ML20236W380
| ML20236W380 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 11/30/1987 |
| From: | Dromerick A Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8712070429 | |
| Download: ML20236W380 (44) | |
Text
{{#Wiki_filter:h, 4 p uc o fg UNITED STATES [. '
; ' j g NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555
\ . . . . . '#g November 30, 1987 '
rocket tio. 50-219 Licensee: GPU huclear Corporation FROF': Alexander W. Dromerick, Project l'anager Project Directorate I-4 Division of Reactor Projects I/II
SUBJECT:
NOVEMBER 13, 1987, MEETING WITH GPU NUCLEAR CORPORATION (GPUN) TO DISCUSS MATTERS RELATED TO OYSTEP, CREEK DRYWELL CORROSION On Friday, !!cvember 13, 1987, a meeting was held at the NRC, Bethesda, Maryland with GPUN, the licensee, to discuss the drywell corrosion problem at the Oyster Creek Nuclear Generating Station.. Attachment 1 is.the list of participants that attended the meeting. Attachment 2 is the meeting agenda. The corrosion of the sand bed cushion area of the drywell shell was the-subject of several meetings and the staff's Safety Evaluations dated December 20, i 1986 and September 22, 1987. In its Safety Evaluation of September 22, 1987, the staff concluded that the licensee met the staff's requirements as specified in the December 29, 1986 Safety Evaluation and also approved the action taken and those planned including the commitments to (1) implement cathodic protection as a means of corrosion arrest (2) measure wall thickness by UT at outages of opportunity for several years, and (3) identify and minimize future water incursions into the' sand bed. During the recent outage the licensee in addition to inspecting-the wall thickness of the dr,Wiell shell sand bed cushion area inspected portions of the upper spherical section at the 50'-2" level and the cylindrical'section at . the 87'-5" level. The results of the inspection of the upper elevation of the dr pell are presented in Attachment 3. The following is a summary of the significant itec.s discussed. The licensee advised the staff that the lowest average thickness among the locations of indicated local pitting at elevation 87'-5" equals 0.619" (the average of UT readings spaced at 1" within a 6"x6" array).' However, there were sone very localized points as low as 0.575". These localized points were surrounded by material of greater thickness. -The material nominal thickness at this elevation per Chicago Bridge and Iron (CBI) Drawing 9-0971.is 0.64". .The minimum allowable thickness based on ASt'E Section VIII code allowable' stress is i 0.639" and the minimum allowable thickness based on actual material test data from CBI material test data is 0.591". J 8712070429 071130 1 gDR ADOCK 05000219 PDR
}
l 1 Similarly, the licensee also advised the staff that the lowest average thickness at elevation 50'-2" equals 0.757", with some very localized points as low as 0.695". The material nominal thickness at this elevation per CBI Drawing 9-0971 is 0.770". The minimum allewable thickness based on Section VIII j allowable stress is 0.725* and the minimum allowable thickness based on actual ! materic1 test data from CBI material test data is 0.671". l The licensee stated that most of the corrosion at these elevations likely occurred before operation and that additional corrosion may occur when the exterior compressible type material sprayed on the drywell during construction (fircbar) is. wetted. The licensee expects a low corrosion rate during wetted periods. They also stated that they have taken steps to minimize / eliminate water intrusion in this area. On the basis of their structural analysis, the licensee stated that Margin exists between the measured wall thickness and the minimum required by analysis. In the case of the upper cylinder, the minimum allowable wall thickness-is based on the use of actual mill certified test data in the analysis. The licensee also stated that future UT inspections are to be perforned to monitor conditions. These inspections will be performed at outages of opportunity fcr several years. Based on the licensee's analyses described in the meeting and documented in Attachment 3, the staff agreed with the licensee that it would be safe to restart and operate the Oyster Creek Nuclear Generating Station. Howevar, we advised the licensee to perform an analysis to show that the drywell shall was still acceptable using code allowable stress values. We also requested that the licensee submit their 10 CFR 50.59 Safety Evaluation regarding this matter for cur review, i M brMFIF l Alexander 11. Dromerick, Project Manager i Project Directorate I-4 Division of Reactor Projects I/II .,
Enclosures:
i Attachments as stated 1 PDI-4 P 4 ADromerick:1m JS 's
/ /87 y//87
I N a
,, u ~m MEETING SUVMARY DISTRIBUTION
' DocketTFilec NRC & Local PDRs PDI-4 Files S. Varga
, B. Boger ! A. Dromerick DGC-Bethesda l EJorder. l JPartlow ! NRC Participants l ACRS(10) l HBClayton NRC Participants I Alexander Drcr!erick Jacque Durr David G. Jerko Felix Litton Khalid Shaukat - Lyman W. Heller Kamal Manoly Jack Strosnider S. D. Leshnoff T. P. Ruggiero D. W. Cov111 Chen P. Tan Walter R. Mikesell Stephen Lewis Goutam Bagchi John F. Stolz Larry Shao Michael Laggart Leo A. Hamersky Mark Jacobs Thomas Ahl Mark Yekta Gary Capodanno David Leighton
- t-
- Mr. P. B. Fiedler Oyster Creek Nuclear-
_ -Oyster Creek Nuclear Generating Station Generating Station-cC: Ernest.L. Blake,= Jr. .
-Resident Inspector _ . .
Shaw, Pittman, Potts and Trowbridge- c/o U.S.'NRC 2300 N Street, NW Post Office Box 445 Washington, D.C. 20037 Forked River, New Jersey ' 08731 J.B.'Liberman, Esquire . Commissioner - 'f1 Bishop, Liberman,' Cook, et al., New Jersey Department of Energy 1155 Avenue of the Americas 101 Commerce Street New York, New York 1003W Newark, New Jersey ' 07102 Mr. David M? Scott,' Acting Chief..
~
Regional Administrator, Region-I Bureau of Nuclear Engineering. U.S. Nuclear Regulptory Comission : Department of Environmental Prote'ction -
' CN 411 631 Park Avenue . .
King of Prussia, Pennsylvania 19406 Trenton, New Jersey 08625 BWR Licensing Manager GPU Nuclear Corporation 1 Upper Pond Road Parsippany, New Jersey 07054 , Deputy Attorney General State of New Jersey Department of Law and Public Safety . H 36 West State Street - CN 112 Trenton, New Jersey 08625 Mayor Lacey Township 818 West Lacey Road Forked River, New Jersey 08731 LihensingManager Opter Creek Nuclear Generating Station Mail Stop: Site Emergency Bldg. { F. O. Box 388 4 Forked River, New Jersey OP.731 { l i J i l i I
- ._ -_ .A
!' l L. ]
^1:
l H Attendance List Oyster Creek Nuclear Generating ~ Station j Docket No. 50-219 November 13, 1987 - Meeting. Name ORGANIZATION Alexander Dromerick NRC/NRR/ Project Manager, PDI-4 Jacoue Durr NRC/RI/DEP DIR (Acting) DRS David G. Jerko GPUN Licensing. Felix Litton NRC/MTEB-Khalid Shaukat 'NRC/RES/DE/EIB. Lyman t!. Heller NRC/RES/DE/EIB/B Kamal Manoly NRC/NRR/ DEST ' Jack Strosnider NRC/RI/DRS , S. D. Leshnoff GPU Nuclear Eng .. T. P. Ruggiero GPU Nuclear Mech., Systems D. W. Ccvill GPU Nuclear Mat'1s Eng. Chen P. Tan NRC/ DEST /ESGB-Walter R. Mikesell Robert L. Cloud Assoc. Stephen Lewis NRC/0GC . Goutam Bagchi NRR/ Branch Chief, ESGB John F. Stolz NRR/DIR I-4 Larry Shao LNRR/ DEST Michael Laggart MGR - BWR Licensing - GPUN' Leo A. Hamersky NJ DEP-BNE Mark Jacobs NJ DEP-BNE Thomas Ahl CBI Na Con Mark Yekta GPU Nuclear Erig _ Gary Capadanno GPU Nuclear Eng. and Design David Leighton GPU; Nuclear - i i _i__.______.__ ._ _ i
ATTACTfENT 2
- Proposed Meeting Agenda Between GPU and NRC Discuss Oyster Creek Drywell Shell Integrity 1
- 1. Introduction by NRC
- 2. Background by GPU
- 3. Describe the scope of inspection and the result of UT tests t
4 Describe the results of material test bores
- 5. Discussion of the causes of the wastage of the shell thicknesses and the status on the process of the corrosion.
- 6. Presentation on the findings the structural integrity of the drywell '
including: a) the method of analysis 4 b) major assumptions made the section and edition of the ASME Code used an: ~ pared with c) the original FSAR comitments d) the results of analyses in tems of stresses as compared with the. allowables in different sections or editions of the ASME e) the need for use of certified mill test results of the steel material and extrapolation of results to design temperature f) comparison of thickness of shell based on simple code equations, finite element analysis, use of code allowable values, use of material certification value g) margin on thickness previously vs. now h) discussion by a Code expert on how the intent of the ASME Code
. is being me,t g ghM
') 7.e44Ac. W
- 7. Assumptions about the corrosion rate and additional midcycle surveillance to assess remaining margin.
B. Conclusion
ATTACH!fENT 3 f
. i 1
1 4 GPUNPRESENTATIONTONRC OYSTERCREEKDRYWELLCORR0SION NOVEMBER 13,1987 i 3966M
- _ _ ..____w
u I. INTRODUCTION II. BACKGROUND-A. DescriptionofDrywell B. Water Intrusion 1~ C. Previous Examinations - Results/ Conclusions D. Previous Structural Anal. and Results ,
- MethodsandAssumptions DesignBasis(CodeandComparisontoFSAR)
+ '
Ill. CURRENT INVESTIGATIONS AND CONCLUSIONS - l A. LeakInvestigation i B. Upper Elevation Inspections l IV. STRUCTURAL EVALUATION Of UPPER ELEVATION , L 1 1 i V.
SUMMARY
l
]
3968M ___- 2_ __ _L___
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CHRON0 LOGY. NOVEMBER,1986: GPUN NOTIFIES NRC Of DRYWELL CORR 0SION DECEMBER 1,1986: -GPUNMEETSWITHNRRANDEXCHANGESINFORMATION ONDRYWELLMEASUREMENTS,ANDITSPLANSFOR ADDITIONALMEASUREMENTSANDCORESAMPLES. 1 DECEMBER 10,1986: GPUNMEETSWITHNRRANDPROVIDESRESULTSOf COREB0RINGSANDDISCUSSESSTRUCTURALCRITERIA 1 FORDRYWELL. DECEMBER 18&19,1986: GPUN LETTER AND SAFETY EVALUATION AND MEE WITH NRR JUSTIFYING INTERIM OPERATION 1012R OUTAGE, COMMITTING"T0CONTINUETHEUTSHELL. THICKNESSTESTPROGRAM~ATFUTUREOUTAGESOf OPPORTUNITYINCLUDINGFORCEDOUTAGESOTHERWIS RE@lRING DRYWELL ENTRY DURING THE DECEMBER 29,1986: NRRLETTERANDSAFETYEVALUATION10GPUN CONCLUDED ADE@ ATE MARGIN TO 12R OUT -l RE@lRING THAT (1) "SHOULD THERE BE N0 FORCED OUTAGES O SUFFICIENT DURATION PRIOR TO THE MID-P1 OfTHEOPERATINGCYCLE,PERFORMTHE-INSPECTIONS 0LATERTHANSEPTEMBER30, i 1987" , 3 AND 1
a
- (2)"GPUSHALL,BYJUNE30,1987,PROVlDE.
4 COMPREHENSIVEPLANSFORHITIGATINGTHE
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CORR 0SIVEATTACKONTHEDRYWELLSHELLAND i ANYOTHERINTENDEDLONGTERMCORRECTIVE ACTIONSIIHAYDEEHWECESSARYFORSTAff. REVIEWANDAPPROVAL" FEBRUARY 26,1987: GPUNHEETSWITHNRRANDDISCUSSESTASKFORCE OBJECTIVESTOHITIGATEDRYWELLCORR0SION' JUNE 11,1987: GPUNHEETINGWITHNRRPROVIDESCOMPREHENSIVE PLANSFORHITIGATINGTHECORR0SIONANDOTHER LONGTERMCORRECTIVEACTIONS SEPTEMBER 22,1987: NRRLETTERANDSAFETYEVALUATIONCONCLUDESGP HETSTAff'SREQUIREMENTSOfDECEMBER24,1986, SAFETYEVALUATION,ANDAPPROVESCOMMITHENTS: (1) TO IMPLEMENT CATHODIC PROTECTION AS HEANSOfCORR05I0N (2) 10 HONITOR WALL THICKNESS BY UT AT O ' Of OPPORTUNITIES FOR SEVERAL YEARS (3) 10 IDENTIFY AND HINIMIZE FUTURE WATE INCURSIONSINTOTHESANDBED OCTOBER,1987: GPUNBRIEFSNRRANDREGION1 REPRESENTATI THROUGWCONFERENCECALLSONTHESTATUSOf
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- 1. WASTAGE OF THE DRYWELL PLATE IS THE RESULT OF AN AQUEOUS GENERAL CORROSION PROCESS INFLUENCED BY LOCALIZED OXYGEN DEPLETION, THE DEGREE TO WHICH MOISTURE IS PRESENT, ,
TEMPERATURE AND CHLORIDE CONTAMINATION, l
- 2. ALTHOUGH VIABLE BACTERIA WERE IDENTIFIED IN THE SAND AND CORROSION PRODUCT, NO EVIDENCE EXISTS AS TO ITS INVOLVEMENT IN THE CORROSION PROCESS.
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- 3. D-METER THICKNESS READINGS, WHICH INITIALLY WERE THOUGHT TO j
BE EITHER PITTING AND LATER CHARACTERIZED BY "A" SCAN UT AS " INCLUSIONS, WERE CONFIRMED BY METALLOGRAPHY TO BE ALUMINIDE . INCLUSIONS IN THE CARBON STEEL.
- 4. THE COMBINATION OF USING A D-METER FOR ULTRASONIC THICKNESS MEASUREMENTS AND AN "A" SCAN FOR QUALITATIVE ASSESSMENT OF THE PLATE CONDITION ARE ADEQUATE FOR ENGINEERING l EVALUATIONS.
S. MAJOR CORROSION IS LIMITED TO THE STEEL IN CONTACT WITH WETTED SAND WITHIN ELEVATIONS 10'3" TO 11'9". BELOW 10'3", CORROSION IS LESS THAN 0.15". THE EXTENT OF CORRO310N IN THE WASTAGE AREAS, CONSIDERING INDIVIDU AL READINGS, IS: BAYS 11,13,17,19 - 0.25" TO ' O.41"; BAYS 1,9 - 0.15" TO 0.25"; BAYS 3,5,7,15 - NONE DETECTED.
- 6. THE AREAS OF OBSERVED CORROSION APPEAR TO BE THOSE AREAS IN WHICH THE SAND HAS REMAINED SIGNIFICANTLY WETTED. - THIS.
WETTING MOST LIKELY OCCURRED DURING INITIAL CONSTRUCTION AND THEN PERIODICALLY AS A RESULT OF LEAKAGE.
- 7. THE AVERAGE CORROSION RATE OVER THE PAST 20 YEARS IS BELIEVED TO BE 17-20 MPY. TYPICALLY, THE RATE WOULD BE HIGHER DURING INITIAL CORROSION AND IS EXPECTED TO BE LOWER NOW.
BATTELLE LITERATURE SEARCH DETERMINED THAT THE CORROSION R ATES, CORROSION, AND pH CHANGES OBSERVED AT OYSTER . CREEK ARE SIMILAR TO THOSE REPORTED IN THE LITER ATURE. i 4196h
LEAKINVESTIGATIONS DURINGCRENTOUTAGE Inspectionsperformedonlower7feetof:refuelingcavity walls. Indications initially found by dye penetrant testing - allinwelds. largeportionoftheseindicationsconfirmedtobe through-wallleakersbyvacuumboxtesting. Undertakingengineeringevaluationtoidentifyfailure mechanismandtodefinepreferredcorrectivemethod. l 3967M/2122
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THELOWESTAVERAGETHICKNESSFORA6"x6" ARRAY; AT EL. 87'5" E@ALS .619". . l THELOWESTAVERAGETWICKNESSFORLAf6"x6" ARRAY AT EL. 50'2" E@ALS .757".~ t 3970M
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t . t s i i 50'2" ELEVATION CORE SAMPLE EVALU ATION: 1 2
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SAMPLE .UT. . SAMPLES' ! NUMBER BAY- CHARACTERIZATION ! UNIFORM THINNING CORE, FIREB AR 8- 5 9 7 UNIFORMLY AT.OR ABOVE- ' CORE, FIREB AR - [ NOMIN AL, OCCASION AL - 1' LOW SPOTS 4195H l i
. 50'2" ELEVATION PLUG EVALUATION PLUG 8, BAY S - UNIFORMLY THINNED, LOCALIZED LOW SPOTS o WHOLE SURFACE CORRODED DARK BROWN OXIDE, VISIBLY UNIFORM IN THICKNESS TIGHTLY ADHERENT, NO LOOSE SCALE TYPICAL OF EXPOSURE IN LOW-OXYGEN ENVIRONMENT.
SIMILAR TO 2 PLUGS REMOVED FROM TOP OF SAND BED IN 1986 o FIREBAR STAINED WITH CORROE)ON PRODUCT CHUNKY NEAR DRYWELL FLUFFY NEAR CONCRETE CONSISTENT WITH APPLICATION OF 1 LAYER HIGH DENSITY, 2 LAYERS LOW DENSITY o LAB EVALU ATION EDAX OF OXIDE MOSTLY IRON, SOME LEAD, LOW CHLORINE AND SULFUR j o METALLOGRAPHY SURFACE ROUGH; R ANDOM SH ALLOW PITS CUT THROUGH REGION OF LOWEST UT (0.693") BROAD SHALLOW PIT - 0.12 -0.22 DI A. MINIMUM MEASURED THICKNESS - 0.714" ; AT PIT EDGES, THICKNESS - 0.750 -0.761" REGION AWAY FROM PIT - 0.722 - 0.752" MANGANESE SULFIDE INCLUSIONS PRESENT. l i 4195H 4 . - -_ -________ _ \
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AT OR ABOVE NOMINAL, OCCASIONAL LOW SPOTS, CENTERED - 'l BETWEEN 0.798 AND 0.710" READINGS l o- ABOUT 80% CORRODED,20% RED LEAD (NOT CORRODED) 1 o ONE REGION OF DENSE, HEAVIER SCALE CORROSION PRODUCTS DARK BROWN, ADHERENT ' ,j o .
.q o- SIMILAR TO PLUG 8 AND 2 PLUGS FROM TOP OF SAND BED FIRE 8AR STAINED WHERE PLUG CORRODED, WHITE IN REGION OF RED- '/
o LEAD o SAME PHYSICAL CHARACTERISTICS AS PLUG 8 FIREBAR-LAB EVALUATION o EDAX LEAD PRESENT IN BOTH OXIDE AND PAINT AREAS IRON, CHLORINE, SULFUR PRESENT IN OXfDE METALLOGRAPHY o CUT THROUGH REGION OF LOWEST UT READING -0.705" BENEATH SCALE (WHICH WAS DIFFICULT TO REMOVE) , BROAD,~ SH ALLOW PIT ABOUT 0.34 DI A. MINIMUM THICKNESS MEASURED - 0.899" , PAINT AREA UT THICKNESS - 0.783" MICROMETER - 0.797" PAINT THICKNESS - 1 TO 3 MILS ! 4195H k l [ J
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PLUG EVALUATION CONCLUSIONS
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o CORROSION IS TYPIC AL AQUEOUS CORROSION OF CARBON STEEL' o MINIMAL SULFUR INDICATES MICROBIAL INFLUENCED CORROSION UNLIKELY' o CORROSION PRODUCT SIMILAR TO THAT OBSERVED ON CORE SAMPLES REMOVED FROM TOP OF THE SAND BED o OXIDE INDICATIVE OF LOW OXYGEN ENVIRONMENT j o LOW UT READINGS A RESULT OF BROAD SH ALLOW PITS o FIREBAR AND CORE PLUGS WERE VIStBLY ORY o CHLORIDE LEVELS IN OXIDE WERE LESS TH AN THOSE MEASURED IN PLUGS t REMOVED FROM THE SAND BED MID-REGION, I l l i i 4195H
CORROSION EVALU ATION o LIKELY THAT MOST OF CORROSION OCCURRED BEFORE OPER ATION. o MAGNESIUM OXYCHLORIDE LIMITS ACCESS OF OXYGEN TO STEEL SURFACE o CORROSION FILM DENSE,-TEN AClOUS WHICH INHIBITS FURTHER CORROSION AFTER FIREBAR CURES AND CORROSION FILM FORMS NO REPLENISHMENT OF OXYGEN o FIRESAR DRIES WITH TIME: o ADDITIONAL CORROSION MAY OCCUR WHEN FIREBAR IS WETTED o EXPECT LOW CORROSION RATE DURING WETTED PERIODS 4195H
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. HISTORYOF. WETTING; SLURRYAPPLIED : june,1966 REFUELINGBELLOWS INPLACE FEBRUARY,.1968 TIMEWET 18 MONTHS-i P0OLSFLOODED TOTALTIMEFLOODEDSINCELEAKAGEOBSERVED 18HONTHS TOTALWETPERIOD3 YEARS t
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Specified AsRecieved herage Corrosion-Assumed (reading).. Rate
.640" .665" .619" 115-16l mpy;
.770" .790" .757" 11 mpy 1
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> CORR 0SION SINCE 1966; CorrosionF 4
Specified AsRecieved Average (readingT Rate, Assumed:
.665"- .619" 2-3 mpy;
.640"
.770"
~.790'F .757" .1-2 mpy ,
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4 i_ / i STRUCTURAL EUALUATION 0F OYSTER' CREEK DRYWELL UPPER ELEVATIONS' 1
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4 DRYWELL MINIMUM PLATE THICKNESSES AT UPPER ELEVATIONS TABLE 1 Minimum Allowable Thickness Nominal Mat'l Thick Based on ASME Sect. Based on Actual Mat . per CBI Owg.9 0971 VIII Allowable Stress Test Data from CBI-Location CYLINDER i Fros .64" .639" .591" el. 72'0" To el. 92-0" i SPHERE From .770" .725" .671" el. 23'6-7/18-To el. 50'11-1/8" t 722 .685" .643" J Fros l el. 50'11-1/8" To el. 65'2-7/16" l l
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l ASME MECHANICAL PROPERTIES Us ACTUAL MILL CERTIFICATE TABLE.2 l ASME Section VIII 1962 Lowest Actual Mill.Certtftcate frem Survey of CBI Material Test Recort- i Sy Allowaoie = ,.I Sm j Su Sy Allowable Su I.1 x Sm Sm 11/4 Su or. 2/3 Sy Location CYLINDER I 75,480 1.1 x 8.870 23.757 ! 7 .000 38,000 i.i.ni7.50 51.170 Frl.72'O. 19.250 To , el. 92'0" l SPHERE From 'f ; el. 23'6-7/18" ! To 70,000 38,000 19,250 75,620 42.930 1.1x18.905 20.796 j el. 50'11-1/8- s
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~' D .526 f,' ' 70,000 38.000 19,250 74,640 48,780 1.1x18.660 el. 65'2-7/16" i
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SUMMARY
Harginexistsbetweenmeasuredwallthicknessand minimumrequiredbyanalysis.
.Hostupperelevationcorrosionlikelybefore initialplantoperation.-
Expectlowcorrosionrateduringvettedperiods. Stepsbeingtakentominimizeleliminatewater intrusions. futureUTinspectionsofselectedareastobe- ! .performedtomonitorconditions. 3969M s _ _ _ _ _ _ -}}