ET 08-0030, Response to NRC Requests for Additional Information Related to License Renewal Application - Closure of the Metal Fatigue Analysis Open Items

Response to NRC Requests for Additional Information Related to License Renewal Application - Closure of the Metal Fatigue Analysis Open Items

ML081440051
Person / Time
Site:	Wolf Creek
Issue date:	05/15/2008
From:	Garrett T Wolf Creek
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ET 08-0030
Download: ML081440051 (28)

Text

W@ELF CREEK

'NUCLEAR OPERATING CORPORATION Terry J. Garrett Vice President, Engineering May 15, 2008 ET 08-0030 U. S. Nuclear Regulatory Commission ATTN: 'Document Control Desk Washington, DC 20555

Reference:

1) Letter ET 06-0038, dated September 27, 2006, from T. J. Garrett, WCNOC, to USNRC

2) Letter ET 08-0007, dated January 25, 2008, from T. J. Garrett, WCNOC, to USNRC

3) Letter dated February 1, 2008, from P. T. Kuo, to T. J. Garrett, WCNOC

4) Letter dated February 28, 2008, from T. Tran, USNRC, to T. J. Garrett, WCNOC

5) Letter ET 08-0019, dated March 26, 2008, from T. J. Garrett, WCNOC, to USNRC

6) Letter dated March 31, 2008, from P. T. Kuo, USNRC, to T. J. Garrett, WCNOC

Subject:

Docket No. 50-482: Response to NRC Requests for Additional Information Related to Wolf Creek Generating Station License Renewal Application - Closure of the Metal Fatigue Analysis Open Items Gentlemen:

Reference 1 provided Wolf Creek Nuclear Operating Corporation's (WCNOC) License Renewal Application (LRA) for the Wolf Creek Generating Station (WCGS). Reference 4 requested WCNOC to provide additional information regarding Metal Fatigue Analyses so the NRC can complete its review of WCNOC's LRA. Reference 3 established the issues documented in the request for additional information (RAI) as open items (01) in the Safety Evaluation Report (SER). Reference 5 established a due date of May 15, 2008 for WCNOC's response to the RAI. Reference 6 acknowledged the May 15, 2008, submittal date. WCNOC and NRC personnel met in Rockville, Maryland on May 1, 2008, to establish the form and content of the submittals for confirming calculations and information for closure of the Metal Fatigue Analyses open items.

P.O. Box 411 / Burlington, KS 66839 / Phone: (620) 364-8831 An Equal Opportunity Employer M/F/HCNET

ET 08-0030 Page 2 of 3 Attachment I provides a follow-up response to Metal Fatigue Analyses RAI for 4.3-1 (0!

4.3-1). Attachment II provides a follow-up response to Metal Fatigue Analyses RAI for 4.3-3 (01 4.3-3).

During the May 1, 2008 meeting, it was questioned whether the WCGS charging nozzles had thermal sleeves. At the time WCNOC, based on research for license renewal, believed we did.

However, WCNOC stated that additional review would be done to validate that belief. WCNOC has since reviewed documentation contacted the vendor.

At this point, the documentation is conflicting and inconclusive.

The issue has been entered into the corrective action program and WCNOC is continuing research.

If necessary, WCNOC will physically validate the configuration of the lines during the refueling outage 17. The current analysis addressed in this letter was performed based on the charging nozzles having thermal sleeves. If WCNOC determines the sleeves are not present, the analysis will be re-performed.

This letter contains new commitments. WCNOC had previously committed to a number of action items concerning metal fatigue in commitment number thirty-eight, most recently addressed in Reference 3. This commitment is considered closed. Attachment III includes additional commitments identified in this correspondence.

If you have any questions concerning this matter, please contact me at (620) 364-4084, or Mr. Richard D. Flannigan at (620) 364-4117.

Snerely, Terry J. Garrett TJG/rlt Attachment I:

Response to RAI 4.3-1 Attachment I1:

Response to RAI 4.3-3 Attachment III:

List of Commitments cc:

E. E. Collins (NRC), w/a V. G. Gaddy (NRC), w/a B. K. Singal (NRC), w/a T. M. Tran (NRC), w/a Senior Resident Inspector (NRC), w/a

ET 08-0030 Page 3 of 3 STATE OF KANSAS

)

SS COUNTY OF COFFEY )

Terry J. Garrett, of lawful age, being first duly sworn upon oath says that he is Vice President Engineering of Wolf Creek Nuclear Operating Corporation; that he has read the foregoing document and knows the contents thereof; that he has executed the same for and on behalf of said Corporation with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knowledge, information and belief.

By_

z, Terry/Aarrett Vice resident Engineering SUBSCRIBED and sworn to before me this,65 day of I"C.-

,2008.

Notary Public s,'oF pt' CINDY 7NO-,/,N/R I

Expiration Date 71V2 TO IMy Apt UP-

Attachment I to ET 08-0030 Page 1 of 19 Wolf Creek Nuclear Operating Corporation (WCNOC) Response to NRC Requests for Additional Information RAI 4.3-1 (01 4.3-1)

I, Attachment I to ET 08-0030 Page 2 of 19 Metal Fatigue Analyses Follow-up RAI for 4.3-1 (01 4.3-1),'

The applicant's responses provided in letters dated October 3, and 17, 2007, did not address the staffs concerns as stated in RAI 4.3-1. The October, 3, 2007, letter stated that 1D transfer functions were developed for HL surge line nozzle and the charging nozzles in the vicinity of the nozzle to pipe welds. It went on to state that the development of the transfer functions takes full advantage of the local geometry and symmetry. However, the staff finds no axis of symmetry at the nozzle corners. Further, at the nozzle to pipe welds, the loading is not symmetric if thermal stratification is present. Therefore, the validity of transfer functions developed by using "1-D peak stress" is not applicable at these locations. In order to enable the staff to make a determination on this issue, the applicant is requested to perform an environmentally-assisted fatigue analysis and provide results to the NRC Staff of a 3-D finite element analysis using an industry-accepted computer code, such as ANSYS. The analysis should cover nozzle corners with geometrical discontinuities and at locations where thermal stratification loading is significant. This analysis shall follow the rules of American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section III, Subsection NB-3200, requiring the use of six stress components to define the stress state and determine the alternating stress intensities.

WCNOC Response to RAI 4.3-1 (01 4.3-1)

This response to RAI 4.3-1 transmits the results of the EAF analysis using ASME Subsection NB-3200 methodology for the charging nozzle and hot leg surge line nozzle locations.

This analysis will provide input in setting the fatigue monitoring program corrective action level for the Cumulative Usage Factor (CUF) to assure that sufficient margin exists to allow the highest fatigue usage per cycle to occur without exceeding CUF=1.0.

The analysis methodology for the charging nozzle and the hot leg surge line nozzle is based on the NB 3222.4/NB 3216.2 of Section III of the ASME Code 2001 Edition with Addenda thru 2003.

A 3-dimensional model was developed for the two nozzles (charging and hot leg surge) and a finite element model was also developed using the ANSYS Finite Element software.

The EAF results of the NB-3200 analyses are then compared to the EAF analysis using the fatigue monitoring program methodology.

Attachment I to ET 08-0030 Page 3 of 19 Charging Nozzle Analysis The details of the charging nozzle NB-3200 fatigue analysis are shown in the following tables:

Table 1 provides a list of transients considered in the NB-3200 analysis and the number of each transient considered. For comparison the transients and numbers of transients considered in the fatigue monitoring program analysis are included in the table.

The selection of transients for the analysis excluded specified design transients meeting both of the following criteria:

Delta-T<25 degrees F Delta-P<250 pounds per square inch Transients meeting both of these criteria do not contribute significantly to fatigue usage.

Table 2 provides a list of load sets that were used to combine transients to define enveloping cycle pairs.

Table 3 shows the calculation of the environmental factors for the cycle pairs that contribute the majority of the total fatigue usage. The calculated Fen factors are based on the strain and strain rates of the transient pairs. For other cycle pairs, maximum Fen factors were used as shown in Table 4. The Fen factor for the NB-3200 analysis was calculated for each time step for steps of tensile strain change, according to the methodology outlined in NUREG/CR - 5704 and MRP 47, Rev. 1. In this process, the strain rates and strain contributions of each time step were calculated.

The overall Fen for each transient was the summation of all tensile strain contributions for each time step and then the Fen for each time step was multiplied by the difference in strain amplitude between the current and previous time step. The results were then summed. The weighted average Fen is calculated to be 5.6971.

Table 4 shows the combinations of load set cycles used for the enveloping pairs of transients in the NB-3200 analysis and the calculated fatigue usage results from each pair. In the table, the load set in column titled "Load Set A" defines one end of the cycle and the load set in the column titled "Load Set B" defines the opposite end of the cycle. The column n defines the number of cycles of the pair included in the usage calculation. Ke is the simplified elastic-plastic stress factor determined from the maximum stress intensity, Sn.

Salt is the peak to peak stress for the cycle pair. N is the number of cycles at Salt that gives a usage of 1.0. The fatigue usage for the cycle pair is then n/N. The total usage is the sum of the usage contributions from each pairing.

Table 4 also provides the environmentally assisted fatigue (EAF) results for the NB-3200 analysis for the charging nozzle. For each cycle combination (each line of the table) the Fen used and the fatigue usage contribution for that line! is shown. The total fatigue usage without Fen, the average Fen, and the EAF total usage are shown at the bottom of the table.

Attachment I to ET 08-0030 Page 4 of 19 TABLE 1:

PROJECTED 60-YEAR CYCLES FOR MONITORING PROGRAM NB-3200 ANALYSIS AND FATIGUE TRANSIENT NB-3200 MONITORING PROGRAM Loss of charging

(---)

55 Chrg and letdown shutoff 50 32 Loss of letdown delay 30 19 Loss of charging delayed return 10 4

Loss of letdown (prompt RTN) 60 38 Loss of charging (prompt RTN) 45

• • not counted Charging flow step increase and 24000

• • not counted return to normal Charging flow step decrease and 24000

• • not counted return to normal Letdown flow step decrease and 2000

• • not counted return to normal Letdown flow step increase and 24000

• • not counted return to normal Plant heat up 90 59 Plant cooldown 90 54 Reduced temperature return to 20 200 power Large step load decrease with 200

• • not counted steam dump Feed water cycling 500

• • not counted Loop out of service 5

7 Refuel 50 39 Turbine roll test 9

13 Primary side leak test 6

9 Loss of load 5

8 Loss of power 5

4 Partial loss of flow 9

3 Reactor trip A (no cooldown) 120 91 Reactor trip B (cooldown & no SI) 20 16 Reactor trip C (cooldown & SI) 5 1

Inadvertent RCS depressurization 5

2 Inadvertent auxiliary spray 5

1 Inadvertent safety injection 15 9

actuation Inadvertent startup of an inactive 2

1 loop Excessive feedwater flow 5

3 RCS cold over pressurization 10 1

(COMS)

OBE seismic (10 cycles/event) 20

• • manually counted Primary side hydrostatic test 1

1

• • Manually counted or not counted by the monitoring program software.

Attachment I to ET 08-0030 Page 5 of 19 TABLE 2: LOAD SETS LOAD SET TRANSIENTS CYCLE 1

1. Charging and letdown shutoff 1 60 2

2. Charging and letdown shutoff 2A 90**

3

2. Charging and letdown shutoff 2B 90**

4

3. Letdown shutoff, prompt return A 60 5

3. Letdown shutoff, prompt return B 60 6

4. Letdown shutoff, delayed return 1A 30 7

4. Letdown shutoff, delayed return 1 B 30 8

6. Charging shutoff, prompt return A 45 9

6. Charging shutoff, prompt return B 45 10

7. Charging decrease and return A 24,000 11

7. Charging decrease and return B 24,000 12

8. Charging increase and return A 24,000 13

8. Charging increase and return B 24,000 14

9. Letdown decrease and return 1A 2,000 15

9. Letdown decrease and' return 1B 2,000 16

10. Letdown decrease and return 2 2,000 17

11. Letdown increase and return 1A 24,000 18

11. Letdown increase and return 1B 24,000 19

12. Letdown increase and return 2A 24,000 20

12. Letdown increase and return 2B 24,000 21

13. Plant heatup 90 22

14. Plant cooldown 90 23

15. Refueling/zeroload 57 24

16. Primary Leak Test 6

25

17. Loss of Load A 156 26

17. Loss of Load B 156 27

18. Inadvertent RCS Depress A 10 28

18. Inadvertent RCS Depress B 10 29

19. Excessive feedwater flow A 889 30

19. Excessive feedwater flow B 889 31

19. Excessive feedwater flow C 889 32

20. Primary hydro test 1

33

21. RCS cold Overpressurization 10

• • Includes 30 cycles of letdown shutoff, delayed return 2.

Attachment I to ET 08-0030 Page 6of 19 TABLE 3: NB-3200 Analysis Calculated Environmentally Assisted Fatigue Factors (Fen)

Load Set #

Transient #

Tensile Strain (YE-)

Fen x Ac (Fen X AE)TEE Fen 2

2A 0.43 1.15 2.86 7

4B 0.31 2.64 8.52 5.12 2

2A 0.43 1.15 2.68

.5 3B 0.12 1.16 9.37 4.17 18 11B 0.06 0.48 7.52 20 12B 0.03 0.42 14.54 9.69 12 8A 0.06 0.44 7.91 13 8B 0.02 0.34 15.26 10.00

Attachment I to ET 08-0030 Page 7 of 19 TABLE 4: NB-3200 Analysis Environmentally-Assisted Fatigue Results (EAF)

Load Set A Load Set B n

Sn, Ke

Salt, N

Usage Fen EAF psi i psi 2 2 ChgLDshut2A 74 LDshutdelB 30 27230 1

126834 816.58 0.0367384 5.125 0.1883 2 2 ChgLDshut2A 53 LDshutprB 60 36640 1

94273 2226.11 0.0269529 4.171 0.1124 1 1 ChgLDshutl 64 LDshutdelA 30 16105 1

39848 113645 0.000264 15.35 0.0041 1 1 ChgLDshutl 4 3 LDshutprA 30 36625 1

39848 113645 0.000264 15.35 0.0041 4 3 LDshutprA 86 ChgshutprA 30 36624 1

39836 113824 0.0002636 15.35 0.0040 8 6 ChgshutprA 9 6_ChgshutprB 15 19786 1

22228 2229200 0.0000067 15.35 0.0001 9 6 ChgshutprB 20 12 Ldinc2B 30 19358 1

22183 2249000 0.0000133 15.35 0.0002 18 11 LDinclB 20 12 LDinc2B 23970 19405 1

21619 2510400 0.0095484 9.693 0.0926 3 2 ChgLDshut2B 18 11 LDinclB 30 10240 1

21196 2731700 0.000011 15.35 0.0002 3 2 ChgLDshut2B 12 8_ChgincA 60 9239 1

19798 3656700 0.0000164 15.35 0.0003 12 8 ChgincA 33 21 RCSoverp 10 19800 1

18634 4737600 0.0000021 15.35 0.0000 12 8 ChgincA 15 9 LDdec1B 2000 15920 1

17444 6894800 0.0002901 15.35 0.0045 12 8 ChgincA 13 8 ChgincB 21930 15701 1

17117 7726700 0.0028382 10.003 0.0284 13 8 ChgincB 29 19 ExcessFWA 889 14347 1

16408 9971400 0.0000892 15.35 0.0014 Total CUF = 0.077298 Average Fen

= 5.6971 Total EAF = 0.4404 The loss of charging/loss of letdown events that have contributed to the monitoring program calculated fatigue usage are shown in Table 5. The fatigue usage increment calculated for the event without consideration of environmental effects, the calculated Fen, and the incremental EAF usage are shown for each event in the table.

The Fen for the monitoring program was calculated using actual plant data using the methodology outlined in NUREG/CR - 5704 and MRP 47 Rev. 1. The analysis procedure is as follows:

1. Evaluate plant data days associated with fatigue usage increments

2. Analyze the candidate days with the monitoring program

3. Select important plant instrument, engineering parameter calculatedvalues and times associated with fatigue usage increments.

4. Evaluate strain rate and strain range for each 10 second step

5. Convert the nozzle temperature to Celsius

6. Compute Fen values for each 10 second period as a function of nozzle temperature and tensile strain rate

7. Integrate the Fen values with the appropriate strain ranges for the full time period of interest to obtain a strain weighted Fen value Using this methodology, an EAF analysis for the charging nozzle was performed using the monitoring program methodology.

Attachment I to ET 08-0030 Page 8 of 19 TABLE 5: Monitoring Program Wolf Creek Normal and Alternate Charging Fatigue Events Events Dates Uinc F en Incremental Description CUF Charging Valve Switch at 4/4/96-4/6/96 0.006413 4.044 0.02594 Full DTs Temperature (Design transients)

Coincident Loss of Letdown/Loss 8/2/98-8/6/98 0.001428 12.633 0.01804 Half DTs of Charging Delayed Loss of Letdown/Loss of Charging 3/2/99 0.009276 5.311 0.04926 Full DTs Delayed Loss of Charging/Loss of Letdown 4/2/99-0.000560 6.842 0.00383 Half DTs Delayed 4/11/99 Represents 4 low Loss of Charging Delayed 5/4/99-5/6/99 0.000022 2.547 0.00006 temperature Loss of Charging Events Loss of Charging Delayed 5/8/1 999 0.005802 4.104 0.02381 Full DTs Loss of Charging Delayed 2/16/2000 0.009945 6.765 0.06728 Full DTs Loss of Charging Delayed 5/4/00-5/6/00 0.005047 5.765 0.02910 Full DTs Use for past 5.1979 For large events DTs inclusive of charging nozzle switches 7.3408 For small DTs Use for past 5.4863 For large and future DTs repeatable events

Attachment I to ET 08-0030 Page 9 of 19 Charging Nozzle Analysis Results Results for the NB-3200 analysis and the monitoring program ASME Code Section III NB-3200 analysis - EAF usage <1.0 meets code allowable Safe End CUF 0.077298 Fen 5.6971 EAF 0.4404 Current monitoring program 60 year EAF Safe End CUF 0.1527 Fen 5.4863 EAF 0.8378 Comparison of Fatigue Strength Reduction Factors As required by the ASME Code, both fatigue analyses done for the charging nozzles and surge nozzle used "fatigue strength reduction factors" (FSRF) to account for the effects of geometric stress concentrations on the peak stress at the points of interest. In order to assist in comparison of the results from the two analysis methods, the FSRF used in the two analyses are provided.

The monitoring program calculations are performed using the plant and location-specific transfer functions. FSRFs are not applied on a general basis, but are applied as appropriate at specific locations. The specific FSRF values used for monitoring program locations are as follows:

Charging Nozzles (safe end location)

Stress From FSRF Used Pressure Moment Thermal 1.2 1.8 1.0 RCS Surge Nozzles (safe end location)

Stress From FSRF Used Pressure Moment Thermal 1.2 1.8 1.7

Attachment I to ET 08-0030 Page 10 of 19 For the NB-3200 analyses for both charging and RCS surge nozzles, FSRFs are applied to the various stress terms before they are combined.. Guidance was taken from the Code stress indices (k Indices) Table NB-3681 (a)-1, as applicable to the location geometry. For the safe end to pipe weld location the indices were:

Stress From FSRF Used**

Pressure 1.2 Moment 1.8 Thermal 1.7

• • For thermal stresses, the FSRF is applied to the Linearized Membrane plus Bending peak stress components.

This comparison shows that the same FSRF values were used for the NB-3200 analyses and for the monitoring program analyses, except that a FSRF of 1.0 was used for thermal stresses in the monitoring program calculation for the charging nozzle. The basis thermal stress for this location in the monitoring program is calculated using a Green's function (transfer function) approach. The transfer function incorporates appropriate formula to make the use of an FSRF unnecessary for the thermal stress. For all other stress factors, the FSRF values used are consistent for all analyses.

Conclusions A comparison to the previously performed monitoring program-based EAF analysis shows the following for the charging nozzle:

1. The NB-3200 analyses indicate the bounding location for fatigue usage is the safe end of the nozzle. The safe end location results were taken and used to compare to the monitoring location results.

2. The 60-year analyzed CUF of 0.0773 (without environmental factors) is lower than the monitoring program 60-year projected CUF of 0.1527. It is noteworthy that the monitoring program charging nozzle CUF is nearly double the value (1.97 times) computed by the NB-3200 analysis. This is despite the fact that the NB-3200 analysis incorporates additional cycles beyond those indicated by the monitoring program 60-year projections.

The monitoring program results are demonstrably conservative.

3. The 60-year design EAF, using the Fen calculated in the NB 3200 analysis is 0.4404.

This is lower than the EAF of 0.8378 calculated in the monitoring program analysis.

This demonstrates that the monitoring program results are conservative.

4. Notably, while the monitoring program EAF results are higher than in the NB-3200 analysis, the effective average Fen at the changing nozzle is higher for the NB-3200 analysis (5.6971) than in the monitoring program analysis (5.4863).

For stainless steel in a PWR plant where low dissolved oxygen is conservative, strain

Attachment I to ET 08-0030 Page 11 of 19 rate is the principal independent variable for determining Fen. Temperature has an effect on the calculation of Fen, however the effect is based on a threshold of 2000C. When the temperature is greater than or equal to 200'C, strain rate and dissolved oxygen content are considered. Since the monitoring program transfer functions over-predict the stress (strain) ranges at the charging nozzle, strain rates computed from those stresses are higher than those determined from a full 6-component finite element stress analysis. The higher strain rates lead directly to lower Fen values in the EAF calculations.

However, the conservatively calculated higher strain ranges for the monitoring program calculations more than compensate for the slightly lower average Fen. Therefore, the monitoring program is overall conservative relative to the finite element NB-3200 analysis.

Hot Leg Surge Line Nozzle Analysis The details of the RCS hot leg surge line nozzle NB-3200 fatigue analysis are shown in the following tables. The arrangement of the tables is similar to that for the description of the charging nozzle analysis.

The selection of transients for the analysis excluded specified design transients meeting both of the following criteria:

Delta-T<30 degrees F Delta-P<250 pounds per square inch

Attachment I to ET 08-0030 Page 12 of 19 TABLE 6:

PROJECTED 60 -

YEAR CYCLES FOR NB 3200 AND MONITORING PROGRAM TRANSIENTS NB 3200 MONITORING PROGRAM Surge Line Thermal Transients Surge line insurge/outsurge

@ 345 F THL = 140 F 10

@ 332 F THL = 140 F 6

@ 320 F THL = 140 F 53

@ 304 F THL = 140 F 115

@ 275 F THL = 140 F 17

@ 270 F THL = 140 F 104

@ 250 F THL = 140 F 47

@ 200 F THL = 140 F 27

@ 175 F THL = 140 F 26

@ 150 F THL = 140 F 184

@ 200 F THL = 550 F 23

@ 150 F THL = 550 F 135 Surge Line Global Stratification Normal Reactor Coolant Transients Plant heatup 90 59 Plant cooldown 90 54 Unit loading /unloading at 5% power/min 2,800 Reduced temperature return to power 20 200 Large step load decrease with steam dumps 200 Feed water cycling 500 Loop out of service 5

7 Refueling 50 39 Turbine roll test 9

13 Primary side leakage test 6

9 Upset Reactor Coolant Transients Loss of load 5

8 Loss of power 5

4 Partial loss of flow 9

3 Reactor trip A with no cooldown 120 91 Reactor trip B with CD and no SI 20 16 Reactor Trip C with CD and SI 5

1 Inadvertent RCS depressurization 5

2 Inadvertent auxiliary spray 5

1 Control Rod drop 10 Inadvertent startup of an inactive loop 2

1 Inadvertent safety injection actuation 15 9

Excessive feedwater flow 5

3 RCS cold overpressurization 10 1

OBE seismic (10 cycles event) 20 Test Conditions RCS Transients Primary Side Hydrostatic test 1

1

Attachment I to ET 08-0030 Page 13 of 19 Notes for Table 6:

• Each PZR I/O transient listed will include two stratification on-off cycles one during the insurge, and one during the outsurge.

• • Surge transients for monitoring programs are calculated using instrumentation for the heat up and cooldown and included in heatup and cooldown, not counted separately.

• • • Manually counted or not counted by monitoring program Pressurizer insurge/outsurge and surge line thermal stratification are treated as independent transients.

Constant surge line stratification conditions will be assumed for all RCS transients. Since Wolf Creek adopted new operating procedures for heat up and cooldown in April 1993, and the new procedures modified the heat up and cooldown operating procedures (MOP), the pressurizer insurge and outsurge transients will be defined in two parts. The first part represents the transients that occurred before MOP was implemented.

The second part will represent post-MOP pressurizer insurge and outsurge transients.

TABLE 7: LOAD SETS LOAD SET TRANSIENT CYCLES 1

Plant heatup 90 2

Plant cooldown 90 3

Refueling/zeroload 57 4

Primary leak test 6

5 Primary hydrotest 1

6 RCS COMS 10 7

Inadvertent RCS depress 5

8 UP group 2820 9

DOWN group 3320 10 DOWNdp group 169 11 UP/Dn dp group A 221/219**

12 UP/Dn dp group B 221 13 PIO 345 hucdA 10 14 PIO 345 hucd B 10 15 PIO 345 hucd C 10/8"*

16 PIO 345 hucd D 10 17 PIO 332 hucd A 6

18 PIO 332 hucd B 6

19 PIO 332 hucd C 6

20 PIO 332 hucd D 6

21 PIO 320 post A 53 22 PIO 320 post B 53 23 PIO 320 post C 53 24 PIO_320 post D 53 25 PIO 304 hucdA 115 26 PIO 304 hucd B 115 27 PIO 304 hucd C 115

Attachment I to Page 14 of 19 ET 08-0030 28 PIO 304 hucd D 115 29 PIO 275 hucdA 17 30 PIO 275 hucd B 17 31 PIO 275 hucd C 17 32 PIO 275 hucd C 17 33 PIO_270 post A 104 34 PIO0270 post B 104 35 PIO 270 post C 104 36 PIO0270 post D 104 37 PIO 250 hucd A 47 38 PIO 250 hucd B 47 39 PIO 250 hucd C 47 40 PIO 250 hucd D 47 41 PIO 200 hucdA 27 42 PIO 200 hucd B 27 43 PIO 200 hucd C 27 44 PIO 200 hucd D 27 45 PIO 175 hucdA 26 46 PIO 175 hucd B 26 47 PIO 175 hucd C 26 48 PIO 175 hucd D 26 49 PIO 150 hucdA 184 50 PIO 150 hucd B 184 51 PIO 150 hucd C 184 52 PIO 150 hucdD 184 53 PIO 200 operA 23 54 PIO 200_oper B 23 55 PIO 200 oper C 23 56 PIO 200 oper D 23 57 PlO 150 operA 135 58 PIO 150_oper B 135 59 PIO 150_oper C 135 60 PIO _150_oper D 135 61 Worst case + OBE 2**

• • Two cycles of the worst 'case (PIO_345_hucd for paths 1 and 2, Up/DndP group A for path 3) are combined with OBE.

Attachment I to ET 08-0030 Page 15 of 19 TABLE 8: NB-3200 Analysis Calculated Environmentally Assisted Fatigue factors (Fen)

Load Transient #

Tensile Fen x AE (Fen x AE)FE Fen Set #

Strain (EE) 8 UpGroup 0.024 0.361 15.348 5.74 61 PIO 345 OBE C 0.101 0.354 3.504 8

UpGroup 0.024 0.361 15.348 5.66 39 PIO 250 hucd C 0.097 0.322 3.316 8

UpGroup 0.024 0.361 15.348 6.02 39 PIO 304 hucdC

, 0.098 0.373 3.787 TABLE 9: NB-3200 Analysis Environmentally-Assisted Fatigue Results (EAF)

Load Set A Load Set B n

Sn, psi Ke

Salt, N

Usage Fen EAF sDi 8 UPgroup 61 PIO 345 OBEC 2

93472 2.643 148194 498.04 0.00402 5.739 0.02305 8 UPgroup 15 PIO 345 hucdC 8

72421 1.517 65507 9104.26 0.00088 15.35 0.01349 8 UPgroup 39 PIO 250 hucdC 47 71398 1.462 63172 10654 0.00441 5.660 0.02497 8 UPgroup 19 PIO 332 hucdC 6

70330 1.406 59005 14848 0.00040 15.35 0.00620 8 UPgroup 27 PIO 304 hucdC 115 67566 1.259 50810 31251 0.00368 6.017 0.02214 8 UPgroup 31 PIO 275 hucdC 17 67420 1.251 50404 32547 0.00052 15.35 0.00802 8 UPgroup 23 PIO 320 postC 53 65307 1.139, 44837 59624 0.00089 15.35 0.01364 8 UPgroup 43 PIO 200 hucdC 27 63487 1.042 39844 113705 0.00024 15.35 0.00365 1 PlantHeatup 35 PIO 270 postC 90 61416 1

36499 182862 0.00049 15.35 0.00756 8 UPgroup 35 PIO 270 postC 14 60009 1

35916 199512 0.00007 15.35 0.00108 8 UPgroup 47 PIO 175 hucdC 26 58073 1

35069 231493 0.00011 15.35 0.00172 2 PlantCooldown 8 UPgroup 90 56655 1

32438 376730 0.00024 15.35 0.00367 8 UPgroup 51 PIO 150 hucdC 184 52725 1

31929 415840 0.00044 15.35 0.00679 7 RCSdepress 8 UPgroup 5

51862 1

29549 710209 0.00001 15.35 0.00011 8 UPgroup 40 PIO 250 hucdD 47 47727 1

27860 1040300 0.00005 15.35 0.00069 8 UPgroup 16 PIO 345 hucdD 10 47689 1

27138 1133400 0.00001 15.35 0.00014 8 UPgroup 37 PIO 250 hucdA 47 44935 1

26670 1199600 0.00004 15.35 0.00060 8 UPgroup 20 PIO 332 hucdD 6

45653 1

25971 1308100 0.00000 15.35 0.00007 8 UPgroup 13 PIO 345 hucdA 10 43442 1

25278 1428700 0.00001 15.35 0.00011 8 UPgroup 24 PIO 320 postD 53 44203 1

25169 1448900 0.00004 15.35 0.00056 8 UPgroup 44 PIO 200 hucdD 27 42403 1

24963 1488300 0.00002 15.35 0.00028 8 UPgroup 28 PIO 304 hucdD 115 43485 1

24745 1531500 0.00008 15.35 0.00115 8 UPgroup 17 PIO 332 hucdA 6

42398 1

24712 1538200 0.00000 15.35 0.00006 8 UPgroup 21 PIO 320 postA 53 41418 1

24177 1652000 0.00003 15.35 0.00049 8 UPgroup 41 PIO 200 hucdA 27 40269 1

24039 1682900 0.00002 15.35 0.00025 8 UPgroup 48 PIO 175 hucdD 26 39666 1

23482 1816600 0.00001 15.35 0.00022 8 UPgroup 25 PIO 304 hucdA 115 39953 1

23337 1853800 0.00006 15.35 0.00095 8 UPgroup 32 PIO 275 hucdC 17 40361 1

23128 1909100 0.00001 15.35 0.00014 8 UPgroup 14 PIO 345 hucdB 10 40847 1

22931 1963100 0.00001 15.35 0.00008 8 UPgroup 45 PIO 175 hucdA 26 37924 1

22742 2022000 0.00001 15.35 0.00020 8 UPgroup 36 PIO 270 postD 104 39314 1

22499 2116900 0.00005 15.35 0.00075 8 UPgroup 55 PIO 200 operC 23 37607 1

22449 2137300 0.00001 15.35 0.00017 8 UPgroup 18 PIO 332 hucdB 6

39816 1

22388 2162300 0.00000 15.35 0.00004

Attachment I to ET 08-0030 Page 16 of 19 3 zeroload 8 UPgroup 57 37501 1

22224 2231000 0.00003 15.35 0.00039 6 RCSCOMS 8 UPgroup 10 36952 1

22011 2324800 0.00000 15.35 0.00007 8 UPgroup 52 PIO 150 hucdD 184 36912 1

21969 2344000 0.00008 15.35 0.00120 8 UPgroup 33 PIO 270 _postA 104 37245 1

21867 2391000 0.00004 15.35 0.00067 8 UPgroup 29 PIO 275 hucdA 17 37311 1

21797 2423900 0.00001 15.35 0.00011 8 UPgroup 49 PIO 150 hucdA 184 35622 1

21492 2574500 0.00007 15.35 0.00110 8 UPgroup 38 PIO 250 hucdB 47 35878 1

19746 3697700 0.00001 15.35 0.00019 8 UPgroup 50 PIO 150 hucdB 184 33616 1

19670 3759400 0.00005 15.35 0.00075 8 UPgroup 10 DOWNdPgroup 169 33754 1

19635 3787600 0.00004 15.35 0.00068 4 Ieaktest 8 UPgroup 6

30828 1

19382 4003900 0.00000 15.35 0.00002 8 UPgroup 46 PIO 175 hucdB 26 33945 1

19358 4025100 0.00001 15.35 0.00010 8 UPgroup 26 PIO 304 hucdB 115 34802 1

19028 4332300 0.00003 15.35 0.00041 8 UPgroup 42 PIO 200 hucdB 27 33557 1

18703 4663100 0.00001 15.35 0.00009 5 hydrotest 8 UPgroup 1

29328 1

18673 4694900 0.00000 15.35 0.00000 8 UPgroup 54 PIO 200_operB 23 31078 1

18094 5532200 0.00000 15.35 0.00006 8 UPgroup 30 PIO 275 hucdB 17 32782 1

18016 5678300 0.00000 15.35 0.00005 8 UPgroup 34 PIO 270 _postB 104 32438 1

17794 6117200 0.00002 15.35 0.00026 8 UPgroup 22 PIO 320 postB 53 30664 1

17644 6437400 0.00001 15.35 0.00013 8 UPgroup 53 PIO 200 operA 23 30328 1

17644 6437900 0.00000 15.35 0.00006 8 UPgroup 59 PIO 150 operC 135 27549 1

16818 8592000 0.00002 15.35 0.00024 8 UPgroup 58 PIO 150 operB 12 27053 1

16510 9605300 0.00000 15.35 0.00002 11Up/DndPgrpA 58 PIO_150_operB 123 24358 1

14965 25278000 0.00000 15.35 0.00008 Total CUF = 0.017289 Average Fen = 8.659 Total EAF = 0.1497

Attachment I to ET 08-0030 Page 17 of 19 TABLE 10: Monitoring Program Hot Leg Surge Nozzle Environmentally Assisted Fatigue factors (Fen) Results Wolf Creek HL Nozzle Fatigue Events Events Dates Uinc Fen Incremental Description CUF Pressurizer 11/25/1997 0.00255 5.627 0.01435 and RCS Heatup For just the steepest Pressurizer 11/25/1997 0.00255 13.728 0.03500 tensile stress ramp and RCS Heatup Cooldown 4/4/1999 0.00001 4.477 0.00005 Pairs with 11/97 peak For just the steepest Cooldown 4/4/1999 0.00001 2.547 0.00003 tensile stress ramp Heatup 5/3/1999 0.00255 5.627 0.01435 For just the steepest Heatup 5/3/1999 0.00255 11.055 0.02818 tensile stress ramp Heatup 11/1/2000 0.00197 4.185 0.00822 For just the steepest Heatup 11/1/2000 0.00197 7.041 0.01384 tensile stress ramp 4.9791 For total time For just the 8.5927 steepest tensile stress ramp The Fen for the NB 3200 analysis was calculated for each time step for steps of tensile strain change, according to the methodology outlined in NUREG/CR-5704 and MRP 47, Rev. 1. In this process, the strain rates and strain contributions of each time step were calculated. The overall Fen for each transient was the summation of all tensile strain contributions for each time step and then the Fen for each time step was multiplied by the difference in strain amplitude between the current and previous time step. The results were then summed. The weighted average Fen is calculated to be 8.659.

The Fen monitoring program was calculated using actual plant data using the methodology outlined in NUREG/CR - 5704 and MRP 47 Rev 1. The analysis procedure as follows:

1. Evaluate plant data days associated with fatigue usage increments

2. Analysis the candidate days with the monitoring program

3. Select important plant instrument, engineering parameter calculated values and times associated with fatigue usage increments

4. Evaluate strain rate and strain range for each 10 second step

5. Convert the nozzle temperature to Celsius

6. Compute Fen values for each 10 second period as a function of nozzle temperature and tensile strain rate

Attachment I to ET 08-0030 Page 18 of 19

7. Integrate the Fen values with the appropriate strain ranges for the full time period of interest to obtain a strain weighted Fen value.

Hot Leg Surge Line Nozzle Analysis Results Results for the NB-3200 analysis and the monitoring program ASME Code Section III NB-3200 analysis - EAF usage <1.0 meets code allowable CUF 0.017289 Fen 8.659 EAF 0.1497 Current monitoring program 60 year EAF CUF 0.08925 Fen 4.979 EAF 0.4443 Conclusions A comparison to the previously performed monitoring program-based EAF analysis shows the following for the hot leg surge nozzle location:

1. The NB-3200 analysis indicates the bounding location for fatigue usage is in the knuckle region of the nozzle. This location results were taken and used to compare to the monitoring location results, which were for the safe end of the nozzle. As shown, the results for the monitoring program are conservative.

2. The 60-year NB-3200 analyzed CUF of 0.017289 is lower than the monitoring program 60-year projected CUF of 0.08925.

It is noteworthy that the monitoring program hot leg surge nozzle CUF is approximately 5 times the value computed by the NB-3200 analysis despite the fact that the NB-3200 analysis incorporates additional cycles beyond those indicated by the monitoring program 60-year projections. This demonstrates that the monitoring program results are conservative.

3. The 60-year NB-3200 EAF, using the Fen calculated is 0.1497. This is lower than the EAF of 0.4443 calculated in the monitoring program analysis.

Even when the maximum Fen is used, the 60-year NB-3200 EAF of 0.2654 is lower than the EAF calculated in the monitoring program analysis. This demonstrates that the monitoring results are conservative.

Notably, while the monitoring program EAF results are higher than in the NB-3200 analysis, the effective overall Fen at the hot leg surge nozzle is higher for the NB-3200 analysis (8.659) than in the monitoring program analysis (4.979). For stainless steel in a PWR plant where low dissolved oxygen is conservative, strain rate is the principal independent variable for determining Fen. Temperature has an effect on the calculation of Fen, however the effect is based on a threshold of 200°C. When the temperature is greater than or equal to 200°C, strain rate and dissolved oxygen content are considered. Because the monitoring program

Attachment I to ET 08-0030 Page 19 of 19 transfer functions over-predict the stress (strain) ranges at the hot leg surge nozzle, strain rates computed from those stresses are higher than those determined from a full 6-component stress analysis. The higher strain rates lead directly to lower Fen values in the monitoring program EAF.

Attachment II to ET 08-0030 Page 1 of 5 Wolf Creek Nuclear Operating Corporation (WCNOC) Response to NRC Requests for Additional Information RAI 4.3-3 (01 4.3-3)

~4. *i'~~;'

Attachment II to ET 08-0030 Page 2 of 5 Metal Fatigue Analyses Follow-up RAI for 4.3-3 (01 4.3-3)

Wolf Creek Generating Station's (WCGS) commitment closure letter (ET 08-0007), dated January 25, 2008, does not address the following commitments on Page 14 of the October 3, 2007, letter (ET 07-0046):

(1)

Since WCGS implemented the modified operating procedure (MOP) prior to 1995, it is reasonable to suspect that heat-ups during PERIOD1 would have more insurge/outsurge cycles than PERIOD2. WCNOC agrees with this assertion, and will commit to updating the baseline to account for this factor. The baseline will be increased based on the expected number of additional insurge/outsurge cycles that would be accumulated in a pre-MOP environment.

(2)

In a follow-up discussion, the reviewers further noted that the cumulative usage factors back-projection did not consider the relative severity of charging and letdown transients.

However, in the revised baseline, Wolf Creek will explicitly consider the differential contribution of fatigue for each category of charging event.

The January 25, 2008, letter did not close commitments made by WCGS in the October 3, 2007, letter as quoted above. Please provide additional calculations and discussions to address the committed actions regarding the additional insurge/outsurge cycles and the differential contribution of fatigue for each category of charging event.

WCNOC Response to RAI 4.3-3 (01 4.3-3)

(1) Insurge/Outsurge WCGS reviewed the method used to develop backward projection of accumulated fatigue usage during plant operation in Period 1 (prior to January 13,1996) and concluded that data collected for transients affecting the hot leg surge line nozzle (HL Surge Nozzle) during Period 2 (January 13, 1996 -December 31,2005) may not be bounding for transients experienced by this nozzle during Period 1.

The basis of this conclusion was the implementation of modified operating procedures (MOP) to maintain a continuous outflow from the pressurizer during heatup and cooldown. Use of MOP has resulted in a significantly reduced number of insurge/outsurge flow events during the heatup and cooldown evolutions.

All of Period 2 was with MOP.

Part of Period 1 (prior to April 1993) was before implementation of MOP.

A conservative baseline fatigue usage for will be calculated using the transients, cycles, and severity as defined in WCAP-12893, "Structural Evaluation of the Wolf Creek and Callaway Pressurizer Surge Lines, Considering the Effects of Thermal Stratification", for pre-MOP heatup/cooldown events, and WCAP-14950, "Mitigation and Evaluation of Pressurizer Insurge-Outsurge Transients", for post-MOP heatup/cooldown events. The stress analysis used for calculation of fatigue usage from these assumed baseline transients will be the three dimensional finite element analysis (FEA) preformed for the response to RAI 4.3-1.

Attachment II to ET 08-0030 Page 3 of 5 For the HL Surge Nozzle, the design basis transient severity for insurge/outsurge transients is defined in WCAP-12893, "Structural Evaluation of the Wolf Creek and Callaway Pressurizer Surge Lines, Considering the Effects of Thermal Stratification." WCAP-12893 postulates that each heatup and cooldown evolution includes a large number of sub-transients (from insurge/outsurge).

For pre-MOP operation, WCAP-12893 states that, on average, 14.215 insurge/outsurge transients occur per heatup and per cooldown. The sub-transients are assumed to have a distribution of severities based on the temperature difference between the HL and the pressurizer (PZR) (Delta T) at the time of the insurge/outsurge. The frequency distribution for Delta T for insurge/outsurge from WCAP-12893 is as shown in Table 1.

The fatigue usage for a heatup/cooldown is a summation of the usage from the postulated insurge/outsurge sub-transients combined with the fatigue usage from the system heatup/cooldown temperature and pressure changes.

According to plant records, there were 15 RCS heatups and cooldowns prior to April 1993, when MOP were implemented (for a total of 30 heat up/cooldown events pre-MOP). Using the WCAP 12893 assumptions, these 30 heatup/cooldown events included 30 X 14.215 427 transient cycles. For the revised baseline calculation, the fatigue usage from 427 pre-MOP insurge/outsurge cycles with the Delta-T distribution shown in Table 1 will be calculated using the FEA and NB-3200 methodology.

For post-MOP operation within the baseline period, two insurge/outsurge transients per heatup/cooldown event will be assumed in accordance with WCAP-14950. The post-MOP insurge/outsurge transient severity distribution (Delta T distribution) will be in accordance with WCAP-14950. Fatigue usage from these transients will be calculated using the FEA NB-3200 analysis results.

Table 1 Transients Distribution for NB 3200 Analysis (based on WCAP 12893)

Surge Line Insurge/Outsurge

@ 345 OF THL =140 OF 10

@ 332 FTHL =140 OF 6

@ 320 OF THL =140 OF 53

@ 304 OF THL =140 OF 115

@ 275 OF THL =140 OF 17

@ 270OF THL =140 OF 104

@ 250 OF THL =140 OF 47

@ 200 FTHL =140 OF 27

@ 175 OF THL =140 OF 26

@ 150 OF THL =140 OF 184

@ 200 OF THL =550 OF 23

@150 OF THL =550 OF 135 Conclusion The baseline will be updated to include the additional insurge/outsurge cycles for pre-MOP as stated in WCAP -12893. The distribution of severities for insurge/outsurge transients will 1 to ET 08-0030 Page 4 of 5 be as defined in WCAP-12893. Stress analysis will be using the three dimensional FEA model, and fatigue usage will be calculated in accordance with ASME Code NB-3200.

(2) Categorization of Charging and letdown events The two charging and letdown events that are counted by the monitoring program (loss of charging and loss of letdown ) are more precisely separated into the following five categories of events:

A. Charging and letdown flow shutoff and return to service B. Letdown flow shutoff with prompt return to service C. Letdown flow shutoff with delayed returned to service D. Charging flow shutoff with prompt return to service E. Charging flow shutoff with delayed return to service The design temperatures vs. time definitions of these five categories are as defined in Westinghouse System Standard 1.3.X. "Nuclear Steam Supply System Auxiliary Equipment Design Transients for All Standard Plants. Rev. 0, Sept. 1978".

The distribution of loss of charging/loss of letdown events over the five categories was evaluated from data available from two time periods. The temperature vs. time histories for the loss of charging and loss of letdown events counted by the monitoring program from January 1996 through December 2005 were reviewed and re-categorized into one of the five events shown above. The events for the period from 1984 to April 1992 were separated into the five categories based on Control Room logs.

Table 2 provides the number of events counted for each precise category for Pre-March 1992 and for January 1996 through December 2005 ( and also provides the total percent contribution of each event to total loss of charging/loss of letdown events.

Table 2 Event category

1. counted

% of total

1. counted

% of total Pre-March 1992 Pre-March1992 Jan 96 - Dec 05 Jan 96 - Dec 05 events Charging and 13 54 6

20 letdown shutoff and return Letdown shutoff 6

25 7

23 w/ prompt return Letdown shutoff 0

0 8

27 w/ delayed return Charging shutoff 5

21 7

23 w/ prompt return Charging shutoff 0

0 2

7 w/ delayed return The events "charging and letdown shutoff and return", and "charging shutoff w/ delayed return" have nearly identical temperature vs. time transient profiles at the charging nozzle.

,. I Attachment II to ET 08-0030 Page 5 of 5 thermal shock due to the initial cooldown before the charging flow stops, and a steeper re-flood shock when it does stop.

These three categories were combined together and analyzed using the bounding time-temperature profile for the group.

Looking at the. results in the above table, combining the three categories together, the aggregate percentage during the period 1996 - 2005 is 54%.

This is the same as the percentage for the same group in 1984-1992, because there were no "letdown shutoff w/delayed return" or "charging shutoff w/delayed return" transients in the pre 1992 cycle records.

The "letdown shutoff w/prompt return" and "charging shutoff w/prompt return" events have similar percentages in the two time periods.

The prompt return categories contribute only a small fraction of the total fatigue usage for loss of charging/loss of letdown events. The 1996-2005 period history includes more of the letdown shutoff w/ delayed return event (which is the most severe of the five transients), therefore this period history will contribute more fatigue usage per loss of charging/loss of letdown event than the 1984-1992 period.

Therefore, using the fatigue usage calculated for the period monitored by the monitoring program times the ratio of the number of events in the baseline period to the number of monitored events to calculate the baseline fatigue usage gives a conservative upper bound for baseline fatigue usage.

Conclusion The differential contribution of fatigue for each category of loss of charging/loss of letdown events has been evaluated to show that the use of the monitored period to estimate the baseline usage is conservative. While the conclusion is that current results are conservative, the baseline will be updated using the severity and number of cycles provided in Table 2.

Attachment III to ET 08-0030 Page 1 of 1 LIST OF COMMITMENTS The following table identifies those actions committed to by Wolf Creek Nuclear Operating Corporation in this document. Any other statements in this letter are provided for information purposes and are not considered regulatory commitments.

Please direct questions regarding these commitments to Mr. Richard Flannigan, Manager Regulatory Affairs at Wolf Creek Generating Station, (620) 364-4500.

Number Commitment Commitment Description Subject 40 Configuration of Validate the presence or absence of charging nozzle Charging Nozzles thermal sleeves. If WCNOC determines that the sleeves are not present, the analyses will be re-performed.

Reference:

ET 08-0030 Due: December 30, 2009 41 Metal Fatigue Backward projection of CUF was used for NUREG/CR-Baseline CUF 6260 Locations (Surge Line Hot Leg Nozzle, and Charging Nozzles).

While the ratios used for back-projection do incorporate accumulated fatigue effects from all transients that occurred during Period 2, it does not account for transients which occurred more frequently in Period 1 than Period 2.

Therefore, WCNOC will prepare an updated baseline for the pressurizer hot leg surge nozzle based on the additional insurge/outsurge cycles accumulated in a pre-MOP environment.

Additionally WCNOC will update the baseline for the charging nozzles with consideration for the differential contribution of fatigue for each category of charging event.

Reference:

ET 08-0030 Due: December 30, 2009