results from the hcpb pebble-bed assembly irradiation · 2016-06-25 · results from the hcpb...
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Results from the HCPB pebbleResults from the HCPB pebble--bed bed assembly irradiationassembly irradiation
L. Magielsen, J.H. Fokkens, J.B.J. Hegeman,
M.S. Stijkel, J.G. van der Laan
a NRG Petten, the Netherlands
Ceramic Breeder workshop 127, 1 December 2005
OutlineOutline
Objectives of the Pebble Bed Assembly irradiationIrradiation characteristics and designIn-pile performance of the capsuleModel developmentsOutlook
ObjectivesObjectives
Study the thermo-mechanical behaviour under neutron irradiation of a section of the solid breeder blanketAchieve DEMO representative levels of temperature and defined thermal-mechanical loads
45 m
m8
45 m
m8
9
Ceramic pebbles: Li4SiO4 : ~ 0.5 mmor Li2TiO3/Li2ZrO3 : ~ 1 mm
Beryllium pebbles: large : ~ 2 mm small : ~ 0.15 mm
BERYLLIUM BINARY PEBBLE-BED
CERAMIC PEBBLE-BED
BERYLLIUM BINARY PEBBLE-BED
Strategy for blanket developmentStrategy for blanket development
Out-of-pileComponent
Tests
Out-of-pileComponent
Tests
Basic Material
Tests
Basic Material
Tests
In-pileSubmodules
Tests
In-pileSubmodules
Tests
Beryllium (ref. & irrad.)Ceramic (ref. & irrad.)Eurofer (ref. & irrad.)
Helica (ref.)Helicatta (ref.)
PBA irradiatiom
TBM design & test blanket moduleTBM design & test blanket moduleD
EM
O b
lank
et d
esig
nan
d de
velo
pmen
tD
EM
O b
lank
et d
esig
nan
d de
velo
pmen
t
Strategy for HCPB Strategy for HCPB pebblepebble--bed irradiationbed irradiation
Basic Materials
tests
ModellingPebble bed
Design pebble bed assembly
In pile performance pebble bed assembly
Improved model
irradiation effects
PIE Pebble bed
deformation, gas gap formation
HCPB – TBM design
Validation of gas gap
formationOut of pile
performance pebble bed assembly
Model improvements by out-of-pile
results
PBA module
thermocouple
Aluminium filler
Aluminium filler
Beryllium bed
dosimeter
heat barrier EuroferFloating plate Eurofer
Beryllium bed
ceramic bedBellow inconel 718
Containment Eurofer
Purge gas tubes
Containment 316L
Pebble bed assembliesPebble bed assemblies
Filling procedure and module assemblyFilling procedure and module assembly
Filling in a number of stepsPre compactionX-ray inspections to check for the plate positions
Filling procedureFilling procedure
After inspection of assembled test-element:Stepped pre-compaction, 1, 2, 3 MPa plus 24 hrs at 350°CLast inspections prior and after sealing.
Purge line splitter
pebbles well aligned with plate
large pebble: low density near wall
Pre-compaction procedure (1)
0
50
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450
0 5 10 15 20 25 30 35
Time [ s ]
Tem
pera
ture
[ °C
]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Pres
sure
[ M
Pa ]
temperaturepressure
Target temperaturesTarget temperatures
Li2TiO3
T= 850 oC
Li4SiO4
T= 650 oC
Li2TiO3
T= 850 oC
Li4SiO4
T= 850 oC
Test element #1 and # 4 same material at different temperatureTest element # 2 and # 3 different in grain size and creep behaviour All first containments are continuously purged with He + 1000 ppm H2 and optionally with Ne/He + 1000 ppm H2 for extra T control
MaterialsMaterials
Test element 1 2 3 4Material Li4SiO4 Li2TiO3 Li2TiO3 Li4SiO4Supplier FZK CEA CEA FZKNRG code NRG 100 NRG 113 NRG 105 NRG 1006 Li enrichmentLithium burn upPebble dimensions mm 0.25-0.63 0.8-1.2 0.8-1.2 0.25-0.63Quantity of breeder material g 24.94 32.28 32.62 25.17Quantity of Beryllium g 91.54 92.7 92.95 92.95Beryllium supplierBeryllium pebble size mmPurge gas 1st containment 2nd containmentGas flow 1st containment ml/min 2nd containment ml/minPressure 1st containment bar 2nd containment barMax. temperature breeder oC < 725 < 900 < 950 < 910Temp. Floating plates oC < 450 < 580 < 600 < 585Temp. Eurofer 1st containment oC < 200 < 285 < 300 < 290Temp. Beryllium beds oC < 420 < 540 < 550 < 540
20-12033
0.9-1.1He + 0.1 vol. % H2
Mixture He/ Ne100
7.5% (natural)plm. 3%
NGK
InIn--pile resultspile results12th cycle ended Nov.2005, with accumulated 300 Full Power Days (~ 7200 hours)Accumulate in 12 cycles, or 7200 hours:
Approx. 2 dpa in Eurofer8 1022 at T productionTotal lithium burn ups 2 to 3 %
Cycle Exp. Orientation Incore position Material filler elementNeutroradiograph -- -- --
03-04 Z H4 AlNeutroradiograph -- -- --
03-06 Z H4 Stainless steel03-07 N H6 Al03-08 Z H6 Al03-09 N H6 Al03-10 Z H6 Al03-11 N H6 Al03-12 Z H6 Al
Neutroradiograph -- -- --04-03 N H6 Water rich04-04 N H6 Al04-08 Z H4 Al04-09 N H4 Al
Neutroradiograph -- -- --
InIn--pile resultspile results
Tritium production: (n,Tritium production: (n,αα) nuclear heating) nuclear heating
0 5 10 15 20 250
0.2
0.4
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0.8
1
Time [days]
IC1
sign
al [
mC
i/min
]
IC1 signal IC1
0 5 10 15 20 250
0.5
1
1.5
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2.5
Time [days]
IC1
sign
al [
mC
i/min
]
IC1
0 5 10 15 20 250
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Time [days]
IC1
sign
al [
mC
i/min
]
IC1 signal IC1
0 5 10 15 20 250
0.5
1
1.5
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Time [days]
IC1
sign
al [
mC
i/min
]
IC1 signal IC1
InIn--pile resultspile results
Before start of in-pile operation, after first cycle and after 8 cycles a radiograph was takenTE-#3 gives best image for evaluation, parallax for other quite significantNo evidence for large gaps found yet; to be detailed with the post-irradiation neutrography
Conclusion from the inConclusion from the in--pile behaviourpile behaviour
PBA irradiation has been completed after 12 irradiation cycles (300 FPD)Power density slightly lower than expected, reducing temperaturecontrol margins; use of Neon in primary containment reference purge gas (He-Ne+0.1%H2)The neutron flux gradient is significant, but allows reconstruction of radial temperature profilesThermocouple tubes interfere with the heat transport, giving underestimate readings for the breeder bed and overestimate readings for the lower floating platesIn addition the thermal contact between the Eurofer test-element and Al filler is enhanced by the thermal flux, and neon addition to primary purge No evidence for gaps from intermediate neutrography
Modelling of pebble bedsModelling of pebble beds
0 1 2 3axial strain (%)
0
2
4
6
unia
xial
stre
ss (M
Pa)
first pressure increase:important for pressurebuild-up at BOL
thermal creep: important for compensation of swelling
first pressure decrease:important for gap formaqtion
1σ ε1
Engineering modelFitting experimental data from oedometric tests
Modelling of the PBAModelling of the PBA
Model improvements with the in-pile operation experienceIncluded the thermal barrier for pre compaction calculation to achieve lower compaction in the upper beryllium bedIncluding the a gas gap between eurofer and lower Al fillerStart up calculation of first irradiation cycle with all power steps to simulate the actual start-up to allow the proper creep compactionCooldown of PBA irradiation at shut down of reactor
InstrumentationInstrumentation
Radial distribution Thermo-couples axial distribution
Temperatures during the first startTemperatures during the first start--upup
Beryllium pebble beds
Upper Beryllium bed, high Upper Beryllium bed, close to breeder
Upper Beryllium bed , close to breeder Lower Beryllium bed, bottom
Ceramic pebble bed
Temperatures during the first startTemperatures during the first start--upup
Ceramic bed, close to centre
ceramic bed, outside radius
Temperatures during the first startTemperatures during the first start--upup
Upper plate, ΔT=30 oC
Lower plate, ΔT=90 oC
Eurofer floating plates
Change of thermal conductivity in berylliumChange of thermal conductivity in beryllium
Due to compaction of the beryllium beds which results in higher contact area between the pebble beds the effective thermal conductivity increases
Creep compaction in the breeder bedsCreep compaction in the breeder beds
Mean stresses in the Pebble Bed AssemblyMean stresses in the Pebble Bed Assembly
Cool down after neutron irradiation Cool down after neutron irradiation
Cool down after 24 hrs of in-pile operation at 45 MWInstantaneous shut-down of the powerAllow for a cool down period of 250 s
Conclusions from the thermoConclusions from the thermo--mechanical mechanical modelmodel
All calculated temperatures for the Be beds are 50oC lower than in-pile measurementsFor Breeder bed calculated tempertures are well comparable to in-pile dataCalculated floating plate temperatures differ more for the lower floating plate, due to heat transport Even after 48 hours the beds did not reach the final compaction state
After cooling gas gaps predicted between the floating plates and the pebble beds
Possible PIE of PBAPossible PIE of PBA
For the validation of the model resultsGas-gap detection by infiltration methods in the 2nd containmentGas-gap (eurofer floating plates and pebble beds) detection by pebble-bed infiltrationPebble bed deformation to estimate compactionPebble deformation (if possible number of contacts and contact area’s etc.)
For the verification of the HCPB conceptPebble fragmentation, porosity, tritium release for ceramic and beryllium pebblesResidual strength of the materialsEurofer-breeder and Eurofer-beryllium interactionsTritium/hydrogen interactions with eurofer
Validation of the instrumentation usedSPND’s, thermocouples, Ionisation chambers
Possible PIE of PBAPossible PIE of PBA
Infiltration of the 2nd containmentPartially infiltration of the PBA pebble beds
Bed deformations
Gas gaps
interfaces
Pebble characteristics
impregnated Separate pebbles
Eurofer with T and H2
RemarksRemarks
PBA combine a number of inherent HCPB performance issues:pebble-bed filling, vibration, packing densitythermal behaviour of pebble-bedsmechanical behaviour of pebble-beds (2-D/3-D)bed-solid interfaces; possibility of gap formationmodelling capabilities (e.g. SCATOLA benchmark)reference gas purge in all pebble-beds & tritium permeation compatibility of ceramic and beryllium with Eurofer-97, and tube clads (vz. TBM instrumentation)Eurofer-97 in a structural function during irradiation, in hydrogen rich environmentBeryllium pebbles in TBM relevant temperature and dose range
OutlookOutlook
Dismantling 2nd containmentsStart cutting and evaluate gas gapsResin impregnationDetailed P.I.E.Neutron dosimetryCutting scheme to be determined along with additional P.I.E. on Be and Eur-97 and interfaces