOCS 8008210248
Download: ML20062H682 (4)

Text

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.,.,2 UNITED STATES

[?} - [' '; NUCLEAR REGULATORY COMMISSION

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• • • • • June 16, 1980

ocket Sos. 50-327/328 MIv.0 5.A N UM FOR: S. S. Pawlicki Chief

, Materials Engineering Branch Oivision of Engineering T:0M: J. H11apatz

.v.aterials Engineering Branch SU3 JECT: EXPRESSION Of DITTERING PROFESSIONAI. OPINION IN T.$iE MAT'"ER OF THE ACEQUACY CT SEQUOYAH UNIT ONE WE;,D DTw\*,GEAO RE7 AIR OF PRISSURIZER REI,IEF PIPE The auther of this =e=orandum, hereinaf ter referred to as the =ir.srity, herewith expresses his minority opinion in the matter of the adequacy of the weld drawbead repair of the Sequoyah Unit One pressurizer relief pipe. The

-inority expresses its differing professional opinion in accordance with Section II. A. 3.J of the memorandum, Sa=uel J. Chilk to William J. Oir:ks ,

dated .v.sy 1, 1990, subject, "TY 1952-96 Policy Planning and Program Gaidance (77P3)."

Ncn 0:nfor ance Fepor , NCR SWP-79-S-8 disclosed, that during the hot fun:tio .al testing of Sequoyah Unit One, 1-ROH-93 pipe support for the

pressurizer relief piping failed to slide in the vertical direction as the pressurizer expanded during heatup of the reactor coolant systen. As a result the 6-inch, schedule 160 (nom. .718 wall) , Type 316 stainless steel pressuricer relief pipe was bent. '"he related safety implicatiica was that f ailure of this piping could lead to an uncontrolled blowdown of the reactor coelant syste=.

As corrective actions, TVA had two options. The first option was to cut out the da. aged pipe and replace it. Sis option, however, would require a system pressure test in ateordance with ('77) ASME Code Section X: IWA-4400(a),

which requires that after repairs by welding on the pressure retaining bou .dary that a system pressure test be performed. Se second eption o.s to straighten the pipe by a repair procedure which would be exempted fras system hydrostatic testing. -"/A , to avoid cutting out the damaged pipe, scught this exemption through 74A-4400(b)(3), which exempts *ran hydrostatic testing repairs by welding on the pressure retaining boundary provided that the repairs did not penetrate through the pressure boundary.

I Sa' correct.ive a: tion used by !"iA to straighten the pipe was the weld drawbead technique. So 270' grooves were ground in the pipe opposite to and straddling the kink. De grooves were filled ith .# eld metal, reground to remove that weld metal, then filled a second time with weld metal. Weld metal shrinkage provided the stressing to plastically straighten the pipe.

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5. S. Pawlicki The repair was accepted by the Materials Ingineering Branch via the m emorand um , Pawlicki to Rubenstein, dated Le ember 4, 1979, sabj ect ,

" Tennessee Valley Authority, Sequoyah Nuclear Unit No. 1." TVA justified the exam; tion from hydrostatic testing of the system after the repair on the basis of TWA-4400(b)(3), claiming that the process of welding to realign the pipe did not result in penetration of the reactor coolant boundary. The minority challenged acceptance of the repair on the basis that more informatilon was needed.

The memorandum, Gastafson to Pawlicki, dated January 25, 1980, subj ect , " Trip Report cf visit to Tennessee Valley Authority Sequoyah Nuclear Plant, Unit-1," ,

which re; 3rted on a visit to the Segaoyah site, found the repair acceptable.

The min:rity, af ter review of this memora9dum and do:umentatis: r elated thereto, recc: mended in the memorandum, Halapatz to Pawlicki, dated Tebruary 27, 1990, subject, "Sequoyah Unit One Weld Orawbead Fealignment of 6" Presscrizer Felief Pipe," tha t the Materials tsgineering Branch defer acceptance of the repair pending the development and revisw of additional in fo rmation. The minority was then advised by his assistant director that he was to personally examine the weld mockup used to qualify the repair which had been made. The memorandum, Pawlicki to Rubenstein, dated Tebruary 29, 1990, subject, " Tennessee valey Authority, Sequoyah Nuclear Plant, Unit No. 1, Fealignment of Pressurizer Rallef Pipe," then reiterated acceptance of the repair and rec:=nended that the minority meet with TVA personnel and exa-ine metallographic samples. On March 5 and 6, 1980, the minority visited TVA at Kncxville and performed a metallurgical examination of the mo:kup used for the _

qualification of the weld drawbead realignment of the Sequcyah Tait One pressuri:er relief pipe. Metallographic evidence was documented which showed that the mo:kup weld was fully penetrated. Pull penetration of the mockup weld, which was supposed to represent the weld repair of the damaged pressurizer relief pipe, obvously did not demonstrate compliance with Se: tion XI IWA-4400(b)(3). This finding, in itself, provided cause for denial of ext ption from hydrostatic testing of TVA's weld drawbead repair of the pressuri:er relief pipe which had been made. Other inconsisten:les were noted between the mockup and the actual relief pipe. For example, a dif ferent material .as used in the mockup. Further, while the mockup had only one weld groove, the actual relief pipe repair used two weld grooves. In addition, metallographic evidence was documentad which showed through-wall sensitization to a significant degree, indicating that a potential through-wall crack propagatien path existed. Since the propagation of cracks through the pipe wall is the essential concern with respect to the integrity of the reactor coolant boundary, it is the minority opinion that intergranular corrosion tests which sould expose to the test environment specimens which represent the through-wall =icrostructure should be performed. However, only tests of :D specimen surfaces were performed.

Given that the mockup weld was fully penetrated, the minority concluded that TVA had not qualified its exe=ption to system hydrostatic testing.

3 sclosure of the above bsfor=ation let to a meeting of TVA and NRO on Mar:h 13, 1990. It was agreed that TVA would perform in situ metallography to evaluate sensitizatica in the actual relief pipe repair and re-radiograph the repair to determine whether or not the pressure boundary had been fully

e S. 5. Pawlicki penetrated. The exa-ination, reported in the memorandum Mills to c'Reilly, dated April 11, 1980, subj ect, "Sequoyah Nuclear Plant Unit 1 - Pressuriter Relief Piping Support - NOR SW7 79-5 Supplemental Inf:rmation" found the weld heat affected zone to be unsansitized and therefore, that sensitizec base metal underlying the weld did not encroach on the pipe ID. In addition, on the basis of radiographic examination of the repair, it was concluded that the weld did not encroach on the pipe ID, i.e., did not fully penetrata the reactor coolant pressure boundary. These results were concurred in by CII-RI!

in the memorandum, Murphy to Thornburg, dated April 22, 1980, subj e rt. "RI' eport No 50-327/30-12 Concerning Inspection Performed to Ivaluate Repair of Sequoyah Unit 1 Pressurizer Relief *ine."

The minority considers that meaningful metallurgical conclusions cannot And should not be =ade from Xerox reproductions of the in situ metallography, which have been made available. Given the carbon content (.052/.059%) of the pressurizer relief pipe, the minority finds it anomalous that the weld heat affected :enes did not show some sensiti stion, since then it is inferred that the base metal at any distance from the molten weld metal essentially did not experience sene time in the 800*F to 1500'F sensitization range during post weld cooling.

The catter of the sensitization of austenitic stainless steels is enveloped in centreversy. Arguments are made that the weld drawbead repeir welds are no different than ad;cining full penetrated in s*.allation welds. In the absence of identical retallurgical histories, however, this argument is tanuous. The nincrity notes the safety implication involved, viz., that failure of the .

repaired piping cannot be isolated, which as a consequence, could lead to an uncontrolled blowdown of the reactor coolant system. The minority is of the opinion that this matter be examined to a much more definitive and conclusive end. It should also be kept in mind that the environment, which will be .

experienced in service by the repair, will be a calculated 0.2 ppm maximum oxygen bearing steam rather Chan reactor coolant water containing a residual oxygen concentration during power operationn of 0.005 ppm. SWR pipe crack experience and the lack of corrosion data on the performance of sensitized austenitic stainless steel weldments in 0.2 ppm oxygen bearing steam would suggest caution in acceptance of the Sequoyah weld drawbead repair of the pressuri:er relief pipe. The argument that PWR service experience hat not '

identified a problem with pressurizer relief pipes is tenuous, because it is unknown how many, if any, operating plants include pressuri:er relief pipes which have been repaired as has Sequoyah's. Given this uncertainty, which the minority feels is related to the in situ metallography performed, the mere definitive laboratory examination and corrosion testing cf boat sa ples parted frem the weld drawbead repaired Sequoyah pressurizer relief pipe is proposed for consideration.

With respect to the finding that the weld repair did not full penetrate the reactor coolant boundary, it is the minority opinion that it has not been demonstrated that the radiographic technique used has the capability *4 develop this conclusien. While evidence that the 2T hole in an AS M No. 12 )

penetrameter was visible to TVA Level III film interpreters and 0:I-RI:

persennel may de-enstrate that defects are not present, these criteria may not necessarily demonstrate the capability of the technique to discriminate in a 1

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S. S. Pswlicki radic;raph between sound weld metal and sound wrought base metal underlying the said metal. The techniqye must be able to provide for this distinction in order to confirm wnether or not the weld has fully penetrated the reactor coolant boundary. The capability of the techniqye could be confirmed or denied by radiographing a known fully penetrated weld and a known partially

>enetrated weld in the sarse material and observing if a distinction can be ade in fil density dif f erences in the weld root area between weld metal and rought base neta.

Oiven the controversy which sometimes attends the interpretation of exa-instion results, inspection by third party is desirable. Attention is

alled .o an N30 position stated in the memorandum, Rubenstein to Farris,

'sted Septe-ber 12, 1979, subject, "Oualifiestion of Inspectors, Inspe: tion S;ecialists, and inspection Agancies for seqacyah." The Rabenstein menorandum states the NA: position that TVA institute third part inspection for the sequoyah nuclear plant._ The Rubenstein memorandum is provided as an attach. ent to this memorandum. The minority opinion concludes that third

-arty inspection is required and should be 1

:plemented in the matter of the a::e; tan:e of the weld drawbead repair of the sequoyah Unit One pressurizer relief pipe.

2^9 J. Balapat Materi:11 Enginee. , 3 ranch Division of Engineering s office of Nuclear Reactor Regulation Inclosure:

As stated c:s V. S. Noonan R. L. Tedeseo A. Sch.encer C. E. Murphy, 0 I-RII A. R. Herdt, 0:E-RII R. M. Gamble C. Stahle

p. K. Van ?>oorn, OIE-RII MTE3 Meading Tile

DISTR!!U ION SEP 211979 Docket Files bec: NSIC NRC PDR TIC Local POR ACRS (16)

TERA R. Mattsen LWR-4 File D. Eisenhut 00cket Nos.: 50-327/323 D. Vassalle J. P. Knight S. Varga L. Shao F. Williams S. Pawlicki Mr. H. G. Parris L. Rubenstein V. Neenan

.ana ar Of Power C. Stahle R. Gam:le Tennessee Valley Authority M. Service H. Conrad S 3A Chestnut Street Towr II ELD . C. Wocchead C. Y. Cheng Chattancega, Tennessee 37401 IE (3) 5. J. 5hatt t 4 18.alapat: J. M. Grant

. ear Mr. Parris: F. 8. Litten M. Hum C. D. Sellers M. L. Ec'vle SUSJECT: CUALIFICATION OF INSPECTORS, INSPECTION SPECIAL!S 5, A.'D

!.1SPECTION AGE.NCIES FOR SEQUCYAH In A.endrent No. 51 to the Secucyan FSAR, you stated that you will previde ycur own independent review of the Secticn XI program of tne ASME Boiler and P e:sure Vessel Code th : ugh the T/A central effice staff in Cha"*--*",

Tennessee. It is T/A's ;0licy t: previde its cwn inspecticn semices en t.se basis that T/A is a Federal agency and it is not subject to State er other non-Federal inspect:rs.

It is cur ;csition that T/A is not e.xempt from any cf the requirerents of 10 CT. Fart 50, Section 50.55a(g)(4). Therefore, we recuirs that T/A institute the third party inspec-icn system of the Secucyah nuclear ;ce r plant.

A letter o'f c: pliance is requested. .

Sincerely, tvigi:21 igest W!

L. S. Rubenstein, Acting Chief Light Water Reacters Sranch No. 4 Division of Pr0fect Management cc: See next page j m g Q ,  % lw k U C 9l-hf -

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..... SEP 211579 Oceke Nos.: 50-327/328 Mr. H. G. FarEis l'anager of Fcwer Tennessee Valley Authority 500A Chestnut Stree Tener II Chattanooga, Tennessee 37401

Dear Mr. Farris:

SU5 JECT: CUALIFICATION OF INSPECTORS, INSPECTION SPECIAL!STS, AND INSFECTION AGENCIES FOR SEQUOYAH In Amendment No. 61 to the Sequoyah FSAR, y:u stated that you will ;r: vide your can indepencent review of the Secti:n XI program of the ASME 5:iler and Pressure Vessel Code througn the TVA central office staff in Cha :ancoga, Tennessee. It is TVA's policy to provide its own inspection services On :ne basis that I'lA is a Federal agency and it is not subjec: to State or other n:n-Federal inspec ors.

It is our position that TVA is not exempt frc any of the re:uirements of 10 CFR Far: 50, Se:: ion 50.55a(g)(4). Theref:re, we require tha: TVA institute the tnird party insoe::icn system of the Sequ:yan nuclear ; *er pian:.

A letter of c; pliance is requested.

Sincerely,

.4 5 ./w' .c L:O L. S. FI.:l:enstein, ac ting Chief Lign: *4ater Reactors 3 ranch No. 4 '

Division of Projet: Management c:: See next page L[dA ,

9,paghus'l .