Liquid Fuel Nuclear Reactors

Liquid Fuel Nuclear Reactors

Dr. Hargrave and Dr. Moir lay out the advantages of the MSR/LFTR approach,

Liquid fuel thorium reactors offer an array of advantages in design, opera- tion, safety, waste management, cost and proliferation resistance over the traditional configuration of nuclear plants. Individually, the advantages are intriguing. Collectively they are compelling.

And indeed they are as the writers explain,

In solid fuel rods, fission products are trapped in the structural lattice of the fuel material. In liquid fuel, reac- tion products can be relatively easily removed. For example, the gaseous fission poison xenon is easy to remove because it bubbles out of solution as the fuel salt is pumped. Separation of materials by this mechanism is central to the main feature of thorium power, . . .
Other fission products such as molybdenum, neodymium and tech- netium can be easily removed from liquid fuel by fluorination or plating techniques, greatly prolonging the vi- ability and efficiency of the liquid fuel.

They note the potential of LFTRs (and indeed other types of Molten Salt Reactors) for solving the problem of nuclear waste. They note,

It has always been the dream of reactor designers to produce plants with inherent safety—reactor assembly, . . . The LFTR design appears, in its present state of research and design, to possess an extremely high degree of inherent safety. . . .

A signature safety feature of the LFTR design is that the coolant—liquid fluoride salt—is not under pressure. The fluoride salt does not boil below 1400 degrees Celsius. Neutral pressure reduces the cost and the scale of LFTR plant construction by reducing the scale of the containment requirements, because it obviates the need to contain a pressure explosion. Disruption in a transport line would result in a leak, not an explosion, which would be cap- tured in a noncritical configuration in a catch basin, where it would passively cool and harden.

One of the more amazing features of molten salt reactors is related to a safety feature, their negative temperature coef-ficient of reactivity, as Hargraves and Moir explain,

In the LFTR, thermal expansion of the liquid fuel and the moderator vessel containing it reduces the reactiv- ity of the core. This response permits the desirable property of load following— under conditions of changing electricity demand (load), the reactor requires no intervention to respond with automatic increases or decreases in power production.

The potential MSR/LFTR cost advantages are discussed. The factory based mass production of small (about 100 MWe) LFTRs is mentioned, as is the usefulness of LFTRs in providing developing nations energy at very reasonable costs.

Given the diminished scale of LFTRs, it seems reasonable to project that reactors of 100 megawatts can be factory produced for a cost of around $200 million. Boeing, producing one $200 million airplane per day, could be a model for LFTR production.