The Sydney Morning Herald
publishes a "sustainable energy" activist's claims that nuclear power does not reduce greenhouse emissions. I am not a big advocate of nuclear power, but propaganda should not be allowed to stand; unless I am very wrong this claim is, to put it mildly, bunk.
Consider the plant itself, beginning with its containment building. Plucking figures from around the web, suppose that the reactor containment is a cylinder 40 meters tall, 45 meters inside diameter
and 1.5 meters thick capped by a hemispherical dome on top and resting on a flat foundation 3 meters thick. The total volume of the concrete part (including reinforcing steel) is 19,290 cubic meters. A maximum-strength, minimum-workability mix is used which has a density of 2400 kg/m^3, is 25% cement by dry weight, and has a water:cement ratio of 0.35
; this mix has 550 kg of cement per cubic meter, or 10,600 metric tons of cement overall (the remainder being sand, stone, steel and water).
The making of cement requires 750 kcal/kg
, or 8.0 trillion calories for the whole building. This amount of energy is equivalent to 33.4 trillion joules, or 9,280 megawatt-hours; the plant will make this much electricity in nine and a half hours of full-power operation; a coal-fired plant of the same output would use 8 trillion calories of fuel in a bit over 3 hours. Energy from the plant could make the concrete for the rest of it in perhaps a day.
Production of raw uranium: The price of uranium is currently around $20/kg; extraction from seawater is thought to cost as much as $200/kg. Suppose that this $200 is the cost of the crude oil or equivalent required to refine it to yellowcake; at today's prices, this would be about 4 barrels of crude at roughly 310 pounds each, or 1240 pounds of petroleum. After enrichment from 0.7% U-235 to 3.5%, each kg of raw uranium yields 200 g of fuel; burnup in an LWR at 50,000 megawatt-days per (metric) ton means each 200 grams yields 10 megawatt-days of heat, or 82 million BTU. The heating value of #2 diesel is about 19,110 BTU/lb, or 2.4 million BTU for the 1240 pounds. Even at $200/kg of uranium, the heat produced by the uranium is around 35 times as much as its cost in fuel oil, assuming the entire cost goes for fuel oil (which is silly).
Next, consider enrichment. According to this reference
, a year's fuel for a 1000 MWe LWR requires between 100,000 and 120,000 separation work units (SWU) to produce. One SWU requires about 2500 kWh in a gaseous diffusion plant, but as little as 50 kWh in a gas centrifuge plant. If the LWR runs at 80% capacity factor, it would produce 7.01 billion KWH per year, while its fuel would require as much as 300 million kWh (120,000 SWU via gaseous diffusion) or as little as 5 million kWh (100,000 SWU via centrifuge). This overhead runs from 4.3% down to 0.071% of its output.
All told the overhead of uranium mining and enrichment accounts for considerably less than 10% of the energy output of a light-water reactor, and we haven't even considered the possibilities of natural-uranium burners (no enrichment) or plutonium and thorium breeders (ditto after the first fuel load) The energy of construction is replaced in days at most, perhaps in the first day of full-power operation.
Should the Sydney Morning Herald's editors be ashamed of themselves for publishing baseless nonsense? Unless I've slipped a few decimals, it sure looks like it.