MOX@EON: EON Operational Experience - Ausgestrahlt

MOX@EONEON Operational ExperienceFall 2011 Meeting of theUS Nuclear Waste Technical ReviewBoardWolfgang Faber, EON-KernkraftSeptember 14, 2011

Irradiation Record of EON-NPPsHM U-FA Reproc. HM MOX Pu(t) (t) (t) (t)Brokdorf 609 187 126 8Unterweser 839 517 107 6Grohnde 739 283 66 4Grafenrheinfeld 793 376 81 5Isar-2 603 181 81 5Stade 496 496 0 0Würgassen 344 344 0 0Isar-1 733 337 0 0total 5155 2721 461 28Pu 57 Pu for EKKMOX still to be loaded: 88 PWR/47 t HM/3 t PuUnterweserEmslandGrohndeBrunsbüttelBrokdorfStadeKrümmelHannoverWürgassenEON shares (3)EON operated (4)Fukoshima decommissioning(4)decommissioned before 2000(2)Balance for EKK operated units(8)5200 t HM in U-FA irradiated2700 t HM reprocessed (50%)60 t Pu created30 t (50%) recycled as MOXGrafenrheinfeldIsar 1 + 2Gundremmingen B + C2

MOX Licensing at EKK units (authorities of 3 differentstates)KBRMOX / reload MOX / core Pufiss/Putot Pufiss U-235 remark1/3 64 equivalent to 4,0w/o U-235KKU 16/20/24(59/71/>71) 96

MOX - Handling Aspects1. Manufacturing2. Transport3. Receiving inspection4. On-site storage5. Reactor-physics properties our area of6. Safeguardsexpertise7. Post-operation storage8. Transport and intermediate storage4

100959085MOX - Physical Properties (1): Pu-BalanceBOLU-Uranium-FA100Pu 242Pu 241235 FP Pu 240Pu-U-238TPu 0,04%Pu 1,2%U-23858721 MWd/tNp 237Am 243Pu 238Pu 239FPU 236U 235U 238959085BOLPu 6,7%239U-238MOX-FATPu0,2%Pu 4,1%FPU-23858613 MWd/tNp 237Am 243Pu 238Pu 242Pu 241Pu 240Pu 239FPU 236U 235U 2385

MOX - Physical Properties (2): General OverviewU Pu Am235 236 238 238 239 240 241 242 241 f,th(b) 583 743 1009 th2,4 2,9 3,0 th0,0070 0,0023 0,0055E/fission (MeV) 201,7 205 210 212,4E n,max, E avg(MeV) 1) 0,65/1,95 0,70/2,08 0,67/2,01heat (mW/g) 560 1,9 6,8 4,2 0,1 114surface dose rate 1kgn-dose (mSv/h) 640 300,0 310,0–dose (mSv/h) 240 270001)p( E)22 ( 3Eavg)3/ 2Ee E / T6

MOX - Physical Properties (3): PWR n-spectra (U andMOX-core)Zry-propertiestransientreaction7

MOX - Physical Properties (4): ConsequencesParameter Affected Area Consequencen-energy fast fluence in structural materials irr.-hardeninglower fraction delayed n ()transientshigher fission energyeffectively nonePu-241, Am-241manufacturingceramicsfuel rod designlower n-absorptionmoderator-condition (density, void)faster transient responseless fission-productsheating of unirradiated materialdose-rateheat conductivity, inhomogeneous matrixcriticality, CRWtransport,inspection8 T

Practical Aspects of MOX - Handling (1): Deliveryon-site receiving inspection:1) radiation dose for staff about 50-100Sv/MOX-FA2) cooling in rack prior to wet-storage (about 1 hour per bundle)on site storage of fresh MOX:only wet-, not dry- storage (capacity)9

Practical Aspects of MOX - Handling (1): DeliverySIFA (truck) and MX4(cask)MX4 loaded with 4 MOX-FAloading of cooling-rackcooling-rack10

Practical Aspects of MOX - Handling (2): ReactorPhysics Reactor-Physics Properties:1. bundle design (enrichment-levels, water-rods)2. reactivity versus burnup3. power-distribution4. measurement vs. prediction5. transients and accidentsfuel rod design properties:1. heat-conductivit2. fuel temperature3. fission-gas release11

Practical Aspects of MOX - Handling (2): BundleDesignBE-Name180 oTSRPNMLKHGFEDCBA270 o1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1690 o0 o /360 oBE-Name180 oTSRPNMLKHGFEDCBA270 o1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1690 o0 o /360 o168 52MOX-BS-Position(4.8 w/o Pu fiss )MOX-BS-Position(3.9 w/o Pu fiss )236 20U-BS-Position(4.4 w/o U 235 )SE-Führungsrohrposition12 4MOX-BS-Position(2.7 w/o Pu fiss )Wasserstäbe20SE-FührungsrohrpositionMOX-FAU-FA12

Practical Aspects of MOX - Handling (2): MOX-Reactivityreactivity-equivalence:edisk0( U )e( e)de disk0( MOX )( e)dek ref4,55w/o Pu fiss ,Pu fiss /Pu tot =63,80%e disalternative:( U )( MOX ) ( ) ( )00krefkekor:• OECD• equilibrium-cycles(EKK-study)eExcess reactivity less pronounced – Pu-238, Pu-240,Pu-242reactivity decline slower – in-situ breed&burn of Pu-241Equivalence dependent onsurrounding U-235 enr.:4,6 4,6 4,64,6 4,0 4,64,6 4,6 4,63,9 3,9 3,93,9 3,8 3,93,9 3,9 3,9MOX-4 andequivalent U-235enrichment13

Practical Aspects of MOX - Handling (2): PowerDistribution14

Practical Aspects of MOX - Handling (2): Exp. vsPredictionAccuracy of core-simulator prediction:1. no influence of MOX loading on difference calculation – aeroballmeasurement2. apparent influence on prediction of critical boron-concentration, butcode specific: only AREVAs CASCADE-simulator affected, not e.g.CMS (Studsvik-Scandpower)15

Practical Aspects of MOX - Handling (2): TransientsMost pronounced examples:1. ATWS: more negative T helps voiding and reduces heat input atATWS2. LOCA: PCT higher in MOX - ECR not limiting in KWU-plants (2 min);core failure rates (German safety criterion) higher in mixed cores;0,40 0,45 0,50 0,55 0,60 0,65 0,70 0,750,006 (%)-2,00-4,00-6,00UranMOXFrequency distribution[% of fuel rods in the core]5432allUO 2UO 2/Gd 2O 3MOX-8,001-10,00moderator-density (g/cm 3 )00 50 100 150Fuel rod inner pressure [bar]FIG. 5. Resulting distribution of rod internal pressures in the core of a German 16x16PWR with 45370 FRs containing UO 2, UO 2/Gd 2O 3, and MOX fuel16

Practical Aspects of MOX - Handling (2): Fuel-Rod-Design• heat-conductivity lower• Pufiss-distribution inhomogenouscompared to U-235 nuclei in U-Matrix:>60% proportion of fissile nuclei inPuO microcrystal vs 5% proportion offissile nuclei in UO2 microcrystal• more reactivity and power at higherbup (reflecting k inf (burnup))• higher fuel temperature• more fission gas release• KWU-plants: generally additionallower fuel-rod-plenum!Fuel thermal conductivity [W/(m K)]65432UO2 and MOX fuel thermal conductivity (95% TD)UO2, B=0 MWd/kg(HM)UO2, B=10 MWd/kg(HM)UO2, B=30 MWd/kg(HM)UO2, B=50 MWd/kg(HM)UO2, B=80 MWd/kg(HM)MOX, B=0 MWd/kg(HM)MOX, B=10 MWd/kg(HM)MOX, B=30 MWd/kg(HM)MOX, B=50 MWd/kg(HM)MOX, B=80 MWd/kg(HM)10 500 1000 1500 2000 2500 3000Temperature [°C]17

Practical Aspects of MOX - Handling (2): Fuel-Rod-DesignStored energy in the rods of a UO2 core at BOCStored energy (rel. scale)Red symbols:Top 5%Red and black symbols: all rods in the coreStored energy in the rods of a MOX/UO2 core at BOC0 10 20 30 40 50 60 70Burnup [MWd/kg(HM)]Stored energy (rel. scale)Red symbols:Top 5%Red and black symbols: all rods in the core0 10 20 30 40 50 60 70Burnup [MWd/kg(HM)]18

Practical Aspects of MOX - Handling (2): keyparametersp imicrostructurefissionnuclei/nenergyk infT F 19

Practical Aspects of MOX - Handling (3): Fast Fluence• RPV-Fluence in U- and U/MOX-core: no practical impact of MOX -effect of different loading schemes dominant(in-out-loading vs. out-in)3,002,506050fast flux: green, whitehighestfast fluence per FPD/1e14 n/cm^2s2,001,501,00403020avg. # MOX-FA per cycle0,5010cycle 28 (40 MOX)cycle 29 (0 MOX)0,001-9 10-17 18-24 25-27Operation Period (cycles)0no difference where it matters (outer row)20

Practical Aspects of MOX - Handling (4): CR-worth• no adaption necessary in KWU-plants• IFM cold shutdown-criterion easy to meet• KKU-example cycle 28 (U/MOX) vs. cycle 29 (U):148 ppm B/%MOX) vs. 138 ppm B/%21

Practical Aspects of MOX - Handling (5): Safeguards1. camera-surveillance system: additional cameras2. IAEA inspections: monthly inspections22

Practical Aspects of MOX - Handling (6): Back-Endtransport and storage container:• max 4 MOX-FA out of 19 FA per cask (expected 6 starting in 2012)• burnup restricted to 55 MWd/kg (U: 65 MWd/kg)• heat load restriction requires longer storage time: MOX-free coresEOPL!!!today:121211161731013 14154918195876

Practical Aspects of MOX - Handling (6): Back-Endfuture (a little bit morefortunate):121211161731013 14154918195876

Conclusions:MOX are …• …more expensive (at least German situation)• …more difficult to fabricate• …more complicated to handle on-site• …more closely supervised by IAEA• …more appreciated by IFM-people• …in need of longer post-operating storage time• …more difficult in intermediate storage period…than Uranium FA.25