Modelling Incineration of Minor Actinides

in the Experimental ADS MYRRHA

E. Malambu, V. Sobolev, W. Haeck, H. Aït Abderrahim

SCK·CEN, Boeretang 200, Mol, Belgium

February 16-18, 2005ARWIF-2005, Oak Ridge, USA

Contents

1. Introduction

2. Irradiation conditions

3. Fuel targets

4. Results of modelling

5. Conclusions

1.1. Introduction

• High level radioactive waste (HLW) is the problem of a high importance in countries using nuclear energy. About 105 t of HLW are into intermediate storages. 2000 t are produced every year in USA and 2500 t in EU(15).

• Pu, MA (Np, Am, Cm) and some LLFP give major contribution to the long term radiotoxicity. Spent fuel -> 10 kg/t Pu, 1.4 kg/t MA, 1.2 kg/t LLFP.

• P&T allows to reduce significantly the amount and radiotoxicity of HLW going to geological disposal.

• Subcritical ADS can be an effective and safe solution for transmutation of MA and Pu burning.

• The Belgian nuclear research Centre SCK·CEN in collaboration with other countries is developing an experimental ADS (MYRRHA) for MA and LLFP transmutation studies and demonstration.

1.2. Introduction: ADS in double strataADS in double strata

1st strata: Recovered Pu and UEnriched U

Standard fuel fabrication Spent fuel reprocessing

MA, depleted Pu, LLFP

Partitioning

Dedicated fuelfabrication

Short-lived FP +remnant

MA, depleted Pu, LLFP

ReprocessingADS-

transmuter

MA, depleted Pu, LLFP

NPP

2nd strata:

Disposal

1.3. Introduction: MYRRHA ADSMYRRHA ADS

Proton beam line

Subcritical core

Reactor vessel Primary coolant

Spallation loop

Secondary coolant

Main performances:

• Proton source: Ep~350 MeV, Ip~ 5 mA

• Liquid Pb-Bi spallation source and coolant

• Highly enriched MOX in the sub-critical core

• keff limited to ~ 0.95

• Total power ~ 50 MW(th)

• Maximal fast neutron flux ~ 1015 n.cm-2s-1

Proton accelerator

1.4. Introduction: MYRRHA ADS coreMYRRHA ADS core

Experimental channels

Reflector zone

Active zone

Spallation target

Experimental channels

Reflector zone

Active zone

Spallation target

Experimental channels

Reflector zone

Active zone

Spallation target

• 99 + 3 hexagonal cells (“macro-cells”) • Target-block hole is made by 3 removed FA in the central region • Surrounding active zone composed of 45 (or more) FA• Outer reflector zone composed of 54 (or less) reflector assemblies

1.5. Introduction: MYRRHA ADS spectrumMYRRHA ADS spectrum

1.0 E -4

1 .0 E -3

1 .0 E -2

1 .0 E -1

1 .0E + 0

1 .0 E -7 1 .0 E -6 1 .0E -5 1 .0E -4 1 .0 E -3 1 .0 E -2 1 .0 E -1 1 .0 E + 0 1 .0E + 1 1 .0E + 2 1.0 E + 3

N eu tron E n ergy (M eV )

Neu

tron

flux

per

leth

argy

uni

t

L B E -targ etT 91 - w a llF A [1 0 0 ]R efl[1 4 0 ]

1.6. Introduction: MYRRHA ADS fluxMYRRHA ADS flux

2.1. Irradiation conditions:Transmutation core optionTransmutation core option

Coolant. channels with dummy steel rods

LLFP rod bundles

Coolant (opened) channels

U-free MA fuel assemblies

(U-Pu)O2 fuel assemblies

LBE spallation target

Coolant. channels with dummy steel rods

LLFP rod bundles

Coolant (opened) channels

U-free MA fuel assemblies

(U-Pu)O2 fuel assemblies

LBE spallation target

D

D

D

A

A

A

2.2. Irradiation conditions : Neutron spectrum in A and DNeutron spectrum in A and D

1.0E-4

1.0E-3

1.0E-2

1.0E-1

1.0E+0

1.0E-4 1.0E-3 1.0E-2 1.0E-1 1.0E+0 1.0E+1 1.0E+2

Energy (MeV)

Neu

tron

per

leth

argy

uni

t

MAs in A

MAs in D

2.3. Irradiation conditions:Flux regimeFlux regime

0

1

2

3

4

0 120 240 360 480 600 720

Time, d

Tota

l ave

rage

neu

tron

flux,

1015

n c

m-2

s-1

Constant flux regime

Constant beam current

Constant LHGR regime

3. Fuel targets:

Composition:40 vol.% (Cm0.1Am0.5,Pu0.4)O1.88 + 60 vol.% MgO

Density 90 % TDFuel column diameter x height: 5.35 x 40.0 mm

Initial fuel isotopic vectors: 2nd strata option.

AMERICIUMIsotope Content

wt.%241Am 66.67243Am 33.33

PLUTONIUMIsotope Content

wt.%238Pu 5.06239Pu 37.91240Pu 30.31241Pu 13.21242Pu 13.51

CURIUMIsotope Content

wt.%244Cm 90.00245Cm 10.00

4.1. Results of modelling:

• ALEPH code system: MCNPX + NJOY + ORIGEN + JEF 2.2 (mod SCK)

• Calculated features:Neutron flux distribution

Neutron spectrum

Effective cross-sections

Fuel isotopic composition evolution

Power density evolution

4.2. Results of modeling:Pu, Am and Cm contentPu, Am and Cm content

0.7

0.8

0.9

1.0

1.1

1.2

1.3

0 240 480 720 960 1200 1440 1680 1920

Elapsed time (days)

Rel

ativ

e m

ass

(m/m

0)

Pu

Am

Cm

Am + Cm

A

A

A

AD

D

4.3. Results of modeling:Cm, Pu and He generationCm, Pu and He generation

( ) ( ) ( )

( ) ( )

16 162241 242 242 238

141242

90%

10%

h d

ym

Am n Am Cm Pu

Am

τ τ

τ

β α= =−

=

+ → ⎯⎯⎯→ + ⎯⎯⎯⎯→ +

→ ⎯⎯⎯⎯→

( ) ( )10.1 18.1243 244 244 240h yAm n Am Cm Puτ τβ α= =−+ → ⎯⎯⎯⎯→ + ⎯⎯⎯⎯→ +

( )87.7238 234yPu Uτ α=⎯ ⎯ ⎯ ⎯→ +

4.4. Results of modeling:He, Xe and Kr generationHe, Xe and Kr generation

0.0E+00

3.0E-04

6.0E-04

9.0E-04

1.2E-03

1.5E-03

0 240 480 720 960 1200 1440 1680 1920

Elapsed time (days)

gram

-ato

ms o

f gas

per

cm

3

He

Kr

Xe

Storage

4.5. Results of modeling:AmAm--isotopes contentisotopes content

0.0E+00

2.0E-01

4.0E-01

6.0E-01

8.0E-01

1.0E+00

1.2E+00

1.4E+00

0 240 480 720 960 1200 1440 1680

Time, d

Con

tent

, g/c

m³

Am-241Am-242mAm-242Am-243

4.6. Results of modeling:Am isotopic compositionAm isotopic composition

0%

10%

20%

30%

40%

50%

60%

70%

80%

start 1stcycle

2ndcycle

3rdcycle

4thcycle

5thcycle

6thcycle

7thcycle

8thcycle

9thcycle

Storage2 y

Isot

ope

frac

tion

Am-241Am-242mAm-242Am-243

4.7. Results of modeling:Cm-isotopes content

0.0E+00

1.0E-01

2.0E-01

3.0E-01

4.0E-01

0 240 480 720 960 1200 1440 1680

Time, d

Con

tent

, g/c

m³ Cm-242

Cm-243

Cm-244

Cm-245

4.8. Results of modeling:Cm isotopic compositionCm isotopic composition

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

start 1stcycle

2ndcycle

3rdcycle

4thcycle

5thcycle

6thcycle

7thcycle

8thcycle

9thcycle

Storage2 y

Isot

ope

frac

tion

Cm-242Cm-243Cm-244Cm-245

4.9. Results of modeling:PuPu--isotopes contentisotopes content

0.0E+00

1.0E-01

2.0E-01

3.0E-01

4.0E-01

5.0E-01

6.0E-01

0 240 480 720 960 1200 1440 1680

Time, d

Con

tent

, g/c

m³. Pu-238Pu-239Pu-240Pu-241Pu-242

4.10. Results of modeling:Pu isotopic compositionPu isotopic composition

0%

5%

10%

15%

20%

25%

30%

35%

40%

start 1stcycle

2ndcycle

3rdcycle

4thcycle

5thcycle

6thcycle

7thcycle

8thcycle

9thcycle

Storage2 y

Isot

ope

frac

tion Pu-238

Pu-239Pu-240Pu-241Pu-242

4.11. Results of modeling: kk∞∞

1.3

1.4

1.5

1.6

1.7

1.8

0 120 240 360 480 600 720 840 960 1080 1200

Time, d

k inf

mul

tiplic

atio

n fa

ctor

MOX

IMF

4.12. Results of modeling:Actinide mass balanceActinide mass balance

m0(BOL)

t1/2 3A+3D 3 A 3 D 3 A 3 D 3 A 3 D

Pu-238 87.7 y 366 326 333 93 92 229% 232%

Pu-239 2.4·104 y 2744 -493 -479 -35.9% -34.9%Pu-240 6550 y 2194 -15 -14 66 63 4.7% 4.4%Pu-241 14.4 y 956 -179 -174 -27 -29 -43.2% -42.6%Pu-242 3.76·105 y 978 79 87 16.1% 17.8%

Pu 7237 -282 -232 132 120 -4.1% -3.1%

Am-241 433 y 6030 -1025 -915 21 22 -33.3% -29.6%

Am-242 16 h; 141 y 124 131 -2 -2 (122 g) (129 g)

Am-243 7370 y 3014 -419 -359 -27.8% -23.8%

Am 9044 -1319 -1143 19 20 -28.8% -24.8%

Cm-242 162.8 d 107 104 -102 -99 (5.2 g) (5.0 g)

Cm-243 285 y 6.1 5.9 (6.1 g) (5.9 g)

Cm-244 18.1 y 1626 103.7 74.3 -68 -60 4.4% 1.8%

Cm-245 8500 y 180.7 25.9 22.2 28.6% 24.5%

Cm-246 4730 y 5.8 5.6 (5.8 g) (5.6 g)

Cm 1807 249 212 -170 -158 8.7% 5.9%

-19 -18 -15.2% -13.1%

∆m2=m2(EOS)-m1(EOI) (∆m1+∆m2)/m0(BOL)

Mass in grams

All actinides 18088 -1352 -1162

∆m1=m1(EOI)-m(BOL)

5. Conclusions (I)

• Studies of possibilities of the MA transmutation in the subcritical ADS MYRRHA are under way at SCK·CEN.

• A code system ALEPH has been developed for the burnup-depletion calculations in the MYRRHA core, and is under validation and testing.

• The evolution of the composition of CERCER IMF with Cm0.1Am0.5Pu0.4O1.88 fuel and MgO matrix, placed into two different positions of the fast core for 9 operation cycles (810 EFPD) followed by 2 years storage, have been modelled with ALEPH.

5. Conclusions (II)

• The net actinide destruction is 2.55 kg over the initial amount of 18.1 kg. The mass decrease of 26.8 % is observed for Am, whereas a mass increase of 7.3 % for Cm.

• He generated in the MA fuels contributes significantly to the rare gas production during operation as well as in storage and can affect significantly fuel properties.The amount of the produced He is ~ 1.5 times higher than Xe+Kr at the end of irradiation and 2.2 times higher after the storage.

• A more detailed analysis aiming at optimisation of the design of the MA fuel targets and of the burning strategy is in progress.