ML072850055

September 2007 Evidentiary Hearing - Intervenors Exhibit 45, Amergen Technical Evaluation 330592-27-27

ML072850055
Person / Time
Site:	Oyster Creek
Issue date:	04/20/2007
From:	Tamburro P Exelon Corp
To:	Office of Nuclear Reactor Regulation
SECY RAS
References
50-219-LR, AmerGen-Intervenor-45, RAS 14362
Download: ML072850055 (12)

Text

Citizens Exhibits 45 2Iq ts 1

(0 OL 3 4 Eval 330592-2-1-21 Page 1 of 12

.Purpose:

The purpose of this Tech Eva] is to document representative thickness of the Drywell Vessel based. on inspection and associated calculations.

This informiation will be ptovided. to Structural Integrity Asso.iates as input in the development of a Finite Element Model of the Oyster Creek Drywell Vessel. (Contract Nuinber 1002562, Requisition Number 846565). As such, the intent per this Tech Eval is to define representative thicknesses based on they 2006 Refueling Outage ultrasonic thickness measurementes to obtain a realistic picture of the margis that.currently exist for

" the Oyster Creek drywell.

This, Tech Eval has been performed in accordance with CC-AA-.309-10.1 Revision 8..

This Tech Eval is classified as Safety Related "Q" A I{U-AA-1212 review has been performed of this technical product. Based on a Medium Consequence Factor (Possibility of a Regulatory Open Item) and three Process and Hurian Performance Risk Factors, the Risk Rank was determined, to be "Y".

Therefore, Independent Re*view in accordance CC-AA-309-101, revision 8 is acceptable.

Assumptions I The purpose of this Tech Eval.is to. provide representative thicknesses for each.

region and elevation'. Oyster CQreek.Engineering lias dveloped several calculations that demonstrate that the inspeetiohi data meets acceptance criteria (References 1. 2, 3, and 5). However, in many cases, the UT data is treated conservatively when compared to the acceptance criteria. -This conservative treatment rTesults in assumed vessel thicknesses that are thinner and more widespread. (i.e., bigger surface area) than is actually in the field. This approach.

is proper and accepfable fo the refereticed doc*nnts since their purpose is to demonstrateall acceptanc.criterion is met.

The purpose of this Tech Eval, however is to provide realistic. representative thickness of a region. These representative thicknesses will be design input to calculations that will demonstrate that both existing margins and the margins that will exist at the end of the period of extended operation are acceptable.

DOCKETED USNRC October 1, 2007 (10:45am)

OFFICE OF SECRETARY RULEMAKINGS AND ADJUDICATIONS STAFF Therefore, the results based on these representative thickness values will be more accurate.

The intent of this Tech Eval is to define representative thia~eesses based ori the actual ultrasonic meiasuremnents taken from inside the drywell.. The UT

..measurements taken from outside the drywell are less representative since these measurements purposely concentrated on thin local areas (less than 2 1/2".ifl diameter) and due to. the surface preparations needed to ob.ta..in accurate external UT reading.

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Eval 330592-27-27 Page 2 of 12 Methodology 1). For regions other than the sandbed, a representative value will be chosein based.on the thinnest average grids values from the monitoring program and associated calculations, and that havebeen provided to the regulator in various presentations and submittals and, therefore, is part of the public record. These values may be values documented for past inspections, rather than the most recent value for that region. Although this remains conservative (selecting the thinnest average value),

the variability in the data is not as significant as in the sandbed region. and the values used are consistent with those previously provided. to regulatory organizations,

2) Since the existing mtargin, in the sandbed region is smaller, more repiesentative mgneral thickness values will be determined based on the following:

a). As noted in the assumptions, -internal grid measurements will be used.as the basis for the representative thickness; These measurements.are consideed to be th6 most accurate since, the coating on. the inside surface of the drywall was removed for the measureTments and a protective grease coating is: Eppliedafter measurements are takeni (to eliminate the posgibility of internal surface corrosion). The averagt6 internal grid mdasurements were used. as the primary indicator of the representative general thickness. of *each bay. However, other data. sources were used to verify or augmentth' applicable values foreath of the bays. These other sources of data were the external data, pictures of the external.surfaces of the sanidbed, and the trench data in bays 15: and 17.-Augmentation of the grid data is described in the sections 2b through 2h.

b) The external -individual UT readings were deliberate attempts to ideiltify the thinest local areas less than. 2 '/27 inches in diameter in each' bay, Therefore,.ising these values (ontly) to defnie representative general thicknes'ses is not Appropriate. However, ttfe external data was usedsto deftie: locally thin areas that are thinner than 0.736" (see item: 3.:below) and that will be included in the analysis niodel.

c) The measurement data makes it evident that;the wall. loss experienced while the" sand was present did not encompass the entire sandbed region from elevation 8'11" to 12' 3" since the regions were -either not completely filled with sand or not completely filled with water. Pictures taken in 1992 of the external shell surface (after sandremoval) confirmed the presence of a "transition" line at approximate elevation 11'.. Above this "transition" line dhe thickness of the ve-selis clos6 to nominal wall

,hickne-s and below the line ar areas. at exhibit wall loss duee.to the corrosion. Therefore, the general wall thictaiess of each sandbed bay has.

beenrdivided into two areas; above and below elevation 11' 0". This will reduce the consenratism that would be introduced by assuming the entire bay'thiOkn.ess is equivalent to an average of the external readings or the average of the intetnal grids readings..'

Eval 330592-27-27 Page 3 of 12 d) Where tfie internal grid measurements were clearly not representative of the corrosion on the shell in that bay, representative measurement from adjacent bays were utilized to provide a representative generaI thickness.

Bay 1 is the prime example of the use of this methodology. Visual and photographic observations of Bay I and Bay 19 indicate these to be two of the most heavily corroded bays. External UT reading in Bay I c6nfirms the presence of corrosion. Yet, the internal Grid UT examination in Bay 1 would indicate near nominal thickness. Since some of the exterMal readings occur above elevation I I' 0", it was concluded that corrosion for the whole bay should be assumed. Therefore, the values from the adjacent Corroded bay (Bay 19) Were deemed to be more representative f-r Bay 1 than the internal grid value.

e) Where the trenches were cut ouit of thd drywell floor (elevafiofl 10' 3")

allowifg UT measurements from inside the Dryvell in arkge areas, these measurements were used to determine the general thickness of these bays (Bays 5 and.17). The trench UT data consists of hundreds of idividual UT readings over a large area, rather than only 49 readings or less over smaller regions. Therefore, the: results of these inspections are concluded to be tepresentative of the general thickness of these two bays.

f W

Where the internaldata. indicates a "trans-ition" line through the. grid, the average of the lower readhig were used to define that Particular bay general thickness below elevation 11'.

g) 1i one-case (bay 1_) there were no internal grid or external in~dividual data available below elevation 11'. Therefore, an average of the two adjacent bays was used. The basis for this approach is the assumption that there is a general wall thickness gradient between the two adjacent bays that would adequately iepresent the general, thickness of the bay between them.

h)j For bays 9, 15, and 17 (above elevation I I) there are multiple iatetnal grids. Therefore in these bays, the weighted average ofthe multiple grids were-calculated by summing the total number of valid thickness readings aid' dividing by the total number of valid readings.

3) In several bays of the sandbed region. there are locally thin areas thAt are thinner than 0.736" and are confined to areas no larger than 36" by 36". These areas will be hiput to the model as defined locally thin circular areas. These areas were selected directly fromi calculation' C-1302-187-5320-024 revision 2. To facilitate computer modlinig of the locally thinned areas, larger circular areas were overlaid over the thin square areas identified in calculation C-i302-487-5320-024 revisioni 2. The circular areas completely capture the square areas. This introduces a small amount of conservatism since the area of the-circles exceeds the area;61f the squares. Although conservative, this is not expected to significantly impactthe overall results obtained from the analysis.

EvaO 3A0592-27-27 Page 4 of 12 Detail Evalrati on..

Regions other than the Sandbed Region Elevations Value in mils References

1) Oyster Creek License Renewal ACRS 1/18/07 Presentations Slide 14 (reference 3)

Cylindrical 71' 6" Region to 604

2) 1994 average grid value -for grid 9-.20 Calculation 93' C-1302-187-5320-037 Revision 3 appendix 7 page.

A7-20 of 29 (reference 4)

1) Oyster Creek License Renewal ACRS 1/18/07 Presentations Slide 14 (reference 3)

Knuckle Region 2

2530*

2) 2006 average grid value for bay 9 Calculation C-to 1302-i87-5320-037 Revision 3 page 11 of 48.

71' V (reference 4)

1) Oyster Creek License Renewal ACRS. 1/1.8/07 Presentations Slide 14 (reference 3)

Upper. Spherical 50' 11V1 676 2).1994 average grid value-for grid 13 -32 Region to Calculation C-1302-18.-5320-037 Revision 3 65' 2, 718" appendix 5 page A5-23 of 38 (reference 4)

1) Oyster Creek License Renewal ACRS 1/1.8/07.

37' 3 Presentations Slide 14 (reference 3)

Middle Spherical to 678 idRegionc 5l to 678

2) 2006 average grid value for grid 13 R n'~

.Calculation C-1302-1 87-5320-037 Revision 3

.__apperidix 3 page A3-24 of 36 (reference 4)

1) Oyster Ctetk License Renewal ACRS 1/18107 lTo 23' 6 7/8" Presentations Slide 14 (reference 3)

Lo erS heiM

.to 1160 Regir n 37S 3p l

2) 2006 average grid value for bay 19-Calculation C41302.- 87-5320-M037 Revision 3 page 11 of 48 (reference 4).

1) Oyster Creek License Renewal ACRS 1/18/07 Embedded Presentations Slide 124 (reference 3)

Region (1154 6' 7" Nominal below 1113

2) Tech Eval 00546049-07, Attachment 7 page 1 of 2 Thickness)

$8' 11" "Water Found in Drywell Bay 5 - UT Data Evaluation,

Embedded Region (676 Below 636

1) Tech Eval 00546049-07, page 8 of 10 "Water Nominal 6' 7" Found in Drywell Bay 5 - UT Dati Evaluation Thickness).

Eval 330592-27-27 Page 5 of t12 Sandbed Regioft Above: Elevation Basis Below BAY Elevation III-Basis

.. 11'.0O (mils)

O," (mils) 26 ame value as used for Bay 19 Same value as used for Bay 19 t1 adjacent bay)

(adjacent bay) 3.

rIIntemal grid average (single 950 Numerical average thickness grid) Ref. 2 page 7 betWeen Bays 1 & 5 Average of internal trench data 5

1185 Internal. grid average (single 1074 oints (six 49 point grids).

grid) Ref. 2 page 7 Refer to page 5 of 10 of A2152754 E09 3 nternal grid average (single Numerical average, tkness 7

.1133 id) IRef.2 page 7.

1034 between.Bays 5 &9

.Weighted avera ge of-two Smaller of the two internalW grid 9

1.074 internal grids (49 point and 7 993 averages (49 point, grid).Ref. 2 jpoint) Ref. 2 page 6 and 7 PP6-11 860.

Average of two internal grids Average of two internal grids (both 49 point) giff 2 page 6 (both 49 point) Ref. 2 page 6 JAverage of two intenal grids.

A-verage of three intemnal g'ids 1-3 907 "

both.49 point; 7 point grid

907, (both 49 point; 7 point grid data not used) Ref. 2 page 6.

9 data not oised) Ref.:2 page 6 And 7 and 7 Weighted average of two Numerical average thickness 15 1062 internal grids (49 point and. 7 935 betwern Bay-s 13 & 17 point) - Ref. 2 page:6 and 7

• Weigh ted averagze of-the eihedaeaeoth Average of internal trenc~h data

~~~~~~bottomi of 'internal grid 17A (28Aergofntmttn*hda 17 t63 t

points) and internal grid 17D 963 (oints (six 49 point grids).

13 o

) ad i a gd 7Refer to page 6 of 10 on Tech 49 points). - Ref. 2 page 6 Eva] A2152754 809 Data for grid 17119 not used.

a 2*

19 826 verage of three internal grids 826 Average of three internal grids

(_11 all 49. points) - Ref. 2 page 6

( a1l 49 points) - Ref. 2 page 6 Locally Thin Areas See Attachment I

Eval 330592-27-27 Page6 of 1.2

==

Conclusion:==

The* attached table provides representative thicknesses of the Drywell Vessel based on 2006 inspection and other pat inspections. These values shall be used as general thiclkess values forthe associated region.

OYSTER CREEK DRYWELL THICKNESSES FOR USE IN BASE CASE ANALYSIS.

L-OCATION.

THICKNESS (mils)

' Cylindrical Region 604.

Knudike Region 2530.

Upper Spherical Region 676.

Middle.Spherlcal Region 678 Low"er Spheri.calRegiOn (Note 1) 1160.

Embedded Reglon (11:54 Nominal 11'

_. 1 Tfiickness)

Embedded Region (676 Nominal 536 Thickness).

SA*NDBED REGION BAY.

Above Elevation 1",0'" Below.Elevatibn 1!V-0`

_______(r!Ils)

,(mils).

• ' 1.

826 826 13180

• 5 1185 1074.

.7.

1i33 1034

.9 1074.*

.993

• 11 860

.860 13 907 907 1B 1062.

936 17

.863 963

.19 826 826 I _

_7 In addition-since there are several locally thin areas in the sarndbed. Specific thin area shall be mindeled per Attachment 1.

Reference:

1) Calculation. C1302-187-5320-024 Revision 2

2) Calculation C-1302-187-5320-041 Revision 0

3) Calculation C-1302-1.87-5320-037 Revision 3

.4) Oyster Creek License Renewal ACRS 1/18/07 Presentation

5) Tech Eval 00546049-07, "Water Found in Drywell Bay UT Data Evaluation

Eval 330592-27-27 Page7 of 12 Attachments - Sketches showing locally thin area. (5 pages)

Prepared By-Peter Tamburro Independent Review:'

f5, 21k

ý12l' The Independent Rev'iew has been completed in accordance with ER-AA-309-01, I have indeperndently v;erified and agreed with the.. methodology.,.inputs, and results of this:

Technical Evaluation. All of my comments.-were answered and incorporated.as:

appropriate.

Indepenidently Reviewed By: Dav'id P. Olszewski Date: 4/20/2007 Manager's Comments: The preparer and reviewer are qualified to performlthis task.

ThAs data is being prepared, reviewed and approved to vefify the inputs to. be used to complete the drywell shell analysis project. Tlxerefore, the HU-AA.-I212 risk rank of 1 is appropriate and the existing process reviews arle acceptable.

/

Manager Approval: F. H.Ray 4/20/2007.

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F.

Eval 330592-27-27 Page 8 of 12 Bay 1. 2006 Input Locally Thin.Area Less Than 736 Mils Center LUneOf Vent Line + 139.

-72

-60

-48

-36

-24

-12 Area C from flgure I-7 from 6

calculation C-1302-187-502M024' 51V diameter circular area that JiS 696 mils thick.

Circular area is centered on Y# - 31 and X+11

.12

24.

36 48..

60 72 Cl)

All X and Y..dimensions. are referenced from 13-inchesto the right. of centerline of the vent line (X.directioq) and the. bottom'of the Peneiration Rehtforcement Pad :(-Y dimension).

Reference NDIEData sheets 92-072-12 page 1. of2 and l!RZ.LR-02Zpage'2:of 2.

Eval 330592-27-27 Page of 12

• 1 Bay 13:2006 Input Locally Thin Area Less Than 736 Mils.

Bottom of Penetration Reinforcement Pad Center Line Of Vent Line

", /

-72

-60

-48

-36

-;24

-12 (fl 12 24 3 6 48 60:

72 E

Area, G from figure 1317 from calculation C-i 302-187-w5320-024 1:8" diameter circular area that is 658. mil-thick

(*irCui~r ArPn.is centered I

on Y=- 21 and.Xk 19

-42 All. Xand Y dimensions. are referenced from: the centerline of the: vent. line (X direction) and the bottom of tthe Penetration Reinforcement Pad (Y dimension).

Reference NDE.Data. sheet 92-0.72-24 page 1. of 2 and 1 LR-01'0 page 2 of.2. -

m.

Eval 330592-27-27 Page 10 of 12 Bay 1:5 2006 Input Locally Thin Area Less Than 736 mils Area A fr'om figure 15-6 from calculation C-1302-187-5320-024 0

C, All X and Y dimexnsions are referenced from.the centerline-of the veut line (X.

direction): and the: bottom of the Penetration Reinforcement Pad (Y dimension).:

Reference NDE Data sheet 9Z-7J72-21 page 1 of I and iR21LR-015.page Z. of 2

Eval 330592-27-27 Page I I of 12 Bay 19 2006 Input Locally Thin Area Less Than, 736 Mils-Area 1 from.figure 19-7 from calculation: C-1302-1687-5320-024 4.

-72

-60

-48

-36 0a, 0

24 36 4B 60 72 51" diamptir circular.

area that :is 720 mils thick Circular area is: centered on Y= - 17.5 and X -3.5 All X and Y dimensions are. referenced-from the. centerline of the vent Hime (X direction) and the bottom of the Penetration% Reinforcement Pad (Yndimension).

Reference NDE Data sheet. 92-072-02 page: 1 of 1 and IR21LR-02Opage Zof 2.

Eval' 330592-27-27 r Page 12' of 12

.:.Bay 17 2006.

Input Locally Thin Area Less Than 736 mils Area. A from. figure 17-6 from ialculation *C.-i302-187-532'0-024:

Inches I rl n

"'" i I

r lip t-72

-60

-48 46

-24

-12 1

1.

Area B from figure 17;41. r.

calculation Ci30.2-187-5320-024 18 inch diameter circular area that is 663: Mils thick 18,,

Both circular areasare; centered on Y=:- 8 and. X+38 i:2 (I~

U * "

-42.

51" diameter circular area that is 850 mils thick All X and Y dimensions are referenced from the centerline of t6e vent line (X direction) and -tde: bottom, the Penetration ReinfOrcement Pad (Y dimension). Reference NDE Data sheet 92-07.2,04 page I of 1 and 1R2I-R-021 page 2 of 2.