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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?