Summary of re-analysis work done on the AVR melt … of re-analysis work done on the AVR melt-wire...
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Summary of re-analysis work done on the AVR melt-wire experiments (summary of HTR 2008/2010 reported work). Presented: Frederik Reitsma This work reported was presented at the HTR2008 and 2010 conferences. Team includes: Carel Viljoen, Sonat Sen, Frederik Reitsma, Heiko Barnert, Peter Pohl and others made contributions 11/07/2012 TM-62606: 10-12 July 2012
Transcript of Summary of re-analysis work done on the AVR melt … of re-analysis work done on the AVR melt-wire...
Summary of re-analysis work done on
the AVR melt-wire experiments
(summary of HTR 2008/2010 reported work).
Presented: Frederik Reitsma
This work reported was presented at the HTR2008 and 2010 conferences.
Team includes: Carel Viljoen, Sonat Sen, Frederik Reitsma, Heiko Barnert, Peter Pohl and
others made contributions
11/07/2012
TM-62606: 10-12 July 2012
11/07/2012 TM-62606: 10-12 July 2012
Content / Overview
• Background
• AVR layout
• The melt wire experiments
• Bypass flows
• Unique 3D power profiles
• Concluding comments
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Background
• AVR (Arbeitsgemeinschaft Versuchsreaktor) – Research reactor
– Test bench for different pebble fuel types
• Operated for 21 Years
• Melt-wire experiments performed with instrumented spheres – Discrepancies between measured temperatures and
calculations / expectations
• Bypass flows were not included in calculations – only considered after melt-wire tests in 1988
• 3D power profiles was not initially evaluated
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AVR layout
Steam
generator
Graphite
reflector
Cooling gas
blowers
Reactor
shroud
Carbon
insulation
Discharge
pipe
Graphite
reflector Carbon
insulation
Outer Core
Control rod
borehole Reflector
nose
Thermocouples
Inner Core
Core
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X-ray of pebble with meltwires
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Core layout & measurements
Melt-wire
measurement
position
Thermocouple
lance position Bypass pipes
Fuelling
lines
Top plug
Control rod
nose
Wall
channeling
Annular
gap
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Outlet Temperature Higher & Uncertain
• Average value =1024°C
• Uncertainty at R=1300mm
Thermocouple lance data
900
950
1000
1050
1100
0 500 1000 1500 2000
Radius [mm]
Te
mp
era
ture
[C
] …
.
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Interpreted Melt-Wire Data Melt-Wire Data in Terms of Radius
900
1000
1100
1200
1300
0 500 1000 1500 2000
Radius [mm]
Tem
pera
ture
[C
]
.
Inner CorePebbles
Outer CorePebbles
• Average value >1136°C
• Little variation in inner core
Reflector nose
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Interpreted Melt-Wire Data Melt-Wire Data in Terms of Radius
900
1000
1100
1200
1300
0 500 1000 1500 2000
Radius [mm]
Tem
pera
ture
[C
]
.
Inner CorePebbles
Outer CorePebbles
ThermocoupleLance
• Average value >1136°C
• Little variation in inner core
• Difference between meltwire data and lance
Reflector nose
?
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Estimation of bypass flows from measurements
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Detail Flow Model
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Impact of fuel loading on gas temperature
700
800
900
1000
1100
1200
1300
0 200 400 600 800 1000 1200 1400 1600
Radius [mm]
Tem
pera
ture
[C
]
1.5
1.7
1.9
2.1
2.3
2.5
2.7
2.9
3.1
3.3
3.5
Po
wer
Den
sit
y (
W/c
c)
Gas Temperature (a)
Gas Temperature (b)
Power Density (a)
Power Density (b)
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500
600
700
800
900
1000
1100
1200
1300
1400
1500
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Gas Temp
Max Fuel
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500
600
700
800
900
1000
1100
1200
1300
1400
1500
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Gas Temp
Max Fuel
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Detailed core neutronic modelling
• AVR is a short core – Effects of conus at bottom and heaps and valleys at top
relatively more important
• Also approximately consider: – Burn-up (pebble residence times) modelled as 2D and 3D
– Thermo-hydraulics modelled as 2D and 3D
– Volume ratio of IC and OC
– Fuelling strategy
– Mass flow (to compare to the above effects)
– The heap and valley formations at the top of the pebble bed
• HTR2010 and NED paper
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Some results
• AVR-1: 3D reference (bypass, conus, heaps)
• AVR-3b: 2D without bypass
• AVR-9: Fuel management (inner:outer) changed ratio
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Some results
• AVR-5: Flat top, Flat bottom
• AVR-6: Flat top, Conus bottom
• AVR-7: Heap and valleys top, Conus bottom
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Conclusion • Analysis shows bypass flows played a significant
role in the AVR flow distribution
• Detail 3D thermo-hydraulic and neutronic analysis is required for accurate predictions of flows and temperatures
• Fuel management (inner / outer) and fuel circulation important
• Much better predictions with modern tools
• Many AVR specific features lead to the high temperatures
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References 1. The re-evaluation of the AVR melt-wire experiment using modern methods
with specific focus on bounding the bypass flow effects, Carel F Viljoen, Sonat Sen, Frederik Reitsma, Onno Ubbink, peter Pohl, Heiko Barnert, Paper HTR2008-58115
2. The re-evaluation of the AVR melt-wire experiment with specific focus on different modelling strategies and simplifications, CF Viljoen, RS Sen, Paper 193, HTR2010
3. The re-evaluation of the AVR melt-wire experiment with specific focus on different modelling strategies and simplifications, R. Sonat Sen, Carel F. Viljoen, Nuclear Engineering and Design (available online)
