Reliability and long term behaviour of novel accident level measurement devices in simulated fuel pool environment
S. Berger1, R. Kilian1, S. Estevez Hernandez1, G. Hasse2
1AREVA GmbH, Germany 2EPCM Global Engineering (Pty) Ltd, South-Africa Ottawa, August 12th 2015
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..2
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Background (1/2) Accident Proof Level Measurement (ALM) devices shall be capable to measure water levels during normal operation as well as during and after a covered accident. ALM-Systems for pressurized water reactors such as the AREVA EPRTM (European Pressurized Reactor) require high robustness and reliability For the EPRTM reactor such systems are used in the:
Fuel Pool
In containment Refuelling Water Storage Tank (IRWST)
Containment Flooding Valve
Heat Removal and Safeguard Pump Sumps
Venturi Vessel
ALM-Requirements:
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..3
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Novel Accident Proof Level Measurement (ALM) device based on the magnetic switching technology (Reed-switches).
The specific design features:
Floater Guide Tube Unit (FGTU) Magnetic Floater Unit (MFU) these systems were assumed to be sensitive to boric acid crystallization caused locking (blockage) in the annular clearance* between the MFU and the FGTU
Background (2/2)
Top-view (section)
MFU Systematic test program using original components to target the influence of boric acid crystallization
*: ID(FGTU) = 53,9 mm; OD(MFU) = 45 mm, annular clearance ~ 4,45 mm (8,9 – 0 mm)
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..4
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Experimental (1/3) Components & Materials
Magnetic Floater Unit/Floater Guide Tube (MFU/FGTU) assemblies used Original MFUs made from titanium
Two different types (materials) of FGTUs* are used:
Original FGTUs (stainless steel) German Material 1.4550 (similar to type 347)
Acrylic glass (PMMA) FGTUs for in-situ investigations of H3BO3 crystallization
Surface conditions tested:
MFUs: current design (as received)
mechanically polished
FGTUs: current design (as received)
electropolished (only outside surface)
*: The overall length of the FGTUs is adjusted to 400 mm to fit the climate chamber
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..5
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Experimental (2/3) Test Setup (3500 ppm B)
Parameters
Parameter Set value Comment Recording interval
Test duration 3 months Start:17.07.2012 End: 15.10.2012
Not applicable
Ambient humidity
~ 52 % RH (40 % RH*
) Climate chamber Continuous
Ambient temperature
24.5 °C Climate chamber Continuous
Water temperature
30 °C Thermocouple Continuous
Initial Water level
250 mm
In the course of the test the level was controlled
decreased at 1 mm/2 days
Daily
Boron-concentration
Basin 1 3500 ppm Accelerated conditions Weekly
Basin 2 1750 ppm Realistic conditions
Surface quality MFU/FGT
U
MFU: current design, mechanically polished
FGTUs: current design, electro-polished (only
outside)
Not applicable
*: 40 % RH was initially chosen according to specifications. However, this value could not be achieved (see 3.1).
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..6
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Experimental (3/3) Test Setup
Basin 1
Basin 2
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..7
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Results
Humidity and Temperature (Climate Chamber)C Evaporation Rate
Highly stable and reproducible environmental conditions
Evaporation rate Basin 1 < Basin 2 (influence of dissolved species)
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Results
Boron Concentration Humidity and Temperature
(SS FGTU)
TWater = 30 °C
Highly stable and reproducible environmental conditions
Humidity inside SS FGTUs < Humidity in the Climate Chamber
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..9
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Results: MFUs MFU in PMMA FGTU (in situ)
MFU in SS FGTU (post test)
No significant H3BO3-Crystal growth on any of the MFUs observed
MFU in PMMA FGTU (post test)
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..10
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Date FGTU current design (3500 ppm B) FGTU electropolished* (1750 ppm B)
17.07.2012 (Start)
20.08.2012
24.09.2012
15.10.2012 (End)
FGTU inner surface
MFU
Results: in situ (in SS FGTU)
H3BO3-Crystal growth on the Inner surface of the SS FGTUs observed First visible crystals are obtained after ~ 1 month of exposure
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..11
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Results: FGTUs
(outer surface)
Significant H3BO3-Crystal growth on the outer surface of the current design SS FGTUs observed Surface condition plays a key role
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..12
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Results: Profilometric
scans (post test)
Pos. Basin 1 (3500 ppm B) FGTU current design
Basin 2 (1750 ppm B) FGTU electropolished*
Inner surfac
e
0 °
tmax = 0.171 mm tmax = 0.050 mm
90 °
tmax = 0.160 mm tmax = 0.023 mm
180 °
tmax = 0.290 mm tmax = 0.020 mm
270 °
tmax = 0.265 mm tmax = 0.042 mm
H3BO3-Crystal growth inside the SS FGTU Influence of H3BO3 concentration tmax values used for growth rate estimation
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..13
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Results: H3BO3 growth
tmax after 3 months /mm
growth /mm/month
extrapolated growth in /mm 12 months 24 months
FGTU current design (3500 ppm) 0,290 0,097 1.164 2,320
FGTU_current design* (1750 ppm) 0,050 0,017 0,204 0,408
*: electropolished only on the outer surface.
Linear extrapolation (high conservatism) reveals a sufficiently big clearance after 24 months No blockage of the MFU is expected
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..14
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Summary ► H3BO3 crystallization takes place at surfaces where the solvent (water) can easily
and completely evaporate. ► The boron concentration and the surface condition (roughness, scratches) generally play a major
role for the crystallization behaviour of H3BO3 ► The humidity and temperature measured in the SS FGTUs indicates the existence of a micro climate
that inherently impedes H3BO3 crystallization. ► After the full testing period of 90 days no crystal growth could be obtained on any of the exposed
MFUs. ► On the inside of the SS FGTUs crystal growth was obtained and quantified by means of
profilometric scans. Assuming a linear growth law (conservative approach) growth rates for H3BO3 are estimated:
Using this growth rate a remaining annular clearance of 4.05 mm is calculated after 24 months
The functionality of the ALM-devices will not be jeopardized during 24 months*. (definition of specific maintanance intervals)
H3BO3 Deposit 3500 ppm B 1750 ppm B
Max. thickness [mm] 0.29 0.05
Estimated growth rate [mm/month] 0.097 0.017
*:under the investigated conditions (IRWST set-point conditions)
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..15
All rights are reserved, see liability notice.
Reliability and long term behaviour of novel ALM –Devices - 17th EnvDeg - S. Berger - 12/08/2015 - AREVA GmbH Proprietary - RESTRICTED AREVA – © AREVA - AL: N - ECCN: N - p..16
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Editor and Copyright [Date]: AREVA GmbH – Paul-Gossen-Straße 100 – 91052 Erlangen, Germany. It is prohibited to reproduce the present publication in its entirety or partially in whatever form without prior written consent. Legal action may be taken against any infringer and/or any person breaching the aforementioned prohibitions. Subject to change without notice, errors excepted. Illustrations may differ from the original. The statements and information in this brochure are for advertising purposes only and do not constitute an offer of contract. They shall neither be construed as a guarantee of quality or durability, nor as warranties of merchantability or fitness for a particular purpose. These statements, even if they are future-orientated, are based on information that was available to us at the date of publication. Only the terms of individual contracts shall be authoritative for type, scope and characteristics of our products and services.
End of presentation Reliability and long term behaviour of novel accident level measurement devices in simulated fuel pool environment
S. Berger1, R. Kilian1, S. Estevez Hernandez1, G. Hasse2
1AREVA GmbH, Germany 2EPCM Global Engineering (Pty) Ltd, South-Africa Ottawa, August 12th 2015