ML17261A160: Difference between revisions

From kanterella
Jump to navigation Jump to search
(Created page by program invented by StriderTol)
(Created page by program invented by StriderTol)
 
(3 intermediate revisions by the same user not shown)
Line 3: Line 3:
| issue date = 12/21/1979
| issue date = 12/21/1979
| title = LER 79-023/01T-0:on 791207,during Inservice Insp of Pressurizer Relief nozzle-to-safe-end Weld,Liquid Penetrant Examination Showed Linear Indications.Possibly Caused by Original Fabrication Contamination or Chloride
| title = LER 79-023/01T-0:on 791207,during Inservice Insp of Pressurizer Relief nozzle-to-safe-end Weld,Liquid Penetrant Examination Showed Linear Indications.Possibly Caused by Original Fabrication Contamination or Chloride
| author name = CURTIS A E
| author name = Curtis A
| author affiliation = ROCHESTER GAS & ELECTRIC CORP.
| author affiliation = ROCHESTER GAS & ELECTRIC CORP.
| addressee name =  
| addressee name =  
Line 17: Line 17:


=Text=
=Text=
{{#Wiki_filter:NRCFORM366I7.77+78CONTROLBLOCK:INYREG1Q2009LICENSEECODE141579-023/01T-0 U.S.NUCLEARREGULATORY COMMISSION LICENSEEEVENTREPORTQi{PLEASEPRINTORTYPEALLREQUIREDINFORMATION) 600000-00Q341111QE~QRLICENSENUMBER2526LICENSETYPE3057CAT58CON'T,~078~03~04~OS~06R"DRT~L~B0500024471207798122179QgSOURCE6061DOCKETNUMBEREVENTDATE7475REPORTDATE80EVENTDESCRIPTION ANDPROBABLECONSEQUENCES Q10Duringnormalinservice inspection ofpressurizer reliefnozzle-to-safe-end weld,liquidpenetrant exa'mshowedlinearindications l-l/8"and3/8"long.(T.S.6.9.2.a(3))UTdidnotshowany.FollowupX-rayexamshowednovolumetric indications.
{{#Wiki_filter:NRC FORM 366                                                                                                                    U. S. NUCLEAR REGULATORY COMMISSION I7.77+                                                                             79-023/01T-0 LICENSEE EVENT REPORT CONTROL BLOCK:                                                  Qi                {PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)
Furtherliquidpenetrant andreplication showedareaofattack6-7"by1/8"consisting ofafamilyoffinecrackssimilartointergranular typeattack.Allpressurizer headnozzle-to-safe-end weldareaswereexaminedwithUTandliquidpenetrant withno~0878otherrelevantindications noted.80~OgSYSTEMCAUSECAUSECOMP.VALVECODECODESUBCODECOMPONENT CODESUBCODESUBCODE~CBQ>>'~EQ12~DQTRP1PEXXQ14~BQEE~ZQs78910111213181920SEQUENTIAL OCCURRENCE REPORTREVISIONLERIROEVENTYEARREPORTNO.CODETYPENO.Q17REPQRT~79+~023QX~01QT-QO2122232426272829303132ACTIONFUTUREEFFECTSHUTDOWNATTACHMENT NPRDXPRIMECOMP.COMPONENT TAKENACTIONONPLANTMETHODHOURS~22SUBMITTED FORMSUB.SUPPLIERMANUFACTURER
I                                6 N Y        R      E    G      1    Q20          0        0    0    0    0    0    -     0    0Q34              1      1    1    1QE~QR 7      8    9        LICENSEE CODE              14      15                    LICENSE NUMBER                      25      26        LICENSE TYPE      30    57 CAT 58 CON'T R"DRT       ~L~B            0    5      0    0  0    2    4    4    7    1    2    0    7    7      9    8      1    2    2    1    7    9
~BQTR~XPTg~APER~AP270416~YP23~YQ24~NQ25Y17120QER3334353637404'I42434447CAUSEDESCRIPTION ANDCORRECTIVE ACTIONSQ270Possiblecauses:originalfabrication contamination orchlorideconcentration occurring duringoperation.
,~0                SOURCE                                                                                                                                                    Qg 7        8                      60          61              DOCKET NUMBER                              EVENT DATE                74      75      REPORT DATE          80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES                              Q10 During normal inservice inspection of pressurizer relief nozzle-to-safe-end weld,
Investigation includesexamining boatsamplewithscanningelectronmicroscope todetermine corrosive species,andinsulation leachinchemicalanalsis.34Clothcoverreplacedwithfiberglass.
~03            liquid penetrant                  exa'm showed            linear indications                l-l/8" and              3/8" long. (T.S. 6.9.2.
Reportofmetallurgical analysisresultstobesubmitted later.Pressurizer headnozzle-to-safe-end weldareastobereexamined in1980AI&O.789FACILITYSTATUS%POWERs~GQEs~000PER789101213ACTIVITYCONTENTRELEASEDOFRELEASEAMOUNTOFACTIVITYQ3s6~~Q33~+Q34NA7891011PERSONNEL EXPOSURES NUMBERTYPEDESCRIPTION Q3g~77~000Q37ZQssNA78911'1213PERSONNEL INJURIESLOCATIONOFRELEASEQB4445METHODOFOTHERSTATUSQDISCOVERY DISCOVERY DESCRIPTION Q32NA~BQ3IRoutineISI444546808080807891112LOSSOFORDAMAGETOFACILITYQ43TYPEDESCRIPTION g~ZQ42NA78910PUBLICITY ISSUEDDESCRIPTION
  ~04            a(3)) UT did not show any.                               Followup X-ray exam showed no volumetric indications.
~XQ44NewsreleasewasmadeDecemberll,1979.78910A.E.CurtisIIINAMEOFPREPARER8080NRCUSEONLYEgI686980o16/546-2700,ext.
~OS            Further liquid penetrant and replication showed area of attack 6-7" by 1/8" consisting
: 2329,  
  ~06            of a family of fine cracks similar to intergranular type attack. All pressurizer head nozzle-to-safe-end weld areas were examined with UT and liquid penetrant with no
~08            other relevant indications noted.
7      8                                                                                                                                                                        80 SYSTEM              CAUSE        CAUSE                                                          COMP.          VALVE CODE                CODE        SUBCODE                  COMPONENT CODE                      SUBCODE          SUBCODE
~Og                              ~CB            Q>>     '~EQ12         ~DQTR              P    1    P    E    X X        Q14      ~BQEE           ~Z    Qs 7      8                        9          10          11            12              13                              18          19              20 SEQUENTIAL                          OCCURRENCE             REPORT                    REVISION Q17 LERIRO REPQRT ACTION FUTURE EVENT YEAR
                                    ~79 21        22 EFFECT
                                                          +23 SHUTDOWN 24 REPORT NO.
                                                                          ~02          3 26 QX 27
                                                                                                                  ~01 28 ATTACHMENT CODE 29 NPRDX TYPE QT 30 PRIME COMP.
31 NO.
QO 32 COMPONENT TAKEN ACTION                  ON PLANT            METHOD                  HOURS ~22        SUBMITTED          FORM SUB.         SUPPLIER          MANUFACTURER
              ~BQTR ~XPTg                   ~APER             ~AP27              0    4    1    6      ~YP23             ~YQ24             ~NQ25          Y17  1    2 0    QER 33        34                  35                  36            37                  40    4'I                42                43            44              47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS Q27 0        Possible causes:                     original fabrication contamination or chloride concentration occurring during operation.                     Investigation includes examining boat sample with scanning electron microscope to determine corrosive species, and insulation leachin                                                                    chemical anal sis.
3          Cloth cover replaced with fiberglass. Report of metallurgical analysis results to be submitted later. Pressurizer head nozzle-to-safe-end weld areas to be reexamined in 4          1980 AI&O.
7      8    9                                                                                                                                                                  80 FACILITY STATUS              % POWER                        OTHER STATUS      Q        METHOD OF DISCOVERY                                DISCOVERY DESCRIPTION Q32 s      ~GQEs         ~00              0    PER              NA                        ~BQ3I            Routine IS I 7      8    9              10                12      13                              44    45        46                                                                      80 ACTIVITY      CONTENT RELEASED OF RELEASE                          AMOUNT OF ACTIVITYQ3s                                                        LOCATION OF RELEASE        QB 6      ~~     Q33   ~+Q34                              NA 7      8    9            10            11                                          44            45                                                                            80 PERSONNEL EXPOSURES NUMBER              TYPE        DESCRIPTION Q3g
~77         ~00            0    Q37
                                    '12 Z  Qss              NA 7      8    9                11                    13                                                                                                                          80 PERSONNEL INJURIES 7      8    9                11      12                                                                                                                                        80 LOSS OF OR DAMAGE TO FACILITY TYPE        DESCRIPTION                     Q43 g     ~ZQ42                                            NA 7      8    9          10                                                                                                                                                      80 PUBLICITY                                                                                                                                    NRC USE ONLY 7      8 ISSUED
            ~XQ44 9
DESCRIPTION 10 News release was made December                                      ll, 1979.                                     68    69                        80 o Eg NAME OF PREPARER                            A. E. Curtis          III                                            I 16/546-2700,ext. 2329,


Attachnant tcLER79+3/01T-0 Rochester GasandElectricCorporation R.E.GinnaNuclearPowerPlant,UnitNo.1DocketNo.50-244EventDescritionOnFriday,December7,1979,duringanormalinservice inspection programexamination onthepressurizer reliefnozzle-to-safe-end weld,linearindications l-l/8"longand3/8"longwerenotedbytheliquidpene-trantexamination method.Theultrasonic examination performed didnotrevealanyindications.
Attachnant tc  LER 79+3/01T-0 Rochester Gas and Electric Corporation R. E. Ginna Nuclear Power Plant, Unit No. 1 Docket No. 50-244 Event Descri tion On Friday, December 7, 1979, during a normal inservice inspection program examination on the pressurizer relief nozzle-to-safe-end weld, linear indications  l-l/8" long and 3/8" long were noted by the liquid pene-trant examination method. The ultrasonic examination performed did not reveal any indications. On Saturday, December 8, 1979, the area of the indications was prepared by mechanical means with a flapper wheel and light grinding. A reexamination with liquid penetrant revealed an area of attack approximately 6-7 inches long by 1/8" wide. Due to other work being performed in the pressurizer head area supplementary examinations were not performed until Sunday night, December 9, 1979. These examina-tions included more liquid penetrant examinations and radiographic g-ray) examination of the area where the original liquid penetrant indication was found. The radiographs of the affected area revealed no apparent volumetric indications. Supplemental ultrasonic examinations of the area also revealed no apparent volumetric indications.
OnSaturday, December8,1979,theareaoftheindications waspreparedbymechanical meanswithaflapperwheelandlightgrinding.
Inplace metallography was attempted without much success due to the restrictions imposed by the piping system that attaches to the relief nozzle. Replication using a plastic material revealed a family of very fine cracks. In a 2 inch long area the indications were ground*out ah about 1/8 inch depth. Confirmation of this finding occurred when in an additional 3 inch long area the indications were ground out after less than 1/8 of an inch of material was removed. On Wednesday, December 12, 1979, a boat sample was removed for further investigation and analysis of the cracks. The results of the investigations made in the field revealed that the cracks were in the 309 weld material that was used for the dissimilar weld between the carbon steel nozzle (SA-216-GR.WCC) and the stainless steel'safe-end material (SA-182 TP, 316) and not the safe-end material as originally thought.
Areexamination withliquidpenetrant revealedanareaofattackapproximately 6-7incheslongby1/8"wide.Duetootherworkbeingperformed inthepressurizer headareasupplementary examinations werenotperformed untilSundaynight,December9,1979.Theseexamina-tionsincludedmoreliquidpenetrant examinations andradiographic g-ray)examination oftheareawheretheoriginalliquidpenetrant indication wasfound.Theradiographs oftheaffectedarearevealednoapparentvolumetric indications.
The repair procedure included removal of the remaining cracked mate-rial, preparing the excavated area for weld repair and welding with the Gas Tungsten Arc Welding Process utilizing ER-309 base filler metal. Post prep-aration, first weld pass and final weld liquid penetrant examinations were performed. A final weld preservice ultrasonic examination of the repaired area was also performed. The results of all examinations did not reveal any indications .
Supplemental ultrasonic examinations oftheareaalsorevealednoapparentvolumetric indications.
Also examined during this investigation were all the nozzle-to-safe-end weld areas on the pressurizer head utilizing the liquid penetrant and ultrasonic examination methods. The ultrasonic examinations included a normal inservice inspection technique and a special stress corrosion tech-
Inplacemetallography wasattempted withoutmuchsuccessduetotherestrictions imposedbythepipingsystemthatattachestothereliefnozzle.Replication usingaplasticmaterialrevealedafamilyofveryfinecracks.Ina2inchlongareatheindications wereground*out ahabout1/8inchdepth.Confirmation ofthisfindingoccurredwheninanadditional 3inchlongareatheindications weregroundoutafterlessthan1/8ofaninchofmaterialwasremoved.OnWednesday, December12,1979,aboatsamplewasremovedforfurtherinvestigation andanalysisofthecracks.Theresultsoftheinvestigations madeinthefieldrevealedthatthecrackswereinthe309weldmaterialthatwasusedforthedissimilar weldbetweenthecarbonsteelnozzle(SA-216-GR.WCC) andthestainless steel'safe-end material(SA-182TP,316)andnotthesafe-endmaterialasoriginally thought.Therepairprocedure includedremovaloftheremaining crackedmate-rial,preparing theexcavated areaforweldrepairandweldingwiththeGasTungstenArcWeldingProcessutilizing ER-309basefillermetal.Postprep-aration,firstweldpassandfinalweldliquidpenetrant examinations wereperformed.
 
Afinalweldpreservice ultrasonic examination oftherepairedareawasalsoperformed.
~ +
Theresultsofallexaminations didnotrevealanyindications
Attachment to LER 79-       3/01T-0                                                2.
.Alsoexaminedduringthisinvestigation wereallthenozzle-to-safe-endweldareasonthepressurizer headutilizing theliquidpenetrant andultrasonic examination methods.Theultrasonic examinations includedanormalinservice inspection technique andaspecialstresscorrosion tech-  
nique. Welds in associated piping of the four nozzles were also examined utilizing the liquid penetrant method with no further relevant indications noted. There were no health or safety consequences to the public or to plant personnel due to this event.
~+
Cause Descri tion Replication of the as polished weld surface revealed a very tight crack pattern, similar to an intergranular stress corrosion. The boat sample analysis revealed three cracks as follows:
Attachment toLER79-3/01T-02.nique.Weldsinassociated pipingofthefournozzleswerealsoexaminedutilizing theliquidpenetrant methodwithnofurtherrelevantindications noted.Therewerenohealthorsafetyconsequences tothepublicortoplantpersonnel duetothisevent.CauseDescritionReplication oftheaspolishedweldsurfacerevealedaverytightcrackpattern,similartoanintergranular stresscorrosion.
Crack 41      1. 4 mm from carbon steel fusion line
Theboatsampleanalysisrevealedthreecracksasfollows:Crack41-1.4mmfromcarbonsteelfusionline0.4mmindepthCrack42-2.3mmfromcarbonsteelfusionline0.7mmindepthCrack43-3.5mmfromcarbonsteelfusionline1.1mmindepthtouchingcarbonsteelbevelFurtheranalysisutilizing thescanningelectronmicroscope isongoingtodetermine ifanycorrosive speciescanbeidentified.
: 0. 4 mm in depth Crack 42      2.3  mm from carbon  steel fusion line
Presently onlyspeculation canbemadeonthecauseofthiscracking.
: 0. 7  mm in depth Crack 43      3.5  mm from carbon steel fusion  line 1.1  mm in depth touching carbon    steel bevel Further analysis utilizing the scanning electron microscope is ongoing to determine if any corrosive species can be identified.
Itmayhavebeencausedbyoriginalfabrication contamination orbyachlorideconcentration thathasoccurredduringoperation.
Presently only speculation can be made on the cause of this cracking.
Aspartofthisinvestigation achemicalanalysisofleachable contaminants fromthethermalinsulation thatsurrounded thereliefnozzlewasperformed asprescribed inRegulatory Guidel.36,Nonmetallic ThermalInsulation forAustenitic Stainless Steel.Theresultsofthisanalysisareasfollowsforsample1-wovenclothcoverandsample2-glassfibrouslayeredmaterial:
It may have been caused by original fabrication contamination or by a chloride concentration that has occurred during operation. As part of this investigation a chemical analysis of leachable contaminants from the thermal insulation that surrounded the relief nozzle was performed as prescribed in Regulatory Guide
SamplePPMPPMCIFPPMPPMCI+FNaPPMSi03PPMNa+Si03989.4107.4100207307301.631.64099139Basedonthisanalysisaccording toFigureIofRegulatory Guide1.36,Sample2-theglassinsulation isacceptable, howeverSample1-theclothcoverisnotwithintheacceptable region.Althoughitwouldbelogicaltoassumethattheinsulating clothprovidedthechlorides thatmighthavecausedthiscrackingphenomena, theclothcouldhavebeencontaminated duringthehandlingofremoval.Therefore, theresultsofthescanningelectronmicro-scopewillhavetobefurtheranalyzedbeforeconfirming theinsulation involvement.
: l. 36, Nonmetallic Thermal Insulation for Austenitic Stainless Steel. The results of this analysis are as follows for sample 1 woven cloth cover and sample 2  glass fibrous layered material:
n Attachment toLER79-3/01T-0Aspartofthecorrective actiontheinsulation materialwaschangedonthepressurizer nozzlestoassurethatpotential leachable contaminants frominsulating materialwillrequirenofurtherconsideration.
PPM        PPM      PPM      PPM      PPM          PPM Sample          CI        F      CI+F      Na      Si03        Na+ Si03 98        9.4      107.4      100      207          307 30        1.6      31.6      40        99          139 Based on this analysis according to Figure      I of Regulatory Guide 1.36, Sample  2  the  glass  insulation  is acceptable, however    Sample 1  the cloth cover is not within the acceptable region. Although it would be logical to assume that the insulating cloth provided the chlorides that might have caused this cracking phenomena, the cloth could have been contaminated during the handling of removal. Therefore, the results of the scanning electron micro-scope will have to be further analyzed before confirming the insulation involvement.
Alsoeachnozzle-to-safe-end areawascleanedtoremoveanycontaminants priortoreinsulation.
 
Afullreportonthefinalresultsofthemetallurgical analysiswillbesubmitted whentheinvestigations arecomplete.
n Attachment to LER 79-   3/01T-0 As part of the corrective action the insulation material was changed on the pressurizer nozzles  to  assure that potential leachable contaminants from insulating material will require no further consideration. Also each nozzle-to-safe-end area was cleaned to remove any contaminants prior to reinsulation. A full report on the final results of the metallurgical analysis will be submitted when the investigations are complete. These nozzle-to-safe-end weld areas will be reexamined during the 1980 refueling and main-tenance outage.}}
Thesenozzle-to-safe-endweldareaswillbereexamined duringthe1980refueling andmain-tenanceoutage.}}

Latest revision as of 10:04, 4 February 2020

LER 79-023/01T-0:on 791207,during Inservice Insp of Pressurizer Relief nozzle-to-safe-end Weld,Liquid Penetrant Examination Showed Linear Indications.Possibly Caused by Original Fabrication Contamination or Chloride
ML17261A160
Person / Time
Site: Ginna Constellation icon.png
Issue date: 12/21/1979
From: Curtis A
ROCHESTER GAS & ELECTRIC CORP.
To:
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML17249A361 List:
References
LER-79-023-01T, LER-79-23-1T, NUDOCS 7912270442
Download: ML17261A160 (8)
v • d • e


Text

NRC FORM 366 U. S. NUCLEAR REGULATORY COMMISSION I7.77+ 79-023/01T-0 LICENSEE EVENT REPORT CONTROL BLOCK: Qi {PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

I 6 N Y R E G 1 Q20 0 0 0 0 0 0 - 0 0Q34 1 1 1 1QE~QR 7 8 9 LICENSEE CODE 14 15 LICENSE NUMBER 25 26 LICENSE TYPE 30 57 CAT 58 CON'T R"DRT ~L~B 0 5 0 0 0 2 4 4 7 1 2 0 7 7 9 8 1 2 2 1 7 9

,~0 SOURCE Qg 7 8 60 61 DOCKET NUMBER EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES Q10 During normal inservice inspection of pressurizer relief nozzle-to-safe-end weld,

~03 liquid penetrant exa'm showed linear indications l-l/8" and 3/8" long. (T.S. 6.9.2.

~04 a(3)) UT did not show any. Followup X-ray exam showed no volumetric indications.

~OS Further liquid penetrant and replication showed area of attack 6-7" by 1/8" consisting

~06 of a family of fine cracks similar to intergranular type attack. All pressurizer head nozzle-to-safe-end weld areas were examined with UT and liquid penetrant with no

~08 other relevant indications noted.

7 8 80 SYSTEM CAUSE CAUSE COMP. VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE

~Og ~CB Q>> '~EQ12 ~DQTR P 1 P E X X Q14 ~BQEE ~Z Qs 7 8 9 10 11 12 13 18 19 20 SEQUENTIAL OCCURRENCE REPORT REVISION Q17 LERIRO REPQRT ACTION FUTURE EVENT YEAR

~79 21 22 EFFECT

+23 SHUTDOWN 24 REPORT NO.

~02 3 26 QX 27

~01 28 ATTACHMENT CODE 29 NPRDX TYPE QT 30 PRIME COMP.

31 NO.

QO 32 COMPONENT TAKEN ACTION ON PLANT METHOD HOURS ~22 SUBMITTED FORM SUB. SUPPLIER MANUFACTURER

~BQTR ~XPTg ~APER ~AP27 0 4 1 6 ~YP23 ~YQ24 ~NQ25 Y17 1 2 0 QER 33 34 35 36 37 40 4'I 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS Q27 0 Possible causes: original fabrication contamination or chloride concentration occurring during operation. Investigation includes examining boat sample with scanning electron microscope to determine corrosive species, and insulation leachin chemical anal sis.

3 Cloth cover replaced with fiberglass. Report of metallurgical analysis results to be submitted later. Pressurizer head nozzle-to-safe-end weld areas to be reexamined in 4 1980 AI&O.

7 8 9 80 FACILITY STATUS  % POWER OTHER STATUS Q METHOD OF DISCOVERY DISCOVERY DESCRIPTION Q32 s ~GQEs ~00 0 PER NA ~BQ3I Routine IS I 7 8 9 10 12 13 44 45 46 80 ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT OF ACTIVITYQ3s LOCATION OF RELEASE QB 6 ~~ Q33 ~+Q34 NA 7 8 9 10 11 44 45 80 PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION Q3g

~77 ~00 0 Q37

'12 Z Qss NA 7 8 9 11 13 80 PERSONNEL INJURIES 7 8 9 11 12 80 LOSS OF OR DAMAGE TO FACILITY TYPE DESCRIPTION Q43 g ~ZQ42 NA 7 8 9 10 80 PUBLICITY NRC USE ONLY 7 8 ISSUED

~XQ44 9

DESCRIPTION 10 News release was made December ll, 1979. 68 69 80 o Eg NAME OF PREPARER A. E. Curtis III I 16/546-2700,ext. 2329,

Attachnant tc LER 79+3/01T-0 Rochester Gas and Electric Corporation R. E. Ginna Nuclear Power Plant, Unit No. 1 Docket No. 50-244 Event Descri tion On Friday, December 7, 1979, during a normal inservice inspection program examination on the pressurizer relief nozzle-to-safe-end weld, linear indications l-l/8" long and 3/8" long were noted by the liquid pene-trant examination method. The ultrasonic examination performed did not reveal any indications. On Saturday, December 8, 1979, the area of the indications was prepared by mechanical means with a flapper wheel and light grinding. A reexamination with liquid penetrant revealed an area of attack approximately 6-7 inches long by 1/8" wide. Due to other work being performed in the pressurizer head area supplementary examinations were not performed until Sunday night, December 9, 1979. These examina-tions included more liquid penetrant examinations and radiographic g-ray) examination of the area where the original liquid penetrant indication was found. The radiographs of the affected area revealed no apparent volumetric indications. Supplemental ultrasonic examinations of the area also revealed no apparent volumetric indications.

Inplace metallography was attempted without much success due to the restrictions imposed by the piping system that attaches to the relief nozzle. Replication using a plastic material revealed a family of very fine cracks. In a 2 inch long area the indications were ground*out ah about 1/8 inch depth. Confirmation of this finding occurred when in an additional 3 inch long area the indications were ground out after less than 1/8 of an inch of material was removed. On Wednesday, December 12, 1979, a boat sample was removed for further investigation and analysis of the cracks. The results of the investigations made in the field revealed that the cracks were in the 309 weld material that was used for the dissimilar weld between the carbon steel nozzle (SA-216-GR.WCC) and the stainless steel'safe-end material (SA-182 TP, 316) and not the safe-end material as originally thought.

The repair procedure included removal of the remaining cracked mate-rial, preparing the excavated area for weld repair and welding with the Gas Tungsten Arc Welding Process utilizing ER-309 base filler metal. Post prep-aration, first weld pass and final weld liquid penetrant examinations were performed. A final weld preservice ultrasonic examination of the repaired area was also performed. The results of all examinations did not reveal any indications .

Also examined during this investigation were all the nozzle-to-safe-end weld areas on the pressurizer head utilizing the liquid penetrant and ultrasonic examination methods. The ultrasonic examinations included a normal inservice inspection technique and a special stress corrosion tech-

~ +

Attachment to LER 79- 3/01T-0 2.

nique. Welds in associated piping of the four nozzles were also examined utilizing the liquid penetrant method with no further relevant indications noted. There were no health or safety consequences to the public or to plant personnel due to this event.

Cause Descri tion Replication of the as polished weld surface revealed a very tight crack pattern, similar to an intergranular stress corrosion. The boat sample analysis revealed three cracks as follows:

Crack 41 1. 4 mm from carbon steel fusion line

0. 4 mm in depth Crack 42 2.3 mm from carbon steel fusion line
0. 7 mm in depth Crack 43 3.5 mm from carbon steel fusion line 1.1 mm in depth touching carbon steel bevel Further analysis utilizing the scanning electron microscope is ongoing to determine if any corrosive species can be identified.

Presently only speculation can be made on the cause of this cracking.

It may have been caused by original fabrication contamination or by a chloride concentration that has occurred during operation. As part of this investigation a chemical analysis of leachable contaminants from the thermal insulation that surrounded the relief nozzle was performed as prescribed in Regulatory Guide

l. 36, Nonmetallic Thermal Insulation for Austenitic Stainless Steel. The results of this analysis are as follows for sample 1 woven cloth cover and sample 2 glass fibrous layered material:

PPM PPM PPM PPM PPM PPM Sample CI F CI+F Na Si03 Na+ Si03 98 9.4 107.4 100 207 307 30 1.6 31.6 40 99 139 Based on this analysis according to Figure I of Regulatory Guide 1.36, Sample 2 the glass insulation is acceptable, however Sample 1 the cloth cover is not within the acceptable region. Although it would be logical to assume that the insulating cloth provided the chlorides that might have caused this cracking phenomena, the cloth could have been contaminated during the handling of removal. Therefore, the results of the scanning electron micro-scope will have to be further analyzed before confirming the insulation involvement.

n Attachment to LER 79- 3/01T-0 As part of the corrective action the insulation material was changed on the pressurizer nozzles to assure that potential leachable contaminants from insulating material will require no further consideration. Also each nozzle-to-safe-end area was cleaned to remove any contaminants prior to reinsulation. A full report on the final results of the metallurgical analysis will be submitted when the investigations are complete. These nozzle-to-safe-end weld areas will be reexamined during the 1980 refueling and main-tenance outage.

Retrieved from "https://kanterella.com/w/index.php?title=ML17261A160&oldid=2433829"