Characteristics of Transmutation Reactor
Based on LAR Tokamak Neutron Source
B.G. Hong
Chonbuk National University
CONTENTS
1. Concept of Fusion Driven System
2. Neutron Source Based on LAR Tokamak
3. Transmutation Characteristics
4. Summary
Transmutation System
 High level waste from NPP
- Long-lived TRU: Pu
- Long-lived MA: Np, Am, Cm
- Long-lived FP: Tc, I, Sr, Cs
 Transmutation methods proposed
- Fast reactor: SFR, LFR, GFR
- ADS (Accelerator Driven System)
- FDS (Fusion Driven System)
 Fission to capture ratio is high for fast neutron spectrum
Thermal
Fast
Np 237
0016
0.19
Am 241
0.01
0.14
Am 242
0.53
5.26
Am 243
0.01
0.12
Cm 244
0.06
0.71
2
Fusion Driven System
Fusion: neutron-rich reaction
Fission: energy-rich reaction
n, 14 MeV
Plasma: D+T→4He+n+17.6 MeV
Blanket: 6Li+n→4He+3H + 4.8 MeV
7Li+n→4He+3H+n‘ - 2.5 MeV
(AC, FP)+n→ X + energy
3
Output Energy of FDS
 Output electrical energy from a FDS
From fusion
Efus
From fission
17.6 MeV/n
fus
effciency
of collecting and converting to electricity the plasma heating
e
energy and the energy produced by fusion.
Qp
Fusion energy multiplication
ε
ratio of energy produced by other exoergic reactions to the energy
produced by fission.

average number of neutrons per fission
Efis
195 MeV/fission
 eblkt
efficiency of energy conversion in blanket
• For 500 MWe, Sfus ~ 1019 - 1020 n/s -> Fusion power ~ a few hundred MW
4
Neutron Source
 Neutron source based on a LAR tokamak concept allows a compact reactor
and a elongated plasma shape which is favorable for a transmutation reactor
 Look for compact neutron source (LAR tokamak) within physics and technology
adopted in ITER design: Sfus ~ 1019 -1020 n/s → Pfus ~ a few hundred MW
 Pfusion = 150 ~ 500 MW, aspect ratio A = 1.5 ~ 2.5
 Transmutation in blanket 1 by 14 MeV neutron and T-breeding in blanket 2 by
neutron produced by fission of wastes. Enrichment of Li-6 may not be necessary
5
LAR Tokamak Neutron Source
• Reactor components must satisfy plasma physics and technology constraints
• Plasma performance characterized by normalized beta, βN, confinement
improvement factor, H and ratio of density to Greenwald density limit, n/nG.
•
k = kmax, qa = qa,min, d = 0.3, βN = βN,max, H = 1.2, n/nG =1.0 with kmax, qa,min,, βN,max
from LAR tokamak physics scaling.
• Shielding requirement for a 40 FPY lifetime with 75 % availability
– fast neutron fluence < 1019 cm-2
– radiation dose < 109 rad
– displacement damage limit < 10-3 dpa
– By both fusion and fission neutron
• Blanket
– For Tritium self-sufficiency, TBR (Tritium breeding Ratio) > 1.05
– Neutron multiplication keff < 1.0 for sub-criticality
S k
– Maximize transmutation rate
TR 
 (1  k )
6
Geometry
Composition of KSNP spent fuel
Nuclide
Volume % Half-life (y)
NP237
6.35
2.14E+06
PU238
2.04
88
PU239
42.86
24,065
Component
Materials
PU240
20.69
6,537
Toroidal field coil
Vacuum vessel
Shield
High temperature shield
Blanket 1
Blanket 2
First wall
Nb3Sn, SUS316, L. He
Borated steel, H2O
WC, H2O
WC
TRU(or MA), SUS316, He, SiC
SUS316, PbLi, He
SUS316, H2O
PU241
1.15
14
PU242
6.90
3.76E+05
AM241
16.78
432
AM243
2.96
7,380
CM244
0.20
18
CM245
0.06
8,500
7
Analysis Method
 Self-consistent coupled analysis
– Fusion physics and technology: Systems analysis
– Blanket: Radiation transport, Burn-up
 BISON-C code
- Li burn-up considerd
8
Optimum Radial Build of a Neutron Source
• The minimum major radius R0 decreases as A increases
• For large A and large fusion power, large neutron wall loading & large shield thickness.
• The required auxiliary heating power increases as the aspect ratio increases.
• When A= 2.5, the magnetic field @ TF coil increases as the fusion power increases and
A=2.0 by the maximum magnetic field(~ 13 T)
A=1.5
the minimum major radius R0 is determined
9
TRU Transmutation
• A=1.5,
A=2.0,
21.7
A=2.5, BL1= 20.2
22.5 cm
• TRU 5%, He 75%, SUS316 15%, SiC 5% in Blanket 1
• PbLi 90% (Nat. Li), He 7%, SUS316 3% in T-breeding blanket
• Transmutation rate is large for large A case due to large GN.
• But the major radius and the reactor height (~ k·a), decreases as A
increases, and loaded TRU amount is smaller than the small A case.
10
5-Batch Equilibrium Fuel Cycle
Blanket 1
00000
1st
plas
ma
2nd
11111
plas
ma
01111
plas
ma
plas
ma
plas
ma
12344
plas
ma
4th
3rd
01222
12222
12333
plas
ma
01233
plas
ma
5th
01234
FDS
plas
ma
12345
plas
ma
Disposal or
reprocessing
11
Transmutation Characteristics
• 5-batch fuel cycle, blanket height = ½ k∙a
Aspect ratio
Burn cycle (day)
A = 1.5
A = 2.5
2,500 5,000 7,500 2,500 5,000 7,500 2,500 5,000 7,500
Trans. rate (kg/y) 557
Burn-up (%)
23.9
Trans. rate (kg/y) 876
300 MW
Burn-up (%)
33.3
Trans. rate (kg/y) 1,184
500 MW
Burn-up (%)
41.3
150 MW
A = 2.0
406
34.9
608
46.3
795
55.4
328
42.3
479
54.6
614
64.2
340
37.2
509
48.3
674
57.0
232
51.0
333
63.3
427
72.3
181
59.6
253
72.2
318
80.8
269
44.1
407
54.5
548
62.2
178
58.4
259
69.5
339
77.1
137
67.2
194
78.1
250
85.1
• For the burn-up fraction to be 50%, fusion power of 500 MW and the burn cycle of
5,000 day are required for A =1.5. → With one unit of the transmutation reactor,
more than 3 PWRs (1.0 GWe capacity) can be supported considering that the TRU
from 1 PWR (1.0 GWe capacity) is about 250 kg/y.
• Less fusion power and less burn cycle are needed for A > 2.0 for the burn-up
fraction to be bigger than 50 %, but less than 3 PWRs can be supported.
• Natural Li can be used for the small A case with the small fusion power and the short
burn-up cycle, while Li-6 needs to be enriched for the large A case with the large
fusion power and the long burn-up cycle.
12
Minor Actinide Transmutation
• Pfusion = 150 MW, A = 2.0
• MA2O3 50%, He 35%, SUS316 15% with BL1= 8.2 cm for keff < 0.95
• BL2: PbLi 90% (Nat. Li), He 7% and SUS316 3%, BL2 determined by
condition TBRav > 1.35
• Keff, power and T.R. initially increase but decrease as the MA burns up.
13
Transmutation Characteristics
5-Batch Residence (day)
TRU
MA
2,500
5,000
7,500
Trans. Rate (kg/y)
340
232
181
Burn-up (%)
37.2
51.0
59.6
DBL2 (cm)
30
40
60
Trans. Rate (kg/y)
286
479
412
Burn-up (%)
15.8
53.1
68.4
DBL2 (cm)
30
30
40
• For MA transmutation, the largest MA transmutation rate is 479 kg/y with
a 5,000 day burn cycle The burn-up fraction increases with residence time.
• For the TBRav > 1.35, DBL2 increases with the burn cycle and 40 cm is
necessary for 7,500 days, which is smaller than the case with the TRU.
• 13 PWRs (1.0 GWe) can be supported with one unit of the transmutation
reactor based on the LAR tokamak producing 150 MWth of fusion power.
14
Fusion Driven System: Pros and Cons
 Physics and technology design basis for a tokamak DT fusion neutron source
exists today (ITER)
 Existing nuclear technology can be applied and GEN-IV will improve the
concept.
 A fusion source can produce a sharp spectrum of 14 MeV neutrons,
compared with the distributed spectrum of an accelerator source.
 14 MeV neutrons can induce various neutron-multiplying reactions easily, can
fission all actinides.
 FDS might have more safety problems, as it basically combines a fusion
reactor with a fission reactor in a tight system.
 Using a fusion source will require tritium, and therefore will increase overall
radioactivity.
 Blanket geometry in fusion reactors is not ideal fission reactor geometry.
Specifically, a tokamak fission blanket will have very high fuel inventory,
compared with an accelerator driven fission reactor.
SUMMARY
 Concept of a transmutation reactor based on LAR tokamak is
investigated as a feasible option for reducing high level, long-lived
waste.
 For self-consistent calculation of the system parameters, the systems
analysis was coupled with the radiation transport code, BISON-C.
 Within the ITER physics and engineering constraints, up to 3 PWRs
(1.0 GWe capacity) can be supported with one unit of the
transmutation reactor based on the LAR tokamak producing 150 ~
500 MW of fusion power with the aspect ratio A = 1.5 ~ 2.5 for
transmutation of TRU.
 For transmutation of MA, 13 PWRs (1.0 GWe) can be supported with
one unit of the transmutation reactor based on the LAR tokamak
producing 150 MW of fusion power.