Sunday, June 27, 2010

White Paper Draft: Deployment and Lowering Post-Carbon Energy Costs, Part 1

Estimates about how much energy must be produced to assure an 80% reduction of CO2 emissions by 2050 differ and it is not necessary to reach a plausible figure in order to formulate the post-carbon deployment problem. The problem is not simply to replace 80% of present carbon based energy production with post-carbon energy systems. Most people on earth use far less energy than people in North America and Western Europe do. It appears to be the aspiration of the peoples who live in less energy intensive societies to enjoy standards of energy use similar to those found in Europe and North America. In order for this to be possible, a global energy use would have to be greatly expanded. The rapid growth of the Chinese and Indian economies, coupled with their rapid growth in energy consumption suggests that the global energy demand in 2050 will be substantially higher than it is in 2010. In order for any global carbon mitigation program to be successful, it must take into account likely future global energy expectations. Thus not only will 80% of present fossil fueled energy generating technologies have to be replaced with post-carbon energy generating technologies, but a very large amount of post-carbon energy relating facilities will have to be built to answer new energy demands.

This massive deployment of new energy sources will create several problems. First is the production problem. Truly massive numbers of new energy sources must be built. The second problem is the source distribution problem. It is not enough to produce large numbers of energy producing units, they must be distributed to final energy production sites, and set up to actually produce energy. If the energy is not consumed on site then it must be distributed off site, and an adequate energy distribution system, one which can be counted on to reliably deliver electricity to the customers must be constructed. If energy customers expect reliable energy, a reliable backup systems have to also be built.

The entire system must be deliverable at reasonable costs.

In order to produce enough energy generation units, the it is very likely that those units will require mass production in factories. In addition to insuring the rapid production of large numbers of generation units, factory production has significant potential for lowering labor costs. It should be noted that major renewable components of renewable energy sources already are largely factory produced, with final assembly from often large components in the field. Field assembly can usually be assumed to cost more than factory assembly.

Most renewable energy systems rely on factory assembly of major components. There is a growing trend in the nuclear industry to factory assemble modular kits, each component weighing up to 40 tons. Major components of large reactors, such as steam generators and pressure vessels weight much more. Pressure vessels can weigh over 1000 tons.

Large components of renewable are often transported by truck to final assembly sites, but even trucks cannot carry large components like entire wind towers, so the towers are halled by trucks in manageable pieces. Wind tower bases are built of concrete, and may cover a 60' by 60' area. Foundations can require 25 tons of rebar, while the concrete in the foundation of a 1.5 MW wind generator will top out at a500 tons.

Most of the components of wind generators are built in factories and arrive at the assembly site on trucks. Building wind generators then becomes a matter of local assembly of factory built parts. Although wind generators require several times the material input of reactors, their overall cost is far less, because their factory manufactured parts cost less and it cost less to assemble them into a wind generator. Were this the end of the story, we would be forced to conclude that nuclear power is not cost competitive with wind. It is not the end of the story. Winds are unreliable, and the average wind generator produces electricity equal to one third of its rated generating capacity. In contrast the average nuclear power plant produces 90% of its rated capacity. When the superior efficiency of nuclear power is included in the cost equation, nuclear power turns out to be less expensive.

Can nuclear power manufacturers learn something from the wind industry's use of factory manufacture? In 200o the United States Department of Energy commissioned a study of potential designs for small factory manufactured reactors. Now it is possible to factory manufacture a large reactor in the form of factory built kits designeds to be assembled locally, just as wind mills are. While there are some real cost savings to be had by the kit approach, assembling the large reactor, still may require as many as 20 million hours of labor.

The 2003 DOE report on factory constructed small reactors was titled, DESIGN AND LAYOUT CONCEPTS FOR COMPACT, FACTORY-PRODUCED, TRANSPORTABLE, GENERATION IV REACTOR SYSTEMS. Research described in the report focused on three reactor types that were assumed to have potential for factory manufacture. They were the Westinghouse International Reactor, Innovative & Secure (IRIS) a reactor rated at 1000 MWt, that was expected to produce about 345 MWs of electricity in full power operation. The IRIS was at the upper range of small reactor which run from 100 MWe to 400 MWe.

The IRIS, a Light Water Reactor (LWR) was not a true Generation IV reactor design. Rather it was a surrogate that was chosen because detailed plans of the IRIS were available from Westinghouse. Light water reactors require a number of massive components. For example, the pressure vessel of a giant economy size LWR is a massive steal object that can weigh as much as 1000 tons. The pressure vessel is but one of a number of large and heavy steel object required to make a LWR work. In reactors the size of the IRIS those objects are smaller than those found in regular size reactors, but they are still very large and heavy. If the whole IRIS power producing unit were treated as a single factory producible object, researchers calculated that it would weigh over 7000 tons. The IRIS was also larger than a football field. Transporting such a large and heavy object from a factory would be a very difficult undertaking and transportation would probably be limited to ships and barges, and possibly even then with difficulty. If our requirements included truck or rail transportation, then clearly the URIS would not work out well. If the IRIS were to be factory built as a kit, we would have to ask if there was any cost advantage to building an IRIS kit as opposed to building a larger reactor from a kit.

Clearly then the IRIS is not the nest candidate for factory construction. A less powerful candidate, the Modular Pebble Bed Reactor (PBMR) was designeds to be transported as a kit. No consideration was given to transporting it as a single unit. Indeed while the PBMR does not require as much steel in its pressure vessel as the LWR pressure vessel does, the PBMR pressure vessel is twice as large as a LWR pressure vessel for a given unit of power output. The Chinese plan to factory build PBMRs kits, but their most recent estimate is that it cost as much per unit of power to build a PBMR from a factory produced kit, as it costs to build a Generation II or III LWR from a Factory produced kit.

From the perspective of 2010, the DOE's third choice for the factory built small reactor was a strange choice. It was a liquid Lead-Bismuth cooled fast reactor. The Report noted,
Liquid metal breeder reactors hold particular promise for future energy supply since they offer sustainability of energy production through effective utilization of fertile and fissile materials. They also can be used to recycle nearly all of the actinide radioactive waste produced by current nuclear reactors, and consequently use the waste for energy production. Many breeder reactors have been designed and a few have been built and operated. However, most designs have an inherent problem with positive coolant voiding reactivity coefficients; thus, they may present more risk than many would prefer to accept. Results from our calculations indicate that proper choices of thorium, plutonium, and uranium fuels, along with some changes in geometry, permit a PbBi cooled reactor to operate with a negative PbBi voiding reactivity coefficient, so that a reactor with considerably more inherent safety than previous designs can be designed and operated.

One significant advantage of PbBi as a coolant is that the reactor spectrum is relatively hard, and this permits significant quantities of actinides to be used as fuel, which eliminates the need to dispose of them as waste. The nuclear characteristics of this design also permit operation for at least five years without refueling, or reshuffling, since the conversion ratio can be maintained very near unit y. The time between refueling is limited by performance of fuel materials rather than by the ability to sustain the chain reaction. Proliferation resistance is improved relative to the reactors in current commercial use since the Pu-239 inventory can be held constant or be diminished, depending on fuel management choices.

In order to accomplish the size limitation for reactor components, the proposed design is constrained by a reactor vessel size that will be transportable on a standard rail car. This limits the height and width to about twelve feet, the length to about eighty feet, and the weight to about eighty tons. This should be adequate for producing 300 to 400 MW electrical, depending on optimization of primary and secondary system performance, while satisfying all licensing requirements.
There is, in fact very little interest in building such a reactor today, although there is a lot of interest in building very similar sodium cooled small reactors that are in many respects similar in design. Compared to LWRs and PBMRs, Liquid Metal Fast Breeder Reactors (LMFBRs) are quite compact. The report found,
It is determined that a PbBi cooled fast reactor that produces 310 MWe can be designed with primary system components that are all rail transportable.
This is a definate move in the right direction. But are we considering a paper reactor, one that would require a lot of money hard work and time to bring to production. The Russians who had experience with PbBi cooled reactors built for for military purposes, are working on a 100 MWe PbBi cooled fast reactor, such reactors are however, unlikely in the United States.

In 2010 there are several proposals to build sodium cooled small (100 MWe to 400 MWe) and mini (under 100 MWe) sodium cooled fast reactors. Most of these reactors will fall in the Mini category, but one plausible candidate with a very credible design, the ARC-100 would produce 100 MWe, and thus would be a small reactor. The ARC-1000 is based on a proven reactor design. This size reactor would have train and/or truck transportable major components, would be large enough to be a primary source of power for the grid, if the ARC-100 cost could be kept low enough. It is not clear, however, that the ARC-100 would be the lowest cost Generation IV reactor candidate. There would inevitably be complaints about ARC-100 safety, but in fact its probably can be made sufficiently safe, making the ARC-100 safe enough might add to its heft and cost. In addition safety mandated modifications to the ARC-100 design, might impose performance penalties. There should be no complaints about nuclear waste from the ARC-100. Indeed the ARC-100 would be a waste eater, that would be started with nuclear waste, of fissionable materials from nuclear weapons. One of the ARC-100 limitations might be that the supply of nuclear waste might not keep pace ARC-1000 start up demand.

The ARC-100 is fairly complex, and the complexity would add to manufacturing and operation costs relative to simpler designs. Some of the fuel reprocessing technologies used by the ARC-100, might not work as well as Argonne National Laboratory veterans hope.

Thus while the ARC-100 might well be a good reactor design, it might not be the ideal factory manufactured reactor candidate.

Let's make a list of qualities that the ideal factory manufactured reactor should possess. It should be:

1. Very safe, and safe at a low cost
2. Should dispose of the most dangerous components of existing nuclear waste
3. Be small enough and light enough for its major components to be truck or train transportable.
4. Produce its own fuel.
5. Be undesirable as a nuclear proliferation tool.
6. Be manufactured quickly and at low costs. Be capable of being placed into operation within 6 months of being ordered.
7. Be either air or water cooled.
8 Be capable of being produced in very large numbers over a relatively short period of time.
9. Be more fuel efficient than conventional reactors.
10. Reprocess its fuel on site and at low cost.
11. Reduce the problem of long term nuclear waste by at least 99% , or entirely eliminate it.

Most people would say that it is impossible for any one type of reactor to do all of this. In fact, one little known and poorly understood type of reactor offers all of these features. Only one class of reactor is capable of accomplishing all of these requirements. I will discuss that reactor and its performance options, in the next part of this paper.


DocForesight said...

Charles, you've probably already seen this pair of papers, but they appear to have the same goal in mind. Would like your feedback - and that also of your informed audience.

They are 18 pages and 7 pages, respectively.

Nathan2go said...

Charles, one disadvantage of fast breeders like the ARC-100 that you didn't mention explicitly is their massive startup fuel load.

According to the company brochure, the startup load (of enriched U) is 20.7 tons. Assuming a 15% average enrichment, that's 31 tons of U235 per GWe, similar to buying 31 years of fuel in advance!

For comparison, most LFTR designs startup on 1 ton/GWe.

Charles Barton said...

Nathan, i plan to talk about both the start up load advantage and the the probable capital cost advantage of the LFTR in a later section of the white paper.


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