ML13094A181

Meeting Handout - Operational Assessment for Cycle 20

ML13094A181
Person / Time
Site:	Saint Lucie
Issue date:	03/14/2013
From:	Cipolla R Intertek APTECH
To:	Office of Nuclear Reactor Regulation
Rodriguez R NRR/DORL/LPL2-2 415-1558
Shared Package
ML13094A174	List: ML13094A181 ML13094A191 ML13094A193 ML13095A347
References
TAC ME9534
Download: ML13094A181 (20)

Text

St. Lucie (PSL) Unit 2 Operational Assessment For Cycle 20 Intertek APTECH Sunnyvale, CA Russ Cipolla March 14, 2013 1

Operational Assessments (OA)

Degradation Mechanisms Evaluated Wear at tube contact with anti-vibration bars (AVB)

Wear at V-Shaped Support Pads (V-SSP)

Wear at Tube Support Plates (TSP)

Tube Integrity Methods EPRI Integrity Assessment Guidelines (IAGL) implemented Flaw Handbook implemented Full bundle probabilistic analysis for AVB wear Deterministic methods used for the other wear mechanisms 2

Operational Assessment Model For AVB Wear Methodology Full bundle probabilistic operational assessment using Monte Carlo simulation method.

Multi-cycle approach which tracks the degradation mechanism over previous inspection intervals at end-of-cycle (EOC) to define the beginning-of-cycle (BOC) 20 wear population (both detected and undetected)

Same basic repair-on-sizing model used for previous cycles (EOC 17 and 18) 3

Operational Assessment Model For AVB Wear Methodology (Contd)

Model and input statistical distributions include:

Tubing strengths (normal distribution)

Probability of detection (log-logistic function)

Wear rate (lognormal distribution)

Degradation lengths (lognormal distribution)

Wear shape (normal distribution)

Initiation function for new wear (Weibull distribution)

Measurement uncertainty (normal distribution) 4

Prior Operational Assessment Benchmark How do the prior OA predictions compare with Cycle 19 Condition Monitoring Results?

Number of detected AVB indications in S/G 2A is 7485.

The number of projected AVB wear indications from EOC 18 OA was 7440 to 8750 for the two analysis cases evaluated.

Distribution of detected indications was well estimated for the larger depths 5

Prior Operational Assessment Benchmark Condition Monitoring Benchmark for EOC 18 OA Results 1.0 0.9 0.8 Cumulative Distribution, CDF 0.7 0.6 0.5 0.4 0.3 0.2 SG 2A EOC 19 0.1 EOC 18 OA Results for Cycle 19 (Case 1)

EOC 18 OA Results for Cycle 19 (Case 2) 0.0 0 5 10 15 20 25 30 35 40 45 NDE Depth, d/t (%TW) 6

Operational Assessment Benchmarks Previous Model Benchmark Cycle 19 Detected TW EOC 18 OA Depth PSL-2 Mechanism S/G Prediction at EOC 19 45.8% TW (Case 1) 2A 41.5% TW 49.6% TW (Case 2)

Anti-Vibration Bar Wear(1) 2B NA 40.8% TW Wear at Tube Support 2A & 2B 32.7% TW 20.6% TW Plates(2)

NOTES:

1) Probabilistic OA model prediction for worst case indication depth. Depth is maximum structural depth and includes systematic sizing error from the profile analysis.

2) Deterministic OA predicted depth includes uncertainty values at the 95-50 level. Depth is maximum peak depth.

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Operational Assessment Model Wear Rates from Cycle 19 Wear rates from Cycle 18 were used for Cycle 19. Wear rates showed correlated behavior with BOC 18 depths.

This was conservatively modeled in previous OA.

Wear rates for Cycle 19 show a weak correlation with BOC depths and wear rates were considered as independent for the next cycle.

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Operational Assessment Model Wear Rates for Cycle 20 Wear rates from Cycle 19 determined from paired bobbin Nondestructive Examination (NDE) depths and used for Cycle 20 Wear rates computed by two different methods as described in EPRI IAGL

- conservative evaluation (only positive growth)

- realistic evaluation (removes sizing error)

The wear rates were increased by a factor of 1.24 (developed by AREVA) to account for power-uprate conditions in Cycle 20 9

Operational Assessment Model PSL-2 AVB Wear Rates for First Three Cycles 1.0 0.9 0.8 Cumulative Distribution (CDF) 0.7 0.6 0.5 0.4 0.3 0.2 S/G 2A (2009) S/G 2B (2009) 0.1 S/G 2A (2011) S/G 2B (2011)

S/G 2A (2012) S/G 2B (2012) 0.0 0 2 4 6 8 10 12 14 16 18 20 22 24 Wear Rate, WR (%TW per EFPY) 10

Operational Assessment Model PSL-2 AVB Wear Rates for Operational Assessment with EPU - S/G 2A 1.0 0.9 0.8 Cumulative Distribution (CDF) 0.7 0.6 0.5 0.4 0.3 0.2 Conservative Evaluation (WR-1) 0.1 Realistic Evaluation (WR-2) 0.0 0 2 4 6 8 10 12 14 16 18 20 22 24 Wear Rate, WR (%TW per EFPY) 11

Input Distributions Other Model Inputs for Cycle 20 No significant changes from previous OA model assessments Tubing properties based on actual mechanical strength data at 650F from Certified Material Test Report (CMTR) data for PSL-2 tubing Indication length and shape characteristics based on profiled data from current and past inspections Probability of detection function developed from EPRI Examination Technique Specification Sheet (ETSS) 96004.1 database for the bobbin coil 12

Probability of Detection Model PSL-2 Bobbin Coil Detection Performance Estimates 1.0 0.9 0.8 0.7 Probability of Detection, POD 0.6 0.5 0.4 0.3 0.2 POD from EOC 17 OA 0.1 ETSS 96004.1 (Logisitc Fit)

ETSS 96004.1 (Log Logistic Fit) 0.0 0 5 10 15 20 25 30 35 40 Depth, d/t (%TW) 13

Benchmarking EOC 19 Results BENCHMARK RESULTS FROM MULTI-CYCLE ANALYSIS FOR WEAR AT ANTI-VIBRATION BARS PSL-2 AT EOC 19 S/G 2A EOC 19 Benchmark Actual Predicted Number of Indications 7485 7384/7497 NDE Maximum Depth 40 -

BE Maximum Depth(1) 43.8 47.8/45.7 Max Structural Depth 41.5 44.3/42.3 Number of Tubes Plugged(2,3) 40 54/32 Notes:

1) Actual best estimate (BE) maximum depth includes systematic sizing uncertainty.

2) Predicted tubes plugged are based on a plugging limit of 37% TW.

Preventative plug campaign included more tubes than just those > 37% TW.

3) Actual number of tubes plugged in S/G 2A with indications > 37% TW is 40.

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Operational Assessment Results RESULTS FROM MULTI-CYCLE ANALYSIS FOR WEAR AT ANTI-VIBRATION BARS PSL-2 AT EOC 19 EOC 20 Probability of Burst EOC 20 Accident Leakage, Wear Rate Determination at 3x NOPD Q95% (gpm)

Conservative Evaluation 2.48% 0 Realistic Evaluation 0.62% 0 Note: Wear rates based on IAGL procedures.

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Other Degradation Mechanisms Wear at V-Shaped Support Pads Located adjacent to AVBs on certain periphery tubes V-SSPs in contact tubes at the extrados and flank regions Observed wear degradation area is small and predominately axial Only 5 indications observed over three cycles - plug on detection Very limited wear rate information. Used largest indication to determine wear rate Probability of Detection (POD) used to assign BOC wear depth for undetected indications Deterministic OA shows acceptable Cycle 20 operation for this mechanism including power-uprate conditions 16

Other Degradation Mechanisms Wear at Tube Support Plates Broached tube support plate design Observed wear degradation area is small and predominately axial 147 indications observed over three cycles - plug on sizing (no tubes required plugging)

Limited wear rate information - used bounding data from other plants Deterministic OA shows acceptable Cycle 20 operation for this mechanism including power-uprate conditions 17

Historical TSP Wear Rates PSL-2 TSP Wear Rates 1.0 0.9 0.8 Cumulative Distribution, CDF 0.7 0.6 0.5 0.4 0.3 2009 Data 0.2 2011 Data (NDD = 5%TW) 2011 Data (Only Paired Points) 2012 Data (Only Paired Points) 0.1 TSP Wear (Industry Data) 0.0 0 2 4 6 8 10 12 14 16 18 20 Wear Rate, WR (%TW per EFPY) 18

Operational Assessment - TSP wear Deterministic Operational Assessment PSL-2 Tube Support Plate Wear - Detected Indications at EOC 19 100 90 Deterministic Method Repair-on-Sizing Method 80 70 3xNOPD Limit Arithmetic Approach Used Worst Case True Depth, (%TW)

- BOC 20 depth + upper 95-50 sizing error 60

- Growth rate at 95-50 upper value 50

- EOC 20 structural limit - 65% TW EOC 21 40 EOC 20 30 EOC 19 20 10 Tube Inspection Unit Outage 0

0 2 4 6 8 10 Operation Time (EFPY) 19

Operational Assessment Summary Tube Integrity Results for Cycle 20, with Power Uprate Scheduled Cycle 20 for PSL-2 is 11,402 EFPH (1.302 EFPY)

Limiting mechanism is AVB wear; S/G A is the limiting generator Probability of burst at the Structural Integrity Performance Criteria (SIPC) margin requirement of 3x Normal Operating Pressure Differential (NOPD) is 2.5% for the conservative method of evaluation for AVB wear rates, which meets the performance standards of < 5%

Deterministic OA for tube support and V-shaped support pad wear show acceptable margins Accident-induced leakage at EOC 20 is negligible for all mechanisms.

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