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Subjects Corrocien Evaluation - Oyrter Creek Nuclear Power Plant, New Jerney Intergranular streco-ascisted corrosion and veld defects vere found in stub tubes and the control-rod houcing of the pritnry preocure veccel at Oyster Creek IMR Power Plant af ter the field hydroctatic test in Oct.,1967.\\l1 Tnic letter ic (a) a review of the literature concerned with intercranular ctresc-accisted corrocion of sencitized Type 304 stai.nlecc cteel in reactor service and in Limulated laboratory tests, and (b) an accecerent of the strecs corro-cion program at G.E.-APED laboratory on the repaired con:ponente of the prescure vescel at Oycter Creek.
I.
Snrvice Failure and Pimulated inboratory Tente The exact inechanism of intergranular stress-assisted corrocion of cen-citized Type 304 in lo N hloride (~ 10 ppm) or chloride-free (< 1 ppm) vater to not known.
However, a review of literature relating to cuch corrocion cracking cf tensitized Type 3Oh ctainless cteel vill give a better percpective in the evaluation of the corrosion program at G.E.-APPD Inboratory.
(1)
U. S. Arny Stationary Medihm Power Plant (SM-1)
Intergranuinr cracking of Type 304L stainless steel cladding occurred in the Army SH-1 pressurized vater reactor and vao believed to be re-
. lated to ' e fuel ascen.bly process, which resulted in(carburization, censitiza-tion, and 1 ornnt4og of cource grains in the cladding. 2) Tnic theory van sup-ported by Peaver\\3/ vho found that the cladding was censitized during fabrication eliminated this problem in subsequent cores. ')304 by Type The replacement of T) bycarbondiffusionfromthefuelmatrix.
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(1) Ibeket 50-219-Amendment No. 37,' Oyster Creek Nuclear Power Plant - Table III-2.
(2)
T., J. Pashos, TID 8540 (1964).
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(3)
R. J. Peaver, OPuiL-2312 (1957).
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July 24, 1968 Mr. Murid Porce (2) Davannsh River Hgnetor Pinnt l
Intergranular c'rece-acsisted corracion cracking van detected in two Type 304 etninlcr.c steel np5(/lec in the high-purity heavy-vater rnoderator of the Savannah River Reactor.
The crackc propagated from incidious int r-granuler pickling dabase to the 1/2-inch thick steel, which had oeen cencitized during initial fabrication of the velded nozcice.
Oracking vac attributed to chloridat ione, although the t,ulk vater contained only 0.006 ppm chloride. Tne chloride ions vere believed to have concentrated in the crevices of the ir,ter-ganular pickling cracho, which vac confirmed in laboratory tecto. Speci*: ens in the form of U-bends that vere pickled to produce intercranular attack choved further intergranular corroclon vithin 450 hours0.00521 days <br />0.125 hours <br />7.440476e-4 weeks <br />1.71225e-4 months <br /> in water containing only 2 ppm chloride at 93*C.
Inter, Rideout } f nvecticated the rode of otrecs corrosion attack on censitized and pickled "'ype 304 ctainicac oteel with rec; met to yll effect.
By using U-bend specimens inerced in 30 ppm chloride vater at 90*C and by ad-i justing the pH vith nitric acid, he nbcerved mixed trantgranular and intergranu-lar cracking in the pH rance from 7 0 to 4.0.
At pH 3 5 and 3 0 cracking van exclusively intergranular. Rideout alec found that oxygen van necessary for cracking, and the cracking tendency increased with increasing oxygen content in water.
(3) Oak Ridce Reactor Loop Intergranular cc. ?cion vna reported on Type 304 stainlece steel cladding that had been irradiated in the helium cooled 0.l?.R. Loop 1 at cladding temperatures to 819 0.
After irradiation, the elements vere stored in an underwater aren for coveral veeks. Tne obcervations indicate that otor-age of. censitized,- irradiated 7ype 304 ctainless steel in high-humidity environ-rents or underwater ray lead to intergranular strecs-ascicted corrocion.
(4) Drecdon Pover Plant In December 1965, operating personnel at Dresden Nuclear power Station No.1 discovered a leak in an SA376 - Typ3 304 bypaso line in "C" loop of the IME secondary-generator recirculation system after six years of cervice.
Microexamination of the pipe revealed intergranular cracks. The microstruc,ture surrounding the' crack chove grain-boundary carbide precipitation as recult of trancient heating in the sensitizing range during velding.
'1he cracking is (4)
-S. P. Rideout, Streso Co g cion Cracking of Type 304 Stainlecs Steel in High Purity Water, proc. bd Inter. Cong. on Matallic Cctrosion, p.159,
. NACE (1966).
(5)
- 8. P. Rideout, Effect of pH on Stress Corrocion Cracking of 18-8 Stain-
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lecs Steel in Lov Cnloride Water, paper precented at NACE, 20th Annual Cont., M1rch leio 4.
.(6)
E. L. Longs Z. C. Michelson, OWL-3684 (1964).
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'rectricted to the heat-affected zone.
he pro;ngatica extends through the plus dsita-ferrito veldmnt.(ry)tal and arrecto at the two-phace auctenitic cingle unce auctenitie. base 1
(5) Sinalate3 laboratory Tecto Copcon and honomy(I} at Irternational Nickel Co. conducted strece corrocion tecto in -*et.curized vater t.t 600*F (316'C) with double U-bend opeci-u nc; the tecte vere conducted in autoclavec. he cor:pocition of the gas phase above the water and zhe pl! of the vater were controlled. In sencitized Type 30h ctainlece cteel, it.tercranular cracks were observed only in crevice arece under tencion when the cac phace above the water contained any ons of these three con-ditione:
(a) 5% oxygen and 95% nitrogen, (b) air, and (c) oxygen. he initial p11 of the demineralized vater vac adjusted to 10 vith ammonium hydroxide. At the end of the tect, the pH of the vater meacured 7 9, 7.6, and 6.7, with rec-pect to the three tect conditionc.
Similarly, th9 chromium content in vater vac 17,(a).6, and 5 7 ppm reclectively. hydrogen, (b) argon, or (c) 1% oxygan an 2
If the cac phace above the water con-tained vac observed during a 3000 hour0.0347 days <br />0.833 hours <br />0.00496 weeks <br />0.00114 months <br /> test.
In the latter three tecta, the fint.1 pH of the water vac 9.6, 9 1, and 8.8, recpectively.
There van racoto detectable increaseinchromiumcontent(<1 ppm).
Copcen et al. postulated that the c.ombination of high oxygen concentration, high ctress, and a crevice vac ra-quired to cauce crack 1ng.
He expected thnt the differential aeration cell vould lover the pH vithin the crevice. htrtherrore, hexavalent chromium was obcerved in the bulk colution and the concentration of such an oxidizing cation within the crevice could to cubctantially higher.
In cu m ry, intercranular otrecs-accicted corrocion of cencitized Type 304 ctainless cteel in a reactor-vater environment can ocour under proper com-binationc of lotalized streco, log pH,+ oxygen and/or chloride ion nnd crevices where oxidizing cations (e.g. Cr+, Fe 3, Cu42) can accumlate.
- Necently, catactrophiegrninboundarycorrocionofan113Cr-Fealloyinneutr(gcodium chloride solution (0 5N NaCf - pH 6.0) vac reported by htler et al.
Tnic form of attack is not expected to c:cu-on a very pure high-chromium alloy.
htler et al. cuccested that the extremely localized nature of the attack van due to t.ome unucual heterogeneity.
Even in a colid-colution alloy of this type,therearedifferencesinchromium(andpocciblyoxygen)levelbetween gra'n and grain-bpundary region due to equilibrium cegregation.during the_an-neel. The attack probably vill start. at boundaries where there is considerable arypliar mictatch, a large difference in chromivfn nontente and considerable free energy. Tnus when repairing the stub tubes with Type 306L veld-overlay of (V)
H. R. Copson and G. &onomy, Effect of Some Ihv1ronmntal C3nditions or.
Stress Corrosion Behavior of Ni-Cr-Fe Allo q in Itessurized Water, Corroefon, Vol. 24.
(8)
G. Butler, 'i. C. K. Icon, and p. Stretton, Cactastro gic Grain Boundary Corrnsion in a Cr-Fe Alloy, Corrocion Sci. p, 231 (19od).
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W. Inurid porte July 2h,1968 ctaitneco steel,creviceo in the forn, of root-veld ernche and localized regrega-tien of reldmntu hre crpected even tuider the bent conditionc.
In which ence, any necclerated or cirulated corroclon tento runt include enevice cpecicene of repaired veldmntc tabu fren reprerentative loentione in the renetor.
II.
0.E.-klTD Inboratory Tecto 7te G.E. kborntory at Vt.llecitoc Uuclear Center conducted a corrocion in 2BP C vnter containing tectbyexporimb)uniaxiallyloadedtencilecMeiment 100 ppm oxygen
-- hereafter referred to as 0.E. necelerator corrocion tect.
Tne rmteriale evaluated included vrouc$ t and veld mtal of 7ype 304 nnd 7ype 30!.L ctainlecc steel. Tne following conclucions are mde:
(a) Solution-anneal materini, with no plactic deformtion other than thnt accocinted with dreccing-ti-yleid, choved no evidence of intergranular crucking after 300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br /> of expecure.
(b) Carbon ic probsbly reopanciblc for intergranulnr rtrecc corro-tion of censitized nuctenitic alloyc.
If carbon content in thece mterinic toe equal to or lecu than 0.03 v/o, then there materiale do not exhibit crach-1ng.
(c) Duplexalloya(ferrite Tuctenite) appea.' to be 11utne to inter-granular otivcc corresion even af ter a neat treatmnt that vould normily recult in censitiention in auctenitic mterialc.
Tnic immunity in indeg ndent of the nature of the ferriie otabilizer enployed.
We choulu view there conclusionc baced on G.E. necclerntor corrocion tect vith extrenc caution in relating then to failuren obccrved nt O/cter Creek Power Plant and itc cubequent service operation.
Note thnt the tept) var Ier-both Itideout(h nnd formd(A the abcence or erevices at the streco area.
Copcon have definitely illudrated that u.aterialc without crevicec nre im-cane to intergranular cracking but become cucce};t(ble to cracking vhen crevicer are precent. Furthermore tickler and Vinckier\\9/ mnde an electron-microccole study of concitfczed austenitic ttainleco eteel ex}ceed to two standard inter-ranular corrocion teste - Strauco colution (CuSG -ilpSO ) and lluey colution 4
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Tne retalto reve tied a mrked difference in corrocion-frneture curface.
g In the Strause test the diccolution of the mtal occurred along a narrow region in the vicinity of carbide particles, which refaain substantially unattacked.
In the Ency tect, both carbide particles and G vider region of mtrix vere com-pletely diccolved, and a thin Fe-Cr oxide inyer was deposited on the corrocion curfaecc. Measurements of electrochemical potential of carbido and steel choved that carbide is core noble than the steel mtrix in.the Strauco colution nnd leco noble in tne lluey celution. Thus, the local intergranular attack of cen-siti.ed oustenttic steel in a certa u corlrocion colution teems to be governed 8
(9)
Ii, Stickler and A. Vinck$cr,12ectron Microccope Invectication of the Intergranular Corrosion Fracture Surfaces in a Sennitized Auctenitic Stainienc Strel, Corrosion Sci. 3, 1 (1963).
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by an electrochemical procecc, and ic dependent on the relative nobility of the carbit.e compared with the steel in the colution under consideration.
Since the exact mechanicm of'intercranuhr ctrecc-assisted corrocion of cencitized stain-lecc uteel ic ? V knovn, any definite conclusion on the 0.E. accelerated corro-sion teet alone vould be premture, pcyticularly when the crevice effect is not understood.
The writer highly reco:nende the following:
(1) Crevices choul'l be included in all Q.E. chort-rance laboratory tects L
an outlined in Table III-2 of Amendment 37. (1)
(2) Consideration chould be civen to corrocion evaluation in the propoced in-cervice inspection (program for the reactor coolant cyctem ac rentioned in IV-S of Amendmeric 37.1)- Tnic includes evaluatinc corrocion speciceno under high strecc and with ecevices in two stepc, (a) in::ndiately after hydrostatic test before reactor ctart-up, and (b) after reactor cervice during(neyt sche-duled chut-dovn.
(Note the Naval Research Inboratory han reported 10) that veld metal io more cencitive to irradiation damse with respect to notch ductility than the base ental of AS24 Type 302-B steel.
Thic informtion vac obtained from the curveillance program at the B1G Rock Point Plant. Tnic ic n 240-tegavatt,' therm 1, boiling vater plant with a 6-inch thick reactor veccel.)
Yours cincerely, 4.4c1././[D 1
raig F. Cheng %
lhtallurgy Divic'.on CFC:cv CC; Peter A. Iberic, Director of Reactor Licensing R. D. Young, Cnief, Containrent (c Component Tech. Branch bec: P. G. Shevrrn T. F. Kacener
- J. E. Draley S. Greenberg l
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R. A. Noland l
(10)
L. E. Steele et al., USAEC Report NLibmo 1731; liL6349; UL6415, N W 6419 (1956).
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Advisory cessaittee en naaetor Safstusrds U.S. Atomic Energy Camaission Washington, D.C.
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Dr. William L. Faith 3540 Iksntingten Drive Desa Duasto J. Palladime San Marino, Calif. 91108 College of testaaertag time Pennsylvania State Ihmiversity Dr. F. A. Gif ford. Jr.
101 Mammond buildias Atmospheric Turbulence &
University Park, Pa. 16402 Diffusion tab.- (t.ssA) e/o USAEC. PO Box E Dr. (bester P. Stees Oak Ridge, Tennessee 37830 Dept. of Civil Bastaearias 3129 Civil Desimmeries Bida.
Dr. Stephen H. Hanauer Daiversity of 111Laois 606 Dougherty Hall t%ana. Illiasta 61801 University of Tennessee Knoxvills. Tannessee 37916 Dr. William R. Stratton las Alamos Scientific lab.
gyremspnrmrmmurr1X P.O. Boa 1663 mrunwrsupnarmamF 14e Alamos Dew Heateo 87544 Dr. Herbert S. Islin Dr. Carro11'W. Habel Dept. of Chemical Engineering Director of Rasaarch University of Minnesota University of Housks Minneapolis. Minn. 55455 Outlan Boulevard Mouston, Tomas 77004 Mr. Harold G. Mangeladorf 78 Eno11 wood Road i
Short Hills, New Jarsey 07078
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Dr. Harry O. Hansen 130 Bldg.10 - Rs. E-139 Arsonne National laboretory 9700 South Casa Avenue Argonne. Illinois _ 60439 f
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<J DEL MAS SMDUIJ:D N'71m Witti REPEsstwrAfrygs or JEa8ET CEWftkL POWER AW "' 4 LIGiff OWNY,1:30 P.M., CCTGIEL 24,1966, RETWE9M, MLET1AE ABC OFFICE.
Tt!E ADEQtlACY Dr MIE OYSTEA CAltK PEE 88URE VES8EL INIFICTION PROGRAW, RSP9CIALLY IN RICARD TO ULTRA 5ONIC AND WYE PERET8 ANT TESTIltG IN TKE AIERA 0F TEE 00Nft0L I
200 DRIVE NO:ZLES WILL kt DISCUSSED.
IT IS Alrt!CIPATTU THAT, WITWIN I
Ar*ROXDMTELY OPfE VtEK, PURnttA TEST!M; WILL BROG(t QUITE D!rFICULT WUE j
TO IMSTAt.tJ, TION or THE CORE INTERMALS, RTC. Acts MEKattS BAYE i&EEN INVITED TO ATTEHD MIIS HEET!!C.
Er TCO PLAN TO Afrte, PLEASE IKrt!rY THE Acta DFFICE.
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Projsett Oyster Creek Unit Nc. 1 S ta tu s t Provisional Operating License Review Jackgroundt The Oyster Creek Subcosmittee met in Washingtoo, D.C. with representatives of the applicant on June 22, October to, Enonbar 17 and Nwember 27, 1967 and on Wevernber 17, 1968. We Subcommelttes also not se July 28, 1967 in Tor s River, New Jarsey. We projset was considered at the Novenber and Deceuber 1967 ACES a+etings.
DRL_ Report No. 4 DRL has concluded that there ere two areas that saust be resolysd with the applicant prior to licensing. neas are:
I 1.
Provision of an interlock in the auto-relief system to preve12t blevduvn unless cyt.ilability of the core spray systoa is assured.
2.
The technical bases upon which plant turnover frce CE to Jersey Central must be resolved.
DRL also needs to determino that the reactor vessel repairs are adequate, and an acceptable set of Technical Specifications needs to be developed.
s DRL has identified the following to be studied af ter initial licaasing:
6 1.
Improved primary syste:n leak detection and the in-service intpec-tion and surveillance programs.
2.
Detailed reviev of design of FVCI prior to systen operation.
3.
Continued review of t.he design and performance espability of the main steam line isolation valves.
DRL currently plans to provide a -aport to the Cournittee in November concern-ing the reactor 3ressure vessel mod quality assurance and control.
Sumary of October 17, 1968 Subcomit tee Meeting During the October 17. 1968 Subcomittee meeting, it was suggested that good in-service inspection and laak detection methods appear to be ways that the opplicant might maka up for inadequacies in the reactor systee. The N-45 Subcomunittee draf t criteria have not been used by the applicant as a basis for tha proposed in-service inspection program.
Dr. Hansuer indicated concern that the auto-relief systen vill actuate even een the ECCS is capable of handling a certain pri. mary systen break else without7h iivu vi-the-ayatea m The-appl-teas.t 1= ta revlev_what information areald be availtble to the.operatdr.ou which tc baseadecidionastovb(ther to s.11 6v the auto relief system to actuate. IF." Itansiier ar'd'~Dr.11endris plan" s m. ur,.
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to visit the Oyster Creek site en Novseber 23,1H8 te see and diesess Go ! %
instrumentation system, particularly regardias subchannel separettes.
The applicant was informed that he should be prepared to disease the fellow-ing, at the November 1968 Acts meetias, durias a presentation of apprestimately one hour durationt 1.
ECCS - Including discussion of diesel power, the aste-relief system, at.J radio 17eis.
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i 2.
Main steam line isolation valves and the i, elation er=d-aer isolation valves.
g 3.
Primary system leak detection methods, i
4.
Vibrational testing of the steam senerators.
5.
In service inopoetion and surveillanee.
(n is item is to be discussed if Amendment No. 44 which sets forth the in service inspection ud surveillance plena La provided in time for review by Caesair, tee membere before the November ACRS meettaa.
Notet It appears that this Amendment will met be provided in time.)
Dr. Stratton stated that discussion of separation of the instrwnentation sub-l channets would be deferred to a later Committee meeting. No also stated that Lt.e ptessure vessel would not be reviewed at the November meeting.
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