ML20199A534

Cns,Unit 2 Class Mc ISI Summary Rept for Refueling Outage EOC9

ML20199A534
Person / Time
Site:	Catawba
Issue date:	01/04/1998
From:	Ferlisi M DUKE POWER CO.
To:
Shared Package
ML20199A533	List: ML20199A529 ML20199A534
References
NUDOCS 9901130058
Download: ML20199A534 (19)

Text

__ _ _ _ -__-_ - - - - _ - - - - - -

Catawba Nuclear Station, Unit 2 Class MC ISI Summary Report for Refueling Outage EOC9 By: _ Date: /2 fg

'tark Q'. Ferlisi,- P.E.)

Reviewed By: Date: /2/30/97 Approved By: [' // -

Date: /)M/98

~

[32"E8!! Zi8sj?g4_

L L

~

}

1 Catawba' Nuclear Stahion,. Unit 2 j Class'MC ISI Summary Report i

.. Refueling Outage EOC9 'l

• Page 2 of 19 i

:. ^

l

- t

-. . Table of Contents j r

'Section ' Subject. Page l A. ASME Code.and Regulatory Requirements for Class 3 -!

v MC ISI Summary! Reports l 1

f jB. . Discussion of Examinations 1and Conditions. 5 i Requiring Evaluation C. - Description of' Degradation, Evaluations,'and' 6 CorrectiveLActions

':/

j h

1 i

i l'-

I~

l l

L i

l u .

i I

e w , , - - - e -- r ,

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

Catawba Nuclear Station, Unit 2 Class MC ISI Summary Report Refueling Outage EOC9 Page 3 of 19 A. ASME Code and Regulatory Requirements for . Class MC ISI Summary Reports Inservice inspections of Class MC components are performed in accordance with the ASME Boiler and Pressure Vessel Code,Section XI, Subsection IWE, 1992 Edition with the 1992

Addenda. Article IWA-6000, Records And Reports, paragraph IWA-6210, requires the owner to prepare inservice inspection .

summary reports inservice inspections performed on Class 1 I and 2 pressure retaining components ano their supports.

! IWA-6000 does not address inservice inspection summary reports for Class MC pressure retaining components and their supports, and the Code does not require preparation and submittal of summary reports for Class MC components. As j such, this Class MC ISI Summary Report does not contain  !

information specified in IWA-6220 or IWA-6230. Please note i that this report is being submitted within 90 calendar days  !

I l following the completion of the refueling outage at Catawba Unit 2, in accordance with IWA-6240(b).

l Duke Energy Corporation is maintaining a separate Inservice l Inspection Program for Class MC pressure retaining l

! components and their integral attachments. Therefore, this l

Class MC ISI Summary Report contains only that inservice i inspection information applicable to Code Class MC components. ISI Summary Reports for other Code Class ,

components are to be submitted separately. l This Class MC ISI Summary Report includes all applicable l information required by 10 CFR 50.55a (b) (2) (x) (A), which i

-states:

l

{ (A) For Class MC applications, the licensee shall evaluate the acceptability of inaccessible areas when conditions exist in accessible areas that could indicate the presence of or result in degradation to such inaccessible areas. For each inaccessible area identified, the licensee shall provide the following in the ISI Summary Report required by IWA-6000:

(1) A description of the type and estimated

extent of degradation, and the conditions that led to the degradation;

s ,.

Catawba Nuclear Station, Unit 2-Class MC ISI Summary Report Refueling Outage EOC9 Page 4 of 19 -

. . I l  ;

i (2) An evaluation of each area, and the result of the evaluation, and; l

. (3)' A description of necessary. corrective actions- ,

J '

1

~

In addition, this Class MC ISI Summary Racort also includes l applicable information required by 1C ' 50.55a (b) (2) (x) l

, (D), which states: j (D) .The following may be.used as an alternative to the requirements of IWE-2430. i I

-(l) If the examinations reveal flaws or areas of  !

degradation exceeding the acceptance r.tandards of Table IWE-3410-1, an evaluation shall be performed to de< ermine whether additional. j component examinations are required. For each flaw or area of degradation identified which exceeds acceptance standards, the licensee shall provide the following in the ISI Summary Report required by IWA-6000:

(i) A description ~of each flaw or area, including the extent of degradation, and the conditions that led to the degradation.

(ii) The acceptability of each flaw or area, and the need for additional examinations )

to verify that similar degradation does '

not exist in similar components, and; (iii) A description of necessary corrective actions.

(2) The number and type of additional examinations to ensure detection of similar degradation in similar components.  !

i i

i i

4 i

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

i Catawba Nuclear Station, Unit 2 1 Class MC ISI Summary Report Refueling Outage EOC9 Page 5 of 19 l

l B. Discussion of Examinations and Conditions Requiring Evaluation-

.Two conditions were observed during refueling outage EOC9 that warrant inclusion in the Class MC ISI Summary Report, l as required by 10 CFR 50.55a 03) (2) (x) (A) and 10 CFR 1 50.55a (b) (2) (x) (D). These conditions were identified during the performance of ASME Code,Section XI, INE General j

. Visual Examinations in accordance with Table IWE-2500-1, l Category E-A, Item El.ll, using Catawba Unit 2 procedure l

1. PT/2/A/4200/078. i i

Please note that other IWE examinations were performed l during refueling outage EOC9, and that no other conditions  ;

requiring evaluation in-accordance with 10 CFR 50.55a 03) l (2) (x) (A) or 10 CFR 50.55a (b) (2) (x) (D) were observed.

Condition #1 li Coatings loss and general corrosio" with minor pitting, was detected on interior surfaces of the Steel Containment Vessel shell plate at the VX Fan Pit floor  ;

at elevation 593' + 8 1/2" (approx.) between azimuths 288 and 297 (approx . ) . These affected surfaces are '

located adjacent o areas that are inaccessible for direct or remote visual examination.

I Condition #2 l

L Moisture barrier -(sealant) was observed to be missing from the Steel Containment Vessel interior embedment zone at elevation 552' + 0" at azimuth 305 (approx.)

for a length of approximately 4 feet. Brown colored staining was observed above this location, and water was observed on the Steel Containment Vessel shell surfaces in this area. General Visual Examinations revealed existing coatings did not completely seal the interface where moisture barrier material was missing and that water may have gained access to embedded L surfaces of the Steel Containment Vessel beneath the Pipe Chase floor at this location. No coatings loss or base metal degradation was observed on adjacent Steel Containment Vessel surfaces.

l l

Catawba Nuclear Station, Unit 2 Class MC ISI Summary Report Refueling Outage EOC9 Page 6 of 19 Please note that moisture barrier material was also observed to be missing or in need of corrective action at 2 other locations on the Steel Containment Vessel interior shell surfaces at azimuths 106 and 348 (approx.). However, because no evidence of moisture intrusion was observed and no other degradation'was detected on the Steel Containment Vessel surfaces at these locations, the condition of the Steel Containment Vessel was considered acceptable and did not warrant reporting in accordance with 10 CFR 50.55a (b) (2) (x)

(A).

C. Description of Degradation, Evaluations, Corrective Actions, and Additional Examinations Required.

Condition #1 (1) Description Of Type And Estimated Extent Of Degradation, And The Conditions That Led To The Degradation Description of Degradation:

.1. Suspect conditions, including coatings loss, general corrosion, with some pitting, were observed on surfaces of the Steel Containment Vessel near the VX Fan Pit floor on the interior surface of the Steel Containment Vessel at elevation 593' + 8 1/2" (approx.) between azimuths 288 and 297 (approx.).

2. Water was observed on VX Fan Pit floor surf aces, including surfaces adjacent to the Steel Containment Vessel.

3. Moisture barrier (sealant) materials along the interface between the VX Fan Pit floor and the Steel Containment Vessel were observed to be degraded. Degradation included sealant that had separated from attached surfaces, cracking along various sealant surfaces, and lack of sealant at some locations.

l

_ _ . _ _ . ~ _ . _ . _ . _ _ _ _ . _ _ . . . _ . . . _ . .___m._ .m _ . _ . _ , _ . _ _

Catawba Nuclear. Station, Unit'2  :

Class MC ISI Summary Report

' Refueling Outage EOC9 .

Page 7 of 19  :

General Location Descripcion:

The VX Fan Pit lis located on the interior side of the Steel ' Containment Vessel, between azimuths 247' and 303 . The VX Fan Pit floor is.a 2'+6" thick concrete' i

slab between elevations 593' + 8-1/2" and 591' + 2- i 1/2". A 2" gap between the Steel Containment vessel ')

- and the VX Fan Pit concrete floor is filled with (2) l 1" thick layers of expansion joint material (cork) I which maintains necessary clearance between these structures. A pressure seal is attached to the

• underside'of'the floor slab to seal upper and lower containment volumes and prevent bypass leakage around I the ice condensers. 1 The Steel Containment Vessel-interior surface is obstructed-from direct or remote visual examination  !

between elevations 593' + 8-1/2" (VX Fan Pit floor elevation) and 590' + 8-1/2" (bottom of pressure seal attachment angle'to underside of VX Fan Pit floor) for the entire length of the VX Fan Pit floor.

Estimated Extent of Degradation:

Based on initial observations, it was estimated that the most significant degradation-was occurring along the top of the expansion joint material at the Steel Containment Vessel interface, near elevation 593'+ 8 1/2", where sealant material was observed to be degraded. This assessment was based on the fact that i this interface was potentially subject to repeated l wetting and drying. It was also estimated that i degradation of the Steel Containment Vessel wall may )

have occurred at locations behind the cork expansion jointimaterial below elevation 593'+ 8 1/2", but that i this degradation, if occurring, would be less  ;

significant because these surfaces would not be as i susceptible to. repeated wetting and drying.

i L

l.

l l

4

?

I- - , , _ - - . , .

Catawba Nuclear Station, Unit 2 Class MC ISI Summary Report Refueling Outage EOC9 Page 8 of 19 Description of Conditions That Led to the Degradation Based on operating experience from previous examinations conducted in accordance with 10CFR50, Appendix J, the following conclusionc were drawn about conditions which led to the degradation.

1. Excessive moisture due to maintenance activities in the VY Fan Pit Moisture from maintenance activities has resulted in water contacting the Steel Containment Vessel /VX Fan Pit floor interface, at the top of the expansion joint cork material. These conditions had been identified (during previous inspections) as a potential concern because excessive moisture contact with Steel containment ,

Vessel surfaces could increase the potential for corrosion. As a result, approved sealant

]

materials were installed over the 2" wide ,

expansion joint to prevent moisture intrusion.

]

2. Failure of Approved Sea e Materials When sealant materials were initially installed, a limited number of materials were available for use inside containment that were qualified for Design Basis Accident conditions. The sealant material used was qualified for use inside containment. '

The following information should be noted:

i

1. The sealant material is an epoxy which j hardens over time. This causes the material I to lose flexibility, and also results in some shrinking and cracking on the material ,

surface, l ii. The VX Fan Pit floor joint is 2" wide, and I increases in width during the performance of I 10CFR50, Appendix J Type A Testing to as much I as 2-1/2". However, the actual displacement ,

of this joint has not been measured during )

Type A Tests.

iii. The use of an epoxy material in this application, where movement could approach 25%, is not ideal. Unfortunately, no other qualified materials were available and use of f

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

L1'. ..

1 . .

j Catawba Nuclear Station, Unit 2 '

Class MC ISI Summary Report Refueling Outage EOC9 y Page 9 of 19 '

L . .

this material was considered preferable to leaving the joint open to moisture intrusion. i iv. The sealant material adheres well to coated surfaces and has been used at many 3 applications within containment where

differential movement between sealed surfaces E is small. It appears that during 10 CFR 50,

[ Appendix J,, Type A tests that the sealant l material-tends to separate from some '

j. containment-surfaces, and has caused some

-loss of the protective coatings'from the containment surfaces.

v. The loss of protective coatings on

j. containment coated surfaces at moisture

• barrier locations, combined with exposure to ,

repeated wetting and drying appears to have l resulted in the corrosion noted in this report'. Over time, some of this corrosion-has progressed to include surfaces of the Steel Containment Vessel just below the. top of the moisture barrier attachment location i near elevation 593' + 9" (approx.).

l (2) Evaluation of the Affected Area and Evaluation Results Discussion of Evaluation of Degradation:

l Catawba Nuclear Station Problem Investigation Report

1. 2-C98-3567 was initiated to address this problem.

l L The following actions were taken to assess the extent E and significance of the observed degradation:

l

1. Damaged moisture barrier materials and portions of l cork expansion joint were removed between azimuths

( 288 and 296 (approx.) between the VX Fan Pit floor and the Steel Containment Vessel. Removal of portions of cork expansion joint material was required to assess whether the noted corrosion extended to other adjacent Steel Containment j' Vessel surfaces below the VX Fan Pit floor, behind the' cork expansion joint material.

2. A more detailed visual examination was conducted

, by engineering (Mark J. Ferlisi and Hesam r

l

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

!? .

L .

l Catawba Nuclear Station,' Unit 2 l Clasr MC ISI Summary Report L Refu .ng Outage EOC9 L Page 10 of 19 t ,

NekooAsl) to assess the condition of the surfaces >

exposed as a result of the moisture barrier and cork removal. The results of this examination revealed,' as suspected, that the most significant degradation was limited to locations along the Steel Containment Vessel /VX Fan Pit floor L interface where damaged moisture barrier materials

! had degraded. This examination identified several pitted locations, with the most significant L pitting located as follows:

l

' Location "A" - Azimuth 295 -11' , El. 593'+ 8".

f' Location "B" - Azimuth 292 -40 ' , El. 593'+ 7 1/2".

l l These were observed to be isolated pits which did not exceed approximately 1/8" in width.

3. Ultrasonic thickness measurements were performed at the above locations, from the interior side of the Steel Containment Vessel.

The results of these examinations are shown in Table 1.

TABLE 1 Location Plate Thickness Nominal Plate at Pit Thickness "A" 0.685" 3/4" "B"

0.701" 3/4" Please note that these examinations were performed from the corroded side of the vessel and that additional UT examinations were performed later from the exterior side of the vessel wall which revealed that the wall thickness at these locations was, in fact, greater than that detected l

from the inside surface. This is attributed to t the fact that more accurate UT results can be l obtained when the transducer is placed on a smooth I

. ~ - - . - .---- - - . . - ~. - - - - - - . - -

I b Catawba Nuclear Station, Unit 2 Class MC ISI Summary Report

, Refueling Outage EOC9

( Page 11 of 19 l- '

l l surface, such as that existing on the exterior l side of the vessel wall.

l L 4. Additional. cork expansion joint material was removed from between the VX Fan Pit floor and the i o

Steel Containment Vessel from azimuths 293 to ,

296 ,. between elevations 593+ 8 1/2" and 591' +

2.1/2". This material was removed to permit a l

, visual examination of Steel Containment Vessel j l

surfaces beneath areas where the most significant corrosion was detected. A more detailed visual i examination-was performed which revealed that l there was some minor corrosion at lower )

elevations, but that the conditions near elevation 593' + 8 1/2" were more significant. I L 5. Additional moisture barrier material was removed l between the Steel Containment vessel and the VX l i

Fan Pit floor between azimuths 247 and 303 , and i cork expansion joint material was excavated to a  !

depth of approximately.2" to 3" below the VX Fan ]

' Pit floor elevation of 593' + 8'1/2". Similar conditions to those between azimuths 293 to 296  ;

j were observed.

6. Because the opposite side of the Steel Containment Vessel is accessible for ultrasonic thickness  !

measurement, UT examinations were performed on vessel surfaces between azimuths 247 to 303 ,

between elevations 593' + 9 3/8" and 592' + 9 3/8" to confirm the extent of corrosion observed on the ]

' interior surfaces. Except for the 0.685" wall -j thickness measured at Location 'A", no readings. l below 0.697" were found. These UT examinations 1 may be used to satisfy the requirement of IWE-2500(c) and Table IWE-2500-1, Examination Category E-C,-Item E4.12 for the first ISI Period.

- Based on examinations conducted during previous inspections, and v 4 sual and ultrasonic thickness

c. examinations conducted during EOC9, the following l examination results and conclusions are made:

i

[ 1. Corrosion of the Steel Containment Vessel is l3 occurring at various locations between azimuths I:

i i

. . . . - _ - - - _ _ _ . . _ _ _ _ . _ . _ _ . - - - .. . ._._m

? A ..

Catawba Nuclear Station, Unit 2 i'

Class MC ISI. Summary Report

. Refueling Outage EOC9 Page 12 of 19 N

247 and 303 , between elevations 593 ' + 9 3/8" and 592' + 9 3/8". '

2. The most significant corrosion is located within approximately 3" of elevation 593' + 8 1/2",

-between 247 and 303 . In this region, the minimum wall thickness detected was 0.685" at Location-l "A".

3. Significant corrosion is not occurring between azimuths 247 and 303 , belov elevation 593 ' +5 L 1/2" (approx.). However, some minor corrosion may be occurring. UT1 data obtained on limited areas

'below elevation 593' + 4 5/8" support the c'nclusion that corrosion is more significant above this elevation.

4. At the minimum wall thickness location measured (Location "A"), the remaining 0.685" plate thickness is 91.33% of the full nominal plate thickness of 3/4". As a result, the remaining i wall thickness is acceptable by evaluation and l

satisfies the acceptance. criteria of IWE-3122.4.

L Because the remaining wall thickness at other locations was greater than at Location "A", these other locations are also acceptable by evaluation and satisfy.the acceptance criteria of IWE-3122.4.

i

The results of these examinations would suggest that metal loss of 0.049" to as much as 0.065" has occurred at Location "A". However, UT examinations performed in 1995 from the' exterior

! -of the Steel Containment Vessel' indicated that the uncorroded plate thickness in this area ranged from approximately 0.712" to 0.725". These thicknesses wereLreviewed against Certified Material Test Reports which indicated that no significant metal loss had occurred. Ultrasonic thickness measurements were also performed on surfaces adjacent to Locations "A" and "B" during EOC9 which indicated that the uncorroded plate thickness is approximately 0.720" to 0.726".

Assuming a maximum plate thickness of 0.726", a 5..

more realistic estimate of metal loss at locations "A" and "B" is 0.041" and 0.025", respectively.

1 . Please note that a General Visual Examination was t-I, l'

I

i e

Catawba Nuclear Station, Unit 2 Class MC.ISI Summary Report Refueling Outage EOC9 ,

Page 13 of 19  !

performed'during.EOC9 which confirmed that no  ;

degradation was occurring on the exterior side of ,

i the Steel Containment Vessel in this area.

.Because mi nor corrosion was observed at these locations during the last ? inspection conducted in r

October, 1995,ait is reasonable to assume that corrosion did.not commence later than October, 1995, and probably started much earlier.  ;

Therefore, an effective (conservative) corrosion i rate can be approximated to be 0.041"/35 months, or 0.001"/ month.  !

l At a rate of 0.001"/ month,;we can predict when the I

~ acceptance limit of 90% of the nominal' wall I thickness may be exceeded.

For Location "A", the predicted. length of time

i. to 90% thickness is equal to (0.685" - 0.675") x (0.041"/35 months) = 8.5 months.

For all other locations, the predicted length of time to 90% thickness is no less than'(0.697" - ,

0.675") x (0.041"/35 months) = 18.8 months. j Please. note that, because' cork expansion joint material and sealant have been removed from-Location "A", and because. water can no longer be l trapped against surfaces at-this location, the environment has changed and the expected corrosion rate should be considerably less than that i predicted above. However, even if Location "A" I were to continue to corrode at the predicted rate l p

of 0'.001"/ month, the expected wall thickness will be approximately equal to 0.663", or 88.4% of the nominal wall thickness-after a period of time ~

i equal to 18.8 months. Local wall thinning such as i this can be easily demonstrated to meet the  !

acceptance criteria of the original Design Code.

Current refueling cycles for Catawba Unit 2 are i approximately 18 months. Based on the above

, discussion, it is considered acceptable to

[ continue operating-until the next scheduled refueling outage without implementing immediate corrective actions. I 4

1 9m -- n pm - p ! y

? .. l l

l Catawba Nuclear Station, Unit 2 l

Class MC ISI Summary Report l Refueling Outage EOC9 l Page 14 of 19 l

(3) Description of Necessary Corrective Actions Immediate Corrective Actions Other than actions indicated above, no other immediate corrective actions are deemed necessary for '

Unit 2.

Long-Term Corrective Actions

1. The Containment ISI Plan shall be revised to require that Containment Vessel surfaces at the ,

Unit 2 VX Fan Pit floor be examined in accordance I with IWE-2500, Table IWE-2500-1, Examination Category E-C, Item E4.11, as required by IWE-3122.4(b), during the next 3 ISI Periods. j Portions of this area which are inaccessible for direct or remote visual examination shall require examination in accordance with Table IWE-2500-1, Category E-C, Item E4.12.

2. The Containment ISI Plan shall be revised to require ultrasonic thickness measurement of all l Steel Containment Vessel surfaces between azimuths i 247 to 303 , between elevations 593' + 8 1/2" and 590' + 8-1/2" (approximately) on both Units 1 and 2 in accordance with Table IWE-2500-1, Category E- l C, Item E4.12. l

3. During refueling outage EOC10, the minimum wall thickness locations on the exterior of tne vessel on the side opposite the _ Unit 2 VX Fs.;- elt shall be reexamined by UT to obtain data necessary for ,

trending corrosion rares. This data shall be used I to determine required completion dates for any additional corrective actions.

Please note that these areas on both Units 1 and 2 have been identified as requiring augmented examination in accordance with IWE-2500, Table IWE-2500-1, Examination Category E-C, Item E4.12 and require examination during the first ISI Period.

I 4. Catawba Nuclear Station shall implement one of the following options to address degradation of the

Catawba Nuclear Station, Unit 2 l

• Class MC ISI Summary Report Refueling Outage EOC9 j Page 15 of 19 Steel Containment Vessels at the VX Fan Pit floor areas on both Units 1 and 2.

Option #1 - Permanently Remove all Expansion Joint Materials Between the VX Fan Pit Floor and the Steel Containment Vessel.

This option would eliminate the possibility that

. water could become trapped against surfaces of the Steel Containment Vessel. An advantage to this l option is that ultrasonic thickness measurements performed in accordance with IWE-2500, Table IWE-  !

2500-1, Category E-C, Item E4.12 would no longer i be required because these surfaces could become l accessible for direct or remote visual examination from both sides of the vessel. j i

Option #2 - Continue To Monitor The Condition Of l The Steel Containment Vessel Behind Surfaces Covered By Cork Expansion Joint Material Between The VX Fan Pit Floor.

The Containment ISI Plan currently requires that ultrasonic thickness measurements be performed in accordance with IWE-2500, Table IWE-2500-1, l Examination Category E-C, Item El.12 on areas just j beneath the VX Fan Pit floor elevation. These j examinations are conducted from the exterior '

surface of the Steel Containment Vessel. However, the scope of these examinations shall be expanded j to include all Steel Containment Vessel surfaces  !

between azimuths 247 to 303 , between elevations 593' + 8 1/2" and 590' + 8-1/2". Note that corrective actions proposed in Option #1 may be I required if examinations reveal wall thickness loss exceeding the acceptance standards of IWE-3500.

(4) Additional Examinations (Number and Type) Required to Verify that Similar Degradation Does Not Exist in Similar Components l

l The following additional examinations were performed:

l

l_* v Catawba Nuclear Station, Unit 2 Class MC ISI Summary Report Refueling Outage EOC9 Page 16 of 19 i

l

1. A visual inspection was conducted by Engineering (Mark

! Ferlisi and Hesam NekooAsl) on the accessible surfaces of the Unit 1 VX Fan Pit floor / Steel Containment

! Vessel interface. This inspection revealed that conditions were not as significant as that identified in' Unit 2 and that no visible evidence of corrosion exists. Please note that examination of this area is required in accordance with Table IWE-2500-1, . Category l.' E-C, Item'E4.12 during the first ISI Period (currently L scheduled to end September 9, 2001).

Please note the following:

1. A General visual examination was conducted on 100% of the accessible Steel Containment Vessel surfaces during the Unit 2 EOC9 refueling; outage. This examination included all accessible surfaces between the interior structure concrete floors and the Steel Containment Vessel. No Steel Containment Vessel degradation was noted at these locations, and nearly all locations with-geometry similar to that in the VX i

Fan Pit area have had moisture barrier (sealant) l materials removed. As a result, no additional visual i examinations on Unit 2 were deemed necessary.

2. The Containment ISI Plan' currently requires - that ultrasonic thickness measurements be performed from the vessel exterior at all locations where interior structure horizontal concrete floors abut the Steel Containment Vessel. These UT examinations shall be performed during the first ISI Period.

Condition #2 (1)A Description Of-The Type And Estimated Extent Of

. Degradation, And The Conditions That Led To The Degradation Description of Observed Conditions:

p

!. Moisture barrier (sealant) was observed to be missing from the Steel Containment Vessel interior embedment zone at elevation 552' + 0" at azimuth 305 (approx.)

7

.for a length of approximately 4 feet. Brown colored

v Catawba Nuclear Station, Unit 2 Class MC ISI Summary Report Refueling Outage EOC9 Page 17 of 19 l

staining was observed above this location, and water was observed on the Steel Containment Vessel shell surfaces in this area. General Visual Examinations revealed that the water may have gained access to embedded surfaces of the Steel Containment Vessel beneath the Pipe Chase floor at this location, because existing coatings did not completely seal the interface where moisture barrier material was missing. No coatings loss or base metal degradation .

was observed on adjacent Steel Containment Vessel I surfaces.

Catawba Nuclear Station Problem Investigation Report l

1. 2-C98-3568 was initiated to address this problem and '

to document the evaluation of potential degradation in the affected area.

Estimated Extent of Degradation:

1 Based on initial observations, it was unknown whether any unacceptable degradation was occurring in adjacent inaccessible areas.

Description of Conditions That Led to the Degradation:

1. Moisture barrier materials were initially installed around the interior periphery of the Steel Containment Vessel at the embedment zone as a result of recommendations from the previous 10 CFR 50, Appendix J general visual inspection performed in 1995. For reasons unclear, sealant material had not been completely installed at this particular location.

2. The water observed on the Steel Containment Vessel shell surfaces is the result of maintenance activities performed in the VX Fan Pit which.is located approximately 38 feet above this area.

The observed brown staining results when water passes through cork expansion joint material between the internal concrete structures. The brown color apparently comes from material within

( the cork expansion joint panels, or from materials t which bind the panels together. This stained

! Water is not, by itself, injurious to coated surfaces of the Containment Vessel and has been

Catawba Nuclear Station, Unit 2 Class MC ISI Summary Report Refueling Outage EOC9 Page 18 of 19 observed during previous general visual l inspections performed in accordance with 10 CFR 50, Appendix J.

(2)_ Evaluation of the Affected Area and Evaluation Results l

To confirm whether moisture intrusion against  ;

inaccessible surfaces of the Steel Containment Vessel {

had resulted in any degradation to inaccessible surfaces '

below the Pipe Chase floor at elevation 552' + 0", the following actions were taken:

l. Portions of the concrete floor adjacent to the affected containment surface area were removed to a depth of approximately 1" to 2".  !

2. A more detailed visual examination was conducted by engineering (Mark J. Ferlisi and Hesam NekooAsl) to I

assess the condition of the surfaces exposed as a result of the concrete removal. The results of this examination revealed that no degradation was occurring, and that protective coatings on the Steel Containment Vessel surfaces in this area remained intact.

3. A sample of the observed water was obtained and tested for pH. The results of this analysis indicated that the water had a pH of 8.8. Because water in this pH range is not injurious to carbon steel surfaces, and because the observed protective coatings were intact, no further evaluation was performed.

As a result of the above evaluation, the condition of the Class MC component surfaces are acceptable at this location. Details of this condition have been included in this Class MC Summary Report because the observed conditions were initially considered to be a possible indicator of potential degradation on the adjacent embedded (inaccessible) surfaces of the Steel Containment Vessel.

(3) Description of Necessary Corrective Actions Necessary corrective actions were limited to repair of the concrete floor adjacent to the Steel Containment Vessel, addition of new moisture barrier materials along l

l l

_ _. ., 4 _ ~ . . _._ _ _.- _._ m _ - . . . -

Catawba Nuclear Station,. Unit 2 Class MC ISI Summary Report Refueling Outage EOC9 Page 19 of 19  ;

• l surfaces which were not previously sealed, and recoating l of the repaired concrete surfaces.

1 Because the condition of Class MC component surfaces was ,

L acceptable at this location and did not require evaluation in accordance with IWE-3122.4, the Steel Containment Vessel surfaces in this. area do not require reexamination in accordance with IWE-3122.4(b) and IWE-2420(b) and (c).

-Examination of the moisture barrier at the base of the Steel Containment Vessel was conducted in accordance L with IWE-2500, Table IWE-2500-1, Examination Category E-A, ~ Item El.11.

In the opinion of the Registered ProfessionalfEngineer conducting'the general visual examination of this area, the' observed conditions did u not exceed the' acceptance standards of IWE-3510.1. As such, this' area need not be' examined in accordance with LIWE-2500, Table IWE-2500-1, Category E-C, Item E4.ll during.the next inspection period. Duke Energy Corporation understands the importance of maintaining the condition'of these moisture barriers and requires that these moisture barriers be examined every inspection period in accordance with procedure

1. PT/2/A/4200/078 (General Visual Examination Procedure).

In' addition to these' visual examinations, moisture barriers are also-examined every ten years in accordance with-IWE-2500,-Table IWE-2500-1, Examination Category E-D, Item E5.30.

l- 1 L (4) Additional _ Examinations (Number and Type). Required to i Verify that Similar Degradation Does Not Exist in Similar Components l

Because 100% of the accessible moisture barriers along the interior embedment zone of the Steel Containment Vessel'were examined during Unit 2 refueling outage EOC9, no additional examinations are necessary for the ,

L interior embedment zone areas.

Because'100% of the accessible moisture barriers along the exterior embedment zone of the Steel Containment  ;

Vessel were examined during Unit 2 refueling outage EOC9 in accordance with Table IWE-2500-1, Category E-A, Item El.11, and Category E-D, Item E5.30, no additional L examinations are necessary for the exterior embedment l zone areas.

l L

m._