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8/14/2019 The Utilization of Thorium for Long-life Small Thermal Reactors Without on-site Refueling
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The utilization of thorium for long-life small thermalreactors without on-site refueling
Iyos Subki a,*, Asril Pramutadi b, S.N.M. Rida b, Zaki Su’ud b, R. Eka Sapta a,b,S. Muh. Nurul a,b, S. Topan a,b, Yuli Astuti a,b, Sedyartomo Soentono a
a National Atomic Energy Agency (BATAN) Indonesiab Nuclear and Reactor Physics Laboratory, ITB, Bandung, Indonesia
Abstract
Thorium cycle has many advantages over uranium cycle in thermal and intermediate spectrum nuclear reactors. In addition to large amount of
resources in the world which up to now still not utilized optimally, thorium based thermal reactors may have high internal conversion ratio so
that they are very potential to be designed as long-life reactors without on-site refueling based on thermal spectrum cores. In this study prelim-
inary study for application of thorium cycle in some of thermal reactors has been performed.
We applied thorium cycle for small long-life high temperature gas reactors without on-site refueling. Calculation results using SRAC code
show that 10 years lifetime without on-site refueling can be achieved with excess reactivity of about 10% dk/k.
The next application of thorium cycle has been employed in long-life small and medium PWR cores without on-site refueling. Relatively high
fuel volume fraction is also applied to get relatively hard spectrum, small size, and high internal conversion ratio. In the current study we have
been able to reach more than 10 years lifetime without on-site refueling for 20e300 MWth PWR with maximum excess reactivity of a few %dk/k.
The last application of thorium cycle has been employed in long-life BWR cores without on-site refueling. Relatively high fuel volume
fraction is applied to get relatively hard spectrum, small size, and high internal conversion ratio. In the current study we have been able to reach
more than 10 years lifetime without on-site refueling for 100e
600 MWth BWR with maximum excess reactivity of a few %dk/k.Ó 2007 Published by Elsevier Ltd.
Keywords: Thorium cycle; Long-life thermal reactors; High internal conversion ratio; SRAC code; Hard spectrum; Excess reactivity
1. Introduction
Thorium cycle in general has better conversion ratio than
uranium cycle in the thermal spectrum. In this study, thorium
cycle is used to extend the thermal reactor operation cycle
without on-site refueling. Basically we have to adjust the mod-erating ratio and fuel enrichment to be able to improve internal
conversion ratio. And by geometrical optimization process we
can get the design of small long-life high temperature gas
cooled reactors (HTGR) without on-site fueling, small long-
life pressurized water reactors (PWR) without on-site fueling,
and small boiling water reactors (BWR) without on-site
fueling.
2. Design concept
In order to extend the refueling cycle without excessive re-activity swing in high temperature gas cooled reactors we need
reactor core with high internal conversion ratio, in general
around unity. In thermal reactors such as HTGR, proper com-
bination of 232The233U cycle gives high possibility to achieve
such objective. Adjusting moderation ratio by appropriately
setting the graphite moderator and fuel composition is one
of important strategy to get harder neutron spectrum so that
much better conversion ratio can be reached.
Here we performed many parametric surveys to understand
the influence of many parameters such as moderating ratio,
* Corresponding author.
E-mail addresses: subki01@cbn.net.id (I. Subki), szaki@fi.itb.ac.id
(Z. Su’ud).
0149-1970/$ - see front matter Ó 2007 Published by Elsevier Ltd.
doi:10.1016/j.pnucene.2007.10.029
Available online at www.sciencedirect.com
Progress in Nuclear Energy 50 (2008) 152e156www.elsevier.com/locate/pnucene
8/14/2019 The Utilization of Thorium for Long-life Small Thermal Reactors Without on-site Refueling
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fuel enrichment, linear power, etc. to the infinite multiplica-
tion factors pattern during burn-up. Using the results of para-
metric survey we can then perform optimization in the core
level.
Similar approach is used for long-life small pressurized
water reactors without on-site refueling and long-life small
long-life BWR without on-site refueling and here we apply
tight lattice concept to get small core with relatively high
internal conversion ratio.
3. Computational method
For computation method we used SRAC code system to
calculate cell calculation and cell burn-up. Whole core
SRAC PUBLIC LIBRARY
JENDL-3.2,
SRAC USER LIBRARY
Flux, Microscopic,,
Macroscopic
CELL CALCULATION.,
BURNUP
START
HOMOGENISATION
& COLLAPSING
CORE
CALCULATION
(CITATION)
CALCULATION
RESULT
END
Fig. 1. Computation scheme in this study.
1.00000E+00
1.05000E+00
1.10000E+00
1.15000E+00
1.20000E+00
1.25000E+00
1.30000E+00
1.35000E+00
1.40000E+001.45000E+00
1.50000E+00
0 2 4 6 8 10
K - i n
f
Time (year)
K-inf vs Time of fuel element
3.00% 3.30% 3.60% 3.90% 4.50% 4.90%
5.10% 5.40% 5.70% 6.00% 6.30% 6.60%
Fig. 2. Infinite multiplication change during burn-up for various enrichment of 233U in the fuel.
153 I. Subki et al. / Progress in Nuclear Energy 50 (2008) 152e156
8/14/2019 The Utilization of Thorium for Long-life Small Thermal Reactors Without on-site Refueling
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calculation is performed using CITATION or FI-ITBCH
codes. For SRAC code system calculation the calculation
scheme is shown in Fig. 1.
When we calculate the whole core calculation using
FI-ITBCH code, interpolation for linear power parameter is
performed to get relatively accurate results with optimal com-
putation time.
4. Simulation results and discussion
4.1. Small long-life high temperature gas cooled reactors
without on-site refueling
Fig. 2 shows the results of cell-burn-up parametric survey
for different fuel enrichments (233U) during 10 years burn-up
without refueling.
From Fig. 2 it is shown that in general higher enrichment
gives longer lifetime but also higher reactivity swing. Core en-
richment of 3% gives smaller infinite multiplication constant
drop after 10 years of burn-up. This trend can be thought as
an influence of higher internal conversion ratio in fuel with
lower enrichment 233U Fig. 3.
As the next steps we performed core optimization and as
one of the optimal results we can see the combination shown
in Table 1 as follows.
So as shown in the above table we used various values of
fuel enrichment (233U) in core optimization. The effective
multiplication factor change during burn-up for the above
core configuration is shown in Fig. 4.
Fig. 4 shows that during 10 years of burn-up without
refueling, the core composition shown in Table 1 in which
30 column of fuel were filled give excess reactivity of about12% dk/k.
4.2. Small long-life pressurized water reactors (PWR)
without on-site refueling
Similar method to that of long-life HTGR was applied to
the long-life PWR without on-site refueling. After some opti-
mizations we get the following pattern for 100 MWth long-life
PWR without on-site refueling based on thorium cycle. Fig. 5
Fig. 3. Core lay-out of small long-life high temperature gas cooled reactors
without on-site refueling.
Table 1
One example of core level optimization results of long-life small high temper-
ature gas cooled reactors without on-site refueling
Position of
fuel block
(from above)
Fuel characteristics No. of fuel zone
1 2 3 4
1 Uranium-233 enrichment (wt%) 5 .4 6.0 6.3 6.6
Number of fuel pins 33 33 31 31
Type of burnable poisson H-I H-I H-I H-I
2 Uranium-233 enrichment (wt%) 4 .5 5.1 5.7 6.0
Number of fuel pins 33 33 31 31
Type of burnable poisson H-II H-II H-II H-II
3 Uranium-233 enrichment (wt%) 3 .6 4.5 4.9 5.1
Number of fuel pins 33 33 31 31
Type of burnable poisson H-II H-II H-II H-II
4 Uranium-233 enrichment (wt%) 3 .0 3.3 3.6 3.9
Number of fuel pins 33 33 31 31
Type of burnable poisson H-I H-I H-I H-I
5 Uranium-233 enrichment (wt%) 3 .0 3.3 3.6 3.9
Number of fuel pins 33 33 31 31
Type of burnable poisson H-I H-I H-I H-I
K-eff vs Time at 30 column for a,b,c,d,e core combination
8.50000E-01
9.00000E-01
9.50000E-01
1.00000E+00
1.05000E+00
1.10000E+00
1.15000E+00
1.20000E+00
0 1 2 3 4 5 6 7 8 9 10
Time (year)
K - e
f f
a b c d e
Fig. 4. Effective multiplication factor change during burn-up and the combination shown in Table 1 correspond to the ‘a’ line.
154 I. Subki et al. / Progress in Nuclear Energy 50 (2008) 152e156
8/14/2019 The Utilization of Thorium for Long-life Small Thermal Reactors Without on-site Refueling
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shows a pattern of multiplication factor change for 100 MWth
10 years long-life PWR without on-site fueling. Detail param-
eters are shown in Table 2 as follows.
4.3. Small long-life boiling water reactors (BWR)
without on-site refueling
Similar process to the long-life PWR was applied to the
long-life BWR and some results are shown as follows.
Fig. 6 shows infinite multiplication pattern change during
burn-up for thorium cycle for various enrichment of 233U.
It is shown that high enrichment fuel (around 6%) giveshigher initial infinite multiplication factor but the value
decreases much faster than that of lower enrichments. On
the other hand, very low enrichment gives low initial infinite
multiplication factor value but then increases. Using the above
0.99000
1.00000
1.01000
1.02000
1.03000
1.04000
1.05000
1.06000
1.07000
1.08000
0 2 4 6 8 10 12
Burnup(year)
K - e f
f
Fig. 5. Effective multiplication factor change during burn-up for the core configuration shown in Table 2.
Table 2
Design Specification of long-life PWR 100 MWth
Parameter Specification
Power (thermal) 100 MWth
Refueling 10 years
Core type Tall
Radial 90e100 cm
Axial 216e266 cm
Fuels Thoriumeuranium dioxide (Th,U)O2
Structure Zircalloy
Coolant Light water (H2O)
Cell type Square cell
Smear density 90% T.D.
Enrichment 1.5e3% 233U
Density (Th,U)O2 9.64 g/cm3
Fuel fraction 60%
Pin size
Clad thickness 0.07 cm
Pitch 1.4 cm
K-inf vs Time for Different Enrichment
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15
1.2
0 1 2 3 4 5 6 7 8 9
Time (Year)
K - i n
f
2.10%2.300%2.500%2.700%2.900%3.100%
3.300%3.500%3.700%3.900%4.100%4.300%4.500%4.700%4.900%5.100%5.300%5.500%5.700%5.900%6.100%
Fig. 6. Infinite multiplication factor change during burn-up for various enrichment of 233U in thorium cycle tight lattice core.
155 I. Subki et al. / Progress in Nuclear Energy 50 (2008) 152e156
8/14/2019 The Utilization of Thorium for Long-life Small Thermal Reactors Without on-site Refueling
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parametric survey results and after some optimization pro-
cesses we could get some designs which can be operated for
10 years of burn-up without on-site fueling with excess
reactivity less than 5%.
5. Conclusion
The thorium cycle has been successfully applied to design
long-life high temperature gas cooled reactor without on-site
refueling, long-life pressurized water reactors without on-site
refueling, and long-life boiling water reactors without
on-site refueling. For small long-life high temperature gas
reactors without on-site refueling. Calculation results show
that 10 years lifetime without on-site refueling can be achieved
with excess reactivity of about 10% dk/k.
For long-life PWR and BWR relatively high fuel volume
fraction is applied to get relatively hard spectrum, small
size, and high internal conversion ratio. For long-life small
PWR without on-site fueling, 10 years lifetime without on-site refueling for 20e300 MWth PWR have been reached
with maximum excess reactivity of a few %dk/k. Similarly
for long-life BWR without on-site refueling, in the current
study we have been able to reach more than 10 years lifetime
without on-site refueling for 100e600 MWth BWR with
maximum excess reactivity of a few %dk/k.
156 I. Subki et al. / Progress in Nuclear Energy 50 (2008) 152e156
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