ML20044D766
| ML20044D766 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 05/17/1993 |
| From: | Dromerick A Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9305200249 | |
| Download: ML20044D766 (24) | |
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UNITED STATES 5"
~,t, NUCLEAR REGULATOFsY COMMISSION I
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,E wAssiuorou. o. c.2osss May 17, 1993 Docket No.
50-219 l
LICENSEE: GPU Nuclear Corporation i
FACILITY: Oyster Creek Nuclear Generating Station
SUBJECT:
SUMMARY
OF MAY 5, 1993, MEETING WITH GPU NUCLEAR CORPORATION (GPUN)
I TO DISCUSS MATTERS RELATED TO THE OYSTER CREEK DRYWELL CORROSION i
MITIGATION PROGRAM.
I On Wednesday, May 5, 1993, a meeting was held at the NRC, One White Flint
[
North, Rockville, Maryland, with GPUN, the licensee to discuss the Oyster Creek Drywell Corrosion Mitigation Program. is the list of 1
participants.
! is the licensee's agenda and the information presented regarding the Oyster Creek Drywell Corrosion Mitigation Program. The following is a i
summary of the significant items discussed.
{l GPUN updated the staff regarding the Oyster Creek Drywell Program since the i
last meeting held in July 1991.
j During operating Cycle 13, the licensee performed structural analyses related to sand removal which were approved by the NRC. The licensee also stated that I
a concrete mockup of the drywell shield was built to demonstrate that the sand could be removed by cutting access holes in the shield wall which permit workers to remove the sand from the sand cushion area. During this period the
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licensee cut holes in all 10 bays of the shield wall and removed 60% of the i
sand in the area.
During the recent 14R refueling outage the remaining sand and corrosion i
products were removed from the sand bed region together with rust and scale i
from the drywell shell. The licensee also cleaned and pressure washed the shell and provided protective coatings.
GPUN provided a summary of 14R outage UT thickness measurements taken from the inside drywell. The current thinnest thickness of the (1) cylinder is 0.614,"
thick, (2) upper sphere is 0.691" thick, (3) middle sphere is 0.743" thick, and (4) sand bed region is 0.800" thick. The licensee stated that the minimum required ASME Code thickness for this area is 0.736" thick. All UT thickness measurements for Bays 3, 5, 7, and 19 are greater than 0.736" thick. All UT thickness measurements for Bays 11, 15 and 17 are greater than 0.736" except for one measurement for each bay.
Bays 1 and 13 each have several locations where the measured thicknesses are below 0.736".
GPUN stated that these locations are isolated. GPUN further stated that on the basis of the measurements the shell was re-evaluated using ASME local stress criteria.
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Based on the above, GPUN concluded that (1) sand removal was successfully completed in refueling outage 14R, (2) external drywell surface in sand bed region was cleaned and coated, (3) corrosion in sand bed region is now stopped, (4) the 14R inspections from the sand bed region confirmed that GPUN's previous inspections from inside the drywell were in the area of highest corrosion, (5) the integrity of the Oyster Creek drywell remains a priority concern of GPUN management and GPUN will continue UT thickness measurements for the life of the plant, and (6) low corrosion rates in sphere and cylinder portions of the drywell, in conjunction with pressure reduction approval, will ensure containment integrity for the full licensed life of the pl ant. The licensee proposed to use 1.1 Smc, to evaluate the overall shell thickness requirements.
The staff disagrees with this interpretation.
However,1.1 Smc could be used in evaluating local areas of shell.
GPUN indicated that priority 1 & 2 UT readings from inside drywell during refueling outage 15R will be taken and that there would be a visual inspection of coating in Bays 1 and 11 at the beginning of 15R. This inspection may be expanded to other bays if found necessary.
GPUN will monitor for water leakage during operating cycles and refueling outages, and take corrective action as appropriate.
GPUN further indicated that post refueling outage UT inspection program scope and frequency will be defined based on 15R inspection results.
Original signed by:
Alexander W. Dromerick, Sr. Project Manager Project Directorate I-4 Division of Reactor Projects - 1/11 Office of Nuclear Reactor Regulation
Enclosures:
1.
Attendance List 2.
Licensing Agenda cc w/ enclosures:
see next page l
t 0FFICE: LA:PD#I-4 P!gD#1,p D:fD\\l-4 NAME:
Ni$rY khdi[ekk:b JStbY "
DATE:
5/J1/93 5/7/93 5/p/93 DOCUMENT NAME: G:\\DROMERICK\\0C50219. SUM 0FFICIAL RECORD COPY
i I
GPU Nuclear Corporation May 17, 1993 i
Based on the above, GPUN concluded that (1) sand removal was successfully completed in refueling outage'14R, (2) external drywell surface in sand bed region was cleaned and coated, (3) corrosion in sand bed region is now stopped, (4) the 14R inspections from the sand bed region confirmed that GPUN's previous inspections from inside the drywell were in the area of highest corrosion, (5) the integrity of the Oyster Creek drywell remains a j
priority concern of GPUN management and GPUN will continue UT thickness j
measurements for the life of the plant, and (6) low corrosion rates in sphere l
and cylinder portions of the drywell, in conjunction with pressure reduction i
approval, will ensure containment integrity for the full licensed life of the plant. The licensee proposed to use 1.1 Sme, to evaluate the overall shell thickness requirements. The staff disagrees with this. interpretation.
i However,1.1 Smc could be used in evaluating local areas of shell.
l r
GPUN indicated that priority 1 & 2 UT readings from inside drywell during refueling outage 15R will be taken and that there would be a visual inspection l
)
of coating in Bays 1 and 11 at the beginning of 15R.
This inspection may be j
expanded to other bays if found necessary.
GPUN will monitor for water l
leakage during operating cycles and refueling outages, and take corrective j
i action as appropriate. GPUN further indicated that post refueling outage UT
?
l inspection program scope and frequency will be defined based on 15R inspection results.
l i
h Alexander W. Dromerick, Sr. Project Manager Project Directorate I-4 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation
Enclosures:
f 1.
Attendance List 2.
Licensing Agenda cc w/ enclosures:
See next page l
i l
lr -- - - - -
DISTRIBUTION:
e Docket File
- NRC & Local PDRs
- PDI-4 RDG File
- T. Murley F. Miraglia J. Partlow S. Varga A. Dromerick
- S. Norris I
OGC E. Jordan R. McBrearty G. Bagchi C. Tan K. Parczewski f
J. Davis ACRS (10)
V. McCree, EDO l
J. Rogge, RGI
- cc w/both enclosures i
?
-i l
Oyster Creek Nuclear Generating Station
]
cc:
Ernest L. Blake, Jr., Esquire
-Resident Inspector Shaw, Pittman, Potts & Trowbridge c/o U.S. Nuclear Regulatory Consnission i
2300 N Street, NW.
Post Office Box 445 i
Washington, DC 20037 Forked River, New Jersey 08731 Regional Administrator, Region I Kent Tosch, Chief i
U.S. Nuclear Regulatory Commission New Jersey Department of l
475 Allendale Road Environmental Protection i
King of Prussia, Pennsylvania 19406 Bureau of Nuclear Engineering CN 415 BWR Licensing Manager Trenton, New Jersey 08625 GPU Nuclear Corporation t
1 Upper Pond Road Mr. John J. Barton Parsippany, New Jersey 07054 Vice President and Director GPU Nuclear Corporation l
Mayor Oyster Creek Nuclear Generating Station Lacey Township Post Office Box 388 818 West Lacey Road Forked River, New Jersey 08731 j
l Forked River, New Jersey 08731 i
l Licensing Manager i
Oyster Creek Nuclear Generating Station Mail Stop: Site Emergency Bldg.
Post Office Box 388 i
Forked River, New Jersey 08731 i
f l
I l-
DISTRIBUTION:
Docket File
- NRC & Local PDRs
- PDI-4 RDG File
- T. Murley F. Miraglia J. Partlow i
S. Varga A. Dromerick
V. McCree, EDO J. Rogge, RGI
- cc w/both enclosures i
f I
I I
I 1
l
ENCLOSURE 1 Oyster Creek Nuclear Generatino Station Docket No. 50-219 Meetino - May 5. 1993 Attendance List
!LA_Mf ORGANIZATION Alexander Dromerick NRC/NRR/PD I-4 Robert McBrearty NRC/RG-I Goutam Bagchi NRC/NRR/DE/ECGB Chen Tan NRC/NRR/DE/ECGB Kris Parczewski NRC/NRR/DE/EMCB Jim Davis NRC/NRR/DE/EMCB Mark Yekta GPUN Dana Govill GPUN-NDE/ISI Phil Manning GPUN-NDE/ISI Mike Laggart GPUN-Licensing Steve Tumminelli GPUN-Engineering Mechanics i
Sam Saha GPUN-Material Engineering i
Julien Abramovici GPUN-Mechanical John Flynn GPUN-Project Manager i
Joe Colitz GPUN-Director Engineer Project Ron Zak GPUN-Licensing l
boaesua OYSTER CREEK DRYWELL CORROSION MITIGATION NRC PRESENTATION - MAY 5,1993 a
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AGENDA e
MEETING OBJECTIVES J. J. COLITZ e
CYCLE 13 ACTIVITIES J. C. FLYNN o
Analysis o
Work Accomplished o
Training i
e 14R OUTAGE ACTIVITIES e
SUMMARY
OF 14R OUTAGE UT THICKNESS MEASUREMENTS (Taken from inside Drywell) l e
SAND BED REGION S.SAHA l
0 Shell Condition o
Concrete Floor Condition j
o Determining UT Locations l
EVALUATION OF SHELL THICKNESS (UT) MEASUREMENTS S. TUMMINELLI -
e i
CONCLUSIONS & FUTURE DRYWELL INSPECTIONS /PL.AN J. J. COLITZ e
i 5
...-----.__,_,_s
MEETING OBJECTIVES e
UPDATE THE STAFF REGARDING THE OYSTER CREEK DRYWELL I
PRESENT THE ACTIVITIES ACCOMPLISHED IN CYCLE 13 AND 14R e
I FOR THE DRYWELL CORROSION MITIGATION PROJECT i
e DISCUSS 14R OUTAGE INSPECTION RESULTS t
DISCUSS FUTURE DRYWELL INSPECTIONS / PLAN e
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1
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4 OYSTER CREEK DRYWELL PROGRAM Phase:
Phase 1 Phaseil Phase ill Otgective:
Develop Success Path Solve the Problem Keep It Solved Timing:
Through 1990 Through 1992 Long Term Focus:
e Examine allinformation e implement plans / engineering developed in e implement life-of-In-hand regarding
. Phase 1.
P ant monitoring l
physical condition and program.
design of the drywell
- Characterize shell condition and and confirm that sheII corrosion mechanism.
e if required, integrity is adequate to
- Arrest corrosion where necessary by strengthen shell.
support plant operation positive means (e.g., remove sand, through Phase 11.
clean and resurface).
- Develop detailed plan e Stop Inleakage of water /take steps to and engineering (for ensure that it stays stopped.
Implementation in Phase 11) to:
o Complete analysis of shell strength, design basis and margin.
- C@W characterize shell e Determine if shell strengthening is condition.
required, engineer methods to do so
- Arrest corrosion in (if required),
any location where
, geyegop ige.og. plant monitoring program.
g continued corrosion would not permit operation for full term plant life.
I lcensing:
Obtain NRC understanding Change licensed design basis if appmpriate.
and agreement.
CYCLE 13 ACTIVITIES (JUNE 1991 - NOVEMBER 1992)
ANALYSIS l
e COMPLETED STRUCTURAL ANALYSIS o
Submitted to the NRC o
SER issued o
Analyzed Shield Wall for 20" Access Holes WORK ACCOMPLISHED e
REMOVED 60% OF SAND e
BUILT CONCRETE MOCKUP e
CUT ACCESS HOLES IN ALL TEN BAYS TRAINING e
ACCESS TRAINING FOR WORKERS AND EMTS e
PROCESS TRAINING FOR WORKERS
14R OUTAGE ACTIVITIES (NOVEMBER 1992 - FEBRUARY 1993) e WORK FORCE OF APPROXIMATELY 50 PEOPLE - COMPLETED ALL TEN BAYS REMOVED SAND ANd CORROSlON PRODUCTS FROM SAND BED REGION e
REMOVED RUST / SCALE FROM DRYWELL SHELL e
t e
CLEANED AND PRESSURE WASHED THE SHELL APPLIED THE COATING SYSTEM,
e o
One Pre-Primer Coat Devoe 167 o
Two Top Coats Devoe 184 o
Caulked mnerface Devoe 142 i
i 4
SUMMARY
OF 14R OUTAGE UT THICKNES_S MEASUREMENTS _
(TAKEN FROM INSIDE DRYWELL)
Vessel Thickness (inches)
Drywell As Minimum Current Previous Region Designed Required at Thinnest Thinnest 1.1 Smc (12/92)
(7/91)
(inches)
(inches)
(inches)
(inches)
Cylinder 0.640 0.580 0.614 0.612 Upper Sphere 0.722 0.650 0.691 0.695 (El. 51' to 65')
Middle Sphere 0.770 0.670 0.743 0.745 (El. 23' to 51')
Sand Bed 1.154 0.736 0.800 0.803 4
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SAND BED _BEGION i
1_4R_OUIAGE_DRYWELL. CONDITION SHELL CONDITION i
e ALL BAYS WERE ENTERED, INSPECTED AND COATED, l
ENTRIES WERE MADE DURING VARIOUS STAGES OF WORK o
CORROSION OBSERVED ON DW SHELL IN ALL BAYS BELOW VENT PIPE REINFORCEMENT PLATE VENT PIPE AND SHELL ABOVE THE REINFORCEMENT PLATE SHOWED NO CORROSION; e
I ORIGINAL RED LEAD PRIMER WAS STILL VISIBLE o
ALL BAYS SHOWED PRESENCE OF A " BATHTUB RING"- AN 8 TO 18 INCH WIDE BAND ABOUT 30 i
TO 40 INCHES LONG JUST BELOW VENT PIPE REINFORCEMENT PLATE CONTAINING HEAVILY CORRODED AREAS l
o
" Ring" very prominent in some bays and less striking in others o
Above this " Ring," shell had no corrosion o
Below this " Ring," uniform corrosion was seen l
o Laterally, beyond this " Ring," uniform corrosion was seen o
The " Ring" is believed to be the air-water interface when sand bed was naturated with water j
e ALL DW SHELL PLUGS INSTALLED IN SAND BED REGION WERE FOUND IN THE CORRODED
" BATH TUB RING" AREAS i
T
CONCRETE FLO_OR CONDITION
(
UPON SAND REMOVAL-THE CONCRETE FLOOR WAS FOUND TO BE UNFINISHED IN ALL BAYS e
Drainage channel, as shown in drawing, was completely missing o
Drain pipes were 6 to 8 inches above floor level and some were clogged o
o Floor was cratered with some craters adjacent to shell. A few craters were big, about 12-13 feet long,12-20 inches deep and 8-12 inches wide i
o Concrete reinforcement bars for the floor could be seen bare in many bays 4
4 TO SUMMARIZE, THE CONCRETE FLOOR CONDITION (S) PREVENTED PROPER DRAINAGE OF e
WATER WHICH, IN TURN, AGGRAVATED THE CORROSION OF DW SHELL 4
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4
D_ELTEEMINitLG_UT LOCATIONS o
PURPOSE - TO OBTAIN AND MEASURE THINNEST AREAS ON DRYWELL SHELL NOW THAT ENTIRE SHELL SURFACE AREA WAS ACCESSIBLE e
UT "A" SCAN CONSISTENTLY SHOWED THAT INSIDE DFiVWELL SHELL SURFACE WAS UNIFORM e
THEREFORE, DEEPLY CORRODED AREAS ON OUr SURFACE OF THE DRYWELL SHELL j
SHOULD BE THE THINNEST AREAS e
BASED UPON VISUAL OBSERVATION, 6 TO 12 DEEPLY CORRODED SPOTS PER BAY WERE MARKED FOR GRINDING AND UT, ADDITIONAL SPOTS WERE MARKED IN SOME BAYS BASED ON FINDINGS i
e MOST OF THESE SPOTS WERE SCATTERED OVER THE ENTIRE BAY AND LOCALIZED e
ABOVE METHOD OF LOCATING AND GRINDING INTRODUCED CONSERVATISM IN SHELL THICKNESS MEASUREMENT o
We forced a bias in selecting the thinnest spots o
Grinding of these spots, to obtain flat surface for UT, removed additional good metal
)
. - -. ~ -
EVALUATION OF SHELL THICKNESS (UT) MEAS _UREMENTS e
THE BASIS FOR EVALUATION IS A SHELL THICKNESS OF 0.736 INCH WHERE BUCKLING IS THE GOVERNING CRITERION.
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e ALL UT THICKNESS MEASUREMENTS FOR BAYS 3,5,7,9 AND 19 ARE GREATER THAN 0.736 INCH.
i ALL UT THICKNESS MEASUREMENTS FOR BAYS 11,15 AND 17 ARE GREATER THAN e
0.736 INCH EXCEPT FOR ONE MEASUREMENT FOR EACH BAY.
4 THESE MEASUREMENTS WERE EVALUATED USING ASME LOCAL STRESS CRITERIA.
e BAYS 1 AND 13 EACH HAVE SEVERAL LOCATIONS WHERE THE MEASURED THICKNESS lS BELOW 0.736 INCH. THESE LOCATIONS ARE ISOLATED.
THESE MEASUREMENTS WERE EVALUATED USING ASME LOCAL STRESS CRITERIA.
l l
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e ONE AREA IN EACH BAY WAS IDENTIFIED WHERE THE MEASURED THICKNESS IS BELOW 0.736 INCH. THESE AREAS ARE 4 X 4 INCHES FOR BAY 1 AND 6 X 6 INCHES FOR BAY 13.
l IN BAY 13 THIS AREA IS APPROXIMATELY 0.33 % OF THE AREA OF THE BAY.
l e
THESE AREAS WERE EVALUATED USING ASME LOCAL ACCEPTANCE CRITERIA AND ANALYSIS WHICH ACCOUNTS FOR THE FOLLOWING FACTORS:
o Shell Roughness o Local nature of individual thickness measurements o Adjustment of buckling capacity to account for general wall thickness found o Adjustment of buckling capacity to account for local thinned area
- - -. ~., - - -
i
.C_ONCLUSIONS e
SAND REMOVAL WAS SUCCESSFULLY COMPLETED IN 14R e
EXTERNAL DRYWELL SURFACE IN SAND BED REGION WAS CLEANED AND COATED e
CORROSION IN THE SAND BED REGION NOW STOPPED e
THE 14R INSPECTIONS FROM THE SAND BED REGION CONFlRMED THAT OUR PREVIOUS INSPECTIONS FROM INSIDE THE DRYWELL WERE IN THE AREA OF HIGHEST CORROSION.
PLUGS WERE IN THE " BATHTUB RING" i
I e
THE INTEGRITY OF THE OYSTER CREEK DRYWELL REMAINS A PRIORITY CONCERN OF GPUN MANAGEMENT, WE WILL CONTINUE UT THICKNESS MEASUREMENTS FOR THE LIFE OF THE PLANT t
i e
LOW CORROSION RATES IN SPHERE AND CYLINDER PORTIONS OF THE DRYWELL, IN CONJUNCTION WITH PRESSURE REDUCTION APPROVAL, WILL ENSURE CONTAINMENT l
INTEGRITY FOR THE FULL LICENSED LIFE OF THE PLANT l
l
j FUTURE DRYWELL INSPECTIONS / PLAN i
r t
PRIORITY 1 & 2 UT READINGS FROM INSIDE DRYWELL DURING 15R (1994) e j
e VISUAL INSPECTION OF COATING IN BAYS 1 & 11 AT BEGINNING OF 15R o
EXPAND TO OTHER BAYS AS NECESSARY e
MONITOR FOR WATER LEAKAGE DURING OPERATING CYCLES AND REFUELING OUTAGES, TAKE CORRECTIVE ACTION AS APPROPRIATE l
POST 15R UT INSPECTION PROGRAM SCOPE AND F"AEQUENCY TO BE DEFINED BASED ON 15R e
l lNSPECTION RESULTS i
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