Wednesday, May 11, 2011

The Future of the Nuclear Fuel Cycle: Can LWRs Meet Post-Carbon Energy Demands?

Any account of the future of nuclear power should place be based on an understanding of the potential future energy resources. We know that in the next 40 years global energy resources are expected to undergo a remarkable transformation. There is little doubt that such a transformation will take place, and that nuclear power will play a major role in that transformation. Indeed, if the analysis offered by Nuclear Green is correct, nuclear power may and probably will play a predominate role in the transformation of our energy resources. The Nuclear Green analysis is also supported by several analyses that have appeared in Brave New Climate.

Climate scientists indicate that in order to prevent significant and expensive economic disruptions due to climate change, fossil fuel dependent energy use must be reduced by 80% over the next 40 years. Even if were were not facing climate change crude oil production has reach or has nearly reached its peak, and can be expected to decline during the next generation. Coal production has already or may soon reach its peak, while the future of natural gas reserves is not clear. In addition a controversy about the carbon mitigation value of natural gas remains unresolved. Thus the future of fossil fuels seems likely to be one of declining long term production.

The major future energy problem then is fossil fuel substitution and any study of the future nuclear fuel cycle must at the very least take future energy needs into account. Currently nuclear power is used primarily to produce one form of energy, base load electricity. But an analysis of fossil fuel use by our society suggests that many energy systems, currently powered by fossil fuels will need to be replaced. Some replacements are possible by expanding the use of base load electricity, but for many other energy demands, current nuclear technology (Light Water Reactors) is not a strong replacement candidate. The problems of current nuclear technology include limited heat generation capacity, high capital costs, and widespread public suspicion of nuclear safety. While Light Water Reactor technology is economically competitive with so called "clean energy" technologies, the cost of nuclear electrical generation would increase dramatically with a drop in capacity utilization. Thus a nuclear response to peak electrical demand using LWR technology would be prohibitively expensive, while the unreliability of "clean energy" sources makes them unlikely candidates for low cost peak electrical generation.

LWRs operate at relatively low heat, making LWR technology an unlikely source of industrial process heat. Again the unreliability and geographic limitations of "clean" heat sources makes the use of clean energy technology in industrial processes heat, very problematic, and impractical for most of the country.

Social issues related to nuclear power arise because of public fear of the accidental release of radioactive materials form reactors. This public opposition leads to stringent and at least partially unnecessary regulation of nuclear sourced energy as well as public support for and demand for "clean" energy. From the stand point of fossil fuel replacement, public support for "clean" energy would not be a problem if clean energy were reliable and low cost, but "clean" energy is both unreliable and expensive.

Future public acceptance of nuclear technologies becomes a significant concern in evaluating the future of the fuel cycle.

During a 40 year period of time, developments in nuclear technologies can profoundly effect the fuel cycle picture. it is probably impossible to say with certainty what the function of nuclear power will be 40 years from now.

Finally, I have already alluded to the importance of capitol costs, in evaluating future nuclear technology. It may be that conventional nuclear technology, while the lowest cost future energy technology, causes economic damage to national economies by failure to generate energy at a cost that is competitive on international markets.

A comprehensive study of the nuclear fuel cycle should include am evaluation of future energy demands, social response to the projected fuel cycle, and the effect of the adoption of fuel cycle technology on national economic competitiveness. At the very least the study should acknowledge that energy demand for base load electricity, load following, backup and peak load electricity, industrial process heat, and ship propulsion could potentially effect both nuclear fuel demand, and the nuclear fuel cycle.

Massachusetts Institute of Technology has recently undertaken to offer an account of The Future of the Nuclear Fuel Cycle. To its credit, the MIT report does not ignore the social, political and economic diminutions of future energy change. Yet the MIT treatment of these considerations are clearly inadequate.

For example, a maj0r finding of the report is that
LWRs will be the workhorse of the nuclear fleet for decades.
Yet only for base load electricity is this likely to be true. LWRs are not likely energy sources if other, lower cost, and technically more adequate energy resources are available. Even for base load power electrical utilities find the capital costs of LWRs daunting. There is incontrovertible evidence of this, at best a mere handful of LWRs are likely to be built in the United States during the next decade. Will LWR building pick up beyond 2020? Who knows? Even if we factor in small Light Water Reactors (SLWRs) it is difficult to see LWR technology penetrating beyond base load electrical generation. SLWRs would be a high cost option, for load following, back up and peak electrical generation. The United States Navy clearly sees advantages for ship propulsion by nuclear power, but hesitates to use it for most of the surface fleet because of its cost. It thus seem likely that sea born shipping with far more significant cost restraints than the naval surface fleet will ever be powered by LWRs.

Both costs and the temperature restraints of LWRs are significant impediments to the use of LWRs in the production of industrial process heat. These considerations might be of passing interest to the study of the future fuel cycle, were low cost, reliable, and flexible non-nuclear energy alternative available. They are not. "Renewable energy" are expensive, inflexible and unreliable, in the face of human energy demands.

Thus there is likely to be demand for energy from nuclear sources that will require alternatives to LWR technology.

The MIT study states,
The viability of nuclear power as a significant energy option for the future depends critically on its economics. While the cost of operating nuclear plants is low, the capital cost of the plants themselves is high. This is currently amplified by the higher cost of financing construction due to the perceived financial risk of building new nuclear plants. For new base load power in the U.S., nuclear power plants are likely to have higher levelized electricity costs than new coal plants (without carbon dioxide capture and sequestration) or new natural gas plants. Eliminating this financial risk premium makes nuclear power levelized electricity cost competitive with that of coal, and it becomes lower than that of coal when a modest price on carbon dioxide emissions is imposed. This is also true for comparisons with natural gas at fuel prices characteristic of most of the past decade. Based on this analysis, we recommended in 2003 that financial incentives be provided for the first group of new nuclear plants that are built. The first mover incentives put in place in the U.S. since 2005 have been implemented very slowly.
And recommends,
Implementation of the first mover program of incentives should be accelerated for the purposes of demonstrating the costs of building new nuclear power plants in the U.S. under current conditions and, with good performance, eliminating the financial risk premium. This incentive program should not be extended beyond the first movers (first 7–10 plants) since we believe that nuclear energy should be able to compete on the open market as should other energy options.
The writers of the MIT report seem to anticipate that the building of 7 to 10 new nuclear plants, facilitated by "incentives" would lead to a steady and growing nuclear build out, as LWRs took their place in the carbon replacement line up. This view fails to even access the impact of SLWRs on the base load market, but even considering that impact we cannot be assured that the transition to LWRs will be smooth or that it will lead us to a satisfactory post-carbon energy supply. Yet the MIT report concludes,
For the next several decades, light water reactors using the once-through fuel cycle are the preferred option for the U.S.
We must ask, preferred option for what. As I have indicated there are a number of significant post-carbon energy demands that can neither be meet by LWRs or by "renewable energy" sources. Thus the possible us of alternative nuclear technologies to meet post-carbon energy demands, cannot be discounted.

There are a number of potential nuclear energy technologies that are potentially available for post-carbon applications. These include Liquid Metal Fast Reactors, Graphite Moderated Gas Cooled Reactors, and Molten Salt Reactors. These reactor options can be ranked by heat output and expense.

By industrial process heat potential the rankings from lowest to highest would be,
* LWRs
* LMFRs
* MSRs
* HTGRs
By levelized electrical cost the probable ranking from most expensive to least expensive,
* LMFRs
* HTGRs
* LWRs
* MSRs
These rankings would require some comment. First, the Industrial heat potentials of tested MSR technology is around 700 degrees C, while the tested potential of HTGRs would be in the neighborhood of 1000 C. The potential top temperature of MSRs would be around 1200 C, while the potential top temperature of the HTGR would be around 1600 C.

Secondly, the levelized costs rankings are based on both potential complexity, as well as labor and materials inputs. The rankings are to a certain extent speculatrive. Gas cooled reactors require larger cores, than thus greater materials inputs. In practice HTGR cost will probably be close LWR costs. LMFR costs have proven rather robustly to be higher than LWR costs. MSRs have smaller and simpler cores, thus decreasing both labor and materials inputs, relative to LWR costs.

Both the HTGR and the MSR offer potential advantages for industrial heat. The MSR would be the clear favorite for low cost industrial heat at temperaturs of up to 700 C, while the HTGR offers maximim heat of around 1000 degrees.

For shipping propultion, and load following, backup and peak generation capacity MSR technology offers attractive cost advantages. Even for a base load generation role, MSR technology would appear to offer a substantual cost advantage over LWRs.

It is not to the credit of the MIT report authors and staff, that they failed to consider the implacations of MSR technology on the future of nuclear fuel cycles.

2 comments:

uvdiv said...

You've linked to the summary only. Here's the correct link:

http://web.mit.edu/mitei/research/studies/nuclear-fuel-cycle.shtml

They do actually discuss thorium MSRs (the solid-fuel AHTR version -- in Appendix B).

I think their key point is not so much the the endorsement of LWRs, but that the choices are extremely flexible. (Because uranium/thorium resources are tremendous, spent nuclear fuel is recoverable, SNF storage is cheap). Saying LWRs are the best near-term choice is tautological -- they're the only commercial designs, so if you build reactors today, you build LWRs. They don't claim LWRs are the best or cheapest, but the most available option, and a safe one.

They do acknowledge process-heat applications, and high-temperature (gas) reactors. Appendix C in particular.

Charles Barton said...

uvdiv, thank you for your comments. I worked back from conclusions to assumptions, and noted what i think are flaws in reasoning. My concern stems from the failure of the report writers to match capacities with needs. Were it noted, for example, that nuclear power will be required to provide industrial process heat, the conclusion that LWRs would be the workhorse of the nuclear fleet, might have been seen as questionable.

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