Our previous discussion of magnetic confinement fusion (MCF), inertial confinement fusion (ICF) and muon catalyzed fusion makes it clear that each represents a different set of physical conditions requiring that the blanket design must be adapted to best suit each case.

The MCF plasma domain can be characterized by a low density gas (~1021 particlesm’3) at a high temperature (~108 K). These properties lead to some very specific design and operation requirements. Evidently, all fueling and diagnostic wall penetrations into the core must sustain a laboratory vacuum. Then, the need for a high plasma temperature requires that the plasma must be separated from the wall surface. Concurrently, the intense neutron flux striking the wall demands that its composition be highly resistant to neutron damage. Finally, provisions have to be made for the removal of the neutron and radiation energy deposited in the blanket. Figure 13.1 suggests some of the essential components and features of an MCF blanket system.

Different conditions apply to an ICF device. In this case, reactor operation involves target pellets on a ballistic trajectory which are struck by extremely intense pulses of ions or electro-magnetic radiation (lasers) when the pellet reaches a specific location. As a consequence of the resulting ablation, compression, fusion, and disintegration of the target, an intense pressure and radiation shock wave is generated which must be absorbed in the first wall. A favoured approach is to protect the wall by a liquid metal so that the debris and

radiation from the explosion are then absorbed in this layer, thus providing both shielding and a moving heat transfer fluid. We suggest this scheme in Fig.13.2.

Magnets and/or Other Auxiliary Equipment

Flowing Liquid Metal

Chamber Wall

In contrast to the above MCF and ICF, a muon catalyzed deuterium-tritium ((XDT) fusion reactor blanket domain may be depicted as suggested in Fig.13.3. Its dominant feature is a central channel containing a deuterium-tritium oxide mixture either in liquid or two-phase form. The reaction product alpha will be retained in the flow but the penetrating neutrons will enter the surrounding blanket region. The first wall may thus possess many of the properties of cladding associated with existing fission reactors.

Liquid or Two-phase D20, DTO, T

A feature common to all deuteron-triton burning fusion systems is the need to breed tritium. Hence, the blanket domain must contain a concentration of lithium, either as a pure substance or in compounds, so that the neutrons emitted in d-t fusion are captured in the lithium to produce tritium. Such a nuclear reaction linkage may well be represented by the following:

(13.1)

Should tritium be available from other sources, such as existing fission reactors, or if additional neutron multiplication is sustained by incorporating suitable (n, xn)-type materials in the blanket, then there may be an excess of
neutrons over that required for tritium breeding. These surplus neutrons could then be used to breed fissile fuel by capture in fertile nuclei. Such a system concept will be discussed in Ch. 15; for now we consider further details of the MCF, ICF and |lDT blankets.