ML16272A347
| ML16272A347 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 08/10/2016 |
| From: | Randy Hall Dominion |
| To: | Office of Nuclear Reactor Regulation |
| Benney B, NRR/DPR, 301-415-2767 | |
| Shared Package | |
| ML16209A375 | List: |
| References | |
| Download: ML16272A347 (14) | |
Text
BADGER* Measurement of Carborundum B-10 Areal Density in Millstone Unit 1 Spent Fuel Racks R. A. Hall Dominion, Nuclear Analysis and Fuel 2016 NEI Used Fuel management Conference 5/5/2016
- Boron-10 Areal Density Gauge for Evaluating Racks 1
History 6/2011 Millstone Unit 1 BADGER campaign Carborundum - 50% B4C in Phenolic Resin 5 plates 31 inches tall between rack cells 0.21 inches thick Contained in welded pocket with vent hole As-built B-10 content ~0.1 - 0.11 g/cm2 Criticality analysis 0.048 g/cm2 Measurements Indicated B-10 content as low as 0.01 g/cm2 No confidence in measured results due to calibration drift, repeatability, noise, etc.
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History Similar to 3/2009 Palisades Same vintage Old BADGER Indicated B-10 loss as high as 2/3 NRC IN 2009-26 Began redesign of BADGER with NETCO MAVRIC/MCNP modeling Equipment improvement Measurement procedure changes New calibration standards New measurements August 2013 3
BADGER Basics Neutron source head Springs for geometry consistency Neutron detector head Shielding Multiple detectors Springs for geometry consistency Calibration stand Analog of rack storage cells Multiple areal density (AD) standards Unpoisoned region (no absorber) 4
Simplified Calibration Model 5
BADGER Basics Sources of bias and uncertainty Head alignment and spacing Detector voltage Electrical noise Gamma background Counting statistics Discriminator setting Pulse pile-up 6
BADGER Process Collect count rate data from calibration stand Multiple AD standards Calculate transmission ratio (TR)
Absorber region CR / Unpoisoned region CR Calibration curve Versus AD Interpolation method Measure in-rack TR Calculate measured AD 7
2013 Calibrations 0
10000 20000 30000 40000 50000 60000 70000 80000 90000 0
10 20 30 40 50 60 70 Total Counts (45 seconds count time)
Axial Position (Inches)
MP1 Typical BADGER Calibration Result CAL 3 DET 3 Unpoisoned region Outofrack Standard1 Standard2 8
2013 Calibration Consistency 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.055 Transmission Ratio B10ArealDensity(g/cm2)
MP1BADGERCalibrationData Detector2TransmissionRatiovsB10ArealDensity Scatterin calibrationTRs representshalf theB10AD!
9 Lessons Learned Material is very B-10 dense Calibration curve is relatively flat Measurement is difficult!
Stability and repeatability are crucial Do not assume all measurements are good Repeat calibrations to verify stability Reject measurements if unstable/inconsistent Rack uncertainty calibration uncertainty Calibrations reveal actual BADGER uncertainty Do a lot of calibrations!
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Panel Measurements Panel Date Time Notes 56IN 8/1/2013 11:28 Rejectedduetosystemdifficulties 56IW 8/1/2013 13:33 Rejectedduetosystemdifficulties 56INFS 8/5/2013 12:30 Finescantoconfirm56IN,notusedinanalysis 510LS2 8/5/2013 15:13 Rejectedduetosystemdifficulties 510LW 8/6/2013 9:02 Suspect,repeated,rejected 57JE 8/6/2013 11:05 Suspect,repeated,rejected 57ME 8/6/2013 12:38 Suspect,notrepeated,rejected 57MW 8/6/2013 14:07 Suspect,repeated,rejected 59ME 8/7/2013 8:54 Suspect,repeated,rejected 59MW 8/7/2013 10:19 Suspect,notrepeated,retainedforanalysis 59MN 8/7/2013 11:48 Suspect,repeated,rejected 59MS 8/7/2013 13:17 Suspect,notrepeated,retainedforanalysis 59JW 8/8/2013 10:44 Retainedforanalysis 59JE 8/8/2013 12:07 Retainedforanalysis 59JS 8/8/2013 13:34 Retainedforanalysis 57JS 8/12/2013 8:51 Retainedforanalysis 57JEVER 8/12/2013 10:15 Repeatforverification,retainedforanalysis 57MWVER 8/12/2013 10:51 Repeatforverification,retainedforanalysis 58IEVER 8/12/2013 11:27 Retainedforanalysis 510LWVER 8/12/2013 13:11 Repeatforverification,retainedforanalysis 59MEVER 8/12/2013 13:46 Repeatforverification,retainedforanalysis 59MNVER 8/12/2013 14:27 Repeatforverification,retainedforanalysis 11 Suspect Results 8/6/13-8/7/13 Repeat measurement does not confirm anomalies 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0
31 62 93 124 155 Transmission Ratio AxialPosition(Inches)
MP1BADGERSFPTransmissionRatio Panel510LW SuspectDET2 SuspectDET3 VerificationDET2 VerificationDET3 The"calzone"(0.05g/cm2 AD)
FAIL PASS 12
0.04 0.06 0.08 0.10 0.12 0.14 0.16 0
31 62 93 124 155 Transmission Ratio AxialPosition(Inches)
MP1BADGERSFPTransmissionRatio Panel59MN SuspectDET2 SuspectDET3 VerificationDET2 VerificationDET3 Interpanel gap confirmed Unconfirmed anomaly 13 Suspect Results 8/6/13-8/7/13 Repeat measurement confirms panel gap at 62 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0
31 62 93 124 155 Transmission Ratio AxialPosition(Inches)
MP1BADGERSFPTransmissionRatio Panel59ME SuspectDET2 SuspectDET3 VerificationDET2 VerificationDET3 14 Suspect Results 8/6/13-8/7/13 Repeat measurement does not confirm anomalies
0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0
31 62 93 124 155 TransmissionRatio AxialPosition(Inches)
MP1BADGERSFPTransmissionRatio Panel57MW SuspectDET2 SuspectDET3 VerificationDET2 VerificationDET3 15 Suspect Results 8/6/13-8/7/13 Repeat measurement does not confirm anomalies Lessons Learned System can generate phantom anomalies When in doubt, REPEAT System can generate biased TR Getting it wrong is easy, harder to get it right Multiple repeat measurements are your friend Dont trust, question the data and verify Stability and repeatability are crucial Do not assume all measurements are good Repeat measurements to confirm Repeat measurements are more valuable than additional panel measurements 16
Effect of BADGER Uncertainty BADGER uncertainty creates a population distribution Calibration measurements display uncertainty Un-degraded material, known B-10 For 0.05 g/cm2 B-10 calibration standard TR Det2 = 0.121 +/- 5.4%
TR Det3 = 0.122 +/- 5.1%
Plot TR data as a CDF Calibration TR = 0.121 +/- 5.3%
0.05 g/cm2 B-10 Rack panel TR= 0.089 +/- 9.1%
> 0.05 g/cm2 B-10 17 Effect of BADGER Uncertainty Low and high TR values may be BADGER artifact, not degradation 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Transmission Ratio FractionofObservations (%)
TransmissionRatioCumulativeDistribution MP1BADGERCalibrationsandRackMeasurements RackMeas Cal0.05AD Cal0.03AD NormalCDF AbovemeanTRdegraded calibrationstandard BelowmeanTRenriched calibrationstandard 18
Lessons Learned System uncertainty Visible in repeat calibrations Quantifiable with repeat calibrations Creates a distribution of results Will be reflected in measured panel results Low TR points not likely super-enriched in B-10 High TR points may not represent low B-10 Statistical artifact or real B-10 change?
Re-measure high and low TR panels / sections High B-10 if low TR persists Low B-10 if high TR persists 19 MP1 Measured B-10 AD Estimate Best estimate avg. AD=0.087 (0.10 - 0.11 as-built) y=41.48x 1.0687 R²=0.9997 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 0.08 0.12 0.16 0.2 0.24 0.28 0.32 InverseTransmission Ratio SquareRootofB10ArealDensity CalibrationCurveExtrapolation AverageRackADEstimation AverageofCalibrations AverageMP1Rack1/TR Linear(AverageofCalibrations) 20
MP1 Results Calibrations vs Panel Measurements Panel average TR max/min range similar to cals 1.24 for panels (10) 1.18 for good calibrations (9)
Expect higher variation in panels (> AD than cals)
Panel TR SD (~9%) > 0.05 AD Cal. SD (~5%)
Possible non-uniform B-10 loss Possible variation in original manufacture AD Expect higher variation in panels (> AD than Cals)
One panel gap found No gross degradation found 21 MP1 Results Point-wise and panel average AD estimates Best estimate AD for panel population 760 measured points 0.087 g/cm2 B-10 (0.048 criticality basis)
Panel average best estimate AD (10 panels) 0.086 g/cm2 B-10 average panel 0.071 g/cm2 B-10 minimum panel 0.104 g/cm2 B-10 maximum panel Variation somewhat higher than calibrations (7.9% SD vs 5.3% SD) 22
MP1 Results The bottom line
~13-21% loss of B-10 (average) in 35 years Consistent with coupon experience Kewaunee coupon trend ~14% loss in 30 years Old BADGER AD results not reliable at MP1 No gross degradation found Measured TR population distribution similar to calibration populations but with more B-10 Re-measure of panel 5-6-I-W 2013 vs 2011 2011 degradation NOT confirmed (next slide) 23 0
5 10 15 20 25 30 0
30 60 90 120 150 InverseTransmissionRatio AxialPosition(in.)
MP1BADGERPanel56IW 2011vs2013 2013_Det_2 2013_Det_3 2011_Det_1 2011_Det_2 2011_Det_3 2011_Det_4 24
Revisiting Palisades Palisades measured gross degradation, BUT MP1 and Palisades have the same material Old BADGER gave invalid results at MP1 Palisades used old BADGER Coupons indicate gradual B-10 loss Is the original conclusion right?
Itisimportanttonotethatthesignificantdegradationofthe Carborundum plateatPalisadesoccurredwithoutany indicationfromTOC[totalorganiccarbon]orthecouponsat anotherplant,indicatingthefailureofthesetechniquesin thisinstance.[NRCTechnicalLetter,June2013]
25 Revisiting Palisades TheonlytwoBADGERcampaignsknowntohavebeen conductedhaveshownsignificantpaneldegradationat bothpools..theseresultsofsignificantphenolic resin absorberdegradationatbothplantstestedbyBADGER, whichrepresenttheonlyinformationavailabletodirectly assessabsorberperformance,arenoteworthyand concerning.[NRCTechnicalLetter,June2013]
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Questions?
27 BADGER* Measurement of Carborundum B-10 Areal Density in Millstone Unit 1 Spent Fuel Racks R. A. Hall Dominion, Nuclear Analysis and Fuel 2016 NEI Used Fuel management Conference 5/5/2016
- Boron-10 Areal Density Gauge for Evaluating Racks 28