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Table II.11 Reactor design parameters of actinide burner reactors
L-ABR 1) P-ABR 2)
Fuel concept pin-bundle coated-particle
material
(64NpAmCm-
36U 3) ) 1.0 N 4) 1.0
(65NpAmCm-
35U 3) ) 1.0 N 4) 1.0
MAs initial loading, kg 918 2870
MAs/U 588/330 1 865/1 005
Reactor power, MWth 180 1 200
Coolant material Lead Helium
Neutron flux, 10 15 n/cm 2·sec 3.1 6.6
Core averaged mean neutron energy, keV 720 720
Reactivity (% ∆k/k)
Coolant-void reactivity/core -1.3 –
Doppler reactivity/core (∆t=300°C) -0.01 -0.01
Kinetic parameters
β eff 2.6×10 -3 2.6×10 -3
l P (sec) 1.3×10 -7 1.5×10 -7
Cycle length, full-power days 550 300
MA burn-up, %/cycle 11 13
1) L-ABR: MA-nitride fuel with lead coolant burner reactor.
2) P-ABR: MA-particle fuel burner reactor.
3) 90% enriched uranium.
4)
15 N enriched.
2.3.4.2 Accelerator-driven transmutation systems
Accelerator-driven systems (ADS, frequently called hybrid systems) combine high-intensity
proton accelerators with spallation targets and a subcritical core with or without blanket (see
Figure II.16). The proton accelerator will be either a linear accelerator (linac) or a circular accelerator
(cyclotron). The high-intensity continuous-wave (CW) proton beam with an energy around 1 GeV and a
current of several tens mA are injected into a target of heavy metal. This results in spallation reaction
that emits neutrons, which enter the subcritical core to induce further nuclear reactions. The subcritical
core can, in principal, be operated with either a thermal or a fast neutron spectrum.
ADSs have unique features to burn MAs and FPs, preferably in the double strata option. They
operate in a subcritical mode and can more easily address safety issues associated with criticality than
in critical systems. They also offer substantial flexibility in overall operation. ADSs can provide more
excess neutrons compared to critical reactors. The excess neutrons may be utilised for transmutation,
conversion, and breeding purposes. These features may be exploitable to prepare a safe and efficient
mean of transmuting nuclear waste. Both homogenous and heterogeneous fuel recycling is possible.
Various concepts of ADS have been proposed with different goals and approaches. Relevant
R&D programmes are being pursued at CEA, JAERI, LANL, CERN, etc. In recent years, all the
system concepts proposed by these groups have converged on a fast neutron spectrum because of its
large neutronic advantage over the thermal one, and the reduced production of higher actinides.
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