WM’03, February 23-27, 2003, Tucson, AZ
MINOR ACTINIDES TRANSMUTATION SCENARIO STUDIES IN PWR
WITH INNOVATIVE FUELS
J.P. Grouiller, L. Boucher, H. Golfier, F. Dolci, A. Vasile, G. Youinou,
Commissariat à l’Energie Atomique, France
ABSTRACT
With the innovative fuels (CORAIL, APA, MIX, MOX-UE) in current PWRs, it is theoretically possible
to obtain different plutonium and minor actinides transmutation scenarios, in homogeneous mode, with a
significant reduction of the waste radio-toxicity inventory and of the thermal output of the high level
waste. Regarding each minor actinide element transmutation in PWRs, conclusions are :
neptunium : a solution exists but the gain on the waste radio-toxicity inventory is not significant,
americium : a solution exists but it is necessary to transmute americium with curium to obtain a
significant gain,
curium : Cm244 has a large impact on radiation and residual power in the fuel cycle; a solution
remains to be found, maybe separating it and keeping it in interim storage for decay into Pu240 able to
be transmuted in reactor
INTRODUCTION
Light water reactors will dominate the production of electricity by nuclear systems during most of the
current century. The future development of fast reactors needs for this period a flexible plutonium and
minor actinides management scheme.
These current reactors (900 MWe), initially licensed to use Uranium enriched UOX fuel, were therefore
slightly adapted to accept plutonium. Currently once through cycling of Plutonium is carried out in
pressurised water reactors (PWR) in a MOX assembly partially loaded core. For a more efficient and less
limiting use of plutonium in a PWR several fuel concepts [Ref. 1] are envisioned. It would be also
possible to introduce minor actinides in these advanced fuels.
Reduction of the plutonium and the minor actinides in the waste is achieved through multi-recycling
which can be carried out in current PWR through rod design or standard assembly composition
modifications.
After presentation of different possible scenarios for plutonium and minor actinides recycling in PWRs,
the paper presents the impact on waste physic characterisations (radio-toxicity, inventory, decay heat).
SCENARIOS OF ELECTRONUCLEAR FLEETS
The different scenarios are based upon a pure PWR reactor type fleet loaded with different innovative
fuels to recycle Pu and minor actinides (Am+Cm).
Fuel Design
Plutonium mass loading during multiple recycling is limited for safety reasons, so fissile materials needed
for targeted burn-up is completed by Low Enriched Uranium (LEU) allowing keeping safety parameters
within an acceptable range.
Two main options are considered:
Fuel assemblies with standard oxide fuel rods,
Inert matrices and over-moderation.
* Oxyde fuel concepts :
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- Use only MOX fuel rods in the subassembly with LEU; this is the MIX or MOX UE concept.
- Mixing in each subassembly standard LEU UO2 rods and MOX rods; this is the CORAIL concept.
MIX [Ref 0] : With homogeneous fuel, we can limit the plutonium content in all assemblies and add
235
U to comply with fuel management constraints. The MOX-UE concept (Figure 1) uses all MOX
rods, in a standard PWR fuel assembly configuration. The plutonium content may vary from
approximately 2 % (MIX) for plutonium dilution in all fleet reactors to a content of 12 % [Ref. 2],
allowing to reduce both 235U enrichment and number of assemblies to be manufactured.
CORAIL [Ref. 3, 4] : In heterogeneous fuel with separate UO2 and MOX rods, we can limit the
Plutonium content in the MOX rods. The CORAIL concept (Figure 2) uses a heterogeneous
arrangement of MOX rods (PuO2 in a depleted UO2 matrix) and LEU UO2 rods in a fuel assembly.
MOX rods
Process tubes
Guides tubes
Fig. 1 : MOX-UE fuel design
MOX rods
Guide tubes
LEU UO2 rods
Process tubes
Fig. 2 : CORAIL fuel design
* Inert matrices and over-moderation
The use of inert matrices (U free fuels) improves plutonium consumption by avoiding their production by
neutron captures in U238. Furthermore, modified rod geometries locally improving neutron moderation
compensates the spectrum hardening induced by plutonium.
APA [Ref. 5, 6] : The APA assemblies consists of a heterogeneous arrangement of PuO2 in an inert
matrix (CeO2) surrounded by LEU UO2 rods. In the case of APA, the geometry of the assembly is
changed in order to obtain a local over-moderation. Several materials and geometries are under
investigation. In Figure 3 four standard LEU UO2 rods are replaced by an annular inert matrix
plutonium rod and in Figure 4, about one third of standard rods are replaced by inert matrix plutonium
crosses.
WM’03, February 23-27, 2003, Tucson, AZ
Fig. 3 : APA annular Pu rods
Fig. 4 : APA Pu crosses
Scenario studies
*Description of chosen scenarios
Scenarios are based upon only PWR fleets with different options for plutonium and minor actinides (MA)
recycling :
Open cycle
Plutonium mono-recycling
Plutonium or plutonium and minor actinides recycling in different fuels (MIX, CORAIL, APA) ; the
minor actinides are recycled in homogeneous mode : the elements (Am + Cm) are mixed in the MOX
fuels.
The fleet's electrical power is 60 GWe producing 400 TWhe per year, reload average burn-up are of the
order of 60000 MWd/t. Prior to reprocessing a minimum cooling time of 5 years is required; ageing time
is 2 years; limit of U235 enrichment is 5%.
Uranium and plutonium have reprocessing loss rates of 0.1 %. The losses of partitioning process are also
0.1 % for minor actinides. Uranium from reprocessing is stored.
* Scenarios at steady state
In this exercise, the study was to set forth a steady state situation for each scenario, that is to say a steady
state mass balance between production and consumption in the fleet and isotope stabilisation in the fuels;
constraints imposed by fuel cycle material management were not taken into consideration, specifically the
transition, warehousing management and the reactor unit commissioning aspects.
The following diagrams give the steady state stabilisation level of nuclear fleets for the various Pu
recycling scenarios and Pu + Am + Cm. recycling scenarios.
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D ia g r a m 1
P W R s – 6 0 G w e – 4 0 0 T W h e /Y e a r
B u r n u p : 4 5 0 0 0 M W d /t
R e p r o c e s s in g lo s s e s : 0 .1 %
P u + A m + C m r e c y c lin g in P W R ( C O R A I L )
A n n u a l b a la n c e
W a ste s
Pu : 38 kg
N p : 600 kg
A m : 4 .0 k g
C m : 2 .6 k g
N at U : 7730 t
U 235 : 5 %
F A B R IC A T IO N
U O 2 750 t
E N R IC H M E N T
5 .9 M S W U
PW R 60 G W e
1100 t
R E P R O C E S S IN G
F A B R IC A T IO N
M O X 350 t
D e p le te d U
6970 t
U . f. R .
1050 t
P u : 3 8 t, A m : 4 .0 t, C m : 2 .6 t
P W R s – 6 0 G w e – 4 0 0 T W h e /Y e a r
B u rn u p : 6 0 0 0 0 M W d /t
R e p r o c e s s in g lo s s e s : 0 .1 %
P u r e c y c lin g in P W R (C O R A IL )
A n n u a l b a la n c e
W a s te s
Pu : 24 kg
N p : 700 kg
A m : 2100 kg
C m 600 kg
N at U : 6290 t
U 235 : 5 %
F A B R IC A T IO N
U O 2 610 t
E N R IC H M E N T
4 .8 M S W U
PW R 13 G W e
170 t
400 t
F A B R IC A T IO N
M O X 210 t
D e p le te d U
5680 t
R E P R O C E S S IN G
650 t
PW R 47 G W e
U . f. R .
740 t
Pu : 24 t
D ia g r a m 2
- 0 T W h e /Y e a r
PW Rs – 60 G we – 40
B u rn u p : 6 0 0 0 0 M W d /t
( r e p r o c e s s in g lo s s e s : 0 .1 % )
P u + A m + C m re c y c lin g in P W R (M IX )
P u r e c y c lin g in P W R (M I X )
A n n u a l b a la n c e
W a s te s
P u : 2 3 k g (1 7 k g )
N p : 6 0 0 k g (6 0 0 k g )
A m : 2 .6 k g ( 1 8 0 0 k g )
C m : 3 .6 k g ( 9 0 0 k g )
N a t U : 7 8 7 0 t.
(7 5 8 0 t)
E N R IC H M E N T
6 .0 (5 .7 ) M S W U
F A B R IC A T IO N
820 t
PW R 60 G W e
820 t
R E P R O C E S S IN G
D e p le te d U
7070 t
( 6770 t )
U 2 3 5 : 4 .8 %
U 2 3 5 : 4 .6 %
P u : 2 3 t, A m : 2 .6 t, C m : 3 .6 t
P u : 1 7 .2 t
U . f. R .
740 t
(7 5 0 t)
WM’03, February 23-27, 2003, Tucson, AZ
D ia g r a m 3
P W R s – 6 0 G w e – 4 0 0 T W h e /Y e a r
B u r n u p : ( ~ U O 2 ) 4 8 0 0 0 M W d /t P W R
(A P A )
6 0 0 0 0 M W d /t P W R ( U O X )
A n n u a l b a la n c e
P u r e c y c lin g in P W R ( A P A )
W a ste s
Pu : 18 kg
N p : 600 kg
A m : 1700 kg
C m : 600 kg
N at U : 6920 t
U 2 3 5 : 4 .9 %
E N R IC H M E N T
5 .2 M S W U
F A B R IC A T IO N
U O 2 720 t
U 2 3 5 : 3 .7 %
D e p le te d U
6200 t
PW R 43 G W e
590 t
130 t
F A B R IC A T IO N
A P A r o d s ( 1 8 t)
R E P R O C E S S IN G
PW R 17 G W e
148 t
U . f. R .
670 t
Pu : 18 t
P W R s – 6 0 G w e – 4 0 0 T W h e /Y e a r
B u r n u p : ( ~ U O 2 ) 4 8 0 0 0 M W d /t P W R
(A P A )
6 0 0 0 0 M W d /t P W R ( U O X )
A n n u a l b a la n c e
P u + A m + C m r e c y c lin g in P W R ( A P A )
W a ste s
Pu : 23 kg
N p : 600 kg
A m : 2 .5 k g
C m : 2 .2 k g
N at U : 6810 t
U 2 3 5 : 4 .9 %
E N R IC H M E N T
5 .1 M S W U
F A B R IC A T IO N
U O 2 710 t
U 2 3 5 : 3 .9 %
D e p l e te d U
6090 t
F A B R IC A T IO N
A P A ro d s 2 8 t
PW R 40 G W e
545 t
165 t
R E P R O C E S S IN G
PW R 20 G W e
193 t
U . f. R .
670 t
P u : 2 3 t, A m : 2 .5 t, C m : 2 .2 t
Plutonium and minor actinides balance
The APA concept has the highest performances in terms of plutonium utilisation due to the use of inert
matrix fuel and local over moderation. This explains why less then 30 % of the reactor fleet is enough to
use the plutonium produced by the other standard UOX cores and obtain the plutonium inventory
stabilization. One notes that, the APA concept allows for the masses of plutonium fuel to be
manufactured in a much lower amount than that of the other concepts (a factor of 15 with respect to
CORAIL and a factor of 50 with respect to MIX); with respect to open cycle scenario, the reduction in
natural uranium and SWU requirements displays the same order of magnitude for the 3 concepts (until 20 %).
Thus, the fleet fraction involved by MIX loading could be between 100 % (diagram 2) and 30 % when
we increase the initial plutonium content to 12% (MOX-UE).
For the only plutonium recycling scenarios, the minor actinides masses produced by the MIX, MOX-UE,
CORAIL and APA scenarios are in the same range even if MIX produces the maximum values for
WM’03, February 23-27, 2003, Tucson, AZ
curium and CORAIL the maximum values for americium. At steady state scenario, figure 5 gives minor
actinide masses produced every year at the reprocessing plant. If we compare to the plutonium monorecycling scenario (only plutonium from UOX is recycling in a standard MOX fuel), the annual curium
production is multiplied by a factor 8 for CORAIL scenario and by a factor 12 for MIX scenario, for
americium production, the factor is between 4 to 5; neptunium production is approximately the same in
each scenario. But in the plutonium mono-recycling scenario, we produce, every year, 8 tons of
plutonium, 0.7 tons of americium and 0.2 tons of curium in the irradiated MOX fuels placed in interim
storage.
Plutonium and minor actinides recycling scenarios reduce americium and curium in the high level waste
(6 kg/year) but they increase their annual flux in the fuel cycle (2.5 tons to 4 tons of americium and 2.2
tons to 3.6 tons of curium) with a large impact in the facilities on radioprotection and thermal decay
evacuation.
tons
3
Np
2.5
Am
Cm
2
1.5
1
0.5
0
Mono MOX (720 t
CORAIL(650 t
MOX-UE(320 t MOXUOX)
CORAIL + 170 t UOX) UE+500 t UOX)
MIX(820 t MIX)
APA(150 t APA + 590
t UOX)
Fig. 5 : Annual minor actinides production at the reprocessing plant
Steady state nuclear parc - 400 TWhe
.
Evolution, over time, of the radiotoxic inventory through ingestion (CIPR 72 coefficients) of ultimate
waste (Pu, Am Cm) produced, every year, by the various fleets, is given in the figure 6 hereunder with a
theoretical 0.1% loss of actinides during reprocessing. To assess the efficiency of an actinide incineration
option, the radio-toxicity inventory is analysed between 500 and 100 000 years; period where the gain is
obtained from plutonium, americium and curium recycling. The gain obtained with neptunium recycling
appears after 500 000 years. With respect to the open cycle, plutonium recycling (MIX-Pu) allows a
reduction factor ranging from 3 to 5, according to the cooling time.
Homogeneous minor actinide multi-recycling, with a loss rate of 0.1 %, allows a reduction factor ranging
between 350 and 250 with APA or MIX and CORAIL. The table, hereunder, gives the times where the
waste radio-toxicity inventory is the same of natural uranium one.
WM’03, February 23-27, 2003, Tucson, AZ
Scenarios
Time (years)
Sv (Scenario) ~ Sv (Unat)
200 000
40 000
~ 500
Open cycle
Pu recycling in PWRs
(Pu+ Am+Cm) recycling in PWRs
1.00E+12
CORAIL
APA
open cycle
nat U
MIX
MIX-Pu
1.00E+11
Sv
1.00E+10
1.00E+09
1.00E+08
1.00E+07
1.00E+06
100
1000
10000
100000
years
Fig. 6 : Radiotoxicity inventory of waste produced every year
steady state - 400 TWhe
* Transition scenarios
Starting from the fleet situation in 2010, the various selected options were studied for each scenario. Use
of COSI code [7] makes possible to take into account the fleet's status in 2010 with both the irradiated
fuels (UOX and MOX) stored in pools, the cycle functions (enrichment, manufacturing, reprocessing),
the various types of reactors and the associated fuels. Pu contained in the irradiated fuels allows a
transition strategy to be implemented with various options introduced (that is to say that the reactors
existing in 2010 are progressively replaced or modified at the rhythm imposed by Pu availability). MIX,
CORAIL or MOX-UE concepts are progressively introduced from 2015 and APA from 2025. This
detailed simulation of fleet evolution allows nuclear material inventory evolution to be calculated (mass
and isotopes), in the installations, in the reactors, storage in facilities, and in waste packages.
Plutonium recycling scenarios
The figure 7 shows fleet plutonium inventory evolution for each plutonium recycling scenario, open cycle
scenario and plutonium mono-recycling. For multiple recycling, the plutonium inventory varies between
230 tons (APA and MIX) and 420 tons (MOX-UE) according to the fuel assembly concept selected.
Between 2050 and 2100, the plutonium inventory in the open cycle scenario increases from 640 tons to
1020 tons.
WM’03, February 23-27, 2003, Tucson, AZ
1200
Open cycle
CORAIL
1000
APA
Mono-MOX
MOX-UE
tons
800
MIX
600
400
200
0
2010
CORAIL,
MIX
MOX-UE
APA
2020
2030
2040
2050
2060
2070
2080
2090
2100
2090
2100
years
Fig. 7 : Pu recycling PWRs - Energy : 400 TWhe
Pu inventory in the cycle (reactors + interim storage + facilities)
300
open cycle : + 650 t Pu in 2050 and + 1000 t Pu in 2100
250
tons
200
APA
CORAIL
Open cycle
Mono MOX
MIX
Mono MOX : + 500 t Pu in 2050 and + 800 t Pu in 2100
150
100
50
0
2010
2020
2030
2040
2050
2060
2070
2080
years
Fig. 8 : Pu recycling in PWRs - Energy : 400 TWhe
Am+Cm accumulating
The plutonium recycling produces minor actinides; the figure 8 gives the evolution of americium and
curium accumulating. In 2100 the americium + curium inventory varies between 220 tons (95% of Am)
(open cycle) and 270 tons (80 % of Am) (MIX); the Pu241 decay in the UOX and MOX fuels producing
a large of Am241 during the interim storage. For open cycle and plutonium mono-recycling scenarios, it
will be necessary to complete the americium and curium inventory with plutonium accumulated in the
irradiated fuels (in 2100, 1000 tons for open cycle scenario and 800 tons for plutonium mono-recycling
scenario).
With respect to the UOX reprocessing, the plutonium recycling increases the americium and curium
fluxes in the high level wastes.
WM’03, February 23-27, 2003, Tucson, AZ
Plutonium and minor actinides recycling scenarios
The figure 9 shows fleet plutonium inventory evolution for each plutonium and minor actinides recycling
scenario, open cycle scenario and plutonium mono-recycling. For multiple recycling, the plutonium
inventory varies between 250 tons (APA) and 450 tons (CORAIL) according to the fuel assembly
concept selected.
1200
CO RAIL
APA
O pen cycle
M ono-M OX
M IX
1000
tons
800
600
400
200
0
2010
2020
2030
2040
2050
2060
2070
2080
2090
2100
years
Fig. 9 : Plutonium, americium and curium recycling in PWRs
Energy : 400 TWh - Pu inventory
The figure 10 shows fleet americium+curium inventory evolution for each plutonium and minor actinides
recycling scenario, open cycle scenario and plutonium mono-recycling. For multiple recycling, the
americium+curium inventory varies between 55 tons (APA) and 80 tons (MIX) according to the fuel
assembly concept selected. With respect open cycle or plutonium mono-recycling scenario,
americium+curium recycling decrease the Am+Cm inventory by a factor from 3 to 5 in 2100.
300
250
APA
CORAIL
MIX
Open cycle
Mono MOX
tons
200
150
100
50
0
2010
2020
2030
2040
2050
2060
2070
2080
years
Fig. 10 : Plutonium, americium and curium recycling in PWRs
Energy - 400 TWhe - Am+Cm inventory
2090
2100
WM’03, February 23-27, 2003, Tucson, AZ
CONCLUSION
Studies on different advanced assembly concepts demonstrate that from the reactor core physics
viewpoint, solutions allowing the multi-recycling of plutonium (Pu) in PWR should be possible. These
solutions can be reached in the generation III PWRs with innovative fuel concepts : options range from a
concentration of Pu in a small number of rods (APA, CORAIL), with or without recourse to an inert
matrix, to total or partial dispersion of Pu throughout the assembly (MOX-UE) (MOX with enriched
uranium), with various consequences on manufacturing, Pu consumption and minor actinides production.
Results show that, when using these innovative fuels in current PWR, it is theoretically possible to obtain
different minor actinides transmutation scenarios, in homogeneous mode, with a significant reduction of
the waste radio-toxicity inventory and of the thermal output of the high level waste. The handling of
objects which include americium and curium entails significant increase of penetrating radiation sources
(neutron and ) in the fuel cycle facilities. Looking at the thermal aspects some technological difficulties
appear with the handling of curium, mainly during the fuel manufacturing process.
Conclusions regarding the minor actinides homogeneous transmutation in PWR with innovative fuels
are :
- neptunium : a solution exists but the gain on the waste radio-toxicity inventory is only significant
after 500 000 years,
- americium : a solution exists but it is necessary to transmute americium with curium to obtain a
significant gain,
- curium : Cm244 has a large impacts on radiation and thermal characteristics in the fuel cycle; a
solution remains to be found, may be separating it and keeping it for Cm244 decay into Pu240 to be
transmuted in reactor.
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