David LeBlanc: ORNL and Too Good to Leave on the Shelf

David LeBlanc of the Physics department of Carleton University, Ottawa, Canada and the Ottawa Valley Research Associates, Ltd., is a highly regarded participant in Energy from Thorium discussions and a reactor scientist of considerable note. David is notable because of a significant accomplishment. He has simplified the reactor core to a point beyond which further simplifications are likely to prove impossible. David's reactor core is nothing more than two metal shells, one inside the other. A fluid fuel carrier/moderator/coolant flow into the inner shell, and then out again. A fluid containing fertile thorium flows in a and out the second, outer shell. That is it. The entire core structure is composed of two sheets of shaped metal, one surrounding the other, with openings through which a very hot salt fluid is designed to flow. In the inner chamber, fissionable material that is chemically bonded to the carrier salt becomes critical.

No control rods are control rods are required to control David's reactor, because the inherent properties of the carrier/coolant salt automatically provide feedback that can control reactivity within the core and even shut the reactor down completely.

David is scheduled to give a talk titled, Molten Salt Reactors: An Exploration of Design Space

on May 18, at ORNL.

The abstract David's talk states:

This talk will first review past and current molten salt reactor design principles covering the main development period at Oak Ridge National Laboratory (ORNL) as well as more recent work such as the Thorium Molten Salt Reactor of France (now called the Molten Salt Fast Reactor) and the FUJI concepts of Japan. Two new proposed design routes will then be presented. First a novel but simple core geometry modification to solve the issues that led to the abandonment of ORNL's Two Fluid efforts of the mid-1960's. Two Fluid designs have separate salts to carry the fertile thorium and fissile 233U and which benefit from greatly simplifying fission product removal but previously called for unworkable core architecture. Secondly, the untapped potential of ORNL's late 1970's work on denatured converter reactors termed DMSRs and proposed improvements will be presented. This more conservative route will be shown to also have attractive resource sustainability and long-lived waste reduction while requiring the minimum of development work and maximizing proliferation resistance.

In addition to his pending ORNL talk, David is the author of a new article in the May 2010 issue of Mechanical Engineering, "Too Good to Leave on the Shelf.". The Article offers a brief history of the ORNL Molten Salt adventure, some fascinating pictures,

Alvin Weinberg and the ORNL MSRE at 6000 hours of operation.

and David's own ingenious solution to a vexing problem that frustrated ORNL researchers in the 1960's. David also discusses the highly proliferation resistant DMSR, which has recently occupied his interest. He states

The amount of fissile material needed to start new reactors is also very important, especially in terms of a rapid fleet expansion. The 1 GWe DMSR was designed for 3.5 metric tons of U-235 (in easy-to-obtain low-enriched uranium) which can be lowered if uranium costs go up. A new PWR, by contrast, needs about 5 metric tons, whereas a sodium-cooled fast breeder such as the PRISM design requires as much as 18 tons of either U-235 or spent fuel plutonium. Any liquid fluoride reactor can be started on plutonium as well, but this turns out to be an expensive option, since removing plutonium from spent fuel costs around $100,000 per kilogram.

The DMSR features a larger, lower power density graphite core than other MSR breeder concepts. So while the graphite would last a full 30 years, the DMSR would still be only a fraction of the size of gas-cooled graphite reactors and would not require a pressure vessel. In fact, the simple thin-walled DMSR containment vessel would be wider but much shorter than those of PWRs and BWRs. The construction of the reactor containment building offers savings as it does not need the huge volume and ability to deal with steam pressure buildup needed for LWRs or CANDU reactors.