Incineration of Plutonium in PWR Using Hydride Fuel Francesco Ganda and Ehud Greenspan University of California, Berkeley ARWIF-2005 Oak-Ridge, TN February 16-18, 2005
Pu transmutation overview Many approaches to plutonium transmutation LWR (thermal) Fast Reactors, Accelerators Full MOX CORAIL Regulatory limits: 50% core fraction 100%? Heterogeneous at the assembly level
Issues with Pu transmutation Smaller β Smaller Boron worth Smaller CR worth Higher void/ mod feedback But BR3 in Belgium operated with 70% MOX in the core; EDF successfully conducted a load-follow experiment with MOX
The case for hydrides Efficient transmutation of Pu requires higher H/HM (softer spectrum) Attainable burnup (GWD/tHM) MOX PuH 2 -U-ZrH 1.6 (PUZH)
The case for hydrides (cont ) Hydrides offer higher H/HM for a given P/D softer spectrum Normalized Flux at BOL Energy (Ev) 1.0E+00 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 Reference geometry (0.95cm; p/d=1.326) Normalized neutron flux 1.0E- 01 1.0E- 02 1.0E- 03 1.0E- 04 1.0E- 05 1.0E- 06 MOX PUZH PWR 1.0 E- 0 1 Normalized Flux at EOL PuH 2 U ZrH 1.6 = PUZH Energy (ev) 1.0 E+0 0 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 1.0 E- 0 2 1.0 E- 0 3 MOX PUZH PWR 1.0 E- 0 4 1.0 E- 0 5 1.0 E- 0 6
Issues to be addressed Attainable burnup with negative reactivity coefficients using soluble boron Transmutation effectiveness versus MOX
Presentation overview Methodology Assumptions and constraints Results: MOX feasibility region Results: PUZH feasibility region Results: Focus on the reference pin cell Discussion: why PUZH is better than MOX
Methodology: Approach 1. Cover wide range of geometries: find BU (3-batches) and reactivity coefficients (for both MOX and PUZH): Design variables: - fuel rod diameter (D) - Pitch-to-diameter ratio (P/D) Reactivity control: soluble boron (no burnable poison) Constraints: Doppler, MTC, Void ρ coefficient < 0 k (3-batch average @ discharge) = 1.05 2. Focus on the reference geometry (if feasible) and compare MOX and PUZH for: Fraction of Pu incinerated Decay heat Neutron source intensity [spontaneous fission and (α,n)] Fiss Pu/tot Pu ratio MA/Pu ratio
Methodology: Benchmark All the calculations are performed in single pin geometry with SAS2H: benchmarked with MOCUP and found reliable for hydrides and plutonium U ZrH1.6 P/D=1.326 CladOD=0.95 cm K-inf 1.5 MOCUP SAS2H 1.4 1.3 1.2 1.1 1 0.9 0.0 10.0 20.0 30.0 40.0 BURNUP (GWD/MTHM) Normalized flux Comparison between MCNP and XSDRNPN fluxes at BOL 1.00E+00 1.E-03 1.E-01 1.E+01 1.E+03 1.E+05 1.E+07 1.E+09 1.00E-01 1.00E-02 XSDRNPN MCNP 1.00E-03 1.00E-04 1.00E-05 1.00E-06 Neutron energy (ev)
Methodology Question: How to best compare MOX and PUZH performance? Answer: Use the indifferent method PWR cycle length 1350 EFPD with 5% enrichment Utilities will likely want the same cycle length with Pu, both with MOX and PUZH. find the amount of Pu (for a given Pu vector) that satisfy the 1350 EFPD requirement.
Methodology: Reference unit cell Reference unit cell: Clad OD = 0.95 cm P/D = 1.3261 Fuel diam. = 0.8192 cm Clad ID = 0.8357 cm Pitch = 1.25 cm Power density = 36.138 W/gHM
Methodology: Composition Plutonium vector loaded For both MOX and PUZH U is depleted (0.25% enriched) PU241 12% PU242 3% PU238 1% MOX PUZH TOT Pu 2.134E-03 1.587E-03 Tot U 2.130E-02 9.834E-03 Pu atom fraction 9.109 13.894 PU240 22% PU239 62%
Results: MOX Burnup (GWD/tiHM) BOL Kinf BOL Coolant temp. coeff. (pcm/k) Required Sol B (ppm)
MOX practically achievable burnup (GWD/tiHM)
Results: PUZH Burnup (GWD/tiHM) BOL Kinf BOL Coolant temp. coef. (pcm/k) Required Sol B (ppm)
PUZH practically achievable burnup (GWD/tiHM)
Result: k evolution; reference geometry w/o B K-inf vs. Burnup (EFPD) 1.4 K-inf 1.3 1.2 1.1 1.0 0.9 0.8 MOX PUZH PWR 0 200 400 600 800 1000 1200 1400 1600 Effective Full Power Days
Result: Reference geometry Soluble Boron (ppm) Soluble Boron Concentration (ppm) 3500 3000 2500 2000 1500 1000 500 0 MOX PUZH 0 500 1000 1500 EFPD
Result: Reference geometry Prompt reactivity coefficient (pcm/k) Prompt reactivity coefficient (pcm/k) 0-0.5-1 -1.5-2 -2.5-3 -3.5-4 Burnup (GWD/MTiHM) 0 20 40 60 80 100 120 PWR MOX PUZ
Result: Reference geometry Coolant temperature coefficient (expansion and heating) (pcm/k) Coolant temperature coefficient (expansion and heating) (pcm/k) 0-10 -20-30 -40-50 -60-70 Burnup (GWD/MTiHM) 0 20 40 60 80 100 120 PWR MOX PUZ
Result: Reference geometry Void temperature coefficient (pcm/% void) Void temperature coefficient (pcm/% void) 0-50 -100-150 -200-250 -300-350 Burnup (GWD/MTiHM) 0 20 40 60 80 100 120 PWR MOX PUZ
Result: Reference geometry Soluble Boron worth (pcm/ppm) 6 5 Soluble Boron worth (pcm/ppm) 4 3 2 1 PWR MOX PUZ 0 0 20 40 60 80 100 120 Burnup (GWD/MTiHM)
Transmutation performance reference geometry PUZH vs. MOX: For same energy production: 25% less Pu 50% less U 103 vs. 50 GWD/TiHM 50% vs. 24% fraction of Pu incinerated Discharged MOX PUZH g Pu/pin 115.00 50.30 g MA/pin 7.77 6.67 g Pu+MA /pin 122.77 56.97 Total n/s from Pu 91560 62892 Watts/pin 231.00 198.00 Ci/pin 72800 58700 fiss/tot Pu 0.629 0.44 MA/Pu 6.76 % 13.25 % Spont n/s-g Pu 467.50 771.19 Tot n/s-g Pu 796.17 1250.34 W/g Pu 2.01 3.94 W/g MA 29.71 29.71 W/g Pu+MA 1.88 3.48
Transmutation performance Max Power Geometry: P/D=1.4, clad OD=0.65 MOX PUZH Burnup GWD/MTiHM : 52.25 108.2 Pu incinerated 72% 45% Pu remaining 28% 55% Discharged MOX PUZH g Pu/pin 49.80 21.70 g MA/pin 2.92 2.24 g Pu+MA /pin 52.72 23.94 TOT n from Pu 35543 22525 tot W/pin 191 148 Ci/pin 66564 50700 fiss/tot Pu 0.630 0.447 MA/Pu 5.86 10.30 spont n 461.06 739.14 n/gpu 713.71 1038.00 W/g Pu 3.84 6.82
Transmutation performance Inert Matrix fuel: Reference Geometry PuH 2 ZrH 1.6 Attainable Burnup: 709.6 GWD/MTiHM EFPD: 1398.5 (specific P: 507.40 W/giHM) Pu incinerated = 78 atom% but Doppler becomes positive @ 900 EFPD 50% incineration in one pass With ThH 2 can get all reactivity worth negative Discharged PuH 2 ZrH 1.6 g Pu/pin 25.5 g MA/pin 6.7 g Pu+MA /pin 32.2 TOT n from Pu 48386 tot W/pin 117 Ci/pin 20700 fiss/tot Pu 0.165 MA/Pu 26.2 spont n/gpu 1296 n/gpu 1897 W/g Pu 4.6
Conclusions Hydride fuels provide higher H/Pu ratio softer spectrum without having to reduce D, increase P or use more water rods Compared to MOX fuel of same dimensions and cycle length, use of PuH 2 -ZrH 1.6 fuel offers: 100% higher burnup: 103 vs. 50 GWD/TiHM Larger fractional transmutation: 50% vs. 24% fraction of Pu Worse Pu quality: 44% fissile isotopes vs. 63% Larger MA/Pu ratio: 13.25 % vs. 6.76 % Stronger neutron source intensity and decay heat per gm Pu But lower neutron source intensity and decay heat per fuel assembly
Conclusions (cont.) Inert matrix hydride fuels might enable even higher Pu incineration per pass Particularly promising are ThH 2 containing hydride fuels they provide negative reactivity coefficients up to high burnups and thereby offer high fractional incineration of Pu It is recommended to consider hydride fuels for recycling Pu in LWR