The discovery by Wittenberg et al. of the favorable energy balance for 3He mining on the Moon has led to a profound change in fusion reactor design studies. The replacement of tritium by 3He in the plasma has been seriously investigated. The reduced neutron flux in a D-3He reactor has substantial engineering, safety, and environmental advantages over a deuterium-tritium (D-T) reactor:
1. no danger of melting structure in case of loss-of-coolant accident
2. no need to replace the first wall every few years, higher reactor availability, much lower occupational radiation exposure
3. sharply reduced tritium release and radioactive waste problem
4. no tritium breeding, no bulky lithium blanket, no liquid-metal hazard.
The D-3He fusion reactor has the following disadvantages:
1. Helium-3 is currently available only from tritium-decay in H-bombs and in the future from space exploitation programs. which few countries can afford, or from deuterium-deuterium fusion
2. Deuterium-3He requires higher temperature, higher beta, and better containment of the plasma than D-T.
The low-beta tokamak is not particularly appropriate for a D-3He fusion reactor: Design studies assume large dimensions and B-field, and a speculative type of direct conversion of synchrotron radiation. There are devices (e.g., field-reversed configurations and migma) that hold more promise for development of small efficient reactors, but lack of funds for experiments has caused them to fall behind with respect to the tokamak database.