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Table II.13 Pu and minor actinide balance of different types of reactors
Pu content of
MOX (%)
Core exit Pu
balance
(kg/TWhe)
Exit MA
balance
(kg/TWhe)
PWR
UO 2
+30 to
35
PWR MOX
(depleted U)
PWR MOX
(2% enriched
U)
HMR
MOX
(depleted U)
HMR MOX
(enriched U)
FBR
(EFR type)
FBR
(Phenix
type)
FBuR
CAPRA
8.6 to > 13 2 8.7 5.9 to 20 5.9 20 30 42
-60 to -70 0 -75 to 60 -70 to -110 -67 to -45 -20 -50 -75
+2.5 +8 to +17 +5 +20 +10 to +34 +12 to +18 +3 +6 +10
2.4 Transmutation of long-lived fission products
2.4.1 Transmutation of fission products in fission reactors
The incineration capacity for long-lived fission products in conventional reactors is very
limited, and these neutron-absorbing substances tend to poison the core. The reactor neutron balance
makes it conceivable to recycle some but certainly not all of them.
Table II.14 shows the production of long-lived fission products and of the corresponding
chemical elements in a PWR with UO 2 fuel. One observes, for example, that 135 Cs, a long-lived isotope,
accounts for only 10% of the mass of the chemical element caesium. Irradiation of the caesium would
thus produce 135 Cs from the isotopes 133 and 134, which would severely compromise the desired
objective.
Table II.14 Production of long -lived fission products (PWR UO 2 50 GWd/t)
Isotope
Half-life
(years)
Isotope quantity
(kg/TWhe)
Element quantity
(kg/TWhe)
14 C(*) 5.73×10 3 0.0013 0.0013
79 Se 6.5×10 4 0.018 0.209
93 Zr 1.53×10 6 2.8 13.7
99 Tc 2.13×10 5 3.2 3.2
107 Pd 6.5×10 6 0.78 4.8
126 Sn 1.0×10 5 0.079 0.2
129 I 1.57×10 7 0.66 0.8
135 Cs 2.3×10 6 1.40 14.0
Total 9.0 37
(*) Activation product
2.4.1.1 Transmutation of 99 Tc and 129 I
In practice, 99 Tc and 129 I are the main FPs to be considered as candidates for transmutation in
present reactors: only 99 Tc has been experimentally studied.
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