ML20059N595

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Summary of 900919 Meeting W/Util in Rockville,Md to Discuss Matters Re Plant Drywell Corrosion.Viewgraphs Encl
ML20059N595
Person / Time
Site: Oyster Creek
Issue date: 10/03/1990
From: Dromerick A
Office of Nuclear Reactor Regulation
To:
Office of Nuclear Reactor Regulation
References
NUDOCS 9010160350
Download: ML20059N595 (116)
v • d • e


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UMTED STATES NUCLEAR REGULATORY COMMISSION

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\ October 3. 1990 Docket No. SJ-219 LICENSEE GPU NUCLEAR CORPORATION JERSEY CENTRAL POWER & LIGHT COMPANY FACILITY: OYSTER CREEK NUCLEAR GENERATING STATION

SUBJECT:

Summary of September 19. 1990 Meeting With GPU Nuclear -

Corporation (GPUN) to Discuss Matters Related to Oyster j Creek Drywell Corrosion. 1 On Wednesday, September 19, 1990, a meeting was held at-the NRC, One White q Flint North, Roc (ville, Maryland with GPUN, the licensee, to discuss the -

j drywell corrosion problem at the Oyster Creek Nuclear Generating Station.

' Enclosure 11is the list of participants that attended the meeting.

Enclosure 2'is the licensee's morning session agenda. Enclosure 3 is the licensee's afternoon session agenda. The following is = a summary of the significant items discussed.

The Licensee indicated that the Oyster Creek Drywell (1) has been examined thoroughly: its present-condition and the ongoing corrosion problem are well understood amplemargIn(2)isarugged,conservativelydesignedpressurevessel;ithas to permit continued safe plant operation for several years while  !

j corrective action is being taken, and (3) program is a very high priority, resource intensive, and multifaceted one and that GPUN intends to arrest the drywell corrosion by positive means and ensure containment integrity for the full licensed life of the plant. During the discussion the licensee-described a three phase program to address the drywell corrosion problem.

The licensee stated that based on analysis performed during the first phase of the program, GPUN concluded that:

1) current best estimates of corrosion rates at the worst areas of the drywell sphere indicate Code allowable stresses will not be exceeded for at '

least three years, even if corrosion extended over its entire surface.

2) Taking into account actual conditions, the 0yster Creek Drywell will be in full compliance with the ASME code for at least three years even at very conservatively projected (95% confidence-level) corrosion rates.
3) The Oyster Creek design basis pressure (62 psig) is conservative by a significant margin.

1 9010160350 901003 PDR P ADOCK 05000219 PDC I '

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.The licensee stated that he'will submit the detai.ls'of his program including

.the structural analysis.by December 1990. The staff advised the-licensee that GPUN should expedite the submittal including plans to arrest corrosion.

42 $

Alexander W. Dromerick, Senior Project Manager I Project Directorate I-4 l Division of Reactor Projects - I/II; t Office of Nuclear Reactor Regulation

Enclosures:

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cc w/ enclosures:

See next page ,

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'Mr. E. E. Fitzpatricki - 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' i Commissioner-

1. H.'Jolles, Executive Vice President New Jersey. Department of Energy  :

GPU Senior Corporation- 101 Commerce Street 100 Interpace Parkway- Newark, New Jersey '07102 Parsipanny, New Jersey 07054 _

Kent.Tosch, Chief.

Regional Administrator, Region-I New Jersey. Department.of Environmental-U.S. Nuclear Regulatory Commission- Protection.

475 A11endale Road. . Bureau of Nuclear Engineering-King of Prussia, Pennsylvania 19406_ CN 415 Trenton, New Jersey 08625-BWR Licensing Manager GPU Nuclear Corporation , i 1 Upper Pond Road Parsippany, New Jersey 07054 i

Mayor Lacey Township 818 West Lacey Road Forked River, New Jersey 08731 Licensing Manager Oyster Creek Nuclear Generating-Station Mail Stop: Site Emergency Bldg.

t P. O. Box 388 Forked River, New-Jersey 08731 4

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-The licensee stated that-he will. submit the details of his program including

- the structural analysis;by: December 1990. The staff advised the licensee that GPUN should expedite the submittal including plans'to arrest corrosion. .  ;

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Alexander W. Dromerick, Senior Project' Manager .

Project' Directorate _I-4.

Division of-Reactor. Projects - I/II. ,

Officeof-NuclearReactorRegulationl ,

Enclosures:

As-stated  ;

cc w/ enclosures:  !

See next page  !

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.[0YSTER MTG

SUMMARY

9/19/90]

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l DISTRIBUTION FOR MEETING: SUMARY DATED: October: 3. 1990

.iBo60 EFifei l NRC & Local PDRs l Plant File- :1 F.:Miraglia J. . Partlow (12G18) '

-- J. Stolz S. Norris A. Dromerick OGC r E. Jordan (MNBB 3302)

NRC Participants

~ACRS (10) .

J. Caldwell.(Region I, 17G21) ,

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ENCLOSURE 1- .

0YSTER CREEK NUCLEAR GENRATING~ STATION DOCKET NO. 50-219  ;

MEETING - SEPTEMBER 19. 1990 j l- ATTENDANCE LIST _ i NAME ORGANIZATION TELEPHONE; l

A. W. Dromerick NRC/NRR/PDI-4 301-492-30491 M. W. Laggart GPU Nuclear- P01-31f.-7968L Ron--Zak GPU Huclear 201-316-7035 Frank Orr .NRC/NRR/PDI-4L 301-492-1462 Dana Covili :6PU Nuclear 717-948-6946. >

Scott Giucobbe GPU Nuclear ~ 215-375-5364  :

Branch Elam GPU Nuclear 201-316-7306:

Harlow Lehigh University 215-758-4127:

D.

S. D.Gary'eshnoff L GPU Nuclear 201-316-7180 ,

4 Peter Tamburn GPU Nuclear 201-316-7405 .!

l Har Mehta GE Nuclear- 408-925-5029 L Stephen Tumminelli GPU Nuclear. 201-316-7042- ,

Nick Trikouros CPU Nuclear 201-316-7124 1 Jack Devine GPU Muclear. 201-316-7246 j; E. E. Fitzpatrick GPU Nuclear -

-609-971-4796 G. Capodanno GPU Nuclear . 609-971-4840

J. J. Colitz ';

GPU Nuclear .

201-316-7457 i Neal Roberts The Press of Atlantic City 609-978-2000 Natthew Guarini -Search Licensing /Bechtel- 301-417-3080 4 Debbie Jackson-

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NRC/NRR/LRPD . 301-492-3148 >

Pat Baranowsky .HRC/NRR/DOEA 301-492-1156 l

Keith Wichman NRC/NRR/EMCB . 301-492-0757 Robert Hermann NRC/NRR/EMCB ~301-492-0768 Jim Richardson NRC/NRR/DET 301-492-0722 S. Varga NRC/NRR 301-892-1403-R. Wessman -NRC/NRR 301-492-1405 G. Bagchi NRC/NRR 301-492-3305- -

Chen P. Tan NRC/NRR 301-492-3315-E. G. Igne NRC/ACRS 301-492-8192 Ron Hernan NRC/NRR/PDI-4 301-492-1445 W. H.-Ruland NRC/ Region I/DRP- 215-337-5227J

.Kama L. Manoly NRC/NRR/DET 301-492-0765-Mike Cullingford NRC/DONRR 301'-492-1276 John Torbeck GE Nuclear Energy 408-925-6101'-

Ron Lloyd NRC/AEOD -

301'49?-4149

1 Tony D'Angelo NRC/AEOD 301-492-4149_-

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ATTENDANCE LIST (Continued)

NAME ORGANIZATION - TELEPHONE Chang-Yang L. NRC/NRR/SPLB 301-492-0830 Herb Kaplan NRC/ Region 1 P15-337-5346

. Thomas M. Cheng. NRC/NRR/EMEB 301-492-0770 Robert L. Rothman NRC/ESGB 301-492-3306 .

David C. Jeng .

NRC/NRR/ESGB '

301-492-0227 i Stephen Koscielny NRC/NRR/DET 301-492-0726 Frank Freyne Asbury Park Press 201-922-6000 Albert Ronald Brenner Lacey Township 609-693-1100 Kent Tosor HJ DEP BNE 609-987-203?

Dennis J. Zar.noni NJ OEP BNE 609-987-?053 Susan M. Todd GPV' Nuclear- 609-971-4017.

John F. Stolz NRC/NRR/PDI A 301-492-1491-W. Norris NRC/NRR/M.S.'217A 301-492-3805 NICHOLSON LANE SOUTH C.Y. Cheng NRC/NRRIENCE 301-492-0924 i

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DRYWELL MEETING WITH NRC 1 MORNING SESSION

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, e INTRODUCTION AND OVERVIEW J.C. DeWine,- Jr. . '

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- Meeting Objectives, Structure

- Keyissues

- GPUN Plan of Attack 4

e PROBLEM DEFINITION J.J. Colitz

- Drywell Configuration j

- Observed Corrosion j e PROGRAM PLAN J.J. Colitz -

Le ASSESSMENT OF DRYWELL N.G. Trikouros I.

- Present Condition / Effectiveness ..

S. TummineIII  ;

- Design Challenge l

j. - Structural Analysis j

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l e CONCI.USION J.C. DeVine, Jr.

j - AFTERNOON SESSION i

  • More Detailed Technical Presentations

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MEETING OBJECTIVES

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l o To communicate the scope. depth, objectives, and expectations of GPUN's Oyster Creek Drywell Program. ~

! O To permit technical exchange among GPUN and NRC technical staff members j

[ on engineering and. analysis issues.

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i o To obtain feedback from NRC on GPUN's course of action ,

o To agree _on subsequent steps and their timing.

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THREE KEY POINTS .

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l I 1. The Oyster Creek Drywell has been examined thoroughly; its present condition

and the. ongoing corrosion problem are well understood. .

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2. -The Oyster. Creek Drywell is a rugged, conservatively designed pressure l vessel; it has ample margin.to permit continued safe plant operation for j- several years while corrective. action is being taken.
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! 3. GPUN's drywell' program is a very.high priority, resource intensive, and

! multifaceted one; .we intend to arrest the drywell corrosion by positive means l- and ensure containment-integrity for the full licensed life of the plant.

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OYSTER' CREEK DRYWELL PROGRAM

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F Phase: Phase 1 Phase 11 Phase III . -

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Objective: Develop Success Path Solve the Problem Keep'It Solved l; j Timing: Through 1990 Through 1992 Lang Term i Focus: - e Examine aII Information e knplement plans / engineering developed In. e knplement Eloet . i'

in-hand. Phase I to
. plant snonitoring
  • Confirm sheIIintegrity - Fully characterize sheII.

through Phase II.

_ g e Othm' M as l e Develop detailed plan- margin. needed.

and engineering for full l solution. - Arrest corrosion. ,

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I e Continue corrosion .'

I prevention activities.

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i BASES FOR OYSTER CREEKEDRYWELL i SAFETY DETERMINATION DURING PHASE II

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t l t I 1. - Based on current best estimates of corrosion rates at the worst areas of.the-

! drywell sphere, Code allowable stresses will not be exceeded for at least three l years, even if-that corrosion extended over its entire surface.

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2. Taking into account actual conditions, the Oyster Creek Drywell will be in 3

, full compliance with the:ASME' Code;from at least three years, even'at very l- conservatively projected (95 percent confidence level) corrosion rates; .

i l- -3. The Oyster Creek-design basis pressure (62Lpsig) is known to be conservative  :

l by-a significant-margin'.

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SUMMARY

@F DRYWELL ACTIVITIES OCT/ JUL/ NOV '88 l ~ DEC '86 NOV '87 OCT '88 FEB '89 (12R). CYCLE 12 l . '90

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UT Readings REGION UT Readings - Installed .

- Energhed CP.. - UT Readings

% cathodic system 3/89

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Core Samples - UT. Readings REGION ' - UT Readings - UT Readings - UT ReedIngs .

(50 - 2 ')

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l to seduce - UT Reedings APd5 water sources W89 - Espended to essvenon

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CYUNDRICAL UT Readings - UT Readings

- UT Readings - UT Reedings

!, REGION L (s7' - 5") - Steps taken I i

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SHELL EXAMINATION

SUMMARY

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Sand Bed Region
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  • Corrosion rate is highest of 3 regions (~39 mils /yr.) 1

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  • This is.the thickest part-of the shell;(initially;:1.154").

[ e Several years margin remain _ based on: '

Best. estimate. corrosion rate in worst area.

- Original design basis.

l - Code requirements.

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SHELL EXAMINATION.

SUMMARY

(Cont'd): ]

i i Spherical Region

  • 2.5 years data-in-hand (although.less extensive than sandbed).-

t e Observed corrosion rate is low (~4.6 mils /yr.)-  ;

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e initial shell thickness is. 722" and .770". i

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  • Several years margin remain based on: .

'. - Best. estimate corrosion rate in worst area.

U j Original design basis.

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- Code requirements.

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1 SHELL EXAMINATION

SUMMARY

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(Cont'd) -

.i i Cylinder Region

e 2.5-years data in-hand (although less extensive than sandbed).
  • No ongoing corrosion observed. j e Environmental conditions make region less prone to corrosion.

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4 e Area.of least margin.  !,

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i OYSTER CREEK DRYWELL PROGRAM a Phase: Phase 1 Phase 11 Phase III j i

L Objective: Develop Success Path Solve the Problem Keep It Solved .

Timing: Through 1990 Through 1992 Long Term l

Focus: e Examine allinformation e implement plansfergir.;;;;rg developed in e Implement Ilfe-of-i in-hand regarding .

' Phase 1. Plant monitoring physical condition and program.

derign of the drywell - Characterize shell condition and .,

! and confirm that sheII corrosion mechanism. e If requised,

integrity is adequate to -

support plant operation - Arrest corrosion where necessary by st @ M . .l through Phase II. positive means (e.g., remove sand, l

clean and resurface)..

l e Develop detailed plan

, and engiMng (fx e .Stop Inleakage of water /take steps to I

. Implementation in ensure that it stays stopped.

i Phase ll) to: o Comptete analysis of shell strength, i

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- Completely design basis and margin.

characterize shell e Determine if shell strengthening Is

condition. required, engineer methods to do so I

- Arrest corrosion in (if required).

j any location where e Develop life-of-plant monitoring program.

continued cormslon [

i would not permit

{ operation for full term plant life. I Licensing: Obtain NRC understanding Change licensed design basis if appropriate.

and agreement.

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CHARACTER ZE SHELL CONDIT ON l-1

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! PHASEI PHASE II- PHASE III ,

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OVERALL. - Ongoing Inspection Program - Ongoing Inspection Program - Implement a_.cg;w

- Evaluate Autornated Inspection -

Implement Autornated i

! Techniques Inspection TecemIque As - . i l- Appropriate -

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} SPHERE - Evaluate / Develop Augmented -

Perfonn Augmented Inspection .

! Inspection Plan Plan  !

- Develop Engi Package to InistaN - InstaN On-Une/Remoto -

Prototype On-Unef Remoto - Monitoring Prototype ,

) Readout Monitor -l l CYLBIDER - Evaluate / Develop Augmented -

Perform Augmented Inspection

Inspection Plan Plan

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  • i ARREST C.ORROS ON .

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i 3 PHASEI PHASE 11- .

PHASE III

. OVERALL - Ocean City Research Program Ocean City Research Program .:

Limit Water Intrusion  !

! - Evaluate Inerting - Decision on Inerting System j

- Limit Water Intrusion - Limit Water Intrusion ~

SANDBED - Evaluate Sand Removal,

- Remove Sand, Surface Clean'&

Surface Cleaning & Recoating Recoat to Extent Possible y

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SPHERE / - Evaluate Firebar D & Fiberglass - Decision on Firebar DI CYLINDER Removal, Surface r "::riq & : '

Fiberglass Removal _

i Recosting i

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1 ANALYSIS -

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~PHASEI PHA'SE II.

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PHASE III

[ OVERALL - OC Contakunent DBA Peak

- Change Ucensing Design Pressugg 6 Raek N A;--;4 4 "_2 d

- Structural EvaIustion

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OYSTER CREEK CONTAINMENT DBA PEAK PRESSURE RE-EVALUATION e History / Background e Current peak pressure evaluation Methods

- Assumptions

- Results

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e Conservatisms in current evaluation e Basis for 62 PSIG design pressure e Re-evaluation approach -

e Test data qualification results e Oyster Creek blowdown analysis results e Containment analysis results e Conclusions

.2 -

Function of OC Contaisunent:

O To fully accommodate the mass and energy resulting from the rapid double ended break of a recisculation line (design basis accident) without exceeding the design pressure.

Goals of Peak' Pressure Evalesation

- O. To determine, using state-of-the-art irei;.edology, what the peak containment pressure from the design basis accident would be.

O To quantify the conservatism in the current 62 PSIG design pressure and establish the technical basis for a reduction of this pressure.

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OYSTER CREEK DRYWELL PRESSURE EVALUATION i

PROGRAM PARTICIPANTS  :

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l j e GPU Nuclear Corp. (GPUN)

  • General Electric (GE) e Science Applications International (SAIC)

[ e S. Levy Inc. (SLI)

  • EPRI (For Generic Applicability)

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i INTRODUCTION  !

l l 0 The intent of current structural evaluations of the Oyster Creek drywell is to mterrogate the existing structure in an effort to define its realistic strength.

l 0 The governing design document for the drywell is the Burns and Roe ,

specification SP-2299-4, Addendum No. 5 dated 1964, which calls out the

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applicable design, fabrication, erection, and testing requirements.

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O The original design and analysis were performed using manual calculations j without the benefit of advanced analytical tools. Strength of materials l approach used. '

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-- _ - _ - _ - - - _ _ _ - -. _ . - - , _ ~ . _ _ _ _ _ -_ --_ _--__ _ _ _ ----- -_

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DRYWELL UNDER INTERNAL PRESSURE 1 N _ CYLINDER b

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,Q"nucxte -

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l INTERNAL SPHERE  !

l Pressure 4 e

j t

l ll DESIGN PRESSURE IS 62 PSIG.

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_ _ _ _ - - - _ . - - , _ _ - -- _ ~ . - _ _ - - - - _ _ - _ _ - - _ _ . - - - - _ . _ _ _ _ _ - - - - - - - _ - - - - - - - - - = - -

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DRYWELL UNDER SEISMIC FORCES i

am$ REACTOR BUILDING SUPPORTS -

=

DRYWELL LATERALLY BUT ALLOWS 4 LATERAL & VERTICAL EXPANSION.

,. 4 4

l 4 i

  • 1 i

SEGMC w ^

FORCES g 4

i' um$ DRYWELL IS BUILT IN  !

TO THE REACTOR BUILDING AT ITS BASE.

l SEISMIC FORCES RESULT 3

FROM GROUND ACCELERATIONS.

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. . . .. . __ _ - _ _ . . . . _ . _ . . _ . . _ . . _ . . _ _ _ . _ _ . . . . _ - _ . _ _ . . _ - . . . _ _ . ~ _ - - _ _ _ _ _ -

i -

2 i.

j ADDITIONAL STRUCTURAL ANALYSIS i a i

l 0 COMPARISON WORK FOR BUCKLING EVALUATION: -

! Capacity margin (buckling) in the sandbed is improved by including the details

] of vent pipe and its reinforcing plates.

Stability analysis comparing 3-D FEM methods and BOSOR techniques (sheII l of revolution) using a similar Mark I drywell has been performed using the l same percentage reduction in wall thicknesses as observed at Oyster Creek in

! the sandbed region.

i Loads were adjusted to produce a stress state at the midpo;.4 of the saruhed equal to that computed for the Oyster Creek stability analysis.

] .The ratio of the FEM results divided by the BOSOR results was computed and j is equal to 2.1. Hence, the previously computed capacity margin of 1.00 is very conservative.

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i / THREE-DIMENSIONAL FINITE

/

ELEMENT MODEL OF SIMILAR 4' MARK I DRYWELL FOR i

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[d OYSTER CREEK COMPARl i y?3y STUDY igs.

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u. - - - - _ _ _ . - _ _. - __ .- _. - . . _ _ . . - - - - -

CALCULATED STRESSES vs. MATERIAL STRENGTH Material: SA 212-GR B i

i SU = ULTIMATE STREN ! 3TH (Miin '

i SU = 70.000 m.i J

_4 E

W ~

<F-2 SY = YlELD STRENGTH (MIN) 11- SY = 38,000 psi o

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0 m 12_s=_= 2_1.irsyst _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ , _ _ _ ,

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'  % W h18270 W ammanssammmmmmmma-g I 18.120 psi - 18.600 psi ,

i CALCULATED COMBIN!!D STRESSES -

CYLINDRICAL 0.722" REGION O 770" REGION D M.

REGION eAsemassmeD  !

t- 0.750"

> BASED ON AS-FOUND

. i- o.str SPHERICAL REGION i

i

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! CALCULATED STRESSES BASED ON FORECASTED THICKNESSES i

, TO 14R USING 95% CORROSION RATE - ASME CODE MINIMUM SU = ULT l MATE STREN 3TH (Miih SU = 70.000 osi i

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T

, W j

<I--

SY = YlELD STRENGTH (MIN)

LL SY = 38,000 psi

. O I

l-- '

0 w _h._ soc _= 2Ja?s_psL __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ , _ _ _ _ _ _ _ _ _

g Smc = 19 N nei I-' 19.830 psi 19 450 psi 19.220 psi

@ 17,700 psi

CALCULATED COMBINED STRESSES CYLINDRICAL 0.722" REGION 0.770" REGION SANDBED RGN.

REGION N M D M AS M M BASED M AS M M 8ASED M AS M M t - 0.67T t-0.723* t- 0.736* i BASED ON AS-FOUND ~

i - o.sw SPHERICAL REGION l

___m__.____ _ __ . - . .._..-__._._____.____u__.___ _ - ____-_m____-= _ - w -__ m er ._. .er e a ,- _ _-__u______s_____ m_ __ . _ _ _ _ _ _L

CALCULATED STRESSES BASED ON FORECASTED THICKNESSES TO 14R USING BEST ESTIMATE CORROSION RATE - ASME CODE MINIMUM SU = ULT! MATE STRENGTH iMiN:-

SU = 70.000 pri I

b x

LU

<1--

SY = YlELD STRENGTH (MIN)

LA- SY = 38,000 psi O

I l-0 g

_!-LS=_. 2.14zs.est ,_ _________ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Smc 19_250 nsi H 19 830 Psi 19.150 psi

^

18'.950 psi CALCULATED COMBIN' DSTRESSES

  • CYLINDRICAL 0.722" REGION 0.770" REGION SANDBED RGN.

REG G PROECTEDON ASTOUND t-0.688-BASED ON ASTOUND 1-0.734*

BASED ON #SfOUND t- 0.758*

""*' t 3.7 SPHERICAL REGION

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i ASME III - SUBSECTION NE EVALUATION i .

i l 0 Code defines " local primary membrane stress intensity" to be greater than i 1.1 Smc and less than 1.5 Smc.

l 0 This 10% variation in allowable stress was provided because of the " beam on j elastic foundation; effects, i.e., stress decays but remains greater than zero for l significant distances.

i

) O Clearly not intended to design for 1.1 Smc, however, given a design that satisfies the code intent, it is not a violation of the code for the membrane stress to be between 1.0 Smc and 1.1 Smc for significant distance.

1 Lo Largest exceedance of Smc is 3%. Therefore, drywell currently complies with

! the code.

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.w.- --- 4 - - . < ----,..-.--.~*=--.-w-- -_-m...,.--+.------++ _

e+,.me-c. -+e. - --*i - .. - --- --. - _ -

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! ADDITIONAL CONSERVATISMS -

I o Revised temperature profile indicates lower thermal demand than previously calculated.

l 0 It is expected that the drywell materials, construction and inapar*lon meets all l the requirements of Section 111, NC. This could have permitted as factors of l safety of 3 for ultimate strength and not 4 as is currently used. -

i l o Ultimate pressure capacity provides margin vs. the design LOCA pressure.

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_ _ _ - - _ _ _ _ _ _ _ _ . _ _ _ . _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ __ . _ _ _ _ _ _ _ _ _ _ ._ _ _ _ - _ _ _ _ _- _J

i I I i

i STATUS OF INVESTIGATION 4

i o Drywell currently in compliance with code. .

O Drywell will still be in compliance'with code at .14R. -t i ,

l 0 - All analyses and supporting documentation will be submitted by December 31, l

1990.

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__ _ __._____ ___ _ .___ _ _ _ _ __m .- . . < -.. -.4 .. .... - ~.. - m. - ,, - ~ ~ --- - , ,-- , , , ,-_.. ~.- . . . .. . . ...., . . . . . . . . . ,,.,,.- ,... _ _ __ , _ . _. .. , _.... , .../

Exc /osare 3 i i

j a

i OYSTER CREEK DRYWELL CORROSION GPU Nuclear i NRC Meeting i

! Septensber 19,1990 '

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1_____________._____._____________ -

_ _ - - ___ _ _ _ _ _ _ _ _ _ - _ _ = _ _ _ _ _ _ _ _ _ _ . _

[

DRYWELL MEETING WITH NRC .

AFTERNOON SESSION e PROBLEM CHARACTERIZATION .

- UT Inspection Results P. Ta m I m rro~ l

- Statistical Inspection S. Leshnoff

- Inspection Methods D. Cov111 i I

i e ANALYSIS i

- Design ChaIIenge N.1Hiscuses ,

- Structural Analysis S. lbneneinellt i

e ARREST CORROSION

- Stop Leekage B. Elane

- Corrosion Mechanism S. GIacobbe i  !

)

i f

! e SHELL REPAIR B. Elam i t 8

- Removal of Sand i

- Removal of Firebar D and ."h.-jsss i

R

- Physical Repairs

....__...__,.._--.___.,..._.._~.-__._.....__.__...___-___..._.___-_____.-__.!

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AGENDA i

! PROGRAM DESCRIPTION

_-____m._

]

suyvasse m'tive.  :'

P

- Brief description of drywell vessel plates.

- Detailed inspections which led to to the ongoing program.

j - Ongoing program inspection locations. -

- i spection frequency and methodology.

- Data coIIection and reduction.

- Corrosion rate calculation and projection.  !

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RESULTS OF SPRING 1990 INSPECTIONS L

- History (since 12R).

L - Results of sandbed inspections.

c c

- Results of upper elevation inspections.

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- Signficant conclusions as of April,1990.

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Projections. f i

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! GPUN DRYWELL VESSEL ,

UT NSPECTION PROGRAM l

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OBJECTIVE: To monitor (over time) thicknesses at specific drywen vessel l socations, cascusate corrosion rates, and to -:+2:r J.r, project l margin for assurance of drywen integrity.

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i 4 DETAILED INSPECTIONS

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l e Sandbed Region, EL.11' e 3" (1986) i

  • CyHndrical Region, El. 8T - 5" (1987) -

a t

l e Spt.;.ics! Region, El. 50'- 2" (1987 & 1990)

[ e Spherical Region, El. 51' 10" (1990) f i

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._________.____m___. _ _ _ _ _ . _ _ _ ..________ _ _ _ _ _ _ _ _ . _ _ _.__ _ . _ _ _

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ONGOING INSPECTION PROGRAM

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e Outage of opportunity

! (aM)

e Drywell entry for reasons other than program in=amw;*Jan j t

!i I j e Priority #1 Locations - 2 3 month frequency t i-

)

e Priority #2 Locations - 218 month frequency t

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___ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ ___ .__ m .__ ._- _ . _ . _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ . _ _ _ . _ . _ . _ _ _ .

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INSPECTION I METHODOLOGY i-I f i  !,

j PRIORITY #1 LOCATIONS i

j I i

l e Qualified NDE Inspectors '

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j e Template - 7 by 7 grid i

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e Low stress stamp on inspection locations (repeatability to 1/8") j i

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4 I____________--_ . _ _ _ . _ _ _ _ _ _ _ - - - _ _ _ - _ - - _ _ _ _ - - - _ _ _ _ _ _ - _ _ - _ _ _ _ _ - - . . _ . , ~ --_._.__.__-__..__n--

-- . _ _ . _ _ - ._. _~- _ ~ -- _ _ _ - _ - - - - - - - _ _ _ , . _ = . _ - . - - - -

[

i CORROSION RATE CALCULATION ~

e Mean of 49 points

.i e Mean is plotted over time i

e Linear regression model/ curve fit? i

- Slope of curve - calculated corrosion rate j e Mean model/ curve fit?

- No slope - No corrosion rate i

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Curve Fit Based On Linear Regression Mean Values T Now i

e H * ~

l e e C ses, estimate o, K J' Corrosion Rate Curve Fit N  ! '

E S

S i -

i TIME CYears)

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__-_m__.___.<.__ ___ ___m.___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - . _ _ _ _+_w'+<w- 4:P"' **_ - - ' - '+ ____ _v_^'-: w, wer+ im've +b_._____ _.-__----_vw. - _--m aw---C_ _ _ _ _ ----__.__a-__+ _ -

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Curve Fit Based On Mean Model T Now -

H _.

Mean Thickness

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K . .

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N Curve Fit

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t TIME (Years) 1

. . . , . . - - . . . . . . . - - ~ ~ . ~ . . _ _

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Projections Based .On inverse Regression (SCHEMATIC) i ab T Now G i H

  • I *
  • Curve Fit  : Upper 96%

{ / Limit Sound Confidence i Lower 96% /

Confidence MIN Limit sound N Thck most Estimate

/

E b W s

S 7 , -

TIME (Years) proi..eio s .o on

' 95% Confidence

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HISTORY i

[ 12R refueling outage - (Nov.1988 to Feb.1989) .

i e Removed water from sandbed j e Installed Cathodic Protection System l4

  • Insp;aied Priority M and #2 locations i

j Operating Cycle 12 (March 1989 to Present)

) e March,1989 - Energized Cathodic Protection System f e June,1989 - insp;sied Priority #1 locations c

  • Sept.,1989 - Insp;aicd Priority #1 locations e Feb.,1990 - Inspected Priority #1 locations l-e March,1990 - Inspected Priority #2 locations I j - Interrogated Elevation 50' - 2" i e April,1990 - Inspected Priority #1 locations 4
- Interrogated Elevation 51' - 10" 4

RECENT INSPECTIONS SANDBED REGION (EL.11' - 3")- 2 FEBRUARY,1990 Priority #1 CP Locations Rates not reduced (apparent)

Bay 13A (no CP) - High rate MARCH,1990 Bay 13A (no CP) - High corrosion rate (cont ...ad)

Priority #2 Locations - Bay 13D, possible snaterial loss APRIL,1990 Priority #1 CP Locations - Rates not reduced (confirened)

Bay 13A (no CP) - High co. usion rate (confirmed)

RECENT INSPECTIONS SPHERICAL REGION FEBRUARY,1990 El. 50' - 2", Bay 5 - Mean Thickness of 742 Mils.

MARCH,1990 El. 50' - 2", Bay 5 - Mean Thickness of 743 Mils El. 50' - 2", Continuous Scan:

- Results indicated Bay 5 location was repiss. dis 4.2 as thinnest APRIL 1990 El. 50' - 2", Bay.5 - Mean Thickness of 749 Mils El. 51' - 10", Continuous Scan - Three locations found thinner than norninal

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RECENT INSPECTIONS

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CYLINDRICAL REGION w-MARCH,'1990 El. 87' ;5", Bays 9,13 and 15 - No ongoing material loss.

, m -. m - -wa - - - - - - - -

SIGNIFICANT CORROSION: RATE CONCLUSION -

(AS OF APRIL,1990) -

e Spherical region, elevation 50' - 2"

- Bounding calculated corrosion rate = 4.611.6 MPY e Sandbed region, elevation 11'~- 3"

- Bounding calculated corrosion rate =- 39.1 13.4 MPY o Sandbed, cathodically protected regions-

- No..significant corrosion rate reduction (15 to 25 MPY) e Cylindrical region elevation 87' - 5"

- No observed ongoing conusion e Spherical region elevation 51' - 10"

- Calculated corrosion rate not available

_ = - - -. -- - - _ -__ - - _ - -_ _ _

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Current Projections

T (Based on Data Up To April 1990) -

H .

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MIN Best Estimate Lower 95%

j Thck timit - _ / _- N i L  :

N L. s N

E  !

Now S

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TIME

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Sandbed. ' Jul 1993 - Mari1994 t

Elev. 50'-2" Jun 1992: Sep 1994 ,

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-Elev. 51'-10' Oct 1991'* . Jul 1993 -

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  • NOTE: Projection Based on Elev. 50'-2" Corrosion Rate-

--- _ -_-- -- _---_ __ - _ ----_ ~ --- -

_ ._. . ~ _ . - ___ ---_---_ . __ - _ - _ _ _ _ - - -

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SUMMARY

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e Program objective. '

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e Program methodology.

i e Data reduction.

e Corrosion rate calculation and-projection. ,

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  • Results of the spring 1990: inspection.

4

! o -Conclusions..

l - e Projection.

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- - - , _____,__________..________________._____________.________.____m.m__

_..m.__ ___.________._,._ms

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l AUGMENTED UT INSPECTION PLAN .  :

FOR OYSTER. CREEK DRYWELL i

! G@AL:

L

! D: sign an augmented inspection plan that p.vv' des a statistically based i

chcracterization of the:drywell'using;a' limited number of plate thickness L maasurements.

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-- ___ ___ ____-___ ___-_ = __- ____ c-__ J ______-_ - __ : -__= _ ,_ _ .__ _________-._ - - - - ._____-__.-___ - ___ _ - -

_ - _ _ _- - - _ _ _ _ . _ . _ - _ _ _ _ _ _ _ _ _ = _ - . . _ - .-

t TECHNICAL APPROACH:  ;

1) A Nonparametric Approach No assumption is made about the distribution 'of material loss'by corrosion.

Attribute sampling is used.

j e

The sand bed is not included since it is characterized by other means.

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2) Proposed f.evel .of: Assurance of Structural Integrity.

i 195% confidence thatL95% of the. drywell surface. satisfies the acceptance  !

criteria. Established statistical theory is used to4;.::sp a random sampling ,

plan for this confidence level. Thickness readings that do not: satisfy the ccceptance criteria:are not reason to conclude that structural. integrity is not cssured.

l 1

3)' Acceptance Criteria . l Observed thickness equals or exceeds a required minimum. thickness'plus a corrosion allowance necessary in order to reach the next. inspection.

Guidanceifor Designing a Sampling Plan -

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Given a proportion of unacceptable observations in the population, a good j sampling plan must~give assurance that these will not go undetected. For the '

j proposed. level of assurance using a sample of 60 observations taken at randomly

. selected locations,:there is only a-5% chance of not finding such an area. Use simulations as a measure of process performance.-

1) Simulation shows the accuracy of the inspection plan. Estimated proportions-are compared with known proportions of population properties.'

Using a-model containing 5% unsatisfactory grids, a simulation of random sampling using a five part: stratified plan results.in an estimate of 4.6% as the average of 100 trials. Simulation also'shows that finding no unacceptable observations occurs less.than 5% of the time, as intended.

2) This also means that if one or more of the 60 observations is found to be less than the minimum. thickness, there is only a 5% confidence that 5% of the drywell is less than the: minimum thickness.

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- 3) in addition, one or more unacceptable. observations can alsoLoccur at a 5%.

probability with 99.9% of the dryweII freelof: unacceptable observations using this. sample. A= conclusion about drywell structural adequacy with one suchJ observation is not appropriate because a better condition can result in an unacceptable observation. Finding ~.none does confirm the original hypothesis.

.4) A different sample is used for each assessment.

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i Disposition oflResults: '

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' 1) Finding an unacceptable.mean thickness is reason to better characterize the '

area in order to show that the region is, in general, in much better condition. lf' I

a-mean thickness, established using a 6" x 6 grid, does not meet minimum'-

requirements, enlarge the inspection grid to an area one and a half feet on a

[ side and obtain additional readings. Use the enlarged grid to compute a new 1

mean thickness. '
1 l 2) ASME code permits unreinforced holes;of diameter 0.2VRE no closer than 2.5VRE in any direction (approximatelyl1% of. the. area). Equate
the requirement c that:99% of:the area is. free of holes to a 99% probability of. finding no locally low! areas."A local area is a 2"!xL2"Lcell .within a .6" x 6"; grid.-

[ Better characterize,fas necessary.

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~k STRATIFIED SAMPLING PLAN: -

The plan usesistratification to " scatter" the observations around the structure. 'I RANDOM INSPECTION LOCATIONS- ,

~ ZONE NUMBER OF i GRIDS l Drip and. Sand Bed Plate 3' l Sand Bed Plate 6 Drip 12.

Sphere 32

Cylinder 4L i

._-~.-_ :w wa.x=.:_i = = . - . . ----- . --:L L.=.-- -

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i CUMMARY:

j This augmented. Inspection-plan, using 60 locations selected at random, provides

..a statistically based characterization of the drywell. The inspection plan provides.

i a sensitive test for unacceptable observations. MeasurementsLof the region edjacent to.a low area, shouldrone be.found,-will'be made in order to show that the condition of the plate is, in general,:much better.'- .

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! OYSTER CREEK DRYWELL INSPECTIONS i

j- Goal: Provide required data In ALARA fashion

Two areas where goal applies 4
1 - Readings.on regular l basis for corrosion rate
:
2 - Random; readings for verifying structural integrity .;

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REGULAR READINGS FOR CORROSIONLRATE 1 1

  • 6" X 6" grids -~49 readings with D-meter

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e .On-going (outage of opportunity) ~

j e New grids

- Flap & polish to remove coating

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- Template.placed on area, wall marked for future template.  !

placement:

- Readings taken

- Temporary. coating ' applied to. area -

e Existingigrids.

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- Temporary coating. removed

- Template. placed on marks

- Readings taken

- Temporary ' coating re-applied

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REGULAR READINGS FOR CORROSION RATE (cont'd)

Dose expended to-date is about 30 man-rem
Evaluating plan for on-line monitoring

- One location during Cycle 13 on existing grid i

- Up to 49-points-Ilmited by multiplexer capability ~

l - Evaluate-performance If Good

! - Select critical locations I

- Install in future outage

if Not

- Evaluate alternatives g

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________.__.____.__._____=.___._______m. _ .- _ . . -

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v BENEFITS TO ON-LINELMONITORING i

e ALARA - avoid going into drywell on regular basis 1

e Real time - sharp increases / decreases in rate.will be picked up l relatively quickly 1 e Wegcan take steps to determine cause more quickly-t i

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"#J'.___.__ .- - " '-'- __m--m--__.___ __ _ -_ - ___ _ -- _--___-- - ____um -.mm_ 1_1_' _ A - _zw___ -.-' nn_a_-..___1-'_-L492m.JL'L_2.m-

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4 9

SOME PROBLEMS WE EXPECT y

e Transducer life in drywell environment -

'e Maintaining couple-3 i

- Maintaining: pressure on transducer

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'e Couplant: life .

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._ , ., _ . . - . . - - - - , .. . -- - . ' ~ ' ' ' - = ~ ' ' ^ * ' ' " * * * * * ~ ' ' ~ ' " ' " ~ ' " ' * ~ ~ ^ " ' ' ' ' ^

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[ - t RANDOM READINGS 2

1 FOR VERIFYING STRUCTURAL. INTEGRITY l i

Two-pronged approach to goei

[

  • Reed!ngs t!srough coating i

- Eliminate coating removal, re-application i ,

e Remote readings. *

- Eliminate scaffolding' - 1

- a

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ACTIONS TO STRENGTHENTREP. AIR STRUCTURALLY.- ,)

i e Repair option evaluation underway - support by GE & MPR ~ l 1

e objectives j

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! (1) For sandbed, spherical, and cylindrical regions, ]

l identify most effective repair methods,Lbefore 13R.  ;

(2) Evaluate: methods for removal of sand,;firebar-D, and i

fiberglass gap materials, for corrosion mitigation. -

1 1 l e Evaluation criteria for repair methods: technical, cost, radiation j l exposure, outage schedule impact.-

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7 r--g.. y.--. ,,_ . - ..e. m,s--9-. ,,w .,,,,*- .c 7- +r- .wnm g w., , .y , . . . , y ~ , -

,3,, -.p.- , 4 , - s -

w-.w.ci y . ww . , n ,

"tr i ACTIONS TO STRENGTHEN 1 REPAIR .

STRUCTURALLY (cont'd). l 4 i

. -l e Alternatives (conceptually defined by previous CBI study) 1

Sandbed
(1) Sand removal, plate replacement - buttwelded.; _ L
(2) Sand removal, doubler plates - flifet and plug welded.-

'(3) Sand removal, add sitifeners- j (4) Sand removal only. ]

1 4

l Spherical and cylindrical: q (1) Plate replacement, buttwelded.

! 1(2) Doubler plates, filiet and plug:weided. i L e Drywell walkdowns inL13R. j i

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  • Repair options ready for: implementation in 14R, if required. . ~

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s , . , m ,,r- 5 .

% i . , ,,w s o -s- , . .

  • m. - . .+-c,, , . . ~ . . .-- . . . - - s,

, M ih i ? Q t O yj P-'

DRYWELL UNDER INTERNALLPRESSURE .

CYLINDER d'

4

  • KNUCKLE

/ -

INTERNAL- _ SPHEHE PRESSURE DESIGN PRESSURE IS 62 PSIG.

lll

i.

. DRYWELL UNDER SEISMIC FO.RCES J t

i --

- REACTOR BUILDING SUPPORTS i 4

um$ =

s-DRYWELL LATERALLY.BUT ALLOWS' I 4 LATERAL & VERTICAL EXPANSION. ,

! 4

4 4

4 .i .

SEISMIC --

4 -

FORCES. g .

i DRYWELL IS BUILT IN -

r iTO THE REACTOR BUILDING- .j

! ' AT ITS BASE.- &

[.  : SEISMIC FORCES RESULT -

FROM GROUND ACCELERATIONS.  ;

e -

, t

. .. _ -. ;- - ._ . . . . . - = - - . - .

. .. . ~ .- . - ,.: - : . . . .. . .- . . . . .s

o

1 I i

!- 1 l

t l CONTROLLING LOAD CASES FOR VARIOUS LOCATIONS:

1 m

-(Reported from analyses cosupleted froen 1986 to 1988) '

i 3 o CYLINDRICAL REGION - (Design t=0.640", min. as found t=0.619") Accident l Condition - Primary membrane stress caused by design pressure dominates

?

. O SPHERICAL REGION (Design t=0.722") - Accident Condition - Primary.

membrane stress caused by design cpressure dominates-l-

1 o SPHERICAL ~ REGION (Designit=0.770")
- Accident Condition - Primary -

1

-membrane 4 stress caused by design pressure dominates- .

be:

" SPHERICAL REGION lSANDBED-(Design t=1154",3 min. as found t=0.808",

assumed t=0.700") - Refueling; Condition l- Buckiing~due to compressive .

i stresses' caused'by-deadweight and/ water in refueling, cavity!+ 2 psi external a j pressure dominate' .

l i i

p,

.% ,..i..,. ..

w',. ,- .4y'...., . + - . ,1.- , -we.. - , ,.m.s .?,w..- _ _ _ -- _ _ _ _ _ _ _ _ =_..m.___ - . _ _ . _

_m.

1 i  !

REVIEW OF RESTART EVALUATIONS (198611987) .

1 t 2

O CYLINDRICAL REGION

. 1 i Established minimum as found thickness of 0.619" accepted using CMTR data I and the fact that there is no ongoing corrosion.

O SPHERICAL REGION SANDBED:

The stress analysis wasl performed to. ensure structural integrity for the sheII i assumed to be 0.700" thick. This configuration subjected to the combined

! Ioad cases yielded the following conclusions- 1

. The tensile stresses were less than the specified allowable stress from the .

1962 issue of the- ASME Code,Section VIII, including the Summer 1964

[ Addendum plus Code Cases.1270N-5 and 1272N-5 (1.1 Sm= 19,250 psi).

i j

) -

The compressive stresses were less than the specified allowable stress l computed according to rules of Code Case N-284.

l I .. . .- ... . -

1.

1 ADDITIONAL STRUCTURALLANALYSIS ,

i

O COMPARISON WORK FOR BUCKLING EVAL.UATION: ~

Capacityimargin (buckling) in the sandbed is improved by. including the details - 1 i

of vent pipe and its reinforcing plates. i

?

Stability analysis comparing 3-D FEM methods and BOSOR techniques (shell i

of revolution) using;a similar Mark I drywell.has been performed using the l-same-percentage reduction in wall thicknesses asl observed at Oyster Creek in

}

the sandbed region.  ;

l Loads.were adjusted to produce a stress state.at the midpoint of the sandbed

! . squal to that computed for the Oyster Creek stability analysis.

m_ .

~ The-ratio.of the FEM results divided by ths BOSORIresults .was computed and.

is equal to -2.1. Hence, the previously computed capacity margin of l

1.00 is very~ conservative. ~

1 l

i l

j .

i e = _ m

_ . , . . - ~ . _ . . . .. . . . . _ _ _ - -

T-e 4 + w

THREE-DIMENSIONAL FINITE - I c;7 ELEMENT MODEL OF SIMILAR .

4 7 MARK I DRYWELL FOR 1 IQ OYSTER CREEK COMPARISON -

/g, STUDYL j w

4: ::.

s.  ;
%.I
h..ji-;

f/ ..

j

  • I'} ,

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l ,

a

+.. -

l y -

$'N %, . ~

i_ _

e 4

4 .

4

!t FEM PLANNED FOR BUCKLING EVALUATION . .

1 4

o Calculated; factor for Mark I drywell of 2.1-indicates l high probability that a - 3 i

similar margin exists'for Oyster Creek.

j Perform a: stability analysis of the Oyster Creek drywell using.3-D FEM j techniques which will-include the-stiffening effects of.the vent pipes and ,

reinforcing-plates. This analysis is in progress.

c

1 o Perform a 3-D FEM: stability analysis:cf the Oyster Creek'Drywell for;the L - configuration where sand has been removed.: ' '

r c - O Will itwestigate any repair options with the use of FEM models..

i .

i '

k 1 i t ..

. [' .s. ,.ys

- . ~ y- -

T*i '

' ' " ' ' ' - ' = ' ' '

A ASME III - SUBSECTION NE EVALUATION O Code defines " local primary membrane stress intensity" to be greater than 1.1 Smc and less than 1.5 Smc.

o This 10% variation in allowable stress was provided because of the " beam on elastic foundation; effects, i.e., stress decays but remains greater than zero for significant distances.

O Clearly not intended to design for 1.1 Sme, however, given-a design that satisfies the code intent, it is not a violation of the code for the membrane stress to be between 1.0 Smc and 1.1 Smc for significant. distance.

o Largest:exceedance of Smc is:3%. Therefore, drywell currently complies with the code.

1 l'

ADDITIONAL CONSERVATISMS- ..

O Revised temperature profile indicates lower thermal demand than previously ~

calculated. .

O lt is expected that the drywell materials, construction and inspection rneets all.

the requirements.of Section lil, NC. This ~could.have permitted as factors of-safety of 3 for ultimate strength and not 4 as is currently used.-

O Ultimate pressure capacity provides-margin vs. the design LOCA pressure.

.- .- - -_ -. .= _

CALCULATED STRESSES vs. MATERIAL STRENGTH Material: SA 212-GR B SU = ULTIMATE STRENGTH (MiiJ; SU = 70.000 pei .

J T

m D

2 SY = YlELD STRENGTH (MNQ u- SY = 38.000 psi o

I F-O b

T e

!-isggic-21d?sget,, _ _ _ _ _ _ _ _ , ________. _ _ _ _ _ _ _ _ ,

JREAMElBJib-se , . . -

g 19 M PS I8,270 psi 18.120 psi 18.6C4 psi CALCULATED COMBHED STRESSES -

C ICAL 0.722" REGION 0.7/0" REG 80N N~

e- e.sw SPHERICAL REGION

P CALCULATED STRESSES BASED ON FORECASTED THICKNESSES TO 14R USING 95% CORROSION RATE - ASME CODE MINIMUM SU = ULTIMATE STfIEtj 3111 If.*!TJ: _

SU = 70.000 pei -

1

_I T

m SY - YlELD STRENGTH (MIN)

IL sv-3s 000 psi O

r V

0 m  !.Lsg!!c-21.fzsjet _., _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ,

g - . Sec -- 19.250 mal F 19.830 psi 19.450 psi 19.220 psi '

CALCULATED COM81RDSTRESSES CYLINDRICAL 0.722" REGION 0.770" REGION SANDBED RGN.

REGION PRNECTEDON ASRMmD BASEDON ASRXMD BASEDON AS40UND t - 0.sTF* 1-e.723" t- e.738-easeDomasammo

i. e.str SPHERICAL REGION l

i l

I CALCULATED STRESSES BASED ON FORECASTED THICKNESSES >

! TO 14R USING BEST ESTIMATE CORROSION RATE - ASME CODE MINIMUM l

1 SU = ULTIMATE STi1EN illi (Miih .

SU = 70.000 osi -

i

! J

! m

til i

. <F-i SY = YlELD STRENGTH (MtN)

IL sv - 38.000 psi j O I

W O

b g

!.lsgnc_-!!!.1?s_gst _, _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ , _ _ _ _ _ _ _ _ _ ,

Srnc = 19250mai

F- 19.830 ps
19.150 psi 18.950 psi -

+ @ -

.17,130 psi l CALCULATED COMBINI.DSTRESSES i CYLINDRICAL 0.722" REGION 0.770" REGION SANDBED RGN.

REGION N C M M AS M M BASEOM ASMW SMOW ASfMND

t- 0.688" t - 0.734- 1-0.758" i BASEDW ASfoUND i- 0. sir SPHERICAL REGION i

I' l

\

. . . .. . _ . _ , - . . _ _ . .~~. . . _ . _ . . _ _ _ _ . . _ . . _ -. _ _ - _ ___ - . . . _ . . _ _ . .

5 J

i i-

~

STATUS OF INVESTIGATION j i

O Drywell currently in compliance with code.

t i

l O DryweII will still be in compliance with code at 14R.

l 0 AII analyses and supporting documentation will be submitted by December 31,

! 1990.

[

i-i l

r

.- . ..,. ,.. -, . -.- - .._, ._~. .-.... ... .- -- .. ..

i a

ACTIONS TO LIMIT WATER INTRUSIONS l D Bioshiaki Gap i

j A. From environment during construction.

i l B. From reactor' cavity bellows lealcs.

i i

C. From reactor cavity or equipment pool liner leeks.

i D. Embedded piping leaks.

E. Condensation.

I i

t r

F 4

I l

i l'

i i-i i

_ _ . _ _ _ _ - . _ . _ _ _ _ _ - . - - _ -____.s - w _ _- . 'E _ e -e.,e - w a ...*+m e- w wv e -e- -e + eme v . . . - - ' ., = - -~ .- .-,*e--=%.e-m_.-==. -

m mm e -mmm__ m_ _.mm_____ -

N S

I b(<

e O

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1

I s

i I.

l l Ly ;s , --- ,

i (f)  !;sium 4ar.:: -:, egge o LLI

> ram ,

i l- s

! Di [--Awe . I r

O )

I i

i

b 2 '

i ,

1.

i i'

DRYWELL TO CAVITY SEAL '

i i

i j

^

OTECTIVE l j

t HIELDING_1 -l I

SSET l DRYWELL _

c!a ~

BOTTOM PLATE- .

- -n j

NS NSULATION MATE i

, i

LIDENTIFICATI@N @F WATER SOURCEO AND ACTIONS TAKEN.

i 1 l

i l I i SOURCE RAETHOD ACTIOOINhEFE

! . i

! Spent Fuel Pool Leeks Vacuum Box RepalRMS By -

1 underwater weksngtf985 i

Reactor Cavity Seal Pressure Test No Laaks/1985

~

Bellows Reactor Cavity Pressure Test Gesiset Joint l Seal Drain Line RepaINNSff985

! i

' i Reactor Cavity Video

~

Repahed Concsete

, Seal Under Drain Tsough Contouett988 3

' Reactor Cavity Uner Visual, Extenske Leeks klendNed.

Laaks Dye Pen. Test Teenporarily Coated During 12R vacuusa sox outage wah S.S. Tape and

h Coedng./1988 l Skimener System Piping Heliuen Isolated System l Equipment Storage Visual, Wold Repaired /1988 Pool Leaks Dye Pen. Test L vacuum sox .

Sandbed Drains: Rotor-Routed in 12R/1988.

W ter Drained From Sandbed.

i l

l __--.___ _--_ _ -.- - .__ _ ___ -_ ____-__- _ _ - _

i i

! IDENTIFICATION OF WATER SOURCES t

AND ACTIONS TAKEN (cont'd) .

j i ONGOING AND FUTURE ACTHNGS j- IDENTIFICArgoOS

. sounca munreson acmofumarm

} Refueling Cavity To Be T:T;-s...i Costed l Laaks Again In 13R 4

l Equipment Storage To Be TemporarWy Coated l Pool Leaks Sindlar To Cavity Uner e

t f

1 QOnOra! N 1

f

. . - - - - ~~_.. ~.. .- --. ..- -- __.-.... -

. ____ __ _________w

m. A a w.ma..a ,-AAh- h-pu.me 4. Ams, h4 4 g.,aaLez -.sw1 A e ACC Aes N.4 +,-ame a.4 ha.ma m. M car p-m a _ wa m-4 -w,-aaa.4w-a man-.s_ - maaa_--_.s.a.m,,-a.wm,s..,a.aw.sw,r_ u.sa------- -

'O O 9 6 g g .g N

j l

i i.

l 1 l

1 M S  !

< 0 i U ,

n  !

I G2n 8g h

v. i

.M > d 93 e l e 1 2e e l

o .o IL g b

E 8E a

,0

=  ;

00 )

....-.-.-.._...-.--:-_-._..-._-...-...---..-.-.-..-.-...._J

i I

i

, i l-GPUN CORROSION ASSESSMENT '

I OC DRYWELL .

1. Analysis of com samples fem 1986-87.

l 2. Establish key factors for corvosion.

3. Analysis of core sample 13A removed 4/90.

l '

a

4. F.wpc;;d corrosion scenario. ,

i

s. corrosion ana
fsis by industry consunants.

t .

6. Conclusions.

]

t

i 4  ?

i

I L ,

i .

1 i

. . - - .___~-._--~__.__..-._.._._._..______._!

CORROSION ASSESSMENT 4

i CORE SAMPLES i

L SAMPLE BAY 1 SAMPLES VISUAL

! NUMBER LOCATION ELEVATION OBTAINED OBSERVATIONS

1 19C 11'3" Core, Sand Corr., Crust, Damp i-l Sand, No Gap 2 15A 11'3" Core, Sand No Corr., Sand j

Dry,1" Gap l- 3 17D 11'3" Core, Sand Corr., Crust, Damp Sand, No Gap i 4 19A 11'3" Core, Sand Corr., Crust, Damp l

Sand, No Gap j 5 11A 11'3" Core, Sand Corr., Less Damp Sand, i

No Gap  :!

l 6 11AH 12'2" Core, Sand No Corr., Dry Sand,. .

[

.3" Gap -

[1986-87 Samples l' .!

! jl iI .I i ; . _. . . - . . , - ~- - - - ~ - - - - - ~ - - - ~ ~ ~ ~ ~ ' ~ - ' ' ~ ~ - ~ - - ~ ~ ' ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ '

. CORROSION ASSESSMENT j CORE SAMPLES (cont'd)

~

i l OAMPLE BAY 1 SAMPLES VISERAL

! NUMBER LOCATION ELEVATION OBTAINED OBSERVATIONS i

7 19AH 12'1" Core, Sand No Corr., Less Damp j

Sand, 4" Gap '

j 8 5 50'2" Core, Corr., Brown Firebar Oxide, Dry i

, 9 7 50':!" Core, Minor Corr.,

i Firebar i Reddish Oxide i ii l:

l 1986-87 Samples  ;!

I l

  • i o

l _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ . . _ _ _ _ _ - -

_ ____ _ _ _ _ ___ _ _______ __ _ _j

k i

KEY FACTORS-FOR CORROSION l ~OF OC DRYWELL .

(

i

! 1. Moisture ~

! - Initial wetting of insulation, sand ~

j

[ - Leaking cavity liner

[ - I.eaking bellows i

2. Contamination i

- Chloride a Marine environment i i

. . Firebar-D l - Sulfate e Firebar-D

i l 8 Oxv9'a .

l - Diffusion in sand

[ - Gaps in. sand /firebar

- Diffusion in. oxide crust 1 i

i l.

i'

L KEY FACTORS FOR CORROSION l OF OC DRYWELL

~

t 1

1 i -

i

)- 4. Temperature l - Gradient exists from top to bottom l

- Firebar region at peak temp. for corrosion -

- Oxygen solubility

! E hic action

- Variations in geometry and environment may lead to establishment of local anodes 1 i

1 i

l l

_ _ _ . _ _ _ _ - _ _ _ _ _ _ _ _ ___ ._ _ _ _ _ _ _ _ , -_ ___ _ __.____ .~ - . - __ __ --... ,

_ _ _ _~_.__.

___..___.-.-.-_.___ ______ .____.___. - - _ __ J

i CORROSION ASSESSMENT 13A CORE SAMPLE a

1. Basis for 13A Sample Selection  :

4 I

e Bay is currently showing highest co Tesion rate, j u

i e Corrosion rate is higher _ than that observed on other bejs prior to CP.

4 l e Provide comparison with 198647 ssmples.

I i e Check for the presence of moisture.

l t

e i.

1990 Sample e

i

.i

- , ,,, -- .. .,a, ,, ,-. -- ,,......a.,_____-_------___________-____._______._________.___.

i.

CORROSION. ASSESSMENT i

13A CORE SAMPLE 1 4 '

2. Visual Observations l
e Grrf!biack corrosion products were adherent to surface and were l similar to previous samples.

l  !

l e Reddish / orange deposits were observed adjacent to the sand.

l i

e Core surface had irregular topography.

q

! e sand appeared dry and nowed easily. a y

1

! J1990. Sample l

i i

i l

t I-1 t .,

. . - . . - ~ . _ . . . .

_ , _ . .---m _. _. . . . . . _ . ., . . _ _ _ _ . . _ , _ _ - . _ _ _ _ _ _ _ .

i L

CORROSION ASSESSMENT j

i.

.i 13A CORE SAMPLE (cont'd) n

3. Corrosion Product a

i j e The oxide appeared porous and multi-layered.

j e The major compound present in the black / gray material was Fe304

. (magnetite). l

.t i e The reddish orange oxide was primarily FeO-OH (';;iidsc._-:Es). 1

/

e The oxide showed a significant chloride content.

\

a L 1990 Sample e

4 i

i l

3 l

. . , . . . , ~ . - . . .

, , . . . . . ~ , . ,s- ,, - . . . . . , . . _ , ~ , , , . .

T ,4 l

1

, 1

[ CORROSION PRODUCT F

1 j.

X-RAY DIFFRACTION 1

1. ~

1 d .

i.

SPECIMEN Fe304 Fe2O3 FeO(OH) ,

1 l Core Surface Oxide 88 % 10 % ~2%

a i

4 Loose Oxide 85 % 12 % 2%

l Bulk Crust 40 % 30 % 30 %

Orange Oxide 4% 2% 93 %

i I  !

f 5

(

t L

(~ I i l 4 i

+ ,

k. L i I I

I  !

i i

! t i'

{.

6 i

N ',

i i

! l i

CORROSION ASSESSMENT l

13A CORE SAMPLE (cont'd)  :

4. Metallurgical Observations 1

{ e- The core surface is best described as containing a series of twood 1 l overlapping pits (scalloped texture).

4

  • No deep pitting was observed.

!

  • No evidence that microbial influenced corrosion was occurring.

i

[

e The microstructure appeared typical for plain carbon steel. ,

i  !

e The corrosion was similar to pneviously evaluated samples.

I

i.  :

1990 Sample i

! t I t i  !

J

~ wa ,.4,--,,,,,-~g -

g, , - ~ - - -ee p + , , <- n. + .w.n-.,,. , _.____-.n _ _ _ - _ _

l 1

i t --

i I.

EDS RESULTS

?

PLUG CRUST SAMPLES

  • PLUG 13A PSAMB 13A PLUG 13A ELEMENT PLUG 17D PLUG 19A (CORE) (RAID) (SABID) l

! S -

0.89

! CL 0.20 1.13 0.02 0.76 i

j CA 0.06 0.33 0.03 0.03-FE 93.29 79.02 97.78 98.25 92.22 i i

9 4 I

i l Weight Percent j i,  !,

! l.

p ,

i n

! I t

! l l

r

1

+

s e

EDS RESULTS 11 1

PLUG SURFACE * -

i l PLUG 13A  !

ELEMENT PLUG 17D PLUG 19A PLUG 11A-H (CORE) i t i c

S 0.18 10.59 .

i i CL 4.32 0.08 4.88 1.51 .

t i  !

l i

CA 0.02 0.41 0.48 1 l- '

4

[ FE 95.31 96.76 25.30 94.80

i. i i

PB 56.19 i i

[ Weight Percent .

, i i  !

I i

l-4 i

l' l . .. ..

'l

b 1

4 )j SAND LEACHATE ANALYSIS t

i t j

(PPM)

BAY 19C 15A 17D 19A 11A-H '43A 1 Moisture M D 1.1 % 2.6 % D .16%

Corr. Rate
  • 24 0 25 21- 0 39 i l Veer 87 87 87 87 87 90

) NA 37 47 9 7 3 11 t K 37 23 17' '

19 9 17

(

CA 47 23 4 12 4 2 L MG 10 .23 2- 5 16 2 L

CL 45 93 2 2 26 20 NO3 17 6 <1 <1 <1 30  ;

SO4 28 79 4- 4- 4 30 TOC 47 ND 5 14 34 12 l' i M= moist, D= dry,

  • mpy

! ~

4

-i

. a e

j t
PROPOSED CORROSION SCENARIO FOR OYSTER CREEK l -

1 1

l e Initial wetting of insulation and sand cushion establishes i electrolyte for corrosion.

i

! -e Marine environment / contamination from Firebar-D enhances ,

electrolyte conductivity. -

i L e Corrosion of drywell initiates - red lead paint provides initial L protection.

i l e Drywell adjacent to oxygenated regions (gaps, drains, holes) j or alkaline concrete become local cathodes.

e DryweII in deaerated regions become anodes. ,

i I

I i i j I-l' l d ,,

i '

I i-

<j -. .

_ ~ - __ _ _ , _ _ _ _ _ - _ . . - __- _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _

i L

l i

PROPOSED CORROSION SCENARIO i FOR OYSTER CREEK (cont'd)
l 2

j _

e i.eaks from cavity liner and other sources contribute air l

saturated water with CL and SO4 leachate from the firebar.

l e Alternate wetting and drying concentrate chloride at the

! metal / sand interface.

L

  • Oxide formation and sand maintain corrosion products at l metal / sand interface.

J

~

l * . As water runs down the drywell surface it can wet the oxide, thus maintaining the corrosion reaction, without contributing l to the sand or firebar moisture content.

^

i i

l L

m. _.____m___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ . _ ,

. 1 - . . - m.. . . . . . - ,..., _~~ . - . . - -.

CORROSION ANALYSIS 1990 CONSULTANTS In May 1990 a group of industry consultants were cornened.to .

discuss the current status _of the drywell and to recomsnend additional courses of action to resolve the conosion probleen. The recomsnendations froen this group are as follows:

e Evaluate corrosion locally and globally. h e The sandbed, fiberglass and firebar-D must be analyzed.as separate conosson environenents.

e Evaluations of proposed remedies for one location enust include the impact of the remedies on other locations.

e The crust p.e2.it on the shell surface acts as it's own local environenent which may be different from the conditions ad",sawit to it.

CORROSION ANALYSIS 1990 CONSULTANTS (cont'd)- .

e The recommended mitigative sneasuse was to rernove the sand, insulation, fireber-D and oxide an coat the exterior surface of the sheII.

e if the above plan was not implernentable in whole or in part the alternate remedy was to utilize an inert gas to displace coggen and to provide a means for moisture rernoval.

  • Additional cathodic pictwiiGiii is not recommended as it would be-necessary to flood the sanded in order to enake the system effecthe and thus necessitate the installation of CP in aR the boys. The presence of large arnounts of water in the sandbed would be counterproducthe. '

- - - - - - " - - --w~' - - -

--_---------maw -- - - - - --

1

. INDUSTRY CONSULTANTS

~

MAY 1990 CONSULTANT COMPANY C.P. Dillon C.P. Dillon ~& Assoc.

E. Draymon PCA Engineering, Inc.

G. Gehdng - Ocean City Research

'B. Gordon General Electric T.M.LLatonge Thomas M. Laronge, Inc.

J.l. Munro Corrosion Services Co.

1J.L. Nelson EPRI S. Nikolakaloos EBASCO J. Von Scriber Jack Wn Scriber Assoc.

o

CORROSION ASSESSMENT CONCLUSIONS y

rDifferent local environments most likely exist within the dryisell annular space which would explain various corrosion rates observed.

-Aqueous corrosion is primarily responsible for the saetal loss.

Galvanic action, oxygen, pH and temperature are most likely influencing the rate.

-Corrosion initigators must be aimed at changing local erwironments cas well as global erwironments, le. we must utilize a mitigative .

scheme which deals with the hulk environment in the san @ed or insulation anaterial and with the environsnent in the oxide crust. ,

  1. Corrosion rates =are within the bounds discussed in the literature for aqueous corrosion. Therefore,.we do not. expect to find regions of the drywell with~ snore extensive metal loss than that already observed..

k

- " - - ' " - * " ' ----"#"t ----" - ~ * + - * = - ' * - - - - - - - " ' - ' - " " ' " - - " " * ' " " - - - - - * - - - - - - - " - - -

-_.,__.____.__am__

[

I i

REMEDY QUALIFICATIONS

~

1 -

, Test program will be broken into two phases:

l 1. Bench top lab experiment to establish corrosion ceII, screen initial l mitigative-measures and evaluate corrosion monitors.  ;

L . . .

.i j 2. Mockup-testing to simulate drywell annulus environment to

! perform final qualification of selected mitigator corrosion monitor..

r

! 'I

!~ i i i l

i i

I 1

^

I I

,_ ..,-_..._,..u..,_, _ . . , . . . , _ . . . .,_ _ . . . . _ __ . _ _ . . ._2,.. . . . _ .

~

c REMEDY GUALIFICATIONS: -

{

! e Use lab test to qualify. corrosion monitoring instrumentation i

for use on mockup and for installation on the drywell. .

t i e Testing lwill include measuring the effect of the following

parameters lon corrosion

l .u-. Oxygen concentration j - a Temperature i

l.

m Humidity:

s Contaminants i~ m Galvanic l couples i

I ., -

i I

i I

i i

i. .

. _ . a- a - -- . . .. ._ ...- ; ~ . - , . . . . .. .. _ _ _ . . _ _ _ _ _ _ _ _

1 r y ,

i

REMEDY QUALIFICATIONS 1 LAB EXPERIMENT .

1 4

i e Evaluate localized corrosion a

[ m Sand environment

! m Fiberglass environment

l. e Firebar' environment 1 l e Evaluate galvanic corrosion m Aerated /dearated i

l e Firsar/6berglass

.a Firebar/ concrete

! e Fiberglass / sand a Fiberglass / concrete

= Sand / concrete i

1 l

i-

~

7-

$ is w v r s' w

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