Energy From Thorium Discussion Forum

Dear Senator [Reid, Hatch],

I have just read of your support of the use of the Thorium fuel cycle in future reactor designs. I highly commend this. As you are aware, the Thorium fuel cycle leads to reactors which have smaller waste streams and are more resistant to proliferation.

I'd like to bring to your attention a type of reactor design that uses the Thorium in a particularly safe and efficient manner, namely the Molten Salt Reactor (MSR). This reactor design is quite innovative: it uses a mixture of molten Lithium and Beryllium Fluoride salts as the working fluid in the reactor. Added directly to these molten salts is a relatively small amount of Thorium and Uranium Fluoride salts. The resultant salt mixture simultaneously works as a moderator, coolant, and fuel medium. The initial research on such a reactor was done at ORNL in the 1960s and 70s, and culminated in a successful reactor. Unfortunately, the funding was dropped by President Carter in 1974, despite the enthusiasm of the scientists working on the project. Nevertheless, the MSR design has been included as an option for the Generation IV Reactor Research Initiative sponsored by the federal government. In addition, scientists in France, the Czech Republic, and Russia have recognized the advantages of the MSR, and are carrying forward the research.

The advantages of the MSR are numerous, including:

1. The reactor system is the only practical way of utilizing the Th-U233 fuel cycle, which unlike the U235-Pu239 fuel cycle, produces far less waste than Light Water Reactors and almost no transuranic nuclear waste. As a result, the waste products have decay times measured in hundreds of years, as opposed to millions. This has an enormous impact on the strategies necessary to deal with the radioactive, potentially eliminating the need for a repository like that at Yucca Mountain in Nevada.
2. Because the boiling temperature of molten salts is so high (1500 C), MSRs can be designed to run at higher temperatures. This makes them much more efficient at converting thermal energy to electrical energy (50% as opposed to 35%). This also enables them to use dry air cooling instead of water cooling. The latter fact is important as this, for the first time, enable reactors to be built far from water cooling sources like lakes or rivers, and therefore further away from population centers. This is particularly important in Western states, like Utah and Nevada, where dry air cooling is often a requirement.
3. The Th-U233 fuel cycle is unique in that it can be configured to produce more fissile material than it consumes without requiring the fast neutron spectra and exotic coolants that doomed the previous breeder reactors.
4. The nuclear materials from the molten salt reactors contain as a byproduct of the reaction U232, which is a strong gamma radiator. This makes the reactor products impossible to redirect for illicit purposes due to the inherent detectability of U232. This property is essential in effort to prevent nuclear proliferation and dirty bomb detection.
5. MSRs tend to burn up most of their nuclear waste; this property can be utilized to eliminate excess plutonium waste from other sources if desired.
6. The design of MSRs enables the possibility of including a very small on-line fuel reprocessing loop within the reactor structure. This prevents the need of shipping nuclear fuels over long distances to be reprocessed. This also lowers dramatically the operating costs, as the plant may be operated indefinitely without shut-down.
7. MSRs have an inherent, strong negative coefficient of reactivity as a function of temperature. This means that there is absolutely no possibility of the runaway thermal event that occurred at Chernobyl, which had a regime in which there was a positive coefficient of reactivity.
8. MSRs will be designed with passive safety systems. For example, should the core overheat, a salt plug at the bottom of the reactor would melt, and the working salt mixture would flow into tanks below the reactor. Since the tanks have no moderator, the reaction would become subcritical and immediately stop.
9. The molten salt coolant has a very low working pressure, as opposed to water moderated reactors. Thus the single most catastrophic event for a water moderated reactor, namely, a container vessel rupture, would not be a particularly dangerous situation for molten salt reactors. And, due to the low working pressure, such a rupture is much less likely.
10. Molten salt reactors can be designed to be much smaller than conventional reactors due to the low pressure/ high temperature operation. The compact design should significantly reduce the initial capital costs.
In short, Molten Salt Reactors promise to be inherently safe, efficient and clean, and as such represent a significant improvement on present designs. I would hope that I can count on your support for MSR research in the future.

Best regards,

Dr. Honzik, Ph.D.

a thorium fuel rod would remain the reactor about three times as long as conventional nuclear fuel, thereby cutting the volume of spent nuclear fuel coming out of reactors by as much as two-thirds.

3. The Th-U233 fuel cycle is unique in that it can be configured to produce more fissile material than it consumes without requiring the fast neutron spectra and exotic coolants that doomed the previous breeder reactors.