ML101110635

RAI, License Amendment Request, Approval of Final Safety Analysis Report Change for Leak-Before-Break of the Pressurizer Surge Line

ML101110635
Person / Time
Site:	Waterford
Issue date:	04/21/2010
From:	Kalyanam N Division of Operating Reactor Licensing
To:	Mason M, Steelman W Entergy Operations
Kalyanam N, NRR/DORL/LPL4, 415-1480
References
TAC ME3420
Download: ML101110635 (6)

Text

From: Kalyanam, Kaly Sent: Wednesday, April 21, 2010 12:46 PM To: STEELMAN, WILLIAM J; mmason@entergy.com Cc: RMURILL@entergy.com

Subject:

RAI on Waterford 3 LAR for APproval of LBB of the Pressurizer Surge Line Billy/Bob, By letter dated February 22, 2010, Entergy Operations, Inc. (Entergy) made a License Amendment Request is for Approval of Leak-Before-Break of the Pressurizer Surge Line, for the Waterford Steam Electric Station, Unit 3 (Waterford 3).

The TAC No. for this request is ME3420.

The NRC Staff has reviewed the amendment request and determined that we require additional information to complete our review. A request for additional information appears below. The prefixes N and R refer to the originators of the question.

The staff requests you to provide a response to the RAI within 45 days from the date of this email. If this is not feasible, please let me know, in advance, when the response will be sent.

Thanks Kaly REQUEST FOR ADDITIONAL INFORMATION LEAK BEFORE BREAK ANALYSIS OF PRESSURIZER SURGE LINE WATERFORD STEAM ELECTRIC STATION UNIT 3 ENTERGY OPERATIONS, INC.

DOCKET NO. 50-382 By letter dated February 22, 2010, Entergy Operations, Inc. requested a license amendment to allow implementation of leak-before-break (LBB) on the pressurizer surge line at Waterford Steam Electric Station Unit 3. The licensees LBB analysis is based on WCAP-17187-P, Technical Justification for Eliminating Pressurizer Surge Line Rupture as the Structural Design Basis for Waterford Steam Electric Station, Unit 3 Using leak-Before-Break Methodology, (proprietary). To complete its review, the NRC staff requests the following additional information.

Question on Attachments to the Submittal Letter dated February 22, 2010

N-1. Discuss whether the reactor coolant system (RCS) leakage detection system capability of 0.25 gallons per minute (gpm) is applicable for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> or for 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

Discuss the requirements of the Waterford technical specifications on the RCS leakage detection systems.

Questions on WCAP-17187-P N-2. Page 2-3. Section 2.4 discusses thermal stratification of the surge line. Thermal stratification is a form of thermal-induced fatigue. SRP Section 3.6.3.III.10 does not permit LBB applied to piping with a history of fatigue cracking or failure. Explain why LBB is applicable to the pressurizer surge line considering thermal fatigue exists in the pipe.

N-3. Page 3-3. Section 3.4, first paragraph, states that the applied loads for the surge line LBB analysis are obtained from Waterford updated pipe stress reanalysis. (a)

Discuss the updated stress reanalysis, including whether the pipe loadings as a result of the proposed steam generator replacement and NRC-approved power uprate are included in the updated analysis. (b) Discuss the impact of the steam generator replacement and power uprate conditions on the pipe supports, routing, and their locations on the surge line.

N-4. Page 3-3. Section 3.4 states that load cases A, B, and C are normal operation conditions and D, E, F, and G are faulted conditions. There should be 12 loading combinations of normal operation conditions plus faulted conditions: A/D, A/E, A/F, A/G, B/D, B/E, B/F, B/G, C/D, C/E, C/F, and C/G. The report states that load cases C and G are for information only. This leaves the loading combinations of A/D, A/E, A/F, B/D, B/E, and B/F. Explain why load combinations A/E and B/D were not shown in Table 3-4.

N-5. Page 3-4, second paragraph, discusses temperatures used for thermal stratification. However, it is not clear how the temperatures were derived. The maximum stratification temperature differential considered was X1 degrees F (temperatures in this paragraph are proprietary information). The bottom-to-top temperature on the pipe cross section was increased from X2 degrees F to X3 degrees F. A temperature of X5 degrees F for node 70 was estimated for the stratification high case. In the normal stratification case, the temperature increased from X4 degrees F to X3 degrees F.

(a) Explain how all these temperatures were derived.

(b) Provide the normal operation temperature at Node 10 (hot leg to surge line nozzle) and at Node 80 (pressurizer to surge line nozzle). Discuss whether thermal stratification occurs at Nodes 10 and 80.

(c) The footnote for Tables 3-3 and 3-5 states that the maximum stratification temperature differential of X1 degrees F was applied for information only. Discuss whether the maximum stratification temperature differential was included in calculating critical crack sizes in Tables 6-1 and 6-2 and leakage crack sizes in Tables 5-1 and 5-

2. If the maximum stratification differential temperature was not included in deriving the critical and leakage crack size for the surge line, provide justification.

N-6. Page 5-2, first paragraph, states that the crack relative roughness was obtained from fatigue crack data on stainless steel samples. Discuss the source of the stainless steel samples. Discuss how the roughness value was obtained.

N-7. Page 5-2. Section 5.4, first paragraph, states that the crack opening area was estimated using the method of Reference 5-3. Discuss in detail exactly how the crack opening area was estimated and provide page numbers in Reference 5-3 which show the crack opening area calculation.

N-8. Page 5-3, first paragraph, states that the air-fatigue crack surge roughness of Y micro-inches (proprietary information) used for leak rate calculation by Westinghouse is about 50 percent higher than the typical surface roughness used by the industry.

Discuss how the 50 percent is derived and discuss whether 50 percent is conservative.

N-9. Page 5-3. (1) Explain why no penalty factor (P = 1.0) was applied to the Alloy 52M material in Equation 5-3. (2) Explain how penalty factor of 1.69 was derived from Reference 5-6 in the report because the staff derived a slightly higher penalty factor of 1.74 based on data in Reference 5-6.

N-10. Page 5-3. The licensee derived the leakage crack size for the overlaid dissimilar metal weld of the surge line by multiplying an effective penalty factor (1.44) to the leakage crack size derived for the original dissimilar metal weld based on the fatigue degradation mechanism. The licensee derived the penalty factor (1.69) from the ratio of the leakage crack size derived for PWSCC and for fatigue in Reference 5-6. The staff questions the validity of this approach because in References 5-5 and 5-6, the leakage crack size was calculated for PWSCC and for fatigue without modeling an overlaid DMW. It appears that the licensees approach was not verified by or based on any finite element or theoretical analysis. The licensees approach may provide a rough estimate of the leakage crack size for the overlaid DMW. However, the staff expects that a fracture mechanics analysis would be performed to obtain the leakage crack size for the overlaid DMW, or at a minimum, the penalty-factor approach should be verified by a theoretical analysis. Justify application of the penalty factors.

N-11. Page 5-3. (1) Explain how the leakage crack in the weld overlaid DMW and in the weld overlay is modeled, how the degradation mechanism in the overlay and in the DMW is assumed, and what input was used for the leakage crack model to predict leak rates. (2) If a computer code is used to calculate the leak crack size, describe the computer code that performed the calculation and discuss the level of validation conducted for this software.

N-12. Page 6-6. Explain why Table 6-3 does not include stability results for Node 10 (the hot leg to surge line nozzle).

N-13. Pages 6-9, 6-10, 6-11, and 6-12. Discuss how the curves on these pages were constructed.

N-14. Page A-1. Cite reference(s) from which equations (A-1 and A-3) were taken.

N-15. The NRC staff plans to use the PICEP computer code from the report, Pipe Crack Evaluation Program, Electric Power Research Institute, EPRI NP-3596-SR, Revision 1, to perform a confirmatory analysis. The NRC staff requests the following information at Nodes 10, 20, 70, and 75 that were analyzed in WCAP-17187-P. (a) primary membrane stress and bending stress, (b) normal operating pressure, (c) 0.2%

offset yield stress, (d) yield strain, (e) Ramberg-Osgood exponents (n) and coefficient (alpha), (f) Is the fluid saturated or sub-cooled before exiting the crack, (g) fluid stagnation pressure and temperature, (h) height of protrusion of the roughness grain from surface (in inches).

R-1. Section 2.2, last two lines on page 2.2. It is mentioned that the temperature and pressure are maintained within a narrow range. Provide quantitative values of the ranges.

R-2. Section 2.3. Provide any prior occurrences of fatigue cracking or primary water stress corrosion cracking in this piping system.

R-3. Section 2.2. Provide quantitative information about historic frequencies on water hammers in surge piping.

R-4. Page 3-1, Loads for Fracture mechanics analysis. In conducting the piping stress analyses for determination of loads, was the effect of the weld overlay included in the analyses? This effect may be minimal for normal operating loads, but may have a larger effect on the safe shutdown earthquake (SSE) load calculation.

R-5. Specify the computer software that was used to conduct the piping stress analysis.

Describe how the weld overlay was modeled in the piping stress analysis.

R-6. Axial shrinkage of the weld overlay can cause a tensile axial stress in the rest of the piping system when the weld overlay is in-situ with the piping system connected to the pressurizer and hot leg. How is the axial shrinkage accounted for in the pipe stress analyses?

R-7. (1) Clarify the procedure for choosing the critical location for conducting the LBB analyses. In Section 3.1, it is stated that the pipe locations were selected based on the magnitude of the moments and their proximity to elbows. Node 70 was chosen as the worst case. However, for Load Case A in Table 3-5, Node 20 had higher moments than that of Node 70. (2) To aid in necessary confirmatory calculations, provide all load components (i.e., moments in the x, y, and z directions and Fx) for each ASME loading category case (A, B, C and D) for Nodes 70, 75, 80, 10, 20, 25, 45 and 55.

R-8. Page 3-10. Justify the acceptability of calculating the critical flaw size in Alloy 182 welds without any displacement-controlled loads such as thermal expansion. In Materials Reliability Program, MRP-216, report, published by the Electric Power Research Institute, analyses were conducted by both Structural Integrity Associates and Quest Reliability that suggested that some of the displacement controlled loads can be eliminated from the calculation of through-wall crack stability. In fact, the work by Quest suggests that for relatively long flaws, only about 50% of the applied moment would be relieved. In the MRP-216 work, since there was still question about how much of the displacement-controlled loads were used in critical crack calculations, the thermal expansion loads were assumed to contribute to the through-wall crack stability.

R-9. Page 4-1, Tensile material properties. Clarify why ambient, not operating, temperature material properties (with temperature correction), taken from the Battelle database, were used in the analyses. In many cases, operating temperature material properties are also available in the database.

R-10. Page 4-4. Describe how the tearing modulus is calculated. For the J-R power-law representation, what crack extension was used to calculate the toughness slope dJ/da?

R-11. Page 4-6, Table 4-1, shows material properties (yield and ultimate strength and modulus of elasticity), for Node 20 taken at 333 degrees F. Page 4-9, Table 4-5, shows fracture toughness values for Node 20 taken at 333 degrees F. Justify why materials properties and fracture toughness values for Node 20 are presented for 333 degree F because under operating conditions D & E, the temperature at Node 20 should be above 333 degrees F.

R-12. Page 5-3, second to the last paragraph. Justify the conclusion that the leakage size flaws are conservative. The licensee states that the weld residual stresses (WRS) from the weld overlay (WOL) will cause compressive stresses on the inside diameter surface, thus making the calculation conservative. From a flaw tolerance standpoint, the WRS will cause the crack faces to close, thus reducing the crack opening and creating a longer leakage flaw size. Therefore ignoring the WRS would be non-conservative.

R-13. Page 6-3, Limit Moment Method. Confirm that the applied moments were multiplied by the applicable Z-factor for determining critical flaw size.

R-14. Page 6-3. For the overlayed Alloy 82 weld, which diameter was used in the Z-factor calculation (e.g., the outside diameter before or after the overlay)?

R-15. Page 6-5. Demonstrate that for Nodes 70, 75 and 20, faulted load case F is the limiting case. For Node 20, at 333 degrees F, this case may not be limiting, since the temperatures will be higher for other load cases and the strengths will be lower, and the critical flaw sizes may be shorter.

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Subject:

RAI on Waterford 3 LAR for APproval of LBB of the Pressurizer Surge Line Sent Date: 4/21/2010 11:23:27 AM Received Date: 4/21/2010 12:45:00 PM From: Kalyanam, Kaly Created By: Kaly.Kalyanam@nrc.gov Recipients:

wsteelm@entergy.com (STEELMAN, WILLIAM J)

Tracking Status: None mmason@entergy.com (mmason@entergy.com)

Tracking Status: None RMURILL@entergy.com (RMURILL@entergy.com)

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