Nuclear Power

Nuclear power's obvious attraction is its lack of CO2 emissions, at least during the operational phase, but it is also expensive and problems of fuel utilization and wastes have not been adequately resolved. Costs for a new nuclear plant range from $6,000/kWe [33] to as high as $10,000/kWe [34]. Despite very complex issues, the world is currently experiencing a nuclear renaissance. However, in open markets generation options nominally compete based on the metric of Levelized Cost of Electricity (LCOE). On this basis gas fired generation yields costs of <$80/MWh compared to new nuclear costs of >$100/MWh.

Nuclear power was once thought to be so inexpensive that it would be "too cheap to meter" [35]. Despite the drawback of spent nuclear waste, the lack of CO2 emissions from nuclear power continues to act as a powerful incentive to revive the industry—that and the increasing cost of some fossil fuels. A significant wave of nuclear power plants was constructed between 1960 and 1980, using two basic plant designs (Boiling Water Reactor, BWR, and Pressurized Water Reactor, PWR.) Even with a developmental head start of nuclear power in the United States Navy beginning in the 1950s, the overall fleet reliability did not reach its peak performance until the late 1990s and early 2000, decades after the peak of the construction boom. In retrospect, it took 20-30 years for owners to optimize the performance of the complex equipment with knowledgeable and trained operators, engineers, and maintenance personnel (see Fig. 10.9). As the costs of carbon capture escalate rapidly, a fair comparison could be made to which technical choice

Nuclear Industry Average Capacity Factor Sustained at High Level

Nuclear Industry Average Capacity Factor Sustained at High Level

Source: Energy Information Administration * Preliminary data for 2007

Fig. 10.9 Improvements in nuclear plant capacity factor with time. It has taken almost 25 years to go from 50% CF to 90% capacity factor (CF) (Source NEI)

Source: Energy Information Administration * Preliminary data for 2007

Fig. 10.9 Improvements in nuclear plant capacity factor with time. It has taken almost 25 years to go from 50% CF to 90% capacity factor (CF) (Source NEI)

is preferable: A relatively simple fossil plant design incorporating a complex system of carbon capture, or a nuclear plant with virtually no carbon emissions. While the financial question is not properly situated in the subject of R & D for emission controls, it will be a deciding factor in rating technology choices. In fact, this is a fundamental feature built into the EPA's BACT (Best Available Control Technology) selection process. However, we have not built a new reactor in nearly 20 years, making it difficult to ascertain what that final cost might be. Both the upfront cost of new nuclear generation and its end-of-life costs continue to be major impediments to expanded nuclear in the US (where market forces play a dominant role).

Since the first wave of nuclear units came on line, capacity factor (the ratio of the actual output from the fleet compared to the maximum amount) has steadily improved. But again, it was an evolving process of learning how to optimize refueling, and improving operating, maintenance, and management practices. Because of their low fuel costs, nuclear plants are operated continuously at their base load. It can be inferred from Fig. 10.9 that in just the last 17 years, there have been significant improvements in what one could describe as technology that was considered fully developed prior to the 1990.

While scores of nuclear plants are being proposed, the issue of what to do with the nuclear waste remains in hiatus. Over 90% of the energy in the original fuel is unused in conventional fission reactors and the by-products can be hazardous for thousands of years. One alternative might be to continue to "burn" the material that is now classified as waste. That is one objective of the Next Generation Nuclear Plant (NGNP). For now, much of the world's designs are essentially limited to efficiencies between 30% and 35%, far lower than a commercial natural gas combined cycle unit.

The United States Department of Energy (DOE) is proposing a new, very high temperature gas-cooled reactor (VHTR) that would yield gas temperatures as high as 900°C. The energy from the reactor could produce electricity or some degree of polygeneration, where both hydrogen and electricity are the products. The fuel will be the transuranic materials that are typically classified as high-level radioactive waste. The process, referred to as 'deep-burn' could utilize 65% of the energy content of the fuel, compared to only 3-5% of the energy in enriched uranium obtained with current reactor designs. The heat transfer medium is expected to look radically different from today, possibly relying upon liquid sodium as a coolant (in contrast to water used in LWR's) [36].

Reaching high cycle temperatures could solve one major problem with current nuclear systems designs. Today's steam turbines are very large because they operate with saturated steam instead of supercritical. Reaching supercritical temperatures could result in significant size and material reductions which would have a substantial positive benefit on overall system economics. There could be 40% reduction in turbine size by being able to move to supercritical steam temperatures. Given the enormous capital cost in a nuclear plant, such savings would make nuclear generation on this scale a much more competitive proposition.

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