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Heavy Water Uranium Reactor

-1-2 Fuel Rods
-1.2% U-235
-44 pounds per bundle
-5-10% efficiency
-1.75 million times more energy than gasoline pound for pound
-1 Gwh per bundle, although the newer canflex may have more

There is about 3400 pounds of gasoline in a typical Abrams tank; the uranium power has 38 times less than this (or 88 pounds). Thus, 1.75 million / 38 = 46,000 times the range and power.

Obviously, all of this won't come out all at once, and even so the fuel bundles will be replaced before their power is completely consumed. As well, while this energy is equal to that released in a breeder, and thus less than 100%, the sterling engine or thermogenerator design would presumably be less efficient in the smaller size than a steam generator (which gets up to 90%), suggesting that there would be even less than this. Still, even at 5% capability of a typical breeder (which is itself only 30% or less of the total energy) this would allow for 2300 times the range. A typical Abrams has a 250 mile range, so this would allow for 575,000 miles, or approximately 71 times the earth's circumference. While actually far less than desirable, it is still a significant improvement over the Abrams.

Additional complications include the life time of the uranium; since it will stop producing sufficient power at some point to allow for continuous operation during much of it's life, unlike in a reactor (since a certain degree of power is necessary to sustain certain speeds and reload times) it's life time will be reduced somewhat, perhaps by half. Furthermore, the uranium will be "burning" or producing power regardless of movement. Since it's more or less self activated, all that can be hoped for is continuous power generation, meaning stationary vehicles will still burn fuel. While it is possible to speed up and slow down the reaction somewhat, it will always be burning.

Exact figures on the time it will produce large volumes of energy, exact conversion effiencies, and the variable level of power output will all be important in determining outright capabilities. While 1-2 bundles are planned per vehicle, more or less may result. Furthermore, improvements in the vehicle itself and it's operating platform in ranges of efficiency and in comparison will be shown. To avoid as many conversion errors as possible, straight levels will be shown; so for instance, range in an M1 abrams will be calculated, rather than say calculating the megajoules of gasoline to uranium and then calculating the energy required to move the vehicle and calculating, from that, potential range. To mitigate factors such as efficiency losses from mechanical sources (such as say, the loss of energy when transferring it from the engine to the wheels to the ground, including breaking, speeding up and slowing down etc.), as much will be mitigated as possible by simply comparing and isolating as few variables as possible, such as total energy, by transferring it over to a well known and existing platform. While the engine may move on to other vehicles, this will be the initial platform essentially where the calculations will be done to gather a base. Relative MPG will be used to compare relative range and other factors.


CANDU Figures
-Two CANDU fuel bundles: Each about 50 cm in length and 10 cm in diameter, and generating about 1 GWh of electricity during its time in the reactor
-The CANFLEX bundle has 43 fuel elements, with two element sizes. It is about 10 cm (four inches) in diameter, 0.5 m (20 inches long) and weighs about 20 kg (44 lbs) and replaces 37-pin standard bundle. It has been designed specifically to increase fuel performance by utilizing two different pin diameters. This reduces the power rating of the hottest pins in the bundles, for the same total bundle power output. Also, the design incorporates special geometry modifications that enhance the heat transfer between the fuel and surrounding coolant. Twenty-four of these fuel bundles have been tested in the Point Lepreau CANDU 6 reactor in New Brunswick, Canada, and results indicate CANFLEX meets all expectations and regulatory requirements.


Heavy Water to Fuel Bundle Ratio
While presumably heavy water will be present, just how much is incredibly important. The added weight of the water could weigh down any vehicle, and additionally increases the price considerably. Furthermore the size of the containment structure is equally dependent on this volume, this increasing the size and weight of the required power source even more. Furthermore, heavywater is expensive, and typically this structure represents the bulk of the cost of the power over the fuel.



Comparison to M1
Each CANDU fuel bundle produces approximately 1-3.6 gigawatt hours during it's life. This is approximately 3600 gigawatts or 3,600,000,000,000 joules, compared to the 46,000,000 joules of gasoline. This is around 78,260 times the amount. Comparatively, an M1 abrams has around 500 gallons of gasoline, or 3400 pounds of fuel, or around 1545 kilograms of fuel. Thus, relatively speaking, a CANDU fuel bundle would produce 78,260/1545 times the energy, or around 50 times the amount per bundle. Thus, two bundles would provide 100 times the energy, or range if the same efficiency was present. Since the electric efficiency increases this around 4-5 times, but the use of a sterling engine drops by a similar amount, the range is around 100 times that of an M1.

This was far less than I was hoping for. Still, it would be possible to increase fuel weights or concentrations of uranium to 1.2%, although I'm not sure what the power output difference would be, exactly. In fact, it may be eve nigher. Since proliferation is less of a concern or risk it will be something to consider, although it will increase the cost marginally, depending on the circumstances or fuel efficiency. This is important to consider; in addition, the faster burn rate will translate potentially to greater power, although this may be counter productive.

Bringing it all Together
The are four primary factors to consider; the relative weight or energy production of the fuels, the efficiency in converting the uranium to electricity, the efficiency of the electric based engine itself in comparison to the gasoline combustion engine, and the variable nature of the power output.

While determining maximum potential range is important, of equal importance will be determining practical range, based on practical, variable time frames allowed by the potential variations of the fuel. What does this culminate too?

Using the M1 Abrams as the base vehicle of choice (for now), and the advanced CANFLEX fuel bundle as the main power source for uranium, what would the potential capabilities of such a vehicle be? The M1 Abrams utilizes approximately 500 gallons of gasoline; this equates to approximately 3400 pounds of fuel. In comparison, the CANFLEX fuel bundles weigh approximately 44 pounds; uranium producing energy in a breeder reactor has, approximately, 1.75 million times the energy, pound for pound, as gasoline. However, these CANFLEX fuel bundles are not pure uranium, nor will they produce energy at 100% efficiency. Thus, each CANDU reactor fuel bundle produces roughly 1 gigawatt hour of energy, and the newer CANFLEX fuel bundles produce

While this energy is already accounting for conversion efficiency losses in a breeder reactor (which is not perfect, as CANDU reactors tend to use 30-40% less fuel than such reactors), there is still the added issue of determining the total energy output of heat to electricity generation. While standard reactors often use steam turbines with around 90% heat to electricity conversion effiencies, these are relatively large and unwieldy, requiring large volumes of water to be continuously added, and being relatively heavy. The two most likely candidates for electricity generation from heat involve sterling engines and thermogenerators. While thermogenerators are more practical, being small, stationary, and possessing no moving parts, they are relatively inefficient, at around only 3-8% conversion efficiencies, and still wear down quickly. In addition to this, they tend to be expensive; while a small a size as possible is preffered, a sterling engine in a vehicle the size of an Abrams or similar motorized transportation vehicle is not unfeasible. While efficiency levels do range considerably, it is not out of the ordinary to achieve an efficiency between 15-30%. Thus, while their electricity conversion efficiency is not quite as high as stationary municipal power generators, it is still sufficient in terms of over-all operations capabilities. Efficiency is also important in helping to determine price; because gasoline is over-all over 6 times more expensive as a fuel source currently than uranium, there is still some room in terms of transportation costs with uranium to meet or be below this price range.

With the primary electricity conversion efficiency aside, how does the mechanical efficiency fair? Because electric vehicles in their own right tend to be more efficient than combustion engines, the potential for higher efficiency is more or less present, generally going from 15-20% to 80% for gasoline powered combustion and electric engines, respectively, or being 4 times higher, on average. How does this fair in comparison to an M1 Abrams, in particular? Given the relatively low efficiency of the turbine engine used by the M1 Abrams, it should in theory do quite well; however, a lack of statistics make this hard to calculate, exactly. It is not out of the line of reason to assume at least 4 times greater efficiency, however. The Honeywell AGT1500 turbine engine has a conversion efficiency of

Thus, the fuel conversion efficiency results in roughly X times less power, the efficiency in converting the uranium to electricity translates to X times less power, and the efficiency of the electric based engine itself in comparison to the gasoline combustion engine translates to 4 times more power (at least). While this determines maximum power output or in this case maximum potential range, the variable nature of the power output suggests a life of approximately X when not in use, and a variable power range of approximately X, thus allowing for the vehicle to last X years in constant motion, or x years without. A realistic life span of X years is therefore not impractical.


Price, Fuel Consumption, and reliability
Switching from gasoline to uranium could result in price increases; while uranium costs will be a significant downpayment to begin with, and there are other variables to consider, which is the price of uranium based power compared to gasoline in terms of transportation range? Uranium power is traditionally considered to be 6.5 times cheaper than gasoline in most cases, and the efficiency losses of moving uranium from a large stationary reactor to a mobile engine put the two more or less, at around or less than the same price, it is not too extreme to assume that, combined with the reduced maintenance needs and reliability of the vehicles, should over-all reduce "maintenance" costs, including that of fuel.

In additional comparisons, electric drive trains and sterling engines tend to be both equally if not more reliable than the comparative turbine engines, reducing cost concerns in regards to maintenance, both financially and practically. Thus, the potential problems with relative life and additional practical concerns seem to be more or less alleviated by the practical nature of the device.


Relative Safety
The final practical concern is thus that finally of safety; would the uranium or heavy water present too much of a risk to the environment or soldiers if the containment structures were compromised? The easy answer is no. While both are radioactive and more dangerous than normal, their relatively safe levels and small usage in comparison means that contamination into the environment at any level does not present a considerable concern.

Because it would take a very large amount of heavy water to replace 25 % to 50 % of a human being's body water (water being in turn 50 % - 75 % of body weight) with heavy water, accidental or intentional poisoning with heavy water is unlikely to the point of practical disregard. Poisoning would require that the victim ingest large amounts of heavy water without significant normal water intake for many days to produce any noticeable toxic effects. Experiments in mice, rats, and dogs have shown that a degree of 25% deuteration causes (sometimes irreversible) sterility, because neither gametes nor zygotes can develop. High concentrations of heavy water (90%) rapidly kill fish, tadpoles, flatworms, and Drosophila. Mammals, such as rats, given heavy water to drink die after a week, at a time when their body water approaches about 50% deuteration.