ML13333C064
| ML13333C064 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 08/27/1984 |
| From: | Mckenna E Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8408280173 | |
| Download: ML13333C064 (39) | |
Text
,pVP PEG,_
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 August 27, 1984 Docket No.:
50-206 LICENSEE:
Southern California Edison Company FACILITY:
San Onofre Nuclear Generating Station, Unit 1
SUBJECT:
SUMMARY
OF AUGUST 23, 1984 MEETING On August 23, 1984, representatives of Southern California Edison Company, and their consultants met with members of the NRC staff in Bethesda, Maryland to discuss the intake structure for San Onofre Unit 1. A list of attendees is provided in Enclosure 1. The handouts used at the meeting are provided in.
The purpose of this meeting was to discuss the degradation of intake structure reinforcing steel (rebar), the evaluations that have been performed, and the structural -repair program. The degradation was.discovered on July 30, 1984,
- when the intake structure was dewatered to do some maintenance activities.
The licensee has mapped the affected areas by chipping away the covering three inches of concrete to examine the underlying rebar, and by taking cores.
Samples were subjected to laboratory analysis to evaluate the concrete strength and chemical composition.
The corrosion is believed to have been caused by diffusion of salt water by capillary action into the concrete to the rebar.
The corrosion progress is accelerated by electrochemical potential effects. The licensee stated this hypothesis is supported by the laboratory evaluations and the observed relationship between the areas of most severe corrosion and high chloride ion concentration.
The most severe degradation was found on the inside walls of the pumpwell with lesser effects in the screenwell.
The problem is limited to the inside surfaces of the walls.
The cores taken through the wall show no degradation beyond the rebar.
Because of the varying amounts of degradation of the rebar and uncertainty about the rate of further corrosion, the licensee has developed a repair program to restore the structural capability of the intake structure which gives no credit for this underlying rebar on the inside walls. The repair consists of steel plates bolted to the walls. The steel and bolts will be coated with a coal tar epoxy for corrosion protection.
Further cathodic protection will be provided by zinc knobs on the plate.
01 B02
0 0
2 -
August 27, 1984 The licensee will file a Licensee Event Report (LER) within 30 days of discovery of the problem and a report describing the problem evaluation and repair program will be submitted for the staff's information.
Original signed by Eileen M. McKenna, Project Manager Operating Reactors Branch #5 Division of Licensing
Enclosures:
As stated cc w/enclosures:
See next page DISTRIBUTION Docket 50-206 NRC PDR L PDR ACRS (10)
OELD ORB#5 Rdg.
WPaulson Camerson EMcKenna JNGrace ELJordan 0
- C EMcKenna:dk WPaulson 8/al/84 8/.-7 /84
Mr. Kenneth August 27, 1984 cc Charles R. Kocher, Assistant General Counsel James Beoletto, Esquire Southern California Edison Company Post Office Box 800 Rosemead, California 91770 David R. Pigott Orrick, Herrington & Sutcliffe 600 Montogmery Street San Francisco, California 94111 Dr. Lou Bernath San Diego Gas & Electric Company P. 0. Box 1831 San Diego, California 92112 Resident Inspector/San Onofre NPS c/o U.S. NRC P. 0. Box 4329 San Clemente, California 92672 Mayor City of San Clemente San Clemente, California 92672 Chairman Board of Supervisors County of San Diego San Diego, California 92101 Director Energy Facilities Siting Division Energy Resources Conservation &
Development Commission 1516 - 9th Street Sacramento, CA 95814 U.S. Environmental Protection Agency Region IX Office ATTN:
Regional Radiation Representative 215 Freemont Street San Francisco, California 94105 John B. Martin, Regional Administrator Nuclear Regulatory Commission, Region V 1450 Maria Lane Walnut Creek, California 94596 NRC/SCE MEETING AUGUST 23, 1984 Name Affilation Eileen McKenna NRC/DL Richard White Bechtel Richard J. Kosiba Bechtel David Johns SCE Mark Medford SCE Gerald E. Hammond SCE Thomas M. Cheng
'NRC/DL Walter A. Paulson NRC/DL George Lear NRC/DE/SGEB Nilesh C. Chokshi NRC/DE/SGEB Dennis M. Crutchfield NRC/DL C. P. Tan NRR/DE/SGEB INTAKE STRUCTURE DEGRADATION AND REPAIR PURPOSE:
(1) PROVIDE TECHNICAL EVALUATION OF INTAKE STRUCTURE REINFORCING STEEL (REBAR) DEGRADATION (2) DESCRIBE REPAIRS
0 0
AGENDA INTAKE STRUCTURE DEGRADATION AND REPAIR SAN ONOFRE NUCLEAR GENEATING STATION UNIT 1 I.
INTRODUCTION (G. HAMMOND -
SCE LICENSING)
II. DISCOVERY OF INTAKE STRUCTURE DEGRADATION (D. JOHNS -
SCE ENGINEERING)
III. EVALUATION METHODS (R. KOSIBA -
BPC)
IV. FINDINGS (R. KOSIBA)
V.
SEQUENCE OF EVENTS IN CORROSION OF REBAR (R. WHITE -
BPC)
VI.
CORRELATION OF LABORATORY RESULTS WITH CORROSION (R. WHITE -
BPC)
VII. STRUCTURAL EVALUATION AND REPAIR (R. KOSIBA -
BPC)
IX.
CONCLUSION (G. HAMMOND -
SCE LICENSING)
II, DISCOVERY OF INTAKE STRUCTURE DEGRADATION A. DESCRIPTION OF INTAKE
- 1.
DESIGN CRITERIA
- 3. INTAKE STRUCTURE DESCRIPTION B. NORMAL MONITORING PROGRAM C. DISCOVERY OF PROBLEM D. CONDITION
- 1.
INTAKE STRUCTURE DESIGN CRITERIA ORIGINAL DESIGN CRITERIA REFERENCE, UNIT I FSAR:
"DESIGNED TO MEET CATEGORY A REQUIREfMENTS TO THE EXTENT THAT WATER IS ALWAYS AVAILABLE TO THE SALT WATER COOLING PUMPS. OTHERWISE CATEGORY B."
UPGRADE CRITERIA
2, CIRCULATING WATER SYSTEM FLOW (2)
CIRCULATING WATER PUMPS =
346,000 GPM EACH SALT WATER PUMP (1.3%) =
4,600 8PM 350,600 GPM
7/
/7' 34' ro,
- 11) oII PLAN SAN ONOFRE NUCLEAR GENERATING STATION UNIT I
//VT 74K 7TUC T/RE
uK u
131 u13'-
EL 3r-Od*
10 TO INTAKE
-I BOX CULVERT EXTRrEME STOP GATE
.. L I/V~~~~~i TA_5S8CJA )24 SAN ONOFRE NUCLEAR GENERATING STATION UNITI
lef 9,'I9 1DEWj S.'ag A 7 0'
9 9
t46P
)
R d 9 71
~C /s/
~/~i. WJ
'~'~j a---.
z e'
,A..~fU i~vr*Ll~~.~0 Aj, P
- e.
~
'fe9 2!Gp ee.8 ON, a?'
-,o F/IMP/ts Li co 5tS C i UNIT I
£t/-o
-- *^
I
. /S.0,-
1 c
7 ~~f4 OW' SCeNWI CiPSSS.r
B.
NORMAL MONITORING PROGRAM INSPECTED DURING PLANT SHUTDOWN (EVERY 18 MONTHS)
INSPECT FOR CONDITION OF CONCRETE, I. E. CRACKING, SPALLING, ETC.
CONDITION OF CONCRETE SURFACE DEBRIS ACCUMULATION RESULTS OF PAST INSPECTIONS
Cl.
DISCOVERY OF PROBLEM 0 DEWATERING OF NORTH PUMP BAY o
DIVER INSPECTION
" DEWATERED INTAKE FOR GATE SLOT REPAIRS D.
CONDITION LOCALIZED SPALLING AT NORTH GATE SLOT RUST SPOTS ON SURFACE
EVALUATION OF DEGRADATION, CAUSES, AND REPAIR 11 Evaluation Methods (R. Kosiba)
A.
Chipping Program B. Coring Program IV Findings (R. Kosiba)
A. Compressive Strength B. Petrographic Findings C. Summary of Deterioration V Sequence of Events in Corrosion of Rebar (R. White)
VI Correlation of Laboratory Results with Corrosion (R. White)
VII Structural Evaluation and Repair (R. Kosiba)
A. Structural Analysis of Existing Degradation B. Structural Repair
EXAMINATIONS AND LABORATORY EVALUATIONS 0
VISUAL EXAMINATIONS AND OBSERVATIONS OF THE STRUCTURE o
VISUAL EXAMINATION OF THE CORES O
VISUAL EXAMINATION OF THE CHIPPED AREAS o
LABORATORY ANALYSIS OF CORES O
LABORATORY ANALYSIS OF WATER o
PETROGRAPHIC EXAMINATION 0
HALF-CELL MEASUREMENTS
N
.4 AP'f FIG4 If
TABLE 1: SuMaTy of Chipping Examination Chipping Remaining Rebar Desiqnat.
Locati-on Remarks A
South Screenwall 80-85 Delamination B
North Wall, pumpwell 15-20 Delamination. Loss of continuity of rebar El, -16 ft.
C North Screenwall 80-85 Delamination. One reba! mostly gone.
D North Wall, near tsunami Qate 100 No delamination. Looks O.K.
E East Wall, north side 50 Delamination F
Center Wall, north side 80 Partial delamination U.1 Pump Deck, top, near salt 100 No rust except slight rusting at visible water pump crack. No delamination.
6.2 Pump Deck, bottom, under G.1 100 No delamination, However, core #8 a few feet away shows delamination, South Wall, pumpwell area 100 Furtner chipping vertically up shows delamination El - 21 anc rust, one bar at 50%
North Wall, below B 75 Delanination. Continuation of bars from B.
K North Pumpwell, floor under SWP 100 No delamination.
More than 4-irch cover. No apparent rust.
L Center Wall, north side near K
No delamination.
screens M
Center Wall, south side 40-50 Signs of delamination.
N South Pumpwell, floor under SP 100 Minor rust, No delamination.
P North Wall of Screenwell 80 Discoloration and delamination of concrete. No Eley. -6 feet rust on the form tie.
R North Wall, transition west of 100 No signs of discoloration or delamination.
screenwell Elev. (-)20.3 S-1 Floor east of Tsunami gate 100 No rust nor delamination.
S-2 Roof east of Tsunami gate 100 No signs of rust discoloration and delamination at first layer of rebars T
Under the north circ water pump 95 No signs of discoloration and delanination.
U Under the north citc water pump 85 Signs of discoloration or delamination
TABLE 1:
Sumary of Chipping Examination Ch ipping Remaining Rebar Designat.
Location Remarks V
Center wall, north side 60 Discoloration and delamination of concrete.
elev. (-)22 W
East wallsouth bay 50 Concrete is severely discolored and celaminated.
Eley. (-)17 Discolored moisture oozing f-o= the cnip.
X South wall of south pumpwell 80 No discoloration or delamination.
Eley. (-)17'-6' E-Ext Extension of Chip B 5
Concrete severely discolored ard delanrinated.
described above E-1 Extension of Chip E east wall, 70 Concrete severely discolored and delarnated.
of north side Elev. (-)18 F-1 Center wall,' north side 70 Concrete appears discolorec and delaminated.
Elev. (-)25 F-2 Center wall, north side 80 Concrete is discolored and delaminated Eley (-)1 J-1 North wall, pumpwell 80 Concrete is discolored and delaninated.
Eley (-)25 J-2 North wall, purpwell 50 Concrete is discolored and delaminated.
Elev (-)22 M-1 Extension of Chip M center wall, 25 Concrete severely discolored and delaminated.
south side Elev (-) 16'-E' AA Roof of South Pump well midway 160 No signs of delaination and discoloration of between circ. water and salt concrete. 4 rebars exposed, show signs of water pump centerline slight rust.
ELev (-)10'-0' BB Roof of South Pump well on 100 No dejanination or discoloration Of Concrete.
circ. water pump centerline 4 transverse and I lonqitudiral rebar exposed, 3-1/2 feet from south wall show signs of Slight rust.
Elev (-)10'-0' CC North Pump Well roof 6 feet 100 No signs of delamination and discoloration Of west of circ. water-pump concrete.
10 rebars exposed, show no siq-E of centeTline rust.
Elev (-) 10'-0' DD Inner face of north wall of 80Concrete delainated and discolored. 4 vertical, and Y screen well between Eley 2 horizontal and I bent rebar exposed, one
(-)6'-0' and (-)10'-0' at horizontal and bent Tebar no signs of rust.
grade bean Remainder rusted to varying degree.
TABLE 1:
Seumary of Chipping Examination Chipping Remaining Rebar Desianat.
Location Remarks R and North wall of transition 100 No signs of delamination and discoloration of RI west of screen well concrete. 7 vertical rebar exposed show slight Eley (-)22'-0.
rust.
Z Rocf of south pump well, 60 Concrete is severely delaminated and discolored.
4 feet west of screen wash pump 4 transverse, I horizontal and I bent reBars Eley (-)10'-0' exposed; all show severe rust.
3/ a(T~tuc.
I SMTS FIGE U2L IN
TABLE 2 LOG OF CORE SAMPLES TAKEN AND OBSERVATIONS CORE NO.
LOCATION O8SERVATIONS ON CORE 1
11'-5' east of stop gate slot on south First 1/2'-1' appeared relatively-sound, next 2' u: to (3'
dia. x 6')
wall of south pumpwell EL (-)21'0' the rebar had coarse aggregate only. Remiaini:n section Area had a rust spot of approximately of core appeared sound.
Core hole displyaed signs of 2'3' diameter with no visible signs of both rebar and concrete in late stage of deterioration.
cracking.
The extent of damnag is inward to first layer of rebar.
Corrosion and deterioration followed layer of rebar along the wall.
2 4'-3' from upstream nose on south Core and core hole appears sound, Rebar is relatively (3'
dia. x 9')
side of north pumpwell vane EL good with signs of minor rusting.
(-)22'O' Area of sample was sound concrete with no signs of rust etc.
3 9'-1' upstream of stop gate on north Core was removed in two pieces separated by rust and (3' dia.-x 9')
transition of pumpwell EL (-)22'-0' exudence. Separation Of core was at 3' to 4' fTSM Area has typical rust spots similar concrete surface. No rebars visible. Core hole shows to core *1 circumferential crack approximately 3' to 4' from concrete surface with rust bleeding.
4 3' downstream of stop gate slot on Core was removed in two pieces. The core separated (3' dia. x 9')
north wall of north pumpwell at the rebar interface, interface filled witn rust EL (-)22'-*
and exudence.
Area cored showed no signs of distress in the imediate area.
5 EL (-)11'-0' directly above repair A zone of approximately 2' wide beginning 4' fr6m the area of north wall gate slot.
surface was discolored to varying degree with two planes about 1' apart where core fractured. Fractured plane is discolored and the fractures passed through aggregate.
Core hole has circumferential cracks separating the layers of concrete. No rebar was cut.
6 1st attempt halfway between the two Hit rebar. Face of hole at the rebar was badly screen slots in the north wall of discolored 'with rust and rebar was corroded on its screen well.
surface 2nd attempt 4' to east.
The core has zone of discoloration about 2' wide starting about 3-1/2' in from the surface with 2 major cracks running through core. Core hole is normal except for rust stained circumferential crack about 3' from the surface of concrete.
TABLE 2 LOG OF CORE SAMPLES TAKiN AND OBSERVATIONS CORE NO.
LOCATION OBSERVATIONS ON CORE 7
North wall of north pumpwell north Core had 2 cracks about 1-1/2' apart, the first ore about east of salt water pump 2-1/2' from surface. The crack planes had rest stains on EL (-)18 their surfaces.- Core hole had circumferential crack which was rust stained about 3' from surface.
No rebars were cut.
8 3 feet north of Salt Water Pump The crack runs through the core at a slight apcgle about opening intercepting a crack that 9' where it angles out of the core. Crack is rust ru~ins from PUMP opening to the north stained and of significant size. There a-e two laminar wall of north pumpwell ceiling.
cracks about 3' and 4-1/2', respectively from conc-ete face. The crack surfaces are rust stainec, crystalline cover of salt, crack passes through some of aggregate.
9 North wall of north screenwell A piece of bar with 3-3/4' cover was cut, slihtlv (1-3/4' dia EL (-)24'*
rusted. Delamination at innermost layer of reta is through core) severe. Both surfaces badly rust stained. Remainder of core in excellent condition. Backfill side rebar nas no rust, concrete is neither discolored nor delaminated.
11 North wall of north pumpwell at Three inches from inner surface typical lamirar crack (1-3/4' dia E! (-)24'-O' at salt water pump with rust discoloration. Remainder of samole is throu;n core) centerline completely normal in all respects. No recars were cut in this sample.
12 Floor of north pumpwell 2 fee!
From top surface inward a delamination appears at 4-3/4 (1-3/4' dia south of north wall inches from the top surface which is severely rust through core) colored. No rebars were cut in this samPle.
Remainder of the sanple is in excellent condition.
13 Back wall of north pumpwell on Innermost layer of rebar rusted. Rust stained laminaT (1-3/4' dia pump centerline crack about 3' into the wall separates the core. Both through core)
EL (-)24'-0' surfaces of the crack rust stained. One vertical and one horizontal bar were cut. Both bars rusted on the surface. Remainder of the core is in good condition.
15 North wall of intake conduit 3 rebars were cut (1 horizontal in the inner layer and (1-3/4' dia 6 feet east of tsunami gate 2 bars in outer layer).
Concrete and rebars in this through core)
EL (-)24'-0*
sample are in excellent condition.
No rust o delamination.
24 Series of four 1' dianeter holes for chloride analysis.
TABLE 2 LOG OF CORE SAMPLES TAKEN AND OBSERVATIONS CORE NO.
LOCATION OBSERVATIONS ON CORE 25 North screen well Core 425-1, -2, and -3 1-3/4' diameter.
Sent for chloride analysis.
These cores had wide laminar zone about 3-1/2' from surface.
Laminar separation severely rust stained. No rebars were cut. Concrete beyond laninar zone is in good condition.
26A South wall of south screen well Inner layer of rebar with 3 inches cover was cut.
Rebar (1-3/4' dia.
EL (-)24'-D' is severely rusted. Concrete at first layer of rebar is through core) delaninated and badly stained with rust. Remainder of sample is in good condition. No outer layer retar was cut. Backfill side concrete is neither rusted nor delaminated.
When core was removed, water cane rusning at the rate of 70 gpm fo, 3-1/2 hours.
27 South wall of south screen well North (screenwell) side concrete is delaninated an:
(1-3/4
- dia, EL (-)15-4*
discolored at 3' depth. No rebar was cut. South through core)
(discharge box) side - no signs of concrete delamination One rebar cut shows no sign of rust.
29 South wall of south pump well North (pump well) side - concrete delaminated and (1-3/4 dia.
half way between circ. water and severely rust stained. No Tebar cut. South side through core) salt water pumps (discharge box) side - concrete delaminated and rust EL (-)15'-4' discolored. No rebar cut.
29 South wall of south pump well North (pun well) side - concrete delaminated and (1-3/4
- dia, on circ, water pump centerline rusted. No rebar cut. South (discharge box) side through core)
EL (-)15'-4' No signs of delamination and rust.
CORING RESULTS -
COMPRESSIVE STRENGTH OF CONCRETE Core No.
Compressive Strength (psi) 2A 8180 2B 6690 2C 7530 3A 7220 3B 5680 4A 6900 4B 6700 SA 8980 Original Concrete Design Specification f
= 3,000 psi
DATA ON CONCRETE UTILIZED original Concrete Condition:
o f
= 3,000 psi @ 28 days c
o Aggregate Size = 1-1/2w max o
Slump =3" o
Admixtures:
Air-Entrainment o
Chloride Limitations:
Chlorides in admixtures not allowed Petrographic Examination (Dr. Mielenz):
o Concrete was well consolidated o
Concrete is air-entrained a
Calcium hydroxide is present as segregation of moderate size indicating cement pastes of moderate water-cement ratios o
No evidence of significant alkali-silica reaction o
Little microcracking
SUMMARY
OF CONCRETE ASSESSMENT
- 1.
The concrete specifications originaliv oreoared were appropriate for the intended acolication.
- 2.
The soecifications, as well as the concrete and reinforcina steel details, represented the then-in-effec-t ACI code orovisions and recommendations for the design environment.
These code provisions were essentially unchanged in the issue of ACI 201.2R.77 in December 1977, still in effect in 1984.
- 3.
Petrographic examination of five samples confirmed that the original design specifications had produced high quality concrete in the structure.
.4.-
The compressive testing of the. in-place concrete specimens clearly demonstrate concrete of excellent quality and integrity.
C22 Li:
7117 Li:
02
SEQUENCE OF EVENTS IN CORROSION OF REBAR
- 1. CHLORIDE ION CONCENTRATION GRADIENT SET UP BETWEEN OUTSIDE (SEAWATER) AND INSIDE (VERY LOW CHLORIDE CEMENT).
- 2.
GALVANIC CELL SET UP BETWEEN STAINLESS STEEL PUMPS (CATHODE)
AND CARBON STEEL REBAR (ANODE).
- 3.
SALT WATER DIFFUSES BY CAPILLARY ACTION INTO CONCRETE UNDER INFLUENCE OF CHLORIDE ION GRADIENT.
- 4.
CRITICAL CHLORIDE ION CONCENTRATION TO BREAK DOWN PASSIVITY (APPROX.0.1 WEIGHT PERCENT) REACHED AT REBAR.
- 5.
CORROSION OF REBAR CAUSES STEEL TO SHIFT FROM PASSIVE POTENTIAL
(-0.2V TO Cu/CuSO 4 ) TO ACTIVE POTENTIAL (-0.5 TO -0.7V TO Cu/CuSO 4).
- 6.
ELECTROCHEMICAL POTENTIAL DIFFERENCE BETWEEN CORRODING STEEL
(-0.5V TO -.7V TO Cu/CuSO ) AND NONCORRODING STEEL (-0.2V TO Cu/CuSO 4) FURTHER ACCELERATE CORROSION OF ALREADY CORRODING STEEL.
- 7.
CORROSION PRODUCTS FROM REBAR CREATE PATH FOR OXYGEN AND CHLORIDE TO FLOW TO REBAR.
- 8. SEAWATER AND OXYGEN FLOW TO REBAR FURTHER ACCELERATING CORROSION.
CONCRETE SURFACE o CI SLOW LOW W/C LARGEDIFSO PROTECTIVE DIFFUSION CONCRETE Z
N
-,\\
Fe++
CI OH_
- iiiANOD A
CA HODEWR Schematic representation of corrosion in concrete of low water-cement ratio and well cured
CORRELATION OF LABORATORY RESULTS WITH CORROSION
- 1.
CHLORIDE iON CONCENTRATION HIGH (0.5 - 1.1 WEIGHT PERCENT)
IN REBAR AREA WHERE CORROSION FOUND (SEAWATER SIDE NEAR PUMPS).
- 2. SIGNIFICANT CORROSION LIMITED TO REBAR CLOSEST TO STAINLESS STEEL PUMPS.
- 3.
CHLORIDE ION CONCENTRATION LOW (0.05 - 0.1 WEIGHT PERCENT)
IN REBAR AREA WHERE NO CORROSION FOUND (BACKFILL SIDE).
- 4.
CORROSION FOUND IN AREAS OF LARGE ELECTRONEGATIVE POTENTIALS
(-0.5 TO -0.7V TO Cu/CuSO 4).
-A-f NALLAL N\\E A
fl-L IL X
WALLS 3 TSLAB R MALL-WiCL"A GOMRATOIB SATWH Uffma T~uMOSCIV wT*EE sncms
~4AT CNMOKA!J4 P& A" & et~
4e 4
MALLL NAALL MJ-.
BEAM P
~L~LQJl
0 w
4 0
0 I
I Ii,.
/
I, I
2
- II ;;i U
~ij ii Ifii~iI I
In' I..J I~j I
I I II I~
~ Iii liii
-~
I Ii
- 4/
~.91 71 I
/f-
~i~~iI
'S.
I'i~J H
I----
K II II I -~--ff--~,
4 I
V A1
~
Nj
~*,
I L-'
Lii I
t I
...d ~ I I ~I :.s I I
W~ Q~O '6
-iL
-1 A
A.
_I4-
.f-a-
- a (
(
LX I,.
-t4 a
4 0.4
- -:.~~C m-1~A
~
.O~(
r..
!DflI low (Fs
-2 ZVW-
(CALCULATION SHEET CALCL.rf
)t.(u(CL SIGNATURE g
DATE-CHECKED DATE
( P~OJECT
£JOBNO.
SUBJECT I i7AA:c r
SHEET.
OF
__SHEETS 3
A c-A la.LTr1:
E -.
lA, 4
HEAVY HX *QU T 5-164 10 13 14 17 is Ln INSUL, SLEEYE k o
GROWT.
-L/t 20z 21*EXS.CbCUAC 22 SrH9 A rE~ DO 90 WNE L ASTM 5*1G4 27 27 m
"--P~~EEN rHREA D TO P9'V(AW r' 30 NuTLoTA TIoN 31 C~~II.
33 34 N
r-V4 rL7r c-T,7 aC7~ r,' 4. -3 C P4L 1C.
35f C6 L
T A
INTAKE STRUCTURE DEGRADATION AND REPAIR CONCLUSIONS:
(1) REBAR CORROSION LIMITED PRIMARILY TO PUMP WELL AREAS (2) CORROSION IS LIMITED TO INSIDE SURFACE (3) REPAIR DOES NOT TAKE CREDIT FOR INSIDE REBAR IN AFFECTED AREAS (4)
SEISMIC DESIGN BASIS FOR REPAIR IS 0.67G GEH:2267F