Paper delivered at the 12th Annual Technical Conference of The International Society of African Scientists (ISAS) held in Philadelphia, PA, August 16, 1996.
NUCLEAR POWER for REMOTE AREAS
It is possible to combine simple cycle gas turbines with nuclear reactor heat sources to produce a simple power generator that can be economically produced in small sizes aimed at distributed power customers.
Atomic engines offer capabilities that cannot be achieved with combustion engines. The fuel for an atomic engine is two million times as energy dense as oil, its closest chemical power competition. In areas where transportation is difficult and expensive, the compact nature of atomic power gives it a significant operational and economic advantage.
In remote areas that house a growing number of people who require some of the comforts and conveniences of an electrified society, small nuclear plants can have a significant impact. By designing and building plants that use simple, low cost gas turbine technology coupled with small, inherently safe reactors, Adams Atomic Engines, Inc. plans to help to improve the living conditions of millions of people in remote areas.
In the early days of the Atomic Age, the United States Army developed a considerable amount of experience in the design, manufacture and operation of nuclear plants in sizes ranging from a truck moveable 300 kilowatt electric generator to a barge mounted 10 megawatt plant. The machines served remote installations such as Greenland, Antarctica, Wyoming, the Panama Canal Zone and Alaska.
In these areas, oil could cost as much as $6.00 per gallon after accounting for the costs of transportation (non-inflation adjusted 1960s dollars). The nuclear plants provided soldiers and scientists with comforts that were previously impossible or very costly to supply.
Unfortunately, the program was limited by law to serving military needs, without the ability to leverage the technology investment by seeking other potential markets. When the United States became more heavily committed to the war in Southeast Asia, funding for projects that were seen as non-essential was greatly reduced. The Army Nuclear Power Program was a victim of this policy, even though it had successfully built eight prototype power generators.
During the years since the ANPP actively built nuclear power plants, there have been some sporadic programs in a number of countries to investigate the possibility of small reactor plants for distributed power needs. None of these projects have produced a machine that could economically serve the identified need.
Brief Description of Proposed Technology
Adams Engines are closed Brayton cycle machines. They combine proven compressor and turbine designs with fully tested gas cooled reactor concepts. They use the inherent stability of a core with a negative temperature coefficient combined with a throttle valve to control power output by controlling coolant flow. Because of the nature of the fuel design and the geometry of the core, fuel melting is not credible even in the event of complete loss of coolant flow at full power.
In order to take advantage of the enormous infrastructure that exists to manufacture and support combustion gas turbines, Adams Engines use nitrogen gas with a maximum system pressure of approximately 10-20 bar as the coolant. This gas has essentially the same thermodynamic characteristics as the mixture of air and combustion products that is the working fluid in existing turbo-machines. The low operating pressure enhances safety for operators and reduces the cost of pressure barriers that are needed to protect the public from radioactive material releases.
It appears that the ultimate capital cost of the machine will be competitive with combustion gas turbines - including fuel delivery systems. Though there are not any Adams Engines currently in operation, this engine concept is essentially a refinement of technology that was demonstrated in military projects as early as the late 1950s.
The Army's truck moveable 300 kwe nuclear power plant, the ML-1, was a similar closed Brayton Cycle machine. Its overall power density was far lower than achievable today, largely because it operated at less than 10 percent thermal efficiency. The current state of the art for reactors and turbines will readily support efficiencies of 33 percent or more.
Need for Distributed Power Systems in the 1990s
There are thousands of areas in the world that are not served by established electrical grids. Often these areas are in lesser developed countries and are isolated from high capacity transportation facilities by mountains, rivers, swamps, deserts, bad roads, or corral reefs.
The people that live in these areas are often trapped in dire poverty. One reason for the poverty is the large portion of potentially productive time is spent in a daily search for fuel for cooking or lighting. In many cases, this search requires several hours because of the distances that must be traveled to find scraps of wood or animal dung. The amount of fuel that can be transported at one time is limited to that which can be carried by a human or beast of burden. Women and children, instead of learning skills that can provide them with enhanced opportunities, are often assigned the task of gathering fuel.
Poverty is also caused by the inability of people to come together to produce goods in specialized businesses. Even a small sewing factory that can produce useful garments is out of the question if there is no reliable source of power to supply the sewing machines.
Despite being surrounded by land that can be farmed, remote areas often suffer from hunger. Harvests are naturally sporadic, but the lack of energy supplies inhibits efforts to preserve food from the good times for the lean times or to provide irrigation to make up for the variations in rainfall.
Though the availability of power will not prevent poverty or eliminate the exploitation of women and children for manual labor, it is one tool that has proven to be effective in helping to meet basic needs. The ability to cook a meal by simply turning on a hot plate and to read at night by switching on an electric light or two has made a huge impact in the quality of life for many of the world's poorest people. In many studies of the needs of developing countries or remote areas, power generation equipment is often at the top of the priority list.
Limitations of Current Supply Options
Unfortunately, purchasing one of the currently available power systems will not solve the problem of getting power to the customers, even if the customer is a large facility that does not need an extensive distribution network. Electrical power, after all, is a manufactured product that often needs a continuous injection of raw material.
The only currently available exceptions to that rule are wind, solar and hydroelectric power. Each of these systems can produce electricity without raw material inputs, but they are all limited by the vagaries of the weather. Humans often consume energy in an attempt to escape from the limitations and discomforts of cold, oppressive heat and darkness yet the output of wind turbines, solar panels and hydroelectric dams is dependent on forces beyond human control.
Though there are some logical applications of these technologies for such purposes as water pumping, crop drying, and some electric power production, traditional alternative energy sources do not have the potential for helping isolated areas grow and develop. Some promoters of such devices readily admit that one of their purposes is to prevent the industrial development of remote regions. That goal may or may not agree with the goals of the people that actually live in the region.
Energy density comparisons
A nuclear fission reactor, unlike any other thermal energy source, has the demonstrated ability to operate for many years without new fuel. It achieves this incredible performance because its fuel is extremely energy dense. A combustion engine will need continuous resupply at a rate that can be readily calculated and compared to that of a nuclear system.
The following example assumes a power system capable of delivering a maximum of nine megawatts of electrical power. The average load over a year is five megawatts. In the nuclear case, the mass delivered includes both protective coverings and fuel that is not consumed and is available for recycling.
Engine type Required fuel for 5 MW-years nuclear gas turbine 1.6 tons per year (one truck every 5 years) diesel engine (11000 BTU/kwhr) 12,000 tons per year combustion gas turbine (14000 BTU/kwhr) 15,400 tons per year
Frequently, fuel deliveries in remote areas are made in small, multi-purpose trucks. A typical arrangement might be a 10 ton truck that can carry 20 standard 55 gallon drums. If this is the means of moving fuel, serving the above fossil fuel generators will require between 9 and 12 deliveries every day. For some remote areas, the truck can consume as much energy as it carries.
This illustrates one of the main impediments to supplying reliable power with today's technology. Diesel engines and gas turbines that can operate reliably for many years are readily available on the world market. Sufficient financial resources exist to supply these generators to the areas that need them. However, once they are installed, combustion generators often become lifeless hunks of metal awaiting the next delivery of fuel from an expensive and unreliable source.
Power Density Comparisons
While atomic engines will, because of shielding and containment structures, weigh more than competitive diesel engines, they will weigh less than competitive diesels if more than a ten day fuel supply is included.
Here are some typical values for specific weight of various types of power plants. There are significant variations within each type depending on the manufacturer and the ultimate purpose of the engine, but these figures provide a reasonable means of comparison.
Engine type Specific weight combustion gas turbine 2.9 kg/kw medium speed diesel 10 kg/kw nuclear gas turbine (including shielding) 15 kg/kw nuclear steam plant (including shielding) 54 kg/kw
It is also worth noting that half of the weight of the nuclear systems listed above is in the shielding and containment structures. These structures can be erected using local supplies of steel, concrete and lead.
When compared to generators supplied by fossil fuel, atomic engines make less of an impact on the local and global environment. Nuclear fission does not release any greenhouse gases, it does not produce any sulfur oxides or nitrogen oxides, and its fuel is in a solid form that will not spill during transportation. As demonstrated by their use on submarines that must remain silent, nuclear fission plants can even help to reduce noise pollution.
One environmental disadvantage that traditional nuclear steam plants have had is that they are somewhat less efficient from a thermodynamic point of view than are traditional combustion power plants. This has ordinarily resulted in a greater need for cooling water, a factor that can cause significant environmental impact in areas where water volumes are limited.
An atomic gas turbine, however, overcomes this efficiency disadvantage by operating at higher temperatures so that its efficiency is essentially the same as comparable combustion engines. Additionally, atomic gas turbines can operate efficiently with air coolers, since the turbine exhaust temperature is far greater than is normally found in a steam plant.
Atomic gas turbines, like combustion turbines, are well suited for use in combined heating and power applications where their waste heat is used in a district heating system. In some remote areas, the best use of the available waste heat might be for water purification.
Thus the only waste product of an atomic turbine that needs to be released to the environment is a bit of hot air that is completely uncontaminated with the residues of the power production process. In the often pristine remote areas where these distributed machines will be operating, this is a significant advantage.
Nuclear Weapons Non-proliferation
Whenever the idea of small nuclear plants for distributed power loads is mentioned, there are some people that raise the question of the current policy of nuclear non-proliferation. It must be remembered that this policy is aimed at nuclear weapons, not nuclear power plants. In fact, the Nuclear Non-proliferation Treaty explicitly states that one of its goals is for nations with nuclear expertise to share that expertise for peaceful applications with all signatories.
The most appropriate form of nuclear technology for developing areas is a power plant small enough to fit into the available grid system, even if that grid only supplies a single factory or health care facility.
Some observers have also indicated a belief that providing nuclear engines will necessarily result in the distribution of knowledge and material that will make it easier for smaller nations to undertake a nuclear weapons program. However, people can be trained to operate nuclear power plants in a safe and effective manner without being trained to produce workable nuclear weapons. A simple survey of the existing nuclear plant operators in dozens of countries can confirm this statement.
An operating nuclear reactor is arguably the world's most secure location to store dangerous materials. The high radiation doses emitted from unshielded fuel materials helps the plant to protect itself from any intruders that would disturb the shielding structures in an attempt to remove material that might be used to manufacture a weapon. It would be a simple matter to seal the plant to ensure that any attempt at intrusion would be detected.
There are some hurdles that must be overcome before small atomic power plants are ready to serve the needs of people in remote areas, but most of the obstacles are political. The basic technology has been demonstrated; the production of simple nuclear gas turbines is a straightforward matter of engineering that requires no scientific breakthroughs.
The future is bright, the benefits are apparent, and the technology is available. The impact of nuclear power on remote areas can be as great as that of the Rural Electrification Commission that brought power and higher living standards to millions of Americans during the period beginning during the Great Depression of the 1930s.
61 Pier Road
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