This paper reviews the development of fast molten salt nuclear reactors (MSRs) to close the nuclear fuel cycle by processing future and existing nuclear waste so that it can be returned safely to the environment. It follows two earlier papers outlining the overall use of a range of MSR types and an outline of future proposed marketing of a universal modular thermal MSR design for general purposes. It is suggested that the future MSR industry will probably evolve into three major competitive global corporations. The first one, serving the Far East, seems likely to become entirely MSR based, whereas the other two serving Europe/Western Russia and the Americas may use the alternative lead-cooled fast reactor for waste disposal, which is the closest competitor to the MSR system. Although construction of full-scale fast (MSR) reactors for closing the fuel cycle may not eventuate until some years into the future, it is concluded that this need not delay the introduction of the general purpose thermal MSR reactor envisaged earlier. This new nuclear technology is considered essential to maintain base-load electricity in a world where agricultural needs are expected to take precedence over space requirements for wind and solar farms. Using Thorium, in addition to Uranium, nuclear fuel is sufficient for the next 1000 years. Thus this energy resource can be considered pseudo-sustainable and give us the time to restore our world to a state of balance and true sustainability. Attention is also drawn to the present dangers of continuing to increase the storage of nuclear waste and the refurbishing of old-design nuclear plant, which are already 40 years old.