-
Study on SiC Components to
Improve the Neutron Economy in HTGR
Piyatida TRINURUK and Assoc.Prof.Dr. Toru OBARA
Department of Nuclear Engineering
Research Laboratory for Nuclear Reactors
Tokyo Institute of Technology, Japan
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Contents
Introduction
Objectives of this study
Computer code and Parametric survey
Results and discussions
Conclusions
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HTGR : High Temperature Gas-cooled Reactor
A graphite-moderator and helium gas-cooled reactor.
HTTR (High Temperature Test Reactor): Prismatic
block type HTGR.
Japan Atomic Energy Research Institute (JAERI) in
1996.
Thermal output 30 MW.
Fuel blocks, control rod blocks, reflector blocks and
irradiation blocks.
Uranium enrichments: 3.4 - 9.9%wt - U235
Introduction
Fuel compact Coated Fuel Particle Fuel block & Fuel rod
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Convention way to compensate
the excess reactivity in HTTR
(Source: N.Fujimoto and et.al., Nuclear design, Nuclear Eng. and
design 233 , 2004)
Pros.
High output temperature
Inherent safety reactor
Cons.
Once-through fuel cycle.
High excess reactivity.
Unavailable in commercial
technique for fuel reprocessing.
Introduction
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Properties of SiC SiC is a compound of silicon and carbon.
Silicon (Si):
Higher absorption cross section
Smaller scattering cross section
Higher mass number
Disadvantage of SiC:
SiC decomposes at lower temperature as compared to IG-110
graphite.
SiC corrodes by Palladium (Pd).
Carbon Si-28
Source: http://wwwndc.jaea.go.jp
Poor moderating material compared to graphite
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Objectives
To evaluate the use of SiC in various parts of fuel block
assembly instead of graphite to take the benefit of
transmutation under the concept of neutron spectrum
shifting.
Shifting the neutron spectrum
Increase the conversion of fertile into fissile material
More fission product by without increasing the U-235
enrichment
The neutron economy
Compensate reactivity and prolong fuel cycle
-
MVP-2.0 : Continuous energy neutron transport Monte Carlo
method
JENDL- 4.0 : Nuclear data library
Computer code and Parametric survey
II. Several fuel block assemblies I. One fuel block assembly
Number of fuel rods / block 33
Burnable poison No
Enrichment of fuel 5% wt of U235
Packing fraction 30%
History / batch 30,000
Batch (Skips + tallies) 50+150
Boundary condition Periodic boundary
Number of energy groups 176
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Parametric survey
Case Conditions Specification
1. Fuel compact material Graphite SiC
2. Fuel sleeve material Graphite SiC
3. Fuel block material Graphite SiC
4. Combination between SiC block and GP block Based on 3 fuel
blocks
4
1
Fuel compact
3
Fuel block
2
Fuel pin Combination between
SiC block & GP block
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Results and Discussions
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I. Effects of SiC on the neutron spectrum
Conditions:
One fuel block assembly.
33 Fuel pins with 30% of packing fraction.
Enrichment : Natural Uranium, 5%, 10%, 20%.
SiC material : fuel compact / fuel sleeve / fuel block.
No burnable poison.
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0.0E+00
1.0E-03
2.0E-03
3.0E-03
4.0E-03
5.0E-03
1.0E-04 1.0E-01 1.0E+02 1.0E+05
Neu
tro
m s
pe
ctr
um
(n
/s/c
m3
/Le
tha
rgy/s
ou
rc)
Energy (eV)
SiC fuel block
Nat. U
SiC sleeve
Ref. case
SiC fuel compact
0.0E+00
1.0E-04
2.0E-04
3.0E-04
4.0E-04
5.0E-04
6.0E-04
7.0E-04
8.0E-04
1.0E-04 1.0E-01 1.0E+02 1.0E+05
Neu
tro
m s
pe
ctr
um
(n
/s/c
m3
/Le
tha
rgy/s
ou
rc)
Energy (eV)
SiC fuel block
En.10%
SiC sleeve
Ref. case
SiC fuel compact
0.0E+00
1.0E-04
2.0E-04
3.0E-04
4.0E-04
5.0E-04
6.0E-04
7.0E-04
8.0E-04
1.0E-04 1.0E-01 1.0E+02 1.0E+05
Neu
tro
m s
pe
ctr
um
(n
/s/c
m3
/Le
tha
rgy/s
ou
rc)
Energy (eV)
SiC fuel block
En.20%
0.0E+00
2.0E-04
4.0E-04
6.0E-04
8.0E-04
1.0E-03
1.2E-03
1.4E-03
1.6E-03
1.0E-04 1.0E-01 1.0E+02 1.0E+05
Neu
tro
m s
pe
ctr
um
(n
/s/c
m3
/Le
tha
rgy/s
ou
rc)
Energy (eV)
SiC fuel block
Ref. case
SiC fuel compact
SiC sleeve
En.5%
I. Effects of SiC on the neutron spectrum
-
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
0 5,000 10,000 15,000 20,000 25,000 30,000
Infi
nit
e m
ult
ipli
ca
tio
n f
ac
tor
MWD/Ton
SiC fuel block
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
0 5,000 10,000 15,000 20,000 25,000 30,000
Infi
nit
e m
ult
ipli
ca
tio
n f
ac
tor
MWD/Ton
En.10% 0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
0 5,000 10,000 15,000 20,000 25,000 30,000
Infi
nit
e m
ult
ipli
ca
tio
n f
ac
tor
MWD/Ton
En.20%
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
0 5,000 10,000 15,000 20,000 25,000 30,000
Infi
nit
e m
ult
ipli
ca
tio
n f
ac
tor
MWD/Ton
II. Effects of SiC on the reactivity
Nat. U En.5%
-
0.0E+00
2.0E-04
4.0E-04
6.0E-04
8.0E-04
1.0E-03
1.2E-03
1.4E-03
0 10,000 20,000 30,000
Nu
cli
de
de
nsit
y
MWD/Ton
U235
2.14E-02
2.15E-02
2.16E-02
2.17E-02
2.18E-02
2.19E-02
2.20E-02
2.21E-02
0 10,000 20,000 30,000
Nu
cli
de
de
nsit
y
MWD/Ton
U238
2.20E-02
2.22E-02
2.24E-02
2.26E-02
2.28E-02
2.30E-02
2.32E-02
0 10,000 20,000 30,000
Nu
cli
de
de
nsit
y
MWD/Ton
U238
0.0E+00
2.0E-05
4.0E-05
6.0E-05
8.0E-05
1.0E-04
1.2E-04
1.4E-04
1.6E-04
1.8E-04
0 10,000 20,000 30,000
Nu
cli
de
de
nsit
y
MWD/Ton
U235
0.00E+00
5.00E-05
1.00E-04
1.50E-04
2.00E-04
2.50E-04
0 10,000 20,000 30,000
Nu
cli
de
de
nsit
y
MWD/Ton
Pu239
0.00E+00
1.00E-05
2.00E-05
3.00E-05
4.00E-05
5.00E-05
6.00E-05
7.00E-05
8.00E-05
0 10,000 20,000 30,000
Nu
cli
de
de
nsit
y
MWD/Ton
Pu241
0.00E+00
5.00E-05
1.00E-04
1.50E-04
2.00E-04
2.50E-04
0 10,000 20,000 30,000
Nu
cli
de
de
nsit
y
MWD/Ton
Pu239
0.00E+00
5.00E-06
1.00E-05
1.50E-05
2.00E-05
2.50E-05
3.00E-05
3.50E-05
4.00E-05
4.50E-05
0 10,000 20,000 30,000
Nu
cli
de
de
nsit
y
MWD/Ton
Pu241
Enrichment : Natural Uranium
Enrichment : 5%
III. Effects on the change of nuclide density
-
2.0E-03
2.5E-03
3.0E-03
3.5E-03
4.0E-03
4.5E-03
5.0E-03
0 10,000 20,000 30,000
Nu
cli
de
de
nsit
y
MWD/Ton
1.82E-02
1.83E-02
1.83E-02
1.84E-02
1.84E-02
1.85E-02
1.85E-02
1.86E-02
1.86E-02
0 10,000 20,000 30,000
Nu
cli
de
de
nsit
y
MWD/Ton
U238
0.00E+00
5.00E-05
1.00E-04
1.50E-04
2.00E-04
2.50E-04
0 10,000 20,000 30,000
Nu
cli
de
de
nsit
y
MWD/Ton
Pu239
0.00E+00
2.00E-06
4.00E-06
6.00E-06
8.00E-06
1.00E-05
1.20E-05
0 10,000 20,000 30,000
Nu
cli
de
de
nsit
y
MWD/Ton
Pu241
Enrichment : 20% (HEU)
U235
III. Effects on the change of nuclide density
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Using SiC in HTTR instead of graphite can make the
spectrum harden.
The benefit of transmutation by the shift of neutron
spectrum is more effective for LEU because SiC can slow
down the depletion of fissile nuclide as U-235 and increase
the utilization of fertile nuclide U-238.
The magnitude of the spectrum shifting depends on the
ratio of graphite which is replaced with SiC.
64.30% 14.22%
17.85%
3.63%
Fuel block
Fuel compact
Fuel Sleeve
Coating layer
The percent of graphite volume of
each component in a fuel block
Effects of SiC in each component
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IV. Combination of SiC blocks & graphite blocks
Condition:
5 % enriched uranium
3 fuel blocks
All graphite blocks
GP : SiC blocks = 2 : 1
GP : SiC blocks = 1 : 2
All SiC blocks
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
1.10
1.20
1.30
1.40
1.50
0 10,000 20,000 30,000 40,000 50,000 60,000 70,000
Infi
nit
e m
ult
iplic
ati
on
fa
cto
r
MWD/Ton
Increase the ratio of SiC blocks in the core can compensate
the excess reactivity and flatten the reactivity.
SiC block results into the reactor operated under the
criticality.
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V. Improvement of reactivity in SiC block
Increase the fuel enrichment in SiC block can success to
improve the reactivity and make the reactor operate at the
criticality.
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0 10,000 20,000 30,000 40,000 50,000 60,000
Infi
nit
e m
ult
ipli
ca
tio
n f
ac
tor
MWD/Ton
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Conclusions
SiC has a potential to make the neutron spectrum harden
and increase the fissile material by the transmutation.
The magnitude of spectrum shifting depends on the ratio
of SiC replacement : more SiC, more effective to harden
spectrum.
LEU and HEU under the harden spectrum can perform as
burnable poison to compensate the excess reactivity, but
it will lead the reactor operated under the critical.
The optimization between the ratio of SiC replacement
and the fuel enrichment is need to pay attention in order
to achieve the neutron economy.
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Thank you
for your kind attention
