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Fast Reactor Physics

Konstantin Mikityuk, FAST reactors group @ PSIhttp://fast.web.psi.ch

Thorium Energy Conference 2013CERN Globe of Science and InnovationGeneva, Switzerland, October 27-31, 2013

2

Outline. Fast reactors: breeding.

Fast reactors: past and future.

Fast reactors: few R&D projects in Europe.

Fast reactors: could Th become a fuel? Sustainability Safety Proliferation resistance Radiotoxicity and decay heat

Summary: advantages and disadvantages of Th for FR

3

Fast reactors: breeding.

4

Fast critical reactorA fast neutron critical reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons.

Such a reactor needs no neutron moderator, but must use fuel that is relatively rich in fissile material when compared to that required for a thermal reactor.

1x10 -2 1x10 -1 1x10 0 1x10 1 1x10 2 1x10 3 1x10 4 1x10 5 1x10 6 1x10 7

Energy (eV)

0x10 0

1x10 14

2x10 14

3x10 14

4x10 14

5x10 14

6x10 14

7x10 14

8x10 14

Flux

per

uni

t let

harg

y (c

m-2

s-1)

SFR

PW R

SFR PWR

5

Breeding

238 239

239

239

92U

93Np

94Pu

91Pa

90Th 232 233

233

233

β–

β–

β–

β–

Thor

ium

fuel

cyc

le

Uran

ium

fuel

cyc

le

(n,γ)

(n,γ)

fertile

fertilefissile

fissile

23.5

m2.

35 d

22 m

27 d

A production of new fissile isotopes in the nuclear reactor is a kind of transmutation called a breeding and non-fissile isotopes (U-238 and Th-232), which give birth to the new fissile isotopes, are called fertile.

6

Neutron balance in a critical reactor

A_fissile

P = A_fissile + A_fertile + A_parasitic + LR

P = A + LR

keff = Production rate / (Absorption rate + Leakage Rate) = 1

A_fissile A_fissile A_fissile

= 1 + BR + L

– Number of n’s emitted per neutron absorbed in fissile fuel

BR – Breeding Ratio: Number of fissile nuclei created per fissile nucleon destroyed

L – Number of neutrons lost per neutron absorbed in fissile fuel

7

Breeding: for main fissiles

1x10 -2 1x10 -1 1x10 0 1x10 1 1x10 2 1x10 3 1x10 4 1x10 5 1x10 6 1x10 7

Neutron energy, eV

0

1

2

3

4

Pu-239

U -235

U -233

0x10 01x10 142x10 143x10 144x10 145x10 146x10 147x10 148x10 14

Flux

per

uni

t le

thar

gy (c

m-2

s-1)

SFRPW R

Average number of fission neutrons emitted per neutron absorbed as a function of absorbed neutron’s energy for three fissile isotopes

Best for breeding

8

Breeding

Burning of Pu-239 and U-233 in a fast neutron spectrum (>105 eV) provides the highest number of fission neutrons per neutron absorbed in fuel.

The extra neutrons can be absorbed by fertile isotopes with a rate which is equal or even higher than the fissile burning rate.

The fast neutron spectrum reactor with BR>1 is called a breeder and with BR=1—an iso-breeder.

Fast neutron spectrum allows to efficiently “burn” fertile U-238 or Th-232—via transmutation to fissile Pu-239 or U-233.

9

Fast reactors: past and future.

10

First "nuclear" electricity – fast reactor. In 1949 EBR-I – Experimental Breeder Reactor I – was designed at Argonne

National Laboratory. In 1951 the world’s first electricity was generated from nuclear fission in the fast-spectrum breeder reactor with plutonium fuel cooled by a liquid sodium.

First “nuclear” electricity : four 200-watt light bulbs. Courtesy of ANL.

11

Fast reactors: 1946 – 2013MWth

HgHg NaKNa LBE

ClementineEBR-I BR-10

DFR LAMPRE

EBR-II Fermi-1

Rapsodie BOR-60 SEFOR KNK-II

BN-350 Phénix

PFR OK-550/BM-40A

JOYO FFTF

BN-600 Super-Phénix

FBTR MONJU

CEFR

1946 19521951 1964

1958 20021959 1977

1961 19631961 1994

1963 19721967 1983

1968 20131969 1972

1972 19911972 1999

1973 20091974 19941974 1990

1977 20131980 19921980 2013

1985 19961985 2013

1994 20102010 2013

USAUSARussiaUKUSAUSAUSAFranceRussiaUSAG erm anyKazakhstanFranceUKRussiaJapanUSARussiaFranceIndiaJapanChina

0.0251.2860162.520040552058750563650150140400147029904071465

12

The Generation IV International Forum (GIF) is a cooperative international endeavor organized to carry out the R&D needed to establish the feasibility and performance capabilities of the next generation nuclear energy systems.

Argentina, Brazil, Canada, France, Japan, Korea, South Africa, the UK and the US signed the GIF Charter in July 2001, Switzerland in 2002, Euratom in 2003, China and Russia both in 2006.

Six nuclear energy systems were selected for further development:

4. Very-high-temperature reactor (VHTR)5. Supercritical-water-cooled reactor (SWCR)6. Molten salt reactor (MSR)

1. Gas-cooled fast reactor (GFR)2. Sodium-cooled fast reactor (SFR)3. Lead-cooled fast reactor (LFR)

13

Sustainability

Safety

Economics

Reliability

Proliferation-resistance

Generation-IV systems: keywords

14

Fast reactors: few R&D projects in Europe.

15

European sodium-cooled fast reactor.

Reactor vessel

Na

Ar 1 bar

core

Primary pumpÍ 6

SGÍ 6

545ºC

395ºC

490ºC

240ºC

Na~1 bar

H2O185 bar

SecondarypumpÍ 6

IHXÍ 6

Na~1 bar

340ºC

525ºC

Air HXÍ 6

35ºC

Na~1 bar

DHR HXÍ 6

DH

R lo

opÍ

6

Power: 3600 MWthCoolant: sodium@1 barFuel: (U-Pu)O2

Clad: stainless steel

ESFREURATOM FP7 project

16

Lead-cooled fast reactor demonstrator.

Core

Primary pumpÍ 8

SGÍ 8

Reactor vessel

H2O180 bar

480ºC

Pb

335ºC

450ºC

Feedwaterpump

Ar1 bar

HPturbine

LPturbine

Condenser400ºC

DH

R c

onde

nser

H2O

1 b

ar

Power: 300 MWthCoolant: lead@1 barFuel: (U-Pu)O2

Clad: Stainless steel

ALFREDConsortium:

Italy, Romania, Poland, …

17

Gas-cooled fast reactor demonstrator. Power: 75 MWthCoolant: helium@70 barFuel: (U-Pu)O2

Clad: Stainless steel

core

PrimaryblowerÍ 2

HXÍ 2

Guard vessel

N2

14 bar

DHRblowerÍ 3

DHR HX

H2O10 bar 50ºC

He70bar H2O

65 bar260º

C

H2O pool1 bar 50ºC

530ºC

N2

1 bar

Reservoir

DHR loopÍ 3Main loopÍ 2

127ºC

197ºCAir cooler

Í 21 bar

Water pumpÍ 2

35ºC

125ºC

ALLEGROConsortium:

Czech Republic, Hungary,

Slovakia, …

18

Fast reactors: could Th be a fuel?

19

Sustainability.

Depleted U stock

Spent fuel cooling

Fuel fabrication

Fast reactors

Geologicrepository

Separation of elements

U-dep

Ac

AcO2 + FP AcO2 + FP

FP + losses

“Ac” = “actinides”,i.e. U + Np + Pu + Am + Cm + ...“FP” = fission products

AcO2

(According to calculations) fast reactors can operate in an equilibrium closed U-Pu fuel cycle with BR=1 (amount of fissile produced = amount of fissile consumed) fed by only depleted (or natural) uranium

20

238237

238

238

237

239

239

239

23523492U

93Np

94Pu

95Am

96Cm

240

240

241

241 242

242 244

244243

245

FP

242 243

+1000

854–140

6

854

1

1853

–16

5–1

5

–146

–678181 102

–8412

–62

10

–6

4 10

–19

9

4

4

–23

–30

28

–421

–33

1717

17

2

2

1

–5 –8

–844 –1

–142 –1000

(Cm)(Am)(Pu)(Np)(U)

242m

feed fuel

6.75

d

2.1

d

87.7 y23

.5 m

2.35

d

7 m

in

14.3

y

4.98

h

26 m

in

18.1 y

16 h

16 h

163 d

–1

(n,2n)

β–

(n,γ)

β+

fissionM

mass number

α

EQL-U: mass balance in SFR (simplified model)

21

Sustainability.

Could the same reactors operate in an equilibrium closed Th-U fuel cycle?

(According to calculations) the answer is yes, but since no U-233 (main fissile isotope for this cycle) is available, we face a problem

Th disadvantage: How to start thorium fast reactor? What fissile material to use? Plutonium? Uranium-235? Uranium-233 generated somewhere else?

22

EQL-Th: mass balance in SFR (simplified model)

237

239

92U

93Np

94Pu

91Pa

90Th 233

233

233

+1000

–35

feed fuel

6 959

95922 m

231

626 h

231 6 232

1.3

d

6

4 234

6.7

h

427 d 955

–877

232 1 79–4

168.9 y

234

–3549 235

–3910 236

–28

8

6.75

d

–26 238

62.1

d

238

–41

1

–1

87.7 y

1

237

1 1.9 y

228 232

1

FP

–5 –2

–957 –0

–35 –999

(Pu)(Np)(U)(Pa)(Th)

Th advantage: very low amount of minor actinides

Th disadvantage: production of U-232—precursor of gamma emitters

23

U -234U -235U -236U -238

N p-237N p-239Pu-238Pu-239Pu-240Pu-241Pu-242

Am -241Am -242m

Am -243C m -242C m -244C m -245C m -246

0.01 0.1 1 10 100

0.070.01

0.0481.59

0.10

0.3110.17

5.780.660.55

0.360.02

0.150.01

0.110.03

0.02

EQL-U and EQL-Th fuel compositions in SFR (%wt)

Th-228Th-230Th-232Pa-231Pa-233

U -232U -233U -234U -235U -236

N p-237Pu-238Pu-239Pu-240

0.01 0.1 1 10 100

0.040.04

85.640.06

0.120.05

9.562.98

0.600.63

0.130.10

0.020.01

24

EQL-U and EQL-Th neutron balance

U 236U 238

N p237N p239Pu238Pu239Pu240Pu241Pu242

Am 241Am 242m

Am 243C m 244C m 245C m 246

Structures

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Th230Th232Pa231Pa233

U 232U 233U 234U 235U 236

N p237Pu238Pu239Pu240Pu241Pu242

Structures

0.0 0.2 0.4 0.6 0.8 1.0 1.2

k-inf = 1.30533 k-inf = 1.17023

Blue bars are isotope-wise contributions to absorption (sum up to 1) Red bars are isotope-wise contributions to production (sum up to k-inf)

Th disadvantage: lower k-infinity

25

Safety. We look at just two reactivity effects: Doppler effect and (sodium) void effect

having in mind other reactivity effects (less fuel type dependent)

strongback

diagrid

core

control rods

vessel

Thermal expansion effects (not considered)Void reactivity effect

26

EQL-U and EQL-Th fuel reactivity effects in SFR

-3 .0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0D oppler e ffect ($)

0.00.51.01.52.02.53.03.54.04.55.05.56.0

Void

effe

ct ($

)

Th-232

U -233U -235

N aC ladding

N aC ladding

U -238

Pu-239

Pu-240

Pu-241

i

i

i

ii

P

A

P

A

0

0

Th advantage: stronger Doppler and weaker void effects

Infinite medium (no leakage component)

Doppler (Nominal → 3100 K)

Void (Nominal → 0 g/cm3)

Isotope-wise decomposition:

27

1x10 -1 1x10 0 1x10 1 1x10 2 1x10 3 1x10 4 1x10 5 1x10 6 1x10 7

N eutron energy, eV

0

1

2

3

4

0x10 0

2x10 -3

4x10 -3

6x10 -3

8x10 -3

(u)

(cm

-2s-1

)

SFR

EQL-U and EQL-Th fuel reactivity effects in SFR

Why void effect is weaker in case of EQL-Th?

Sodium removal leads to spectral hardening—shift to the right

Pu-239: grows quicker

U-233: grows slower

28

Proliferation resistance.

238 239

239

239

92U

93Np

94Pu

91Pa

90Th 232 233

233

233

β–

β–

β–

β–

Thor

ium

fuel

cyc

le

Uran

ium

fuel

cyc

le

(n,γ)

(n,γ)

fertile

fertilefissile

fissile

23.5

m

2.35 d

Th disadvantage: fissile precursor has higher half life, potential to be separated22

m

27 d

Th advantage: misuse of U-233 is protected by presence of U-232

231

232

232

β–

231

29

EQL-U and EQL-Th fuel RT and DH (no FP)

10 100 1000 10000 100000 1000000Tim e, years

1E-006

1E-005

1E-004

1E-003

1E-002

Deca

y he

at, W

/g

SFR -USFR -Th

1

10

100

1000

10000

Radi

otox

icity

, Sv/

g

SFR -USFR -Th

Th advantage: Radiotoxicity and decay heat of EQL fuel are lower for ~10000y

30

Summary.

31

Summary... Th disadvantages Past and current fast reactors were/are based on U-Pu cycle.

Operational experience with thorium-uranium fuel is low.

Experience in fuel manufacturing and reprocessing is lower for Th-U fuel compared to U-Pu.

Fissile fuel for Th-U cycle (U-233) is not available.

U-232—precursor of hard gamma emitters—is produced in Th-U cycle (n2n reaction is higher in fast spectrum).

k-infinity of equilibrium fuel is lower for Th-U cycle compared to U-Pu one. This means that to reach iso-breeding the blankets of fertile material can be required.

Fissile precursor of U-233 (Pa-233) has higher half life (compared to Np-239)—potential to be separated and decayed to pure U-233.

32

Summary... Th advantages Calculational analysis with state-of-the-art codes shows that fast

reactor can operate as an iso-breeder in Th-U cycle closed on all actinides.

There is very low amount of minor actinides in EQL-Th fuel cycle.

Doppler effect is stronger and void effect is weaker in EQL-Th fuel compared to EQL-U.

Misuse of U-233 is protected by presence of U-232 (predecessor of hard gamma emitters).

Radiotoxicity and decay heat of EQL-Th fuel are lower during the first 10000 years of cooling compared to the EQL-U fuel.

Thank you. Questions?