summary of re-analysis work done on the avr melt … of re-analysis work done on the avr melt-wire...
TRANSCRIPT
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
11/07/2012 TM-62606: 10-12 July 2012
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
11/07/2012 TM-62606: 10-12 July 2012
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
11/07/2012 TM-62606: 10-12 July 2012
Core layout & measurements
Melt-wire
measurement
position
Thermocouple
lance position Bypass pipes
Fuelling
lines
Top plug
Control rod
nose
Wall
channeling
Annular
gap
11/07/2012 TM-62606: 10-12 July 2012
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
] …
.
11/07/2012 TM-62606: 10-12 July 2012
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
11/07/2012 TM-62606: 10-12 July 2012
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
?
11/07/2012 TM-62606: 10-12 July 2012
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)
11/07/2012 TM-62606: 10-12 July 2012
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
11/07/2012 TM-62606: 10-12 July 2012
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
11/07/2012 TM-62606: 10-12 July 2012
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
11/07/2012 TM-62606: 10-12 July 2012
Some results
• AVR-1: 3D reference (bypass, conus, heaps)
• AVR-3b: 2D without bypass
• AVR-9: Fuel management (inner:outer) changed ratio
11/07/2012 TM-62606: 10-12 July 2012
Some results
• AVR-5: Flat top, Flat bottom
• AVR-6: Flat top, Conus bottom
• AVR-7: Heap and valleys top, Conus bottom
11/07/2012 TM-62606: 10-12 July 2012
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
11/07/2012 TM-62606: 10-12 July 2012
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)