Tuesday, February 2, 2010
Would Thorium Powered Ships be better for the Navy?
The Navy is studying using alternative "green" fuels for powering Navy ships and would like to be climate conscientious while it defends the nation's shores. The Navy uses nuclear power for its largest ships but must use fuel oil for its smaller vessels. There is a style of nuclear energy that produces no green house gasses and is well adapted to mobile applications and safe operation under dangerous conditions as might exist in a sea battle.
The Navy could build substantially better nuclear power particularly appropriate for smaller Navy vessels based on alternative Thorium nuclear fuel in Molten Salt Reactors. Molten Salt Reactors have the highest energy density of any style of nuclear reactor (mostly because the molten coolant salt has the highest thermal transfer efficiency of any reactor coolant) and can safely change power levels and quickly respond to real time demands for varying power levels. Molten salt reactors tend to be physically smaller for a given power output and are not subject to core meltdowns or high pressure coolant accidents. When used in appropriate alternative reactors designed to burn it Thorium produces one hundredth the amount of nuclear waste .
In an effort to appear sensitive to the larger themes of the Obama Administration the Navy (and other services) appear to be making efforts to qualify their military systems to burn bio-fuels. I personally feel that down-grading range and performance of military systems to reduce carbon or import of foreign oil is perverse. It is better to chose technology that allows you to improve the performance of your military systems to levels that exceed anything your enemies can achieve.
The Navy would be better off with nuclear ships and would be a more effective integrated fighting force with both large and small ships able to operate at full speed for unlimited distances. A navy where only the largest ships are nuclear powered runs the risk of having to reduce speed and restrict range just to avoid outrunning smaller fossil fuel powered support vessels.
The power density and power to weight characteristics of Molten Salt Reactors is without peer among current Gen-4 nuclear designs (shielding must be provided for all reactors and shielding requirements can tend to swamp some of the advantages Molten Salt Reactors over other reactor concepts). The fact that salt coolant for Molten Salt Reactors operates at low pressure makes MSRs a safer and more suitable choice under battle conditions. If an enemy shell goes through the ship and damages the reactor plumbing or the reactor core of a MSR the fuel salt just drips into a flat collection tray pre-placed under the reactor and via this passively safe mechanism fission stops and the reactor stops operating. This beats core meltdown scenarios that other reactor concepts suffer when there is damage to coolant pumping in the primary coolant area. Physically small high power to weight reactors are important to get excellent high levels of performance out of small ships - MSRs can be successfully built in sizes as small as 2 MW and this permits use in even quite small Navy ships. MSRs do not require heavy forged steel reactor containment vessels to be safe – this is responsible for many performance advantages and high power to weight ratio when applied in naval applications in smaller ships.
Why not make plans for a future in which all Navy ships, not just the very largest, perform at high levels and exhibit extraordinary range and capability to stay on station as ordered without requirement for refueling?
Why compromise naval performance to be politically trendy when a better technology choice would eliminate production of GHG and preserve unmatched world class naval performance and safety?
 Le Brun, C., "Impact of the MSBR concept technology on long lived radio toxicity and proliferation resistance"