ML113350563

Licensee Presentation from 12/1/11 Meeting Via Conference Call to Discuss Risk-Informed GSI-191,Assessment of Debris Accumulation on Pressurized Water Reactor Sump Performance

ML113350563
Person / Time
Site:	South Texas
Issue date:	12/01/2011
From:	South Texas, ALION Science & Technology Corp, Univ of New Mexico
To:	Balwant Singal Plant Licensing Branch IV
Singal, B K, NRR/DORL, 301-415-301
References
TAC ME5358, TAC ME5359
Download: ML113350563 (25)

Text

CHEMICAL EFFECTS IMPLICATIONS OF WCAP-16530-NP FOR SOUTH TEXAS PROJECT December 1, 2011

Discussion Overview Conservatism in chemical effects - WCAP-16530-NP Corrosion/release Precipitation Reduction of conservatism Casa Grande Hypotheses of chemical effects occurrences without conservatisms Objectives of new chemical effects testing Preliminary testing ideas Conclusion Areas for requested input 2

Corrosion/precipitation scenario Step 1 Step 2 Step 3 Step 4 Metal Corrosion/Release Saturation/Precipitation Transport Head Loss Spray Immersion Aluminum Al+3 Sump Screen OH-Al(OH)3 (amorphous)

Free metal ions released from Saturation limit exceeded Transport to sump Collection solids and dissolved in water suspended solids form on fiber or past strainer to core 3

Conservatism: Corrosion/release Corrosion rates were determined in studies of relatively short duration Over longer time, base metal corrodes but oxide layer forms at surface, limiting release of corrosion products into solution Passivation of surface by silicon and phosphate Contribution of soluble aluminum from un-submerged (sprayed) sources vs submerged sources Results in conservative estimate of soluble metal concentration 4

Corrosion/precipitation scenario Spray Immersion Formation of oxide layer on surface Aluminum Localized higher concentration of aluminum in Al+3 boundary layer causes surface precipitation, preventing supersaturation of aluminum in solution OH- Release of free ions into solution is reduced 5

Aluminum release into solution in ICET 450 400 Unfiltered Aluminum 350 Filtered Aluminum Concentration (mg/L) 300 250 ICET Test 1 200 150 100 50 0

0 5 10 15 20 25 30 Time (Day) 6

Al(OH)3 solubility vs. Al concentration 7

Aluminum release:

Experimental vs. Estimated WCAP Introduce this amount into strainer test in 80 batches near time = 0 Aluminum concentration (mg/L)

Test 5 unfiltered 70 Test 5 filtered 60 50 40 30 20 10 0

0 5 10 15 20 25 30 Time (days) 8

WCAP 16530 vs ICET 100 ICET #1 Corrosion Rate (mg/m2-min) 10 ICET #5 1

WCAP-16530-NP Equation 6.2 at 140 F ICET #2 0.1 ICET #3 (max) ICET #4 (max)

All ICET tests were done at 140 F 0.01 0 2 4 6 8 10 12 pH 9

Passivation of Al corrosion in ICET Tests ICET Test pH Al (mg/L) Si (mg/L) 1 9.3-9.5 360 7 2 7.1-7.4 BD 45 3 7.3-8.1 BD 45 4 9.5-9.9 BD 82 5 8.2-8.5 50 4

• BD is below instrument detection limit

• Approximate concentrations at day 30 of testing 10

Soluble aluminum contribution:

Sprayed vs Submerged sources Literature Sprayed aluminum corrosion rate higher than submerged aluminum ICET Test Submerged Sprayed Experimental 1 -98.6 0.7 Contribution of soluble 2 -0.9 0.4 aluminum from sprayed sources is negligible 3 0.6 0.4 Net Effect 4 0 0.6 Corrosion rate may be 5 -11.2 0.4 higher but low contribution from sprayed aluminum to Mass change (g) in aluminum coupons soluble aluminum after 30-day ICET tests concentration 11

Conservatism: Precipitation WCAP 16530 estimates precipitate formed NaAlSi3O8 and/or AlOOH Another possible form:

Al(OH)3 Molecular weight of precipitate determines quantity STP WCAP calculation predicts 83 kg of Al in solution 650 kg of NaAlSi3O8 and 36 kg of AlOOH OR 237 kg of Al(OH)3 Quantity of precipitate is used to predict head loss Over or under estimation of actual head loss 12

Conservatism: Precipitation Amorphous phase precipitate Occurs in solution Transported to screen Assumed by WCAP-16530-NP Greater head loss ?

Mineral phase precipitate Occurs on surfaces Not transported Occurred during VUEZ chemical effects tests Less head loss ?

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Amorphous vs crystalline phases 1000 100 Aluminum concentration required to precipitate amorphous product, Al(OH)3 Aluminum concentration, mg/L 10 1

Measured aluminum concentration in VUEZ testing 0.1 Aluminum concentration required to precipitate crystalline product, AlOOH (Boehmite) 0.01 0 100 200 300 400 500 600 700 800 Time, hr 14

Casa Grande:

Limiting excessive conservatism Risk assessment philosophy Stochastic analysis and uncertainty quantification Allows for educated reduction of previously demonstrated conservatism 15

Hypothesis of Chemical Effects at STP during a LOCA - Corrosion/Release The release of aluminum into solution resulting from corrosion is less than predicted by WCAP-16530-NP Passivation effects Formation of oxide layer Aluminum exposed to spray releases less metal into solution than submerged aluminum 16

Hypothesis of Chemical Effects at STP during a LOCA - Precipitation Calcium phosphate precipitation will be minimal Crystalline aluminum precipitate will occur in fiber bed or on surfaces in the containment pool and not in the bulk solution Amorphous aluminum precipitation may occur in bulk solution when passed through heat exchanger Precipitation will be less due to less corrosion products in solution 17

Hypothesis of Chemical Effects at STP during a LOCA - Overall Little or no impact of chemical effects on the STP plant Reduced release of aluminum into solution, thus smaller quantity of precipitation Crystalline precipitation onto the fiber bed with possibility of amorphous precipitation in solution due to heat exchanger exposure 18

Objectives for new chemical effects tests Determine the significance of chemical effects on the resolution of GSI-191 at the STP plant without excessive conservatisms Generate data that can be used to develop a model of system of equations that will provide input to Casa Grande Equations predicting concentrations of Al, Si, Ca, and PO4 in solution as a function of pH, temperature, pool volume, spray duration and quantities of materials in containment Equation predicting incremental increase in head loss as a function of soluble Al, Si, Ca, and PO4 concentrations, pH and temperature 19

Path to reach objectives CASA Grande Existing Benchtop/

knowledge Autoclave Testing base on Corrosion rates chemical effects Dissolution rates Release rates Solubility limits Precipitate Calculator (Type and Quantity)

Thermodynamic/Kinetic Modeling High Temperature Relative Integrated Chemical Vertical Loop importance of Effects Tests with a Head Head Loss Tests various Loss Loop parameters Head loss given variations in:

Corrosion/dissolution/release rates Fiber quantity Solubility limits Particulate quantity Precipitate characteristics Precipitate quantity Effect of fiber bed dissolution on HL Effect of precipitate formation on HL NUREG/CR-6224 Head Head Loss Loss Correlation Calculator 20

Preliminary testing ideas ICET Tank Tests 30-day test integrated corrosion/head loss tests Blank Test Examine fiber bed dissolution and associated headless in buffered/borated water only Medium break LOCA Large break LOCA Shorter term test Effects using NaTB as buffering agent at STP Examine contribution from spray metals under different spray conditions Force precipitation for identification purposes Will allow for more accurate head loss correlation Batch Tests Clarify the composition of precipitates that form Impact of variable concentrations of silicon Flow rate effects on formation of aluminum oxide scale 21

Experimental Apparatus ICET Tank 250 gallons Racks and capacity for all materials present in STP containment Recirculation loop to provide required turbulence and mixing in tank RWST chemistry at the STP plant would be simulated in the tank 22

Modifications to ICET Tank Head loss loop, using pre-formed fiber debris beds Heat exchanger loop Scaling parameters to STP Ratio of materials (aluminum, etc) to pool volume Recirculation time through screen / hydraulic residence time Water velocity through fiber bed Hold up time at lower temperature before re-introduction into pool Declining temperature profile similar to LOCA Flow variations to simulate plant evolutions 23

Conclusion Casa Grande is a tool for reducing conservatism Will include chemical effects Overall hypothesis for non-conservative scenarios Little or no impact of chemical effects on the STP plant Testing to prove hypotheses 30-day testing Short term test Batch tests Modified ICET tank 24

Areas for discussion Use of pre-formed fiber beds Orientation of fiber bed: vertical or non-vertical Use of multiple beds in parallel Use of two beds in series with an intermediate heat exchanger 25