[1] The blanket may also act as a cooling mechanism, absorbing the energy from the neutrons produced by the reaction between deuterium and tritium ("D-T"), and further serves as shielding, preventing the high-energy neutrons from escaping to the area outside the reactor and protecting the more radiation-susceptible portions, such as ohmic or superconducting magnets, from damage.
For instance, a large quantity of water makes an excellent cooling system and neutron shield, as in the case of a conventional nuclear reactor.
However, tritium is not a naturally occurring resource, and thus is difficult to obtain in sufficient quantity to run a reactor through other means, so if commercial fusion using the D-T cycle is to be achieved, successful breeding of the tritium in commercial quantities is a requirement.
ITER runs a major effort in blanket design and will test a number of potential solutions.
[5] These materials, mostly in a pebble form, are used to produce and extract tritium and helium; must withstand high mechanical and thermal loads; and should not become excessively radioactive upon completion of their useful service life.