ML051220436

Nrc/Exelon Working Level Meeting Slides OTSG Kinetic Expansions

ML051220436
Person / Time
Site:	Three Mile Island
Issue date:	02/16/2005
From:	AmerGen Energy Co
To:	Office of Nuclear Reactor Regulation
References
Download: ML051220436 (61)

Text

NRC / Exelon Wor king Level Meeting OTSG Kinetic Expansions February 16, 2005 I

TMI-1 Draft RAIs re: Kinetic Expansions

• Information:

• TMI-1 Planning for SG Replacement in Fall, 2009 Outage.

(2005 and 2007 planned refueling outage exams)

>> April, 2005 scheduled Exelon Board review o Background

• TMI-1 installed kinetic expansions (KE's) in 1982-1985

• TMI- 1 created and first used KRE MRPC inspection criteria in 1997

• Significcant Scope Commnitmnents

• Summaiy:

>> Plug circs in pressure boundary 100% scope each outage

> Plug new indications

17? KINETIC EXP AlHS10 H (TYPI CAL}

ow T S'iLE' 1 I TCf OF UPPER BURESHEET 3

Several Staff Issues to Discuss Excerpt:

1. Suitability of leaving circumferential flaws in-service

2. Leakage assessment including thermal hydraulic analysis model

3. Basis for assumption of no growth/no initiation of new flaws

4. Structural integrity assessment

a. Basis for steam line break axial load

b. Determination of the limiting accident

5. Consistency with recent industry experience

6. Inspection practices/techniques

7. Other issues ... "

• Also, issues listed in "TMI-1 MSLB ANALYSIS FOR GENERATING INPUTS TO DEFINE THE OTSG TUBE LOADS (RAls FROM SRXB)"

4

1 Suitability of Leaving Circumferential Flaws In Service

• Issue:

• "...a. The large-break loss-of-coolant accident (LBLOCA) issue applies to TMI-1, (based on request for additional information (RAI) responses provided in the October 4, 2002 submittal) and circumferential flaws are of particular concern in this event due to the increase in axial loads. This issue is not currently addressed in the August 16, 2004, TMI-1 KE report, ECR #02-01121, Revision 1, "Inspection Acceptance Criteria and Leakage Assessment Methodology for TMI OTSG [once-through steam generator] Kinetic Expansion Examinations," which is inconsistent with industry practice for joint repairs, therefore this issue remains unresolved."

0 Exelon Response:

- Exelon proposes to plug all circumferential flaws in the kinetic expansions' required lengths upon detection (--including circumferential flaws that were detected during prior 1997 through 2003 outage exams that rnemain in service in the kinetic expansions' required lengths).

- This is $1.5M and I day duration commitmient.

5

1.(cont'd) Suitability of Leaving Circumferential Flaws In Service o Issue:

"...b. For a 0.64-inch long circumferential crack, what is the factor of safety against tube severance under a main steamline break (MSLB), based on elastic analysis? For this same crack, does the axial thermal stress behave as a primary or secondary stress? (For design in accordance with Section III of the American Society for Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code), axial thermal stress is always considered secondary. For circumferentially cracked tubes, if the crack is large enough such that deformation occurs largely at the crack rather than being relatively evenly distributed along the length of the tube, then the net section stress at this location is not "self limiting" and should be treated as primary. Industry representatives (e.g., NEI) have stated they are developing guidance for when thermal loads should be considered primary versus secondary). If the licensee has an alternative justification for the 0.64-inch circumferential crack criterion other than elastic analysis, the licensee is requested to provide that justification including justification for the value of the safety factor assumed to the applied load." 6

1. (cont'd) Suitability of Leaving Circumferential Flaws In Service Exelon Response:

0 1997 analyses were elastic

• Thernmally-induced axial stresses were secondary

• Safety factor for structural (i.e., tube severance) is at least 1.8 based on axial tube loads

( 1310 lbs. by analysis versus 2400 lbs. assumed for KE analyses)

• Recent scoping calcs. indicate that strain concentration at circ. ciacks will not prevent full load relaxation of the secondaty MSLB thermal loads. The calculations indicate that the strain concentration for a 0.64" circumferential flaw is approximately 3%.

- As previously described, Exelon proposes to plug all circumferential flaws in the kinetic expansions' required lengths upon detection (--including circumferential flaws that were detected during prior 1997 through 2003 outage exams that remain in service in the kinetic expansions' required lengths).

• Recent work perfornied for the BWOG shows load relaxation ulider displacement control for 90 degree/l 00% TW cracks in OTSG tubes. An elastic load of 2920 lbs. relaxed by 454 lbs. under displacement control at maximum load. This is an effective factor of salety of approximately 1.18 with respect to maximum load. The self limiting characteristic of the secondaty, displacement controlled, load is maintained in the presence of a TW circumferential crack.

7

1. (cont'd) Suitability of Leaving Circumferential Flaws In Service o Issue:

• "...c. Based on recent industry operating experience, circumferential flaws are likely to initiate in the KE expansion region at TMI-1. The staffs concerns related to the "no growth" and "new initiation" statistical assessments have not been resolved and are discussed in more detail in Item 3 below."

0 Exelon Response:

- Exelon proposes to plug all circumferential flaws in the kinetic expansions' required lengths upon detection (--including circumnferentik1 flaws that were detected during prior 1997 through 2003 outage exams that remain in service in the kinetic expansions' required lengths).

- Will address further in Item 3.

8

1. (cont'd) Suitability of Leaving Circumferential Flaws In Service e Issue:

• "...d. No other domestic plant leaves circumferential flaws in service in the steam generator (SG) tube pressure boundary. Based on this and other issues associated with circumferential cracks (identified above), the staff would like the licensee to discuss the suitability of its proposal to leave circumferential flaws in service."

• Exelon Response:

- Exelon proposes to plug all circumferential flaws in the kinetic expansions' required lengths upon detection (--including ci r-Cellu eeletiaI flaws that were detected during prior 1997 through 2003 outage exams).

9

2. Leakage Assessment Including Thermal Hydraulic Analysis Model

• Issue:

"...a. Did the leak tests, performed in support of this inspection/repair criteria, use deoxygenated water? Recent industry experience indicates tests not performed with deoxygenated water may be non-conservative."

• Exelon Response:

- Leak testing performed for this 1997 KIE criteria did not use deoxygenatecl water.

- WCAP for CE Explansions, Sect 4.7: "...tests demonstrated that a difference in water chemistry (deionized-oxygenated water and deoxygenated primary water) (lid not affect leak rate."

- Room temperature leak rate testing very conservative due to lack of flashing (I.e.,

choking) at the crack.

- The TMI- I leak testing was very conservative:

> Tle tubes were not even expanded into the tubesheet niockup. (They were only clamped, with no plastic deformation of tube sample or tubesheet mockups). This method was conservative because the tubing sample was not expanded into the clamp; thus, "flattened contact" was not attained.

> Leak rates were calculated for freespan. tubing (i.e., no tubeshleet present),

which is conservative and maximizes the delta P across a tube flaw.

> Leak testing was only used to determine a single leak reduction factor (LRF) to apply to the calculated freespan rates. I0

2. (cont'd) Leakage Assessment Including Thermal Hydraulic Analysis Model

• Issue:

• "...b. The proposed leakage model assumes zero leakage from flaws located above the region of the tubing which is inspected and evaluated in accordance with the structural integrity criteria (i.e., the SG tube pressure boundary). This is inconsistent with industry practice for similar repair criteria. Recent industry experience indicates the leakage from this region may not be minimal, when assumed for all in-service tubes. Therefore, the assumption needs to be modified to reflect this."

• Exelon Response:

>> Exelon will revise wording in the report and revise its approach:

> Negligible leakage vice zero leakage

> The KE's were designed to be leak-limiting, vice leak-tighL (--sum of leakage firom all KE's less than I lb./hr during normal operation.

> The test block qualification leak test results in Section 2.6.3.2 of BAW- 1760, Rev 1, indicate a measured average leak rate equal to 44.72E-6 lbs/hr at all internal pressure of 1400 to 1500 psig. This pressure difference corresponds to the maximum pressure difference for the MSLB as evaluated using tile TMI specific thermal /hydraulic analysis model. The total leakage per OTSG is < 0.7 lbs/lr. It is conservative to use this value for leakage froom above tile KE rninimlurn required contact length because the effect of the added tubesheet hole constriction is not included. II

2. (cont'd) Leakage Assessment Including Thermal Hydraulic Analysis Model

• Issue:

• ...C. Is the leakage assessment conservative for volumetric intergranular attack (IGA),

given that the axial and circumferential extents (i.e., components) are independently assessed? Is there experimental and/or analytical evidence which indicates that summing the leak rates from projected axial and circumferential crack components of volumetric IGA indication give conservative leak-rate estimates?"

• Exelon Response:

- This is a very conservative treatment of possible leakage from volumetric IGA

- TMI-l has in-situ pressure tested more than 60 volulmetric ]GA flaws in the freespan, without leakage, as part of its freespan ARC

- This method was chosen for its conservatism. There was no evidence that summing the leak rates from axial and circumferential components was necessary.

(There is quite a bit of evidence to the contrary.)

- Volumetric flaw, if parted, would part in a single direction in response to the maximum stresses.

- The backing of thc tubesheet prevents a volumetric flaw from becoming a "hole".

12

2. (cont'd) Leakage Assessment Including Thermal Hydraulic Analysis Model

• Issue:

• "...c. Laboratory tests were performed by the licensee to develop a leakage reduction factor (LRF). Information from other sources indicate lower reductions in leakage due to pressure. 1) The licensee calculated the LRF by putting a clamp over an electro-discharge machined (EDM) notch and measuring the reduction in leakage. To account for internal pressure, the licensee used the zero-applied contact pressure results as the basis. Clarify how these adjustments (relative to the zero-applied contact pressure) were made and the basis for concluding they are conservative. 2) Discuss whether use of a notch is conservative when the results are applied to cracks/volumetric IGA given that cracks have much lower leak rates."

• Exelon Response:

- The clamping pressure was achieved by adjusted torques of clamp bolts.

- This method was conservative because the tubing sample was not expanded into the clamp; thus, "flattened contact" was not attained.

- The use of notches is conservative since the delta P across the "expansion" is maximized. (delta P across a crack is greater than delta P across an open notch.)

- The LRF is applied to both small and larger leakage cracks only when the resistance through the annulus is larger than through the wall. The issue of whether a different LRF should be derived and used for smaller cracks is addressed by requiring that the LRF can only be applied when the resistance through the annulus is greater than the resistance through the wall. In this way, the LRF is independent of the size of the crack. A leaking, through-wall, crack must have a lower delta P than two expanded surfaces in contact over a %" minimum length.

13

2. (cont'd) Leakage Assessment Including Thermal Hydraulic Analysis Model o Issue:

• o...e. Based on the information submitted, the NRC staff understands the following: 1)

Flaws are assumed to be 100% through-wall for the entire measured (via eddy current) extent for the structural analysis. 2) Flaws less than 67% through-wall are assumed not to leak for the leakage assessment. 3) Flaws exceeding 67% through-wall are assumed to be 100% through-wall for the entire measured (via eddy current) extent for the leakage assessment. Please confirm the above understanding. [Please note: Table 111-6 of the 1R1.4 SG Outage Report implies that the length of assumed 100% through-wall crack length is less than the measured (via eddy current) crack length. Please clarify this discrepancy.]"

• Exelon Response:

• The staffs understanding is correct for the KE indications.

• Table 111-6 of the 1R14 SG Outage Report was for freespani volmtr11etic ID IGA indications, not KE indications.

14

2. (cont'd) Thermal Hydraulic Model for the Leakage Assessment

• Issue:

"...a. Thle NRC staff has determined that the thermal hydraulic model used f-or tile leakage assessment is different than that used for the structural assessment and has not been reviewed by the staff. Considering the resulting axial loads are signiFicantly lowei (i.e., 13 10 pounds (Ibs)) than those used for the structural assessment (i.e., 2400 lbs.),

the staff has concluded that the thermal hydraulic model used for tile leakage assessment must be reviewed."

• Exelon Response:

• The thenmial-hydraulic leak modeling used for leakage assessment used actual plallt design responses, rather than assumptions.

• Exelon can provide these documents to the staff.

• Conservatisms of thermal hydraulic model for leakage assessment (driving RCS temperature down): High RCP flow, Maximum MS line break flow, lower primary temp, maximum secondary inventory, failure of feedwater reg, valve, rapid HPI actuation, actual\

perfonmance of turbine-driven EFW pump.

• Lower RCS and tube temperature -> Maximum axial loads on tubes -> Maximum crack opening displacement of a hypothetical flaw -> maximum leakage 15

2.(cont'd) Thermal Hydraulic Model for the Leakage Assessment

• Issue:

• ...b. The leakage assessment is performed for a MSLB using revised tube loading conditions (based on use of a different thermal hydraulic model as discussed above).

The loads onl the tube for the revised MSLB analysis are lower than for other accidents (e.g., small and large brea-sLOCA). As a result, it is not clear whether thle MSLB is still the most limiting accident in terms of assessing the consequences of leakage Froml these joints given the differences in loading conditions between the accidents and the different assumpltions for assessing the radiological consequences of these accidents."

o Exelon Response:

• The MSLB condition results in the most limiting nuclear-safety related consequence with respect to the joints.

• LOCAs result in decreased primary pressure and, therefore, decreased pressure dirlerences across the joints.

• Consistent with original design of the KE, and other industry expansion repairs.

16

2.(cont'd) Thermal Hydraulic Model for the Leakage Assessment

• Issue:

• "... c. In tile thermal hydraulic analysis for the leakage assessment, tlhe licensee appears to have tried to maximize tile cooldown rate to increase the axial tube loading.

However, it is not clear whether this results in an overall conservative result given it may have decreased tile differential pressure across the tubes (and the driving force ror the leakage). In addition, it appears that the leakage assessment wvas performed based on the actual loads on the tUbe at various time intervals and the leakage over these intervals were smmied. Regarding this approach, it is not clear how the licensee accounted for all of the uncertainties in all of the models (e.g., thermal hydraulics, tube material properties, PICEP, etc.) to ensure that the leakage estimates have high confidence (e.g.,

a 95'S, prediction interval at 95% confidence). Provide the details of how the leakage calculations are perforrmed."

• Exelon Response:

Conservative estimates of operator action and general plant response were key factors ill evaluiatilig axial tube loads. No attcmpt was made to decrease the pressure difference across a tulbe. Best estimates of thermal-hydraulic conditions, material properties, and PICEP properties were applied in the absence of information in the literature regarding range of variation of key parameters. 17

3. Assumption of No Growth/No Initiation of New Flaws

• Issue:

• a. .. a. Statistical tests performed to determine whether flaws are growing compare data from the current outage to data from the prior outage. The NRC staff believes the licensee should use data from the outage during which the first rotating probe examination was performed of each KE. This would ensure that potential slow flaw growth rates would be more evident. Discuss your plans to perform the statistical tests in this manner."

• Exelon Response:

• Exelon agrees to revise its acceptance criteria to implement this requirenlellt.

o Some early data may only have useable +Point data. (The pancakes weren't required if no ID IGA was identified.) Exelon will use the earliest acceptable data for determining axial and circumferential extents.

I8

3. (cont'd) Assumption of No GrowthlNo Initiation of New Flaws

• Issue:

• "...b. An extreme value test is performed to identify possible outliers or erroneous data. Erroneous data is corrected prior to using that data in the subsequent statistical tests. Outliers (i.e., indications with large apparent growth rates) are used in the subsequent statistical tests. Industry experience indicates that when a population of flaws grow, some grow faster than others. Therefore, the staff would like to discuss why the outliers are not, in and of themselves, considered evidence of flaw growth, and therefore, an invalidation of the no-growth assumption used to calculate the flaw acceptance criteria."

° Exelon Response:

• Outliers are considered evidence of flaw growth if they are "real". (Outliers may be due to such things as typographical error.)

• Outliers, if real, will be plugged.

• Exelon proposes to revise its acceptance criteria to plug any K.E.'s wvill new indications in their required expansion length that were not detected during the 1997 through 2001 examinations. "Lookbacks" wvill be used to determine whethfer indications were present in the earlier outage data.

• "No-growth assumption" based on actual results, conservatism of analytical methods, and capture of K.E.'s withill tubesheet.

19

3. (cont'd) Assumption of No Growth/No Initiation of New Flaws e Exelon Response (continued):

Growth of ID Kinetic Expansion VOLs TMI-1 SG A 0.6 0.5 x 1R14to1R15DeltaExtenl

- Extreme Valtm Box 0.4 c 0.3 e

-J XI a] 0.1 l rx~if X 1 ~I wwwl I i1 Xxz

-0.1

-0.2

-0.3

.t033 -0.2 .0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 Measured Della Axial Lenoth 20

3. (cont'd) Assumption of No Growth/No Initiation of New Flaws A Exelon Response (contintled):

Growth of ID Kinetic Expansion VOLs TMI-1 SG B 0.B 0.5 - x 1Rt4 to 1R15DdlaExlent

- Extreme Value Box 0.4 0.3 a 0.2

• 0 0.1 ---

-0.1iI 1

-0.2

-0.3II

-0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 Measured Delta Axial Length 21

3. (cont'd) Assumption of No GrowthlNo Initiation of New Flaws

• Issue:

• "...c. The NRC staff is not confident the threshold value of 0.05 new indications per kinetic expansion examined is truly indicative of an active degradation mechanism. In addition, different criteria for circumferential and volumetric degradation may be appropriate since they are potentially two different populations. Industry guidance on this subject would indicate that one new crack results in a declaration of active degradation. Discuss why the size of the indication is not a consideration or why comparisons to prior data are not sufficient (i.e., if it cannot be seen with hindsight, it is new). Lastly, based on the information provided in Table B in Section 3.2.1.9 of the August 16, 2004 submittal, it could appear that degradation is active with an initiation rate of 0.03 indications per kinetic expansion. Please provide a discussion of the above issues."

• Exelon Response:

• Exelon proposes to revise its acceptance criteria to plug any K.E.'s with new indications in their required expansion length that were not detected during the 1997 through 2001 examinations. "Lookbacks" will be used to determine whether indications were present in the earlier outage data.

• TMI-I intends to revise the report to require 100% of the inservice kinetic expansions in both generators be examined during each planned steam generator examination. TMI- I will revise tile subject report section as necessary to dovetail with this revision.

22

3. (cont'd) Assumption of No Growth/No Initiation of New Flaws

• Issue:

• "... d. The licensee indicated that some KE indications "drop out", or disappear, each outage. These should be discussed in more detail, including: examples of several indications (e.g., largest, smallest, theory on reason for disappearance, etc.); if threshold-of-detection is ascribed to be the cause of disappearance, be prepared to discuss the criteria for the threshold-of-detection.

• Exelon Response:

- Exelon proposes to revise its acceptance criteria to plug any K.E.'s with new indications in their required expansion length that wvere not detected during the 1997 through 2001 examinations. "Lookbacks" will be used to determine whether indications were present in the earlier outage data.

23

3. (cont'd) Assumption of No Growth/No Initiation of New Flaws

• New indications ("drop-ins") and "drop-outs" are small:

Typical New Indication (Tube A 82-24; 2003 data). Note Horizontal Plot

- " I .-, Iot'l II _o:4 ,'^r','?

7is-. ;, .WS i:';; -~~~~~~~~~~~~. ssS £-i,!AlssJi&$blFtJ#;ln4w

. --- - --- -.-- l. . -~t___________________

rlo. Layo.st 5tI WLI L9III If SkI tLiC L114S lll 'E val "III% 11 SI Ntt (IU I i I .t..I +/-!!t - I 21yt1 t2j I}t

'-1'-- - -

Cr tlt Vp ltIhK Vc 19I t L it VFP ll

, . CI,In

• 1.9O - I-Z . EtL

• 3.9J,

'4 lit,~ i:A iltI:;, zIrIi!

11 1 v?i '.'I.i~rji*t  ;.i.~i:FtvtO ,.i.~ ltesux I. t~i-7. t  :.:' tr-I1:::..  : . L1 t Vlie:tlT Fts/SWan48I-Y st4 rLw XPnttki ZA.t.A3 I t - - I _ _-: ri: .5 SWi-nisrpi IWfjltY I H1FIZ MT0I UXISsTCHI :& -

af I, r I mlf In 5:!2 Clpr:

1.s-I

_E.T j mc aSCitl ut

<PL1I) F OT05

'M I g yrU 1.02 I 0

"'II lT'WSIT

.. __ .2.'

91 41 j *2l 1.s.2 clo I -nr

?I 13D.5 1.02 u

.1 clot ii FFUl l .10 mirAs lilhit 9

0 4  ;

27;0 w

IF*

' ' I-_,,

H I -

ANr l

Fitt I -'. -

1QQIC 24

3. (cont'd) Assumption of No GrowthlNo Initiation of New Flaws a New indications ("drop-ins") and "drop-outs" are small:

Typical New Indication (Tube A 82-24; 2003 data). Note Vertical Plot Uln taynmit . IIWLI iIS SEIOIL(LUMS .l Ikl WUII IMS Cii IiIS r4] ull Dal Cl Ww._-_II U V.. I VA 180 VI . 1 cm 0K o0

.. I'% . 1.90 ,- C!II 4IL

• 1.0 EIL S _L 11K ILF E111 *(fill . , , , l . z5

_ _ 41001,550 I ls tev fl ID t an.w b 1tm Av I 13{1.5 *1-0 l1.

n R-_ ER

-- lS tBT;fM I Tl- qSI .

138_ =IPC

- -0.1 8l[A$ F

___ ___ la_

II 25

3. (cont'd) Assumption of No Growth/No Initiation of New Flaws

• New indications ("drop-ins") and "drop-outs" are small:

Typical New Indication (Tube A 82-24: 1997 data). Note H-lorizontal Plot

!.A,'._.z:-.\@,__

17un Laymiti UT VW1LullS SE1 till. LtMfS .~l bEI % )I (tils1E "le. tlIVM.

I'sttil Dat Vpp H.IR Vx. CLR V lC tA ilt

, . IL .1.48 l (IL

• 1.40 0.9;-

fllla~:fl` Xr(s x~.Texi~

Si I11 ISTAI fl I r't,/5cw4 vl MillS i .PZox

( -iuai r

_lI l'T lP:21 Pr 0.9 LSCM 1W' 995 V.02T

.a _ ri .. . u... . f.

-1 - R.1EI o I 26

3. (cont'd) Assumption of No Growth/No Initiation of New Flaws New indications ("drop-ins") and "drop-outs" are small:

Typical New Indication (Tube A 82-24: 1997 data). Note Vertical Plot rrlba Loyatit r 1TZ InSM£&l (uL(UWS 1(1I¶LEt UI11 1LI (1.fls

! XE11 in!

.WP Ht.9 CI 1 H LIL *t 1.4 GR [(IL X Is 1.48te r I

_ _ ~~~~~~rtltfOrF C tltt.cv>l=6 XTra.!l;) Utraw- Xl)t,51) .Z~t-JOG _ t* - El

-- ilral 11111o IIMIIFY IMIWl101 (AW.411101 >li rcr OF r (Tv r . _ PI? nPl 0.9 CSfbEI lo.)

-0.?T ri . Sci Itf.1 J-IFF(L1

- 3 s*,s~~ mls _ Fail j _.0l

~M¶r,rl-~t

.=_

II 27

3. (cont'd) Assumption of No GrowthlNo Initiation of New Flaws

• I-lorizontal Plot Fron Calibration Stanclald 20%, 40%, and 60% TW ID CircuLm1erential Notches

-. 1 -- l-I.............. ..... .  :- .- '-.-  :* - -

-I - -I Ul -.' II I FlII Ltyault i S l 1W l !1 - SIN stI El 5.1 MU1s V illS !1 III. U14S1 I i~JIJNull Dot, 1ES _ar Cl 5'P RIP Vx CrAl 1C WR , CA ILVi I.1.? wiots 18 d6g 271t _

-0. 95 4. 1413 t 4114Z 1113 Xl,5 , :..*o 15:2 f<18  !

4_ _ o-l. I tl T _'tl-GSF I __

- ( 11 1l) 1101

-u 0..515 b W1LE yI5C1L 0 CI 270 ~.. r courP

_ _- ~

__ ____ __ __ __ __ __ __Fall 113 . 2 .01+61w Ui o1l0 08.9 kc S.'_J_ flk

_ I M

_ C__ _)._ _ _ _in 28

3. (cont'd) Assumption of No Growth/No Initiation of New Flaws

• Vertical Plot From Calibration Standard 20%, 40%, ald 60% TW ID Circutmlferential Notches lla. Layoldt

~~61 Si hl 13411 E LIWll1 5 (J .s; 61 (l;tss.1 ;ilt

II (i Njr.S SE . 1I lls SET (I 1'AS 4, H ull Dat 2311.;VI. 12( lII

,.6l0 CA IE Filter (IT Fu/'Scrn73 Xlr".n Ylramuj IftfzhSG 2totiS *I

,.a ifH (

ilFIF low (iFl 15ojo:2

• C161.

(fit'" 21e1

_ 1

• [1tOT) blUC

-o 20(8 TO(W

_.t Iot

• 0.0440 c'ili.

A54(ir.

,roi tO T

U.8 _

MG 10 0,351n MIA TO WIFE2

. . .oI Mt 270 29

3. (cont'd) Assumption of No GrowthlNo Initiation of New Flaws

• Hlorizonital Plot Firom 1997 Tube Pull ID IGA (0.030" Axial x 0.018" Circ Length b)y Metallography) 2 300tPrytr6 4llt~t S 1 We %1.Iiil;S 1Ch 135A Me III Caf I £315r CA-- c (k5 Utt/Sc-11, ... 4 Lft O

'A21 l IU 01 l CfF P1:2 UPI

• 41'.0I)FtCTO

-1.2J i,-,1n23

• StI11 Y!1db

- oct;r i-irmy 27 /'U g 142.0 -

WSf 1 105. I ilt5 miT

_ ~ ~ ~ ~ J _ _Jb.o_

3(0

3. (cont'd) Assumption of No GrowthlNo Initiation of New Flaws

• Vertical Plot From 1997 Tube Pull ID IGA (0.030" Axial x 0.018" Circ Lengtil by Metallography) rile Layuet SI 'KA111tt1S 511 [A IIC," Gl U %ILISS .,,

5r .. '

ItrrSl '

r15i Nu!l~l Dot Gi 23.4)'!? 1O6'SYE CS ciF e l1 :5 W l J n - C to Ill v.# GGA

. II Filtte:CFT Pt&,'Scr.71 K)5ar-A. aiT,an..SJS-kGu7P.t.732 I 19.0

-1.23 , CssI Ut.P .

1.23 _ , sid' stil) U10 900 IC 142.0 rim1 M'f.Ic Sinil NO1IUIS-70 2.- 1190 so 252 31

3. (cont'd) Assumption of No Growth/No Initiation of New Flaws

• Largest drop out was due to change in location in tube:

Tube B 14-48; 2003 data (AKELmin = 5.2")

.1 ra*=T - -. . . ^- .Z,; . ....I. - -, I"

...-. . -1 I ___ -  : f. L4 4.113ii,- 4r _. , :t,

- -. . .-, '. n, .:' -,

III

7, zj! t i;. i. . 1:! 1; -. . I rufn . t.Dyntif

1. Ci , 4 .. !i i,.

(I.-*6.44 0.,1 L 6.54

-P v.-

-0* 67 . .- .-.- r.8l~t: -ca Pt~U;m:J 1--

h(1(ry I wn ntf I muiuij~tio

- qviillt0

-mm 05:2 *CILE 0.6? I ESCGdl IT101 Stu? SuffC X!fC-E MA IE 101N C2.0 Lo2.

2706 Ml I t-UmSE ton-

-O.EC FI *i II 145.8 tilt oot. AXIIL lfl 1(111 PUT1 in fall I.-I 11 II Of . _ l  %) lo" 271, 0 N I File T.OI.

l _ _

- - . . 4 - -a . -I 32

3. (cont'd) Assumption of No Growth/No Initiation of New Flaws

• Largest drop ou.t was due to change in location in tube:

Tube B 14-48; 1997 data (AKELmin = 5.2")

!;" -. I "I - ;" , , "; -V, -. 4--.,

- " -- - --, '.-'--r

, -'- ' j; '- II I- I L, 'r - 'j -.-, - .. I, -"- - I- "I -- - -if .1 I - is, i.' 4""' 'i ' " .  ;' . I U ,AM SLt ls V U11WlL 'AES l *UiAUlllS 1-rEil Ishyn I - Sfl fit tIMSt i3JKl NMiluDat Nk

~I

-_ Cs W. E Wi VP V.u H Go IE4 VR P R H K 11 (A 11 I)

I._j ,1l Er " *- 5.20 ,, I EIL

• 5;Zt

_l-.;,, 1l

-FWI7; -1tt> lYrU}E~wi~sZ - -- .. . I 9r1M aIuaO iwfhIPYxir FIlI l't'r Iii; l (fF r IF lF (FF l IfF I ______

I taw IW tawl I (FRi 4./-) j !allECIt I M-) -I -r(o

-0,59 Xl~rtlE.l Y5st11F

.3.0 .1.'.

ScifsCti l Iff5EI

.. _ . ~ I VR;

.71 . .

CIFrl CIFXS 1,'.JU RKLt. I' "Irst.

FF!I

~ ___

nxlfL 10

. _ _ -0 0 .

_ _ =.

_70 1R

_I Fil Tools r - ._-

Note: 1997 (lata was acquired on the push to comply with "Points of Light" issued by EP1RI. All subsequeent K1E dn(a has been acquired on the pull and similar locating deltas have not been identified.

33

3. (cont'd) Assumption of No Growth/No Initiation of New Flaws Largest 2003 "drop in" was due to previous 1999 MCI called as 2 SCI's in 2003:

Tube B 101 -9; 2003 data Elle Laynout U! %Wtis !1 IL UMS IU s $E-l M. u-.W

[l iii3§J Nnilt D7at\\

%IP HR 9 ClW' 1V. VpPP1 1 jIa¢

• l4 EIL

• L3S i . lL El 1.33 L

IT_

Ih "nrFr Fllte:rFF FtL/Sex7J Xfruns=-2YI,.wd kPvt5317Ratr IIF 0)4HN 2Fo CM591TC1 :ftuo F (rF ,5:2

L.

rua

• ClFf.

770 o I__

1.4 .._.) _, . _ .

Will St ar XWAE 0-SUE J- L r nioi ii lnE Cu EIP tCI

' 0 rr~ii To 21.1jf irlfcre. iaXl.

27 F0ile Tools jfl1 34

3. (cont'd) Assumption of No Growth/No Initiation of New \

Flaws

• Largest 2003 "drop in" was due to previous 1999 MCI called as 2 SCI's in 2003:

Tube B 101-9; 1999 data riElgla ntit SE. WI&S I IUIS ii SEI IIL LUES SEI

• l UHIS'A tt Ui S

- -l rim

_ atIeR v!l IL . WSp V!1. IHR

• I j4

_ LF EI ' 1.76 1 _ .

In Eta

• t.7C ESWI 1

_ Ftlttr~tfF Fl!/5eern7 11 yr~sn-2 llra.O 0w.t~ 7Pot=191 @l t2 Cilittl I IF j1 ..43 SID 10 hWX 270 0FileTool 35

4. Structural Integrity Assessment Basis for MSLB Axial Load

• Issue:

"...a. The licensee's August 16, 2004, report states that the 3140 pound axial load corresponds to an axial membrane stress of 49.5 ksi (thousand pounds per square inch) and a design-basis tube strain of 0.16%. The licensee further states that tubes with a lower bound yield.'

strength and nominal geometry will experience load relaxation (from 3140 lbs.) due to yielding, resulting in an axial load of 2400 pounds. This load is used to determine the size of the needed "defect free zones" in the KE.

• The "design basis" tube strain of 0.16% was determined assuming that all tubes were behaving elastically (Topical Report BAW-10146). The corresponding axial membrane stress of 49.5 ksi exceeds the nominal yield strength of the tubing at a MSLB temperature of 235 degrees F. Had the actual stress strain properties of the tubes been assumed in the licensee's analysis, rather than elastic properties, the resulting tube strain could exceed 0.16% since the tube bundle and tubesheet would provide less resistance to the desire of the SG shell (with temperature in the range of 520 to 575 degrees F) to expand axially relative to the tubes. If credit is taken for load relaxation in the tubes due to yielding (as is the case for TMI-1), why is it not necessary to also consider the corresponding increase in tube end displacements (and, thus, tube strain) when determining the axial loads in the tubes? What are the tube end displacements and tube strains under MSLB temperatures if a realistic distribution of stress/strain properties are assumed to exist within the tube population? What would be the effect on the axial loads and minimum required defect-free lengths assuming use of the realistic distribution of stress/strain properties? (Continued on next slide) 36

4. (cont'd) Structural Integrity Assessment Basis for MSLB Axial Load

° Issue: (Continued from previous slide)

• What factors of safety are applied to the axial loads to ensure the joints don't slip when determining the necessary size of the "defect-free zones? What is the technical basis for the safety factors? [Note, a factor of safety of 1.0 is reasonable for thermal loads behaving as secondary, as acknowledged in the structural performance criteria in the latest Technical Specification Task Forcer (TSTF) submittal from NEI of the generic license change package and in the forthcoming revision to NEI 97-06, "Steam Generator Program Guidelines". But this safety factor criterion is based on the assumption of elastic analysis, recognizing that load relaxation will take place prior to failure. A safety factor of 1.0 is not appropriate if one\

is taking explicit credit for load relaxation, since components at the point of incipient failure under design-basis loadings would be contrary to ASME Code,Section III and Section Xl philosophy.]."

37

4. (cont'd) Structural Integrity Assessment Basis for MSLB Axial Load o Exelon Response:

Recent scoping calculations addressing tube end displacement for a tube bundle witih only low yield strength tubes show an increase of 10.5%. Strain hardening for low yield strength material is negligible for this increase in tube end displacement. The resulting load increase is negligible.

• The factor of safety against slip is at least 1.8. This factor of safety would increase as the axial load is reacted in the tube joint.

38

4. (cont'd) Structural Integrity Assessment Basis for MSLB Axial Load

• Issue:

b. The licensee states that the design-basis MSLB load for the SG tubes of 3140 pounds was determined by assuming that all tubes remain fully elastic. It was necessary to adjust the results obtained for the high yield strength tubes and greater wall thickness for consideration of minimum yield strength and nominal wall thickness tubes that may be present in the steam generators. Additional details are required for the staff to fully understand this adjustment.

• Exelon Response:

Tile adjustment refers to two issues:

- The first is to bring the analysis model that was developed to benchlimark the pre-qualification test results into alignment for use with a low yield strength tube having nominal wall thickness.

- Tle second adjustment involved developing a representative low yield strength stress/strain curve from actual stress/strain data obtained using a TMI OTSG tibe specimen. This ad justment was accomplished by shifting the tube specimen stress/strain characteristic downward for the same permanent off-set. Using tile design basis tube strain (0.1 6%) and tile stress/strain CuIrve for the lower bound yield strength material, the maximum axial load that must be considered is 2400 lbs. This result adjusts the 3 100 lbs design basis load to 2400 lbs.

39

4. (cont'd) Structural Integrity Assessment Basis for MSLB Axial Load

• Issue:

What are the dimensional tolerances for the nominal 0.625" diameter, 0.034" thick tubing?..."

• Exelon Response:

- Allowable tolerances (based on tubing Purchase Order)

- Outside diameter 0.625" plus 0.005", minus 0.000"

- Wall thickness 0.034" plus 0.005", minus 0.000"

- Min wall and miii. yield strengths were used for analyses

- Tube pulls have validated these dimensions (e.g., 1997 tube pull samples typical O.D.'s were 0.625" to 0.629"; typical-I.D.'s were 0.554" to 0.555".)

40

4. (cont'd) Structural Integrity Assessment Basis for MSLB Axial Load o Issue:

"...What are the estimated nominal, upper bound, and lower bound yield strengths of the tubing at room temperature and at the temperature associated with the maximum MSLB load (i.e., 235 degrees F as reported in BAW-10146) ?"

o Exelon Response:

Section 2.2.3.1 of GPUN TR 007, "Three Mile Island Unit 1 Once-Thlrough Steam Generator Repair: Kinetic Expansion Technical Report", (March, 1983) provides TMI-l tubing yield strength information that was used to develop tile ICE acceptance criteria.

>> "...Tubes that are positively traceable as being in tile TMI-I steam generators have 0.2% offset yield strength values -from 41.0 to 6 1 .1 ksi. Tubes that may be in the generators, but which are not individually traceable as such, have 0.2% offset yield strength values from 41.0 to 64.9 ksi."

>> 4l1 Icsi tubing was assumed for tle derivations/calculations or'the KE acceptance criteria.

>> Thle reduction in yield strength at MSLB temperature should nlot exceed approximately 5%. This is compensated by not including thermal tightening in the structural analysis model, and other conservatismls.

4. (cont'd) Structural Integrity Assessment Basis for MSLB Axial Load

• Issue:

"... It is not evident to the NRC staff, based upon its review of BAW 10146, that the 3140-lb. MSLB load is based on a larger than nominal tube wall thickness as is suggested in the licensee's words above. For a nominal 0.625" outside diameters (OD) tube with a nominal 0.034" thick wall, the cross-sectional area of the tube is 0.0631 square inches. BAW-10146, Table 5-6, indicates that the 3140-lb. load is based on this same nominal cross-sectional area. Provide an explanation for this apparent discrepancy. Provide a description of tube wall dimensions assumed in the calculation of the 3140-lb. MSLB load."

• Exelon Response:

• Exelon assumes the words that the staff is referring to are in the sentence on Parge 8 of thc KE report that rea ds:

- "..It vas necessary to adjust tie results obtained forihigl yield stircigthl til)es and greater tvall thickness for consideration of minimiuimi yield strength and nominal wall thickness tubees that may be present in the steam generators."

Th'lle load results were not adjusted. What was adjusted were the results of the original 1980's pull testing. (What was adjusted was the finite element analysis model so that it was applicable to niininluni wall thickness and lowest yield strength tubing. Pull testing was not done witih minimium wall thickness or lowest yield strength tubing.)

• Exelon did not intend to suggest that a larger than nominal tube wvall thickness was used in BAW 1 146.

What was intended was to point out that it was necessary to adjust the results of the pre-qualification tribe pimll tests because those tests involved both hligher-than-minimium yield and larger-than-nominal wvall thickness tubes.

• Exelon will revise the report to clarify as necessary. 42

4. (cont'd) Structural Integrity Assessment Basis for MSLB Axial Load o Issue:

"...The pullout resistance of the tube from the tube sheet is a function of the contact pressure caused by the expansion process, the effects of thermal tightening (differential thermal expansion between the tube and the tube sheet), tube internal pressure, and tube sheet bow. During a steam line break transient, the tube internal pressure and the tube temperature are changing. In addition, the yield strength of the tube changes with temperature. The yield strength of the tube affects the system response (e.g., the applied load due to load relaxation). It is not clear whether the analysis provided truly represents the most-limiting conditions of the transient. The licensee should confirm that the most-limiting point of the accident was evaluated for the most-limiting situation (high-yield strength tubing/low-yield strength tubing) using the most-limiting input parameters (lowest contact pressure/pullout resistance of any of the test data). This approach is consistent with how we have assessed other similar amendments. The goal is that all tubes have adequate integrity so worst-case assumptions are generally made."

• Exelon Response:

• MSLB transient analysis was performed over time, including primary-to-secondary delta 1', tube axial loads, etc. Leakage was calculated over the duration of the transient, assuming minimum tube yield strengths, elc.. A single point in time (i.e., a "nmost-limiting point of the accident") was not used; transient analyses were performed up to a 1410 minute duration.

• Most limiting primary-to-secondary delta P and tube axial loads do not occur at the same moment during

[lie MSLB transient.

• Low yield strength material results in the lowest pullout resistance. I-lighi yield strength material results in proportionately higher pullout resistance. 43

• Refer, as necessary, to Slide 15 conservatisms.

4. (cont'd) Structural Integrity Assessment Determination of the Limiting Accident e Issue:

In determining the limiting accident, it is not clear what factors of safety were applied under all events considered (e.g., LOCA, normal operating, feedwater line break conditions, etc.). Question 4a., above, focuses on the factor of safety used in assessing the MSLB accident; however, it is not clear whether another event may be more limiting if appropriate safety factors were used (this question assumes the correct safety factors were not applied)."

• Exelon Response:

• The MSLB condition results in the most limiting nuclear safety consequence with respect to leakage through the joint.

• Slippage at the upper expansion does not result in unlimited tube clisplacement due the presence of the lower tube end expansions and ivell.

44

5- Consistency with Recent Industry Experience

• Issue:

".Analysesof kinetically expanded joints in other designed steam generators has indicated that "defect free" lengths greater than what is being proposed for TMI-1 are needed to ensure structural and leakage integrity. In addition, the contact pressures for the TMII-1 kinetic expansions appear to be significantly larger than those at other plants with KEs. Therefore, please compare and contrast the expansion process used at TMI-1 to the KE processes used at other plants to help the NRC staff understand the potential differences (e.g., joint tightness, resistance to cracking, etc.)."

• Exelon Response:

• The kinetic expansions were detonated thrice to maximize their contact pressure.

(Transition designs were investigated to minimize residual stresses.) The first of the two detonations was intended to expand the tube into contact with the tubesheet. The second detonation was intended to maximize the interference and, lhence, the residual contact pressuLre.

• 1980's achieved design objective was 99% confidence that 99% of the kinetic expansions had pullout strengths of greater than 3140 lb. tensile load.

45

5. Consistency with Recent Industry Experience

• Exelon Response (Cont'd):

• Comparison wvith hydraulic expansions at an Exelon plant:

Hydraulic expansion:

Avg. force to displace 0.25" was 541.16 lbs/inch of expansion KIE:

Avg. force for "initiation of tube pull motion" for low-yield tubes at 330F was 4310 lbs for 6 inch expansion, or about 720 lbs./inch of expansion

• Comparison with explosive expansions at some other U-tubed plants:

- Structural-required length was 2.25 to 4.25 inches from the secondary face or the tubesheet. (Minimum yield strength at these plants is 35 ksi). These are similar to TMI-1 required expansion lengths.

- MSLB is also the limiting transients at those plants.

- Required lengths to assess leakage are much longer (i.e., up to about I I") at these plants because ". ..the greatest dilation is at the secondary face of the tUbesheet reducing linearly until the tubesheet flexure results in a compressive force below the axial mid-plane of the tubesheet."

- Thle TMI-1 KE are located near the mid-planes of the tUbesheets. MinimuILm yield strength at TMI- 1 is 41 ksi.

46

6. Inspection Practices/Techniques o Issue:

"... a. On page 23 of the August 16, 2004, report, the licensee indicates that if "localized" degradation occurs at a KE, then the scope of the inspection will not be expanded to 100%. The specific example given was damage from a maintenance tool. If growth or new degradation is occurring, the scope should be expanded to 100%. It is not clear what other "localized" degradation could be occurring.

Discuss the intent of this statement."

• Exelon Response:

TMT- I intends to revise the report to require 100% of tile inservice kinetic expansions in both generators be examined during each planned steam generator examination. TMI-1 will revise the subject report section as necessaty to dovetail with this revision.

This is an approximately' $1.5M and 3-day duration commitment during the next 2005 outage. Similar additional costs are expected to be incurred for tile 2007 scheduled inspection.

47

6. (cont'd) Inspection Practices/Techniques

• Issue:

"... b. On page 23 of the August 16, 2004, report, the licensee states that if growth of existing degradation or initiation of new degradation in the KE region is detected, then an examination of 100% of the KEs in the affected generator(s) will be undertaken. However, the proposed statistical tests combine data from both steam generators because there is a limited data population in the "B" steam generator. Therefore, the NRC staff assumes the 100% scope expansion would occur in both steam generators. Please confirm this assumption."

• Exelon Response:

- TMI-I intends to revise the report to require 100% of the inservice kinetic expansions in both steam generators be examined during each planned steam generator examination. TMI-1 will revise the subject report section as necessary to dovetail with this revision.

48

6. (cont'd) Inspection Practices/Techniques

• Issue:

"...c. The licensee states that the eddy current measurements always result in conservative overestimates of the flaw size. This is attributed to lead in and lead out affects and the flaw being small in comparison to the coil field. How did the licensee confirm that measurement uncertainty is not a function of flaw size (i.e.,

is there a flaw size beyond which the flaw size could be underestimated (at a 95%

confidence level))? In addition, did the licensee confirm that the 95% confidence levels on uncertainty for cracks and for volumetric IGA (i.e., non-notch specimens) when analyzed separately from the notch data still result in overestimates of the flaw size?"

e Exelon Response:

The average measured length for tile sizing study actual PWSCC and ID ]GA flawvs still indicated an overestimate of flaw length.

• TMI did not do a study to determine where eddy current measured length may become non-conservative due to probe coil size because the flaws encountered at TMI are relatively small and the sizing study results generally bounded the in-generator conditions.

There has not been a great deal of industry study on ECT performance flor short PWSCC flaws in expanded tubing.

• During last outage (Outage 15R) no indications measured greater than 0.60" axial or circ length. Out of greater than 1100 indications measured only eight had a measured circ length greater than 0.40" and none exceed 0.40" axial length.

49

S Exelon Response (continued):

- Not vety important where the sizing error becomes non-conservative because TMI- I K.E. flaws are relatively small:

Measured K.E. Flnw Sizes During 2003 Outage Inches Vol Axial Vol Circ Circ Circ Ext 0.00 to 0.10 230 92 0 0.11 to 0.20 715 769 34 0.21 to 0.30 47 126 54 0.31 to 0.40 3 7 15 0.41 to 0.50 0 1 4 0.51 to 0.60 0 0 3 Total 995 995 110 1105 50

• Exelon Response (continued):

-Actual OTSG flaws in the sizing qualification are as follows:

• Six lab-grown PWSCC flaws ranged from 0.08" to 0.32" in length

• Nine TMI ID IGA flaws ranged from 0.02" to 0.066" axial length and 0.016" to 0.032" circ length. (Eddy Current generally measured 3 to 7 times larger than actual.)

Measured average of the actual OTSG flaws still indicated a conservative measurement.

51

6. (cont'd) Inspection Practices/Techniques o Issue:

"...d. Discuss the inspections performed of the parent tube/sleeve assembly in the upper tube sheet region. Describe the flaw acceptance criteria utilized for the portion of the sleeve/tube assembly located in the tube sheet."

• Exelon Response:

• All TMI-I sleeves are 1-690.

• Flaws in TMI-1 sleeves are 'plug-on-detection'.

• The parent tube, behind the sleeve in the kinetically-expanded region, has been removed fiom service and is not examined.

52

7. Other Issues o Issue:

"...a. The proposed reporting requirements should be supplemented to include the '

KE length and the tubesheet radius associated with each tube with degradation in the KE region."

o Exelon Response:.

• Exelon agrees to revise the report to require this information.

53

7. (cont'd) Other Issues

• Issue:

"...b. Discuss the axial loads simulated during insitu pressure tests for the purposes of demonstrating structural and leakage integrity."

o Exelon Response:

• Insitu pressure tests have not been performed on kinetic expansion flaws (--

due to the presence of the tubesheet 'behind' the flaws and questionable ability to seal in the damaged tubing above the kinetic expanlsions.)

l Numerous freespain flaws have been in situ pressure tested, including some with additional axial loads.

• Axial loads, when applied, were consistent with loads resulting from the thermal-hydraulic analyses for leakage.

54

7. (cont'd) Other Issues o Issue:

"...c. The number of tubes in Section 1.3.2.39 of the revised Updated Final Safety Analysis Report pages does not add up (i.e., the number of tubes in-service versus the number of tubes plugged do not correlate). Discuss this inconsistency.

o Exelon Response:

The FSAR text reads:

"... Of the 31,062 tubes in both steam generators, 29,838 with no known defects below 16 inches from the primary (top) surface of the UTS were repaired by kinetic expansion and returned to service. A total of 347 tubes had been removed from service by plugging prior to the start of the kinetic expansion repair program.

An additional 1195 tubes with greater than 40 percent through-wall indications 16 inches or more below the primary surface of the UTS were removed from service by plugging after kinetic expansion. Additional tubes may be plugged each refueling outage and a report filed with the NRC as required by Technical Specifications...."

• Exelon proposes to revise these sentences to both clarify and update them.

55

TMI-1 MSLB ANALYSIS FOR GENERATING INPUTS TO DEFINE THE OTSG TUBE LOADS (RAIs FROM SRXB)

Issue:

"...1) Please confirm that the methodology and input assumptions used for your MSLB analysis for generating inputs to define the OTSG tube load are consistent with that used in the MSLB analysis documented in Section 14.1.2.9. Identify any deviations from the licensing basis methodology, analysis assumptions and initial conditions and provide proper justification for such deviations."

• Exelon Response:

• MSLB analysis for OTSG tube loads was not the same as the MSLB analysis for DNBRlContainment Response, which is described in the bulk of Section 14. 1.2.9.

• MSLB analysis for tube loads deliberately used conservative conditions for the steam generator tubes.

- "MSLB Analysis for OTSG Tube Integrity", GPUN Calculation C- 1101 -900-E6 10-061

- "TMI Main Steami Line Breal at 2569 MWt", GPUN Calculation C-I 101-900-E610-043

• There are a number of differences. For example, in MSLB for OTSG loads calculation, BOL reactor kinetics are used to minimize the temperature of the primaiy. In MSLB for DNBR/Containnment response analyses, EOL reactor kinetics are assumed.

56

TMI-1 MSLB ANALYSIS FOR GENERATING INPUTS TO DEFINE THE OTSG TUBE LOADS (RAIs FROM SRXB)

Issue:

"...2) Provide the justification for why a reactor trip setpoint of 1900 psig plus a 30 psi error will result in a conservative calculation with respect to SG tube temperature for OTSG loads."

• Exelon Response:

- Tube axial tensile loads are aggravated by a cooler primary and warmer secondary (tube-to-shell delta T is maximized).

57

TMI-1 MSLB ANALYSIS FOR GENERATING INPUTS TO DEFINE THE OTSG TUBE LOADS (RAIs FROM SRXB)

Issue:

"...3) In long term analysis, operator actions are credited in the analysis. Please confirm that all operator actions credited in this analysis are consistent with the plant emergency operating procedures (EOPs) at TMVI-1 and that the reactor operators are properly trained on the plant simulators for these operations. Justify that the time allowed for operator action is adequate, and has been verified on the plant simulator."

• Exelon Response:

• Two types of operator action assumptions/credits were made in the analyses:

- (1) Operator actions credited in analysis for successful mitigation of the event, and

- (2) Analysis assumptions about operator actions which ensure that the analysis produces a bounding conservative result.

58

TMI-1 MSLB ANALYSIS FOR GENERATING INPUTS TO DEFINE THE OTSG TUBE LOADS (RAIs FROM SRXB)

• Exelon Response (cont'd):

• Terminating EFW within 10 Minutes is clearly Type 1. Controlling SCM at 75F or higher for RCP NPSH to ensure that OTSG tube leakage is maximized is clearly Type 2.

There are two Type I actions:

- Terminating EFW and controlling TSDT

- Terminating EFW with 10 minutes of a MSLB is accomplished lAW RULE 3 (part of EOPs). Thle time critical aspect of this action is recognized in the EOP prograni (I00I E Encl 8), and the performance time is re-validated if any changes were made to the EOP which could effect this performance. Controlling TSDT is required IAW Guide 14 (part of EOP). There is no specific time requirement for this action.

• Operators are regularly trained on the EOPs.

59

TMI-1 MSLB ANALYSIS FOR GENERATING INPUTS TO DEFINE THE OTSG TUBE LOADS (RAIs FROM SRXB)

Issue:

"...4) Please compare the transient curves between the new analyses for OTSG tube load and the licensing analysis in Section 14.1.2.9 of FSAR. Identify each deviation and provide proper justifications. (We noted quite a few differences.)"

• Exelon Response:

- We assume the staff is referring to Figures 14.1-22A and 14.1-22B of the FSAR, and the differences between those transient curves and the transient curves in the '

Kinetic Expansion Acceptance Criteria.

- MSLB Analysis for OTSG theoretical tube loads/leakage versus MSLB Analysis for DNBR and Containment response. (More than 1 MSLB analysis since worst case for tube loads and dose is not always worst case for DNBR and containment response)

- If the above is the NRC issue, Exelon agrees to clarify the FSAR Section(s) as necessary.

60

TMI-1 MSLB ANALYSIS FOR GENERATING INPUTS TO DEFINE THE OTSG TUBE LOADS (RAIs FROM SRXB)

• Issue:

5) In Section 14.1.2.9 of FSAR, it is concluded that the results of the analysis confirm that the maximum temperature differential that occurs in the OTSG does not produce excessive stress, and steam generator integrity is maintained.

Discuss why this 100 second analysis supports such a conclusion and you[r] new analysis require[s] both 10 minutes and long term analysis to assess the SG tube integrity."

• Exelon Response:

• Original 100 second analysis supported the statements in the FSAR. This analysis was performed for DNBR and Containment response.

• 1997 longer term analyses (I.e., 600 sec and 84600 sec) were performed to determine OTSG tube stresses and tube leakage was assumed for the "Environmental Consequences" section of the FSAR (Sect. 14.1 .2.9, c).

61