Text

Response to NRC Request for Additional Information for Generic Letter 96-06, Waterhammer Issues
	ML032740069
Person / Time
Site:	Saint Lucie
Issue date:	09/29/2003
From:	Jefferson W; Florida Power & Light Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	GL-96-006, L-2003-244
	Download: ML032740069 (26)
	v • d • e

0 Florida Power & Light Company, 6501 S.Ocean Drive, Jensen Beach, FL 34957 FPL September 29, 2003 L-2003-244 10 CFR 50.4 US Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 RE: St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 Response to NRC Request for Additional Information Generic Letter 96-06 Waterhammer Issues The Florida Power & Light Company (FPL) supplemental response to Generic Letter 96-06, for St. Lucie Units I and 2 is attached. This supplement provides a response to the NRC second request for additional information (RAI) dated August 1, 2003.

GL 96-06 concerns whether the cooling water system for containment air coolers is susceptible to waterhammer or two phase flow conditions during postulated design basis accidents and whether piping systems that penetrate the containment are susceptible to overpressurization from thermal expansion of entrapped fluid. Under previous correspondence:

. NRC accepted FPL's responses and actions concerning two-phase flow and thermal pressurization issues and has closed these issues.

NRC accepted FPL deferment of the waterhammer issue pending review and approval of an EPRI developed design-basis approach to waterhammer evaluation.

NRC letter dated April 3, 2002 documented acceptance of EPRI Report TR-1 13594 for use in evaluating GL 96-06 waterhammer issues and requested FPL response to the remaining waterhammer issues.

FPL Letter L-2002-149 dated July 29, 2002, provided a schedule for completing GL 96-06 analysis and modifications and indicated that FPL intended to preclude containment fan cooler (CFC) voiding by moving the component cooling water (CCW) pumps to an earlier emergency diesel generator (EDG) load block. To reduce modeling uncertainty for the time-to-boil and void size calculations, FPL subsequently performed benchmark testing of the CCW pump stop and start transients. These tests indicated that CFC voiding could be expected within Unit 1 Train B for the design bases accident with loss of offsite power (DBA/LOOP) scenario.

FPL Letter L-2003-069 dated March 13, 2003 responded to the NRC using an analysis based on the method of characteristics (MOC) methodology to determine waterhammer occurrence and magnitude as described in the EPRI Report.

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an FPL Group company

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Page 2 On August 1, 2003, the NRC issued an RAI with respect to this response requesting clarification of specific issues and additional analysis information.

As discussed by phone with the NRC staff on July 30, 2003, FPL will update Question 6

& 7 responses to address final design information within 30 days after return to power following the Unit 1 spring 2004 refueling outage (SLI1-19). Please contact George Madden at 772-467-7155 if there are any questions about this submittal.

Willn Jr.

Vic resident St. Lucie Plant WJ/GRM Attachment

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 1 Attachment St. Lucie Units I and 2 Response NRC Request for Additional Information Dated August 1, 2003 Regarding GL 96-06 Waterhammer Issues NRC Question I - Page 2 of the March 13, 2003, submittal discussed benchmark testing of Component Cooling Water (CCW) system pump coastdown and recovery following restart. Provide a comparison between these tests to a postulated loss of offsite power (LOOP) event at St. Lucie. Provide comparisons of steam formation within the CCW piping, number of pumps starting, maximum flow rates within the system after pump restart and waterhammer produced. Also, identify the location of the test section, discussed on page 3, relative to the CCW pumps and the containment coolers.

FPL Response Benchmark testing was performed to confirm HYTRAN's velocity predictions following pump shutdown were reasonable (heat transfer analysis indicated sensitivity to pressure and flow transients) and to confirm HYTRAN's predicted water-solid dynamic pressure oscillations on pump stop and start were real. Benchmark testing results showed the HYTRAN analysis predictions were accurate.

The St. Lucie Units employ a closed loop CCW System for cooling containment fan coolers (CFCs) and other essential cooling loads. Without containment heating from a Loss of Coolant Accident (LOCA) or main steam line break (MSLB), the LOOP-only event for St. Lucie represents a water-solid transient associated with pump coastdown and pump start.

GL 96-06 modeling for St. Lucie Units 1 & 2 considered combinations of LOOP with containment heating scenarios (LOOP/LOCA, LOOP/MSLB). As discussed with NRC staff by phone on July 30, 2003, no analysis of the LOOP-only event was performed by FPL in response to GL 96-06. It is FPL's understanding that a LOOP-only event analysis is not required by the GL 96-06 work scope and, based on discussion with the NRC staff, is not required with respect to this RAI.

While the LOOP-only condition was not modeled, a water-solid response would be expected without steam formation within the CCW piping. Pump coastdown for benchmark testing would approximate the expected hydraulic transient for a LOOP event. Primary differences would stem from differences in the hydraulic resistance and inertial aspects of the LOOP-only scenario vs. the tested scenario.

In the LOOP scenario, the non-essential CCW header (N-header) would remain in service and the restart of the two CCW pumps would produce flow in the A, B, and N-headers. For the test condition, the N-header was isolated and the shutdown cooling (SDC) heat exchanger was valved in service. The hydraulic resistance of the SDC heat exchanger flow circuit is somewhat less than the N-header while the inertia of the N-header is likely greater than the SDC heat exchanger flow circuit.

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 2 Information concerning the number of pumps starting in the benchmark test and LOOP-only scenario, and maximum flow rates expected within the system after pump restart is provided as follows:

Parameter Test Condition LOOP Only Condition Number of Pumps Starting 1 (half system w/SDC Hx) 2 (N-header not isolated)

Maximum flow rates -7640 gpm per pump -5700 gpm per pump Flow rate at the CFC -1350 gpm -1400 gpm Benchmark test measurements were taken at pipe penetrations adjacent to the outside containment shield building wall. Relative locations to system components are shown on the following figure.

row" CD o r-5Xr COMPONENT COOLING WATER ACOPOENT COMPNEN COOING13Z COOLING -

CD HEAT EXCHANGERS A. 2575 F. (m

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St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 4 NRC Question 2 - Figures on page 3 of the submittal indicate that a CCW system hydraulic (HYTRAN) code predicts higher waterhammer pressures when a reduced speed of sound is used. It is the U.S. Nuclear Regulatory Commission (NRC) staffs understanding that when a reduced speed of sound is used in waterhammer calculations, lower waterhammer pressures should result. Explain this discrepancy.

FPL Response As discussed in the response to Question 1, the water-solid dynamic pressure response shown in the figures on page 3 of the submittal do not represent column closure waterhammer conditions following heating of the containment. The water-solid dynamic pressure oscillations occur as a result of pump shutdown and startup.

FPL concurs with the NRC staff's understanding that when a reduced speed of sound is used in waterhammer calculations, lower transient pressures would be expected. The Sargent & Lundy (S&L) HYTRAN code also predicts lower waterhammer pressures with a reduced speed of sound (following the Joukowski equation).

The following additional information is provided to place the submittal's comment concerning the speed of sound into context. The benchmark testing showed the predicted pressure oscillations were real and the magnitude of the oscillations was well represented. However, the wave frequency was over-predicted and the oscillation's rate of decay was under-predicted as shown in the top figure on page 3 of the submittal. It was noted that by changing the speed of sound used within the HYTRAN analysis, there was much better congruence of wave's period and rate of decay in this water-solid condition.

The comment on page 3 of the submittal indicated that air coming out of solution may act to locally reduce the speed of sound and account for this field test result. This conclusion was offered as an observation for the likely cause of the phase shift in the calculated water-solid dynamic pressure response. The shift of the periodic pressure oscillation to coincide with the pressure rise of the pump start did result in a higher calculated maximum pressure indicated in the second figure on page 3 of the submittal.

This can be explained by in-phase reinforcement of the water-solid pressure oscillation with the water-solid pump start pressure transient.

The speed of sound criteria contained within the EPRI Report was used for all HYTRAN runs made in support of the formal GL 96-06 response for St. Lucie Unit 1 & 2 LOOP/LOCA and LOOP/MSLB scenarios.

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 5 NRC Question 3- The submittal states that the HYTRAN code was used to predict peak pressure produced in the waterhammer analysis. The NRC staff has not previously reviewed the HYTRAN code for waterhammer analysis within CCW piping. Provide either the HYTRAN code for staff review, or provide an analysis of the most severe waterhammer postulated within the CCW piping using the Electric Power Research Institute (EPRI) methodology that the staff has approved. If you choose to apply the EPRI methodology rather than submitting the HYTRAN code for staff review, provide the following information:

a. The maximum CCW velocity following pump restart.

b. Mass of gas in the void. Provide justification that the minimum noncondensible mass for use of the EPRI methodology will be present.

c. Amount of cushioning credited. Reference the nomograph used to determine cushioning.

d. Assumptions regarding pressure pulse shape.

e. Assumptions regarding pressure pulse duration.

f. Transmission coefficients used to track the pressure wave through the CCW piping.

g. Pressure pulse clipping.

FPL Response In correspondence dated April 3, 2002 (Reference 1), the NRC accepted use of EPRI Report TR-1135941 and provided a safety evaluation presenting the bases for their acceptance. NRC Safety Evaluation Report (SER) acceptance was based on general agreement with EPRI's testing and analytical approaches, stipulation of limitations, and a risk perspective analysis of potential pipe failure as a consequence of a postulated GL 96-06 waterhammer event.

EPRI provided two acceptable methods for calculating GL 96-06 Column Closure Waterhammer (CCWH) loads within Reference 2. The first of these methods, the Method of Characteristics (MOC) method, is provided in Chapter 8 of Reference 2. The second EPRI method, the Rigid Body Method (RBM), is a simplified, approximating approach explained in Chapter 9 of Reference 2 and in more detail within Reference 3.

The NRC SER indicates on page 7 that use of either MOC (Method of Characteristics) or RBM (Rigid Body Method) methodology requires that licensees first perform an evaluation sufficient to obtain the necessary analytical inputs for the methodology and that certain specified conditions must be met.

As discussed in FPL Letter L-2002-149 dated July 29, 2002, Sargent & Lundy (S&L) performed a plant specific MOC analysis to model the St. Lucie CCW pump coastdown and CCW pump start phase of the DBA/LOOP event to determine the necessary analytical inputs for entry into one of the two EPRI test methodologies. FPL EPRI adopted a new report numbering system after the original report numbers (TR-1 13594, Volumes 1 and 2) were assigned. The final report numbers and publication dates are provided in References 2 & 3. The reports include the NRC safety evaluation for the EPRI waterhammer methodology.

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 6 subsequently elected to continue the St. Lucie analysis of the CCWH event using the more accurate EPRI MOC methodology. As discussed in FPL Letter L-2003-069 dated March 13, 2003, the HYTRAN/MOC analysis was performed in accordance with the NRC SER limitations and restrictions provided and a risk perspective analysis demonstrated the overall risk of piping failure was similar to that contained within the SER.

Based on discussion with the NRC Staff on September 2, 2003, it is FPL's understanding that use of the MOC methodology by S&L within their HYTRAN code requires further review to ensure the analysis correctly implements the EPRI MOC method. Per discussion with the NRC staff, the following material is prepared to assist in the review.

Further information will be provided to demonstrate that the HYTRAN CCWH analysis correctly implements the EPRI MOC method.

The HYTRAN MOC results will be compared to EPRI RBM results to show consistency.

EPRI MOC METHOD/HYTRAN HYTRAN is a Sargent Lundy, LLC (S&L) proprietary computer program designed to model transient hydraulic phenomena in piping systems. It has been the standard analysis tool for virtually all single phase transient analyses at S&L over the past 30 years. Use of this code has been proven in the design of major piping systems (e.g.,

feedwater, main steam, circulating water, etc.) on numerous nuclear and fossil power stations. The HYTRAN code is listed as an analysis tool in several UFSARs (e.g.,

Clinton).

HYTRAN was originally developed at S&L in the period 1971 through 1972. Using the fixed grid Method of Characteristics (MOC) solution procedure as given in Streeter and Wylie (References 4 & 5), HYTRAN is able to simulate a wide variety of hydraulic transients such as pump start or column closure in liquid systems and steam hammer on stop valve closure in gaseous systems. Over the years the program has been modified to add new boundary conditions and to update the solution procedure to conform to the latest methods. HYTRAN falls under the S&L QA Program, which complies with 10CFR50, Appendix B. HYTRAN is validated and verified (V&V) against a standard problem set, primarily from Reference 4, which tests significant modeling within the code.

Further, as part of a V&V effort for acquisition of software, results from a commercially available code (AFT ImpulseM) were compared to HYTRAN results. This work was completed in 2002 and showed accurate agreement between the codes.

St. Lucie Units I and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 7 For FPL's St. Lucie GL 96-06 analysis, a Containment Fan Cooler boundary condition (steam-air filled void) was added to HYTRAN. This version of HYTRAN complies with the EPRI MOC methodology described in Reference 2, including the modeling of heat transfer within the steam-air void. To demonstrate this, HYTRAN was benchmarked and validated against the test and analysis results EPRI provided in Reference 2.

The V&V compares HYTRAN to three EPRI test cases and to EPRI's MOC simulations of the test cases. Further, the V&V compares HYTRAN MOC simulations to EPRI's MOC simulations of two Rigid Body Method cases. For all five cases, HYTRAN results correlate well with the EPRI results.

Within the next section, a comparison between the HYTRAN MOC and RBM maximum pipe segment loads for the St. Lucie specific analysis also demonstrates that the loads calculated by HYTRAN are reasonable. In addition, the CCWH pressure pulse calculated by HYTRAN at the point of column closure is shown to correlate well with the RBM peak pressure and shape.

The HYTRAN calculation is available for NRC staff review at the St. Lucie site. The HYTRAN source code is available for NRC staff review at the S&L corporate office in Chicago.

EPRI RBM METHOD The EPRI RBM approach is a simplified, standard approach approved by the NRC. As such, it can be compared to other methods of calculating CCWH loads. The intent of comparing loads from the EPRI RBM approach with HYTRAN, is to demonstrate that the HYTRAN results are reasonable and can be used as input to qualify the subject piping for CCWH loading resulting from a postulated GL 96-06 event.

The EPRI Rigid Body Method (RBM) is used below to calculate GL 96-06 CCWH maximum pipe segment loads and pressures downstream of St. Lucie Unit 1, Loop B CFCs HVS-1C and HVS-1D, including the CFC HVS-1C return manifold piping. These loads are then compared to those formally calculated using the EPRI MOC approach, developed using the HYTRAN computer program. The HVS-1C & HVS-1D return piping is representative of piping in both loops and units of the St. Lucie Component Cooling Water Systems.

The EPRI RBM approach (References 2 & 3) is used to calculate the peak pressure, rise and duration of a pressure pulse, and the associated maximum pipe segment loads, resulting from a worst case CCWH GL 96-06 scenario. Application of the RBM approach to estimate maximum pipe leg forces in constant diameter legs adjacent to the point of column rejoining is straightforward, assuming that the water column differential velocity is known.

The maximum differential velocity of the two water columns from an uncushioned HYTRAN analysis is equated to Vi, 1 in the RBM approach delineated in the EPRI User's Manual. The uncushioned HYTRAN analysis does not include the effect of either

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 8 steam or air cushioning. However, the steam pressure in the cavity corresponding to the flashing point of the hot water is considered, and the downstream water column velocity prior to column rejoining results from the steam cavity pressure.

The cavity closure point is located at a 10 inch by 8 inch reducer, which is at the high point of the CCW system downstream of the HVS-1C outlet. To be conservative, the RBM calculation is based on the minimum air requirement for a 10 inch pipe and the maximum differential velocity for an 8 inch pipe. From an uncushioned HYTRAN analysis, the maximum differential velocity of the two water columns in an 8 inch diameter pipe is approximately 9.5 feet per second (Vinual). The requirement that the differential water column velocities be less than 30 feet per second is met, which allows use of the nomographs in the EPRI Users Manual.

Based on the volume of boiling water in the tubes of approximately 11.28 cubic feet, an initial water temperature of I OOF and the EPRI Methodology (pages 5-5, 5-6, and 5-7 of Reference 3), 2.87 grams of air from water in the cooler tubes can be credited in calculating the air cushioning effect.

The EPRI Methodology also credits a percentage of the gas in the mass of water in the heat exchanger headers and attached piping through which steam passes. The steam reaches the high point of the attached piping just downstream of HVS-1C prior to CCWH. The steam passes through an estimated 5 feet of 3 inch nominal diameter piping for each of 6 coils, and an estimated 24 feet of 6 inch nominal diameter piping, and over 2 feet of 10 inch diameter piping. The total water mass that steam passes through is estimated to be 464 pounds. Taking credit for a portion of the air in this water mass per EPRI, another 0.95 grams of air can be credited in calculating the air cushioning effect. While some steam will likely pass through the supply side headers, no credit was taken for this effect.

The total amount of air that can be credited for cushioning the GL 96-06 CCWH event initiated by the HVS-1C cavity is 3.82 grams of air compared to 1.5 grams of air needed in a 10 inch diameter pipe and 0.960 grams of air needed in an 8 inch pipe. Note that the HYTRAN analysis credited 2.8 grams of air in order to provide a calculation margin.

For the purposes of this RBM comparison, 2.8 grams of air will also be credited. Since L. is approximately 200 feet, the Figure A40 nomograph, with K = 40, is used to obtain Vcushlon/Viniaai = 0.84. Therefore, V cuhion = 8.0 feet per second.

Peak pressure = 1%pCVshi 0, = (2

1.93 sugs/f 3

4200 ft/sec* 8.0 fIsec)I(14 4 n2/ft2) = 224 psi Pressure rise time = 33.6 milliseconds, using Equation 9 -11 of Reference 2

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 9 The pressure pulse duration time is twice the distance from the point of column rejoining to the nearest downstream header (about 290 feet) divided by the water sound speed (about 4200 feet per second) for a 69 millisecond duration time. To be conservative, the duration time is increased by adding the rise time. Therefore the pressure pulse is calculated to be a trapezoid with a peak pressure of 224 psi having a linear rise time of 33.6 milliseconds, a dwell time of 35 milliseconds and a linear decay time of 33.6 milliseconds. The RBM peak pressure and shape correlate well with the HYTRAN/MOC peak pressure and shape as shown in the figure at the end of this response.

The method for calculating pipe segment forces provided in Figure 6-4 and associated text of Reference 3 is used to calculate the maximum leg forces. The longest straight pipe segment downstream of HVS-1C is leg name 107 at 20.2 feet. Using the RBM approach, the maximum force in this leg is 1605 pounds.

At pipe area changes, such as tees and reducers, transmission factors using the methodology of References 2 & 3 are applied. In order to simplify the calculation, pressure pulse clipping is not credited except as noted below for the junction of the return piping from HVS-1 D. Not crediting pressure pulse clipping is conservative as clipping acts to reduce the magnitude of the pressure wave. These transmission and clipping factors, where applied, are tabulated in the following table.

The 8-inch lines from the HVS-1C and HVS-1D coolers join together outside containment and then the combined line joins the 20 inch header to return to the CCW pump suction. The 20 inch header is within 17 feet of the tee joining the HVS-1C and HVS-1 D return lines. This header reduces the pipe pressure transmitted from the tee upstream to Cooler HVS-1D. Without considering the effect of the 20 inch header the transmission factor at the tee is 0.667. Using Equation 9.2 of the EPRI Technical Basis Report (Reference 2), the transmission factor is reduced to 0.366.

The following Load Comparison Table compares RBM and HYTRAN/MOC maximum leg forces. The accompanying Node Point/Leg Sketches indicate the locations of the legs.

The CCWH MOC pressure pulse from the HYTRAN analysis at the point of closure is compared to the peak pressure and shape of the RBM pressure pulse in a following figure.

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 10 Load Comparison Table of RBM and HYTRANIMOC Maximum Leg Forces Leg [Leg RBM HYTRAN RBM Max Transmission Lg.Nm Area Length Max Load Max Load Pressure Factor/Pressure Leg Name (sq. In) (feet) (Dounds) t_ __ __, punds Pulse (psi) Clipping Point of Column Combinin Is at Svstem High Point just Outboard of ! :4oler C - 10"x8" RedlLeg 100 to 10 1 101 50 7.8 620 864 224 1.000 102 50 3.3 262 406 224 1.000 103 50 16.8 1335 1315 224 1.000 104 50 3 238 412 224 1.000 105 50 2.3 183 431 224 1.000 106 50 6.8 540 854 224 1.000 107 50 20.2 1605 1877 224 1.000 108 50 1.7 135 358 224 1.000 109 50 14 1112 1281 224 1.000 110 50 3.1 246 438 224 1.000 111 50 11.7 930 1228 224 1.000 112 50 2 159 351 224 1.000 113 50 5.7 453 329 224 1.000 114 50 2 159 375 224 1.000 115 50 13.4 1065 1341 224 1.000 116 50 2.7 215 464 224 1.000 117 50 12.5 993 1320 224 1.000 118 50 2.3 183 412 224 1.000 119 50 10.3 818 962 224 1.000 Leg Name 1isends at C&LD D Return Tee - Leg Name 48 staarirts outboard of Cooler D 48 50 1.6 46 139 1 82 1 0.366 49 50 33 959 1042 82 0.366 50 50 11.5 334 415 82 0.366 51 50 1.4 41 131 82 0.366 52A 50 11.4 331 435 82 0.366 52 50 9.8 285 302 82 0.366 53 50 1.8 52 148 82 0.366 54 50 1.6 46 148 82 0.366 55 50 32.3 938 945 82 0.366 56 50 1.4 41 129 82 0.366 57 50 5.6 163 138 82 0.366 58 50 8.1 235 315 82 0.366 59 50 9.8 285 355 82 0.366 60 50 9.8 285 353 82 0.366 61 50 5.3 154 161 82 0.366 62 50 4.9 142 151 82 0.366 63 50 13.5 392 410 82 0.366 64 50 11 320 553 82 0.366 65 50 8.4 244 408 82 0.366 66 50 2 58 205 82 0.366 67 50 14.4 418 610 82 0.366 68 50 2.6 76 187 82 0.366 69 50 12.6 366 591 82 0.366 70 50 2.3 67 200 82 0.366 Leg Name 70 ends at C & D Return Unes Tee - Leg Name 71 Provides C & D Return Water to Header 1 71 1 50 1 13.2 383 1 1509 1 82 0.366 1 72 1 50 T 3.6 1 105 1 542 82 1 0.366 Leg Name 72 Flows Into 20" Return Header - Leg Name 73 Is 20" Header Return 73 278 1 47.0 1 3659 1 4042 1 40 1 0.176 74 _ 278 1 5.0 1 389 1 391 1 40 1 0.176

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 11 Load Comparison Table of RBM and HYTRANIMOC Maximum Leg Forces HYTRAN H Nme Leg f Leg Area Leg Length RBM Max Load HYTRAN Max Load RBM Max Pressure Trans-Mission Leg Name J (sq. In) (feet) l (pounds) (pounds)

Pulse (p si) _ _ _

Factor Leg Na e 99A starts at Cooler C Tul AIn 99A 1 10.2 12.0 118 285 136 0.606 99B 10.2 12.0 104 283 120 0.537 99C 10.2 12.0 166 277 192 0.855 99D 10.2 12.0 118 285 136 0.606 99E 10.2 12.0 104 283 120 0.537 99F 10.2 12.0 166 277 192 0.855 Leg Name 99F ends Cooler C-Tu blng - Leg Name 99G starts 3" Manifold to 6" Manifold 99G 7.3 1.5 11 86 136 0.606 99H 7.3 1.5 11 73 136 0.606 991 7.3 2.5 18 81 136 0.606 99J 7.3 1.5 9 21 120 0.537 99K 7.3 1.5 9 30 120 0.537 99L 7.3 2.5 16 78 120 0.537 99M 7.3 1.5 15 50 192 0.855 99N 7.3 1.5 15 26 192 0.855 990 7.3 2.5 25 78 192 0.855 99P 28.8 0.8 20 21 120 0.537 99Q 28.8 3.3 81 95 120 0.537 99R 28.8 3.3 92 186 136 0.606 99S 28.8 1.3 41 300 153 0.684 99T 28.8 0.8 25 129 153 0.684 99U 28.8 5.9 185 251 153 0.684 Leg Name 99U Is 6" Return to 6"x :6x10" Tee - Le Name 99V starlts 3" Manifold to 6" Manifold 99V 7.3 1.3 9 86 136 0.606 99W 7.3 1.5 11 73 136 0.606 99X 7.3 1.5 11 81 136 0.606 99Y 7.3 1.3 8 21 120 0.537 99Z 7.3 1.5 9 30 120 0.537 99AA 7.3 1.5 9 78 120 0.537 99BB 7.3 1.3 13 50 192 0.855 99CC 7.3 1.5 15 26 192 0.855 99DD 7.3 1.5 15 78 192 0.855 99EE 28.8 0.8 20 21 120 0.537 99FF 28.8 3.3 81 95 120 0.537 99GG 28.8 3.3 92 186 136 0.606 99HH 28.8 1.3 41 300 153 0.684 9911 28.8 0.8 25 129 153 0.684 99JJ 28.8 4.4 138 251 153 0.684 Leg Name 99JJ Is 6" Return to 6"x6"x1o" Tee - Leg Name 100 Is 10" Return Leg from 6"x6'xlO" Tee 100 1 78.9 1 2.8 1 1 272 1 823 1 174 1 0.776

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St. Lucie Units I and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 14 RBM to HYTRAN/MOC Comparison Pressure Time History at Point of Column Closure l-HYTRAN -RBM 300 25ran 2C0 0

E15 0

10 50 lO1, I I 41.5 41.55 41.6 41.65 41.7 41.75 41.8 41.85 41.9 41.95 42 Time (sec)

Pressure Time History for Cavity Closure Point

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 15 Conclusion of the HYTRANIMOC vs. RBM Method Review The correlation of maximum pipe segment loads between EPRI RBM and HYTRAN/EPRI MOC is good, especially in the HVS-1C return line downstream of the point of water column closure. In the remaining part of the system, HYTRAN calculates consistently higher maximum pipe segment loads than the RBM approach, except for isolated cases. One reason for this in the CFC manifold region is that with a one millisecond calculation time, HYTRAN internally treats legs shorter than 4 feet (sound speed*time step) as being 4 feet long. This causes HYTRAN to overestimate the associated pipe segment loads.

The RBM peak pressure at the point of water column closure correlates well with HYTRAN/MOC, as does the overall shape of the pressure pulse.

The RBM to MOC comparison demonstrates that the St. Lucie GL 96-06 CCWH loads calculated by HYTRAN are suitable for qualification of the CCW System under CCWH loads resulting from a postulated GL 96-06 event. A significant advantage of using HYTRAN in an MOC approach is that the pressure time histories of each pipe leg are calculated and used as input into a dynamic piping analysis program to calculate pipe support loads. This approach results in more accurate modeling of piping response than applying the simplified approaches provided in the EPRI User's Manual.

References

1. NRC Letter dated April 3, 2002, NRC Acceptance of EPRI Report TR-1 13594, Resolution of Generic Letter 96-06 Waterhammer Issues, Volumes 1 and 2.

2. EPRI, Generic Letter 96-06 Waterhammer Issues Resolution: Technical Basis Report - Proprietary, EPRI, Palo Alto, CA; Report Number 2002.1003098.

3. EPRI, Generic Letter 96-06 Waterhammer Issues Resolution: Users Manual -

Proprietary, EPRI, Palo Alto, CA; Report Number 2002.1006456.

4. Streeter, V. L., and Wylie, E. B., Hydraulic Transients, McGraw Hill, New York, NY 1967.

5. Wylie, E. B., and Streeter V. L., Fluid Transients in Systems, Prentice Hall, 1993.

NRC Question 4 - The submittal states, on page 6 that calculated results from a water heatup transient are used as input into HYTRAN. Describe the assumptions and equations used in this calculation andjustify whether the methodology is conservative.

FPL Response The assumptions and correlation equations used within the heat transfer analysis and justification of their use were previously provided in FPL's response L-97-18 dated January 28, 1997.

In summary, heat transfer on the outside of tubes accounts for fins, condensing heat transfer (4x Uchida), and forced convective heat transfer (Hilpert - for the MSLB event).

Heat transfer on the inside of tubes accounts for the forced convection (Dittus-Boelter),

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 16 natural convection (Catton), subcooled nucleate boiling (Rohsenow), and bulk pool boiling (Chen) regimes. The methodologies employed are standard formulations utilized within commercial and nuclear industries for many years and are considered applicable to the case-in-point. Assumptions within the heat transfer modeling were selected to conservatively determine the time-to-boil.

Based on phone conversations with the NRC staff, it is FPL's understanding that the previous L-97-18 response adequately addresses this question.

NRC Question 5 - The submittal states, on page 7, that the peak pressure generated in the analysis is 270 psig, the piping design pressure is 150 psig, and that the Component Fan Cooler cooling coils have a design pressure of 225 psig. Provide justification that these components will not fail under the calculated waterhammer load.

FPL Response CCW system piping and the CFC cooler manifolds are constructed of A-106 Gr B standard wall or greater material in sizes ranging from 2-inch to 24-inch diameter.

Larger sizes of piping generally have a lower maximum working pressure.

The location of column closure occurs within 8 and 10 inch Schedule 40 piping.

Published maximum working pressure (NAVCO Piping Datalog, 1th Edition) for 10-inch A-106 Gr B Schedule 40 piping is 912 psig.

The bounding CCW system pipe size of 24-inch Schedule 20 has a tabulated maximum working pressure of 415 psig while the peak pressure expected at this remote location (CCW pump) is 112 psig for the 24-inch suction piping and 200 psig for the 24-inch discharge piping.

The containment fan cooler cooling coils are constructed of 3-inch copper pipe and 5/8-inch tubes. The fabricated cooling coil assembly (coils and headers) was hydro-statically tested at a pressure of 300 psig.

Maximum pipe stresses for the waterhammer conditions are addressed within Question 6 and provides the formal justification that the piping and fittings will not fail under the calculated waterhammer load. An additional consideration, not included within the stress analysis, is that the elevated containment pressure at the time of the event effectively reduces the pressure stress.

St. Lucie Units I and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 17 NRC Question 6 - Provide the maximum loads calculated for the CCW piping, supports, orifices, bends, and penetrations for the worst case column closure waterhammer.

Also, provide the ratios of the maximum loads within the service water system to the loads required for failure.

FPL Response The load combinations utilized for the CCW piping and supports under GL 96-06 are as defined in the St. Lucie Unit I & 2 UFSAR Sections 3.9. Specifically, the piping and components are evaluated for pressure, dead weight, thermal, and the square root sum of the squares (SRSS) of seismic DBE and waterhammer. Pipe supports, nozzles, and containment penetrations are evaluated for dead weight, thermal, seismic anchor movement, and the SRSS of seismic DBE and waterhammer.

Waterhammer loads were developed from the HYTRAN generated pressure time histories of each pipe leg and input into a dynamic piping analysis program to calculate pipe stress and support loads. These dynamic loads were appropriately combined with other piping code of record loads to evaluate the integrity of the piping. The results of these analyses indicate the piping and in-line components comply with ASME Section III Code requirements, with a maximum stress ratio of 0.52. In addition, the pipe supports, with some limited modifications, and penetrations were found structurally adequate for the applied loads.

The following table provides a summary of the affected pipe supports and penetrations, support type, maximum calculated waterhammer load, resulting design load, and design margin (either component load rating or limiting stress ratio of structural steel frame or weld). In addition, the table identifies those supports that require modification for the revised loads.

This table does not specifically address orifices and bends as these components fall under the scope of the piping stress analysis and are evaluated therein. As discussed with the NRC staff on July 30, 2003, the stress analysis demonstrates compliance with ASME Section III Code requirements and such demonstration is adequate to respond to this question.

As discussed with the NRC staff on July 30, 2003, FPL identified several analytical discrepancies within the stress analyses of record for the affected CCW piping that are unrelated to GL 96-06. These discrepancies included incorrect seismic response spectra and omission of or incorrect seismic anchor and thermal accident movements.

FPL's review of this condition determined the system remains operable. FPL is currently revising the affected Unit I CCW supply and return piping stress analysis to correct these discrepancies, while taking into consideration the GL 96-06 waterhammer loads. Unit 2 CCW system stress analyses are not affected by this issue.

As discussed by phone with the NRC staff on July 30, 2003, FPL will provide results of the final CCW piping and support design analyses within 30 days of return to power following Unit 1 Spring 2004 SL1-19 refueling outage (new commitment).

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 18 Calculated Loads for Pipe Supports. 1C & 1D CFC Coolers - Return Piping Inside Containment to RAB CCW B Return Header Dynamic Loads New Combined Design Loads Marin Stress Pipe Support Support Water Hammer (Ibs) Faulted (b s) rg Cac Mark No. Typert Catalog Items Limiting Remarks Horizontal Vertical Transverse Horizontal Vertical Transverse Capacity Stress Ratio

- - - - _________ ~~~~~~~~~~~~~~~~~~(Ibs)

Frames/Welds_________

+1853 Modification-CCH-212 Strut +/-169 -873 4000 0.05 Replace Rod Hanger

-873 ~~~~~~~~~~~~~~to Strut CC-1899-6210 Frame +/-295 +/-741 -1498 +/-857 N/A 0.155 CC-1899-2208 Snubber +/-3263 +/-3293 15000 0.08 CC-1899-6208 Frame +/-489 +/-1615 -1490 +/-2407 N/A 0.233 0.

o0 CC-1899-6206 Frame +/-1496 +/-1158 -2472 +/-1231 N/A 0.566

°~ c CC-1899-6204 Frame +/-693 +/-1880 -1763 +/-2657 N/A 0.307 E

E CC-1899-6202 Strut +/-528 -1650 3000 0.22 4-43 CC-1899-29 Strut +/-610 +/-1267 3000 0.22

° U CC-1899-2200 Snubber +/-577 +/-744 6000 0.24 CCH-169 Frame +/-881 +/-257 -2075 +/-788 N/A 0.19 CC-1899-6173 Frame +/-762 +/-454 +/-484 +/-1417 -2185 +/-1981 N/A 0.627 e Modification-0 CCH-184 Frame +/-833 -2142 N/A 0.78 Replace U-bolt to O _ __ __ _ __ __ _ _ _ _ _ __ _ _ _ _ _ _ _ _ __ ___ ___ _ _ __ _ __ __ _ F ra m e CC-1899-2184 Strut +/-277 +/-564 3000 0.01 CC-1899-48 Snubber +/-262 +/-335 6000 0.01 CC-1899-1187 Strut +/-501 -1257 3000 0.02 CC-1899-6187 Strut 1+/-1047 +/-1530 3000 0.04

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 19 Calculated Loads for Pipe Supports - IC & ID CFC Coolers - Return Piping Inside Containment to RAB CCW B Return Header Dynamic Loads New Combined Design Loads Margin Stress Pipe Support Support Water Hammer (Ibs) aulted lbsL ;)_Margin Calc Mark No. Type x Y Z X Y Z Catalog Items Limiting Remarks Horizontal Vertical Transverse Horizontal Vertical Transverse Capacity Frames/Welds

S CC-1883-6198 Rigid Bar 12306 -4086 6000 0.13 CC-1883-1198 Strut +/-2735 +/-3380 6000 0.14

o. E* CCH-196 S

Strut +/-805

~~~~~~~~~~~~~~~~~~~~~~~~~-1095

+773 4000 0.04 Modification- Replace Rod HanetSr Q Q CC-1883-6196 Strut +/-1461 +/-1673 3000 0.04 8 CC-1883-6194 Frame +/-444 +/-933 -1845 +/-1130 N/A 0.114 E' CC-1883-6192 Strut +/-1338 +/-2080 3000 0.32 CCH-192 Strut +/-350 -1437 4000 0.11 Modication Replace 0 __ _ __7557____ _ _ _ _ _ __ _ _

CC-1883-6190 Frame +/-848 +/-2768 +/-605 +/-2240 +/-1131 N/A 0.54

+1225 CCH-47 Strut +/-1399 -6881 25000 0.32 Modification- Replace e ___ Rod Hanger to Strut CCH-51 Strut +/-492 -1518 25000 0.12 Modification- Replace

____ ~~~~~~~~~~~~~~~~~~~~~~

Hanger to Strut

. N CC-23-1 Strut +/-1273 +/-4790 10000 0.14

. I C =

CC-23-3____

Frame +/-172

____+2870

+/-865 +/-2434 N/A 0.17 o CC-23-4 Frame +/-196 +/-680 -350 +/-876 6N N/AA0 0.96

_ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ +1300+/-8 9

E Spang 0 CCH-46 San Dead load support only - evaluation not required CCH-50 Spring Dead load support only - evaluation not required

_ _ _ _ __ __ _ _ _ _ _ _ an Dynamic Loads New Combined Design Loads Penetration ID Type Water Hammer (lbs/ft-lbs) Faulted (lbs/ft-lbs MARGIN Fx/Mx Fy/My Fz/Mz FZx Limiting p-15_8_P-7_Type_1_3109/43

___ _ l F472y/M128 496/2698_____ 4721/91 lx Fy/My Stress Ratio

________PJ15 & P-17 Ctmt Pen 3109/432 496/2698 472/1128 4721/916 2686/4139 960/3156 0.7

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 20 NRC Question 7 - Page 11 of the submittal states that the piping, pipe support, and cooler structural analysis for the design basis case were ongoing. Provide the results of the structural analysis and include a summary of the licensing basis load combination along with the results of the stress analysis.

FPL Response A summary of the licensing basis load combinations, piping and pipe support analysis, and its status was addressed in the response to Question 6. The response to Question 7 will summarize the cooler structural analysis and its status.

The cooler analysis addresses the copper cooling coils, cooler manifold piping up to the 10 inch diameter flanges on both the supply and return lines and the cooling coil and manifold supports. The 10 inch piping flanges are the interface points between the cooler analysis and the CCW piping analysis.

As discussed by phone with the NRC staff on July 30, 2003, the cooler analysis completed thus far has developed the waterhammer loads but has not formally combined them with pressure, deadweight, thermal, and seismic loading in an analysis which would support the FSAR design basis loading combination. The following information is provided to indicate the results of the dynamic analysis completed to date.

CFC Layout The containment fan cooler is a 12 x 11 x 24 ft assembly constructed of structural steel members and sheet metal to support a fan, motor, ducting, cooling coils and supply/retum manifold piping connected to the CCW System. The steel manifold piping serving the 6 cooling coils consists of 6 x 10 inch tee in a horizontal run serving two 6-inch vertical risers which supply flow to 3 coils each via three nominal 3-inch flanged branch connections. The supply manifold and return manifold have a nearly identical layout and are supported by two supports on the horizontal run and two supports on each vertical leg. The 5/8 inch copper cooling coils are of a serpentine construction supported by a radiator type fins in a steel frame. Each coil has 44 copper tubes, which make 4 passes and each of the tube passes is approximately 80 inches in length. The outside diameter of each copper tube is 0.64 inches, and the tube thickness is approximately 0.049 inches, leaving the copper tube inside diameter at approximately 0.542 inches. Three inch nominal diameter copper pipe headers are drilled to accept the 5/8 inch copper tubing. The copper pipe headers have a brazed joint for steel or 90/10 copper/nickel stub and flange for connection to the steel manifold piping.

Cooling Coil Nozzle Loads The limiting condition for the cooling coils is governed by the piping nozzle allowable value, which is expressed in a six-factor interaction equation by the coil manufacturer.

Fluid transient piping loads acting on the 3-inch flanges are compared to the faulted

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 21 nozzle allowable values provided in vendor documentation with adjustment for actual tube wall thickness and for plant specific stress allowable values (3.0 Sm). The nozzle allowable criterion is met for each of the 6 coils connecting to the manifold on the return line piping. Suitable margin is provided for additional consideration of combined loads.

Manifold Piping Stresses Carbon steel and copper piping stresses are compared to a Faulted Condition allowable of 3.0 Sm, where S is the applicable material allowable stress in the hot condition.

Suitable margin is provided for additional consideration of combined loads.

Manifold Support Evaluation Piping supports are qualified using the acceptance criteria based on ASME Appendix F stress allowable values. The location with the maximum faulted stress interaction is in the 3x3x1/4-inch tube steel member; consistent with the critical member identified in the vendor seismic stress analysis. Suitable margin is provided for additional consideration of combined loads.

Coil Support Structure Loads applied to the cooling coil nozzles are transmitted to the frame of the cooling coil, which are in turn transmitted through structural members to the cooler foundations. As discussed in the vendors original seismic design report, the construction of the cooler is made of substantial members. The limited nozzle loads allowed from the cooling coils, precludes the need for rigorous analysis of the cooler structural members.

Summary - Cooler Analysis for Waterhammer Loading

Piping nozzle allowable values adjusted for the actual tube wall thickness and faulted stress allowable are met for each of the six coils connected to the return piping. As the tubing connected to the copper header is the weakest location of the CFC and the nozzle loads are controlled based on this criterion, the CFC coil design is adequate to withstand GL 96-06 CCWH loading.

Return side manifold piping is shown to meet Appendix F allowable values. Due to the location of the column closure, the supply side piping is expected to have similar or lower GL 96-06 CCWH loads than the return side piping. Since the supply side piping routing is nearly identical to the return side piping, the supply side piping is also acceptable. The manifold pipe supports meet their stress allowable values under the GL 96-06 CCWH loading.

St. Lucie Units I and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 22 As previously mentioned, the analysis performed to date has not formally combined deadweight, thermal, seismic and dynamic (waterhammer) stresses and loads. This analysis will be completed prior to making the GL 96-06 piping system modifications committed for completion during SLI-19 (existing commitment). The available margin in the cooler analysis indicates the expected load combination will be acceptable without the need for further CFC manifold support modifications. Should manifold support modifications be required, they will be completed on the same schedule previously committed for piping support modifications.

As discussed by phone with the NRC staff on July 30, 2003, FPL will provide final design information with respect to the cooler structural analysis within 30 days of return to power following Unit 1 Spring 2004 SL1 -19 refueling outage (new commitment).

NRC Question 8 - Page 11 of the submittal states that the loads and stresses are not sensitive to void size." Explain.

FPL Response From a qualitative viewpoint, review of the EPRI methodology indicates:

Release of a fixed percentage of the dissolved gas (air) in the total mass of CFC water is credited if the water is exposed to a tube temperature satisfying a temperature criterion, plus a fixed percentage of the dissolved gas from the total mass of header water is credited assuming the steam passes through the volume.

Accordingly, smaller cavity sizes would generally be expected to be associated with reduced column closure velocities and reduced waterhammer loads, since various void sizes result in similar credited air cushions.

A constant heat transfer coefficient is assumed over a constant area regardless of steam mass. The effect of this at St. Lucie is that larger voids have more credited steam cushioning.

For St. Lucie, the combination of these two effects limits the variance in the column closure velocity with void size and hence limits the variance in waterhammer forces with void size.

A parametric review was performed with respect to the affect of void size on maximum pipe segment loads for the 45 legs in the CFC return lines within the Unit 1 B CCW train for five arbitrary void volumes. The effect of void size on pipe segment loads is shown below. The results indicated that the loads were very small at low void size (1.71 ft3),

increased as void size increased (2.58 ft3 to 4.72 ft3), decreased slightly at 7.38 ft3 and dropped off again at a void size of 31.37 ft3. The variance in the maximum loads between the analyzed case (7.38 ft3) and other void sizes reviewed ranged from 10% to 25%.

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 23 Maxim urn Forces at 45 PIpe Legs for Various Vold Sizes 2500 31.27 ft3 (18.5 sec)

--- 7.38 t3 (11.5 sec)

-_-4.72 t3 (10.5 sec)

A 2.58 t3 (9.5 sec)

--- 1.71 ft3 (9.0 sec) 2000 1500

.0 0

02 1 000 500 0 ...... If -1 0) I.

Wf N. 0) CW UW

- - _ - _ Cal N N N N X Pipe Leg Index Number NRC Question 9 - Page 13 of the submittal establishes commitments for completing modifications that are necessary for resolving the waterhammer issue. Provide a status update for these items.

FPL Response

Modifications to implement Unit I EDG load block changes were completed during SL1-18 as committed.

Modifications to implement Unit 2 EDG load block changes were completed during SL2-14 as committed.

Support modifications for Unit 1 will be implemented during the SI1-19 refueling outage (currently scheduled for spring 2004). Design package development is currently underway to support this existing commitment.

Update RAI Question 6 & 7 responses to address final design and provide within 30 days of return to power following SI1-19. Final design analysis of the CCW piping and CFC is currently underway to support this new commitment.

St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2003-244 Attachment Page 24

Support modifications for Unit 2 will be implemented during the SL2-15 refueling outage (currently scheduled for fall 2004). Design package development is planned to support this existing commitment.

Text

0 Florida Power & Light Company, 6501 S.Ocean Drive, Jensen Beach, FL 34957 FPL September 29, 2003 L-2003-244 10 CFR 50.4 US Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 RE: St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 Response to NRC Request for Additional Information Generic Letter 96-06 Waterhammer Issues The Florida Power & Light Company (FPL) supplemental response to Generic Letter 96-06, for St. Lucie Units I and 2 is attached. This supplement provides a response to the NRC second request for additional information (RAI) dated August 1, 2003.

GL 96-06 concerns whether the cooling water system for containment air coolers is susceptible to waterhammer or two phase flow conditions during postulated design basis accidents and whether piping systems that penetrate the containment are susceptible to overpressurization from thermal expansion of entrapped fluid. Under previous correspondence:

. NRC accepted FPL's responses and actions concerning two-phase flow and thermal pressurization issues and has closed these issues.

NRC accepted FPL deferment of the waterhammer issue pending review and approval of an EPRI developed design-basis approach to waterhammer evaluation.