Mhtgr’s Essay, Research Paper

Our planet is home to over five billion people, all consuming natural resource, and most producing finished goods. From bicycles to automobiles and houses to skyscrapers, this constant production takes an immense amount of energy. Not only human energy, but electricity too. It is need to power the assembly lines that make bicycles and automobiles. It’s essential to run your home appliances, and business computers, and its all produced using similar methods. You heat water to produce steam, which turns a turbine, and generates electricity. Its not quite that simple, but for the purpose of this paper it will suffice. By far the most widespread source of fuel are fossil fuels. They are still abundant, and are relatively easy to obtain. However there is one main problem with the burning of fossil fuels. It produces pollution, in the form of dirty air, polluted water, and greenhouse gasses. This pollution is one of the main causes of global warming, the impact of which has the potential to destroy the planet. It is unreasonable to ask humanity to give up electricity, but the two main problems still exist. Pollution, and an eventual exhaustion of fossil fuels. Therefore an alternative form of energy must be found. Several ideas exist. There is hydroelectric power, solar power, wind power, and nuclear energy.

Many people support the idea of alternative energy, yet there is no move to implement it as a viable alternative to fossil fuels. It is the burning process that makes fossil fuels so bad for the environment. An alternative source that does not require combustion is necessary to avert the process of global warming. Wind power and hydroelectric power both turn the turbines directly. Wind power uses windmills to turn a turbine, while hydroelectric power uses falling water. The problem with these forms of energy are that they can not be used everywhere. In order to replace fossil fuel plants the energy source must be available anywhere. Solar power, while it uses a different means of energy production, has the same problems as the other possibilities. That leaves the idea of nuclear energy.

Current nuclear reactors use water as a main means of both cooling and energy production. The water is pumped through the reactor core, heated to about 325? C, then the superheated water is pumped through a steam generator, where, through heat exchangers, a secondary loop of water is heated and converted to steam This steam drives one or more turbine generators, is condensed, and pumped back to the steam generator The secondary loop is isolated from the reactor core water and, therefore, is not radioactive. During operation, and even after shutdown, the reactor contains a large amount of radiation. Radiation emitted from the reactor during operation and from the fuel after shutdown is absorbed in thick concrete shields around the reactor and primary coolant system. Other safety features include emergency core cooling systems to prevent core overheating during malfunction of the main coolant systems and, in most countries, a large steel and concrete containment building to retain any radioactive elements that might escape in the event of a leak. These are all containment-based ways to stop radiation from leaking. If the concrete shields were to break, and the containment building was breached the radiation from the core would escape.

Current nuclear energy is not very widespread for a number of reasons. First and foremost is the fear of an accident. It is extremely unlikely that a nuclear reactor will have an accident resulting in the release of radiation, and it is even less likely that a meltdown will occur. Although the chances of these events are slim, the results could be catastrophic. It is this fear that has stopped the progress of nuclear power.

“Although over 100 nuclear power plants were operating in the United States at the beginning of the 1980s, safety concerns and economic factors blocked any additional growth in nuclear power after the Three Mile Island accident. No orders for nuclear plants have been placed since 1978, and some plants that have been completed have not been allowed to operate. In 1990 about 20 percent of the electric power generated in the United States came from nuclear power plants whereas in France almost three-quarters of the energy being generated was from nuclear power plants.” (http://linux.chs.edu.sg/~961f02/reactors.htm)

The effects of a meltdown are similar to those of a nuclear weapon. The other problem is the storage of nuclear waste material that is radioactive, and takes years to decay to a non-radioactive state. What is needed is a nuclear reactor that simply cannot meltdown and has fuel that after use is not radioactive.

In the mid 1980s General Atomics began work on a nuclear reactor for the Department of Energy that is practical for widespread use. The Nuclear Regulatory Commission has realized that fossil fuels are finite, and they are “calling for ‘highly reliable and less complex shutdown and heat decay removal systems’ and for ‘designs that minimize the potential for severe accidents’”. In response to these demands General Atomics came up with a concept reactor called the M.H.T.G.R. M.H.T.G.R. is an acronym for Modular High Temperature Gas-cooled Reactor. This reactor meets the standards set forth, and is a viable option solution to the upcoming energy crisis. The M.H.T.G.R. has several passive safety features. Not only is it innately safe, but it has two very important alternative uses. It can be used to destroy weapons grade Plutonium, and for desalinization of seawater.

The passive safety features of the reactor are three fold. The first feature is the reactor itself. General Atomics realized the need to eliminate completely the possibility of a meltdown. The only way to do this is to make the outer casing of the reactor heat-resistant enough to contain any heat the fuel could produce.

Graphite fuel elements and reactor internals which make up the reactor

core have a high heat capacity and maintain their strength at temperatures

beyond 2760 C (5000 F). As a result, temperature changes in the core occur

very slowly and without damage to the core structure in the event of design

basis transients and accidents.

The coolant of the M.H.T.G.R. is another interesting idea. Instead of water which is used in the current nuclear reactors and could eventually corrode the pipes it flows through, the M.H.T.G.R. uses helium. The principle of the reactor is the same, a stream of helium is superheated in the core, and then has the same type of heat exchange with a stream of water that is heated to steam and turns the turbine in the same way as a normal rector. However the helium is not necessary as a coolant because the reactor can never get hot enough to melt. The third and possibly most important thing, the thing that makes the M.H.T.G.R. so safe is it’s fuel. An article in Time magazine, July 21, 1986 explains the fuel pellet.

“In the MHTGR, bits of uranium fuel are encapsulated in tiny grains made of carbon and silicon compounds. The fuel particles, which are embedded in racquetball-size ”pebbles” of graphite, will remain intact up to 3600 F. But the configuration of the core and the reactor’s size (it generates only 80 megawatts of power, compared with 1,000 megawatts for large conventional reactors) ensure that temperatures never rise above 2900 F.”

The fuel and the reactor itself completely eliminate the possibility of a reactor meltdown. Because the fuel pellets themselves keep radiation from escaping there is no problem with storing spent fuel.

Not only does the M.H.T.G.R. present a nuclear reactor that is inherently safe, it brings advantages along with it. The reactor is small and can be mass-produced. It can then be set up at different sites all around the world, and because it is easy to produce each site could choose how many reactors they would need. It can be used to destroy weapons grade plutonium. First the site must construct a particle accelerator. The system is called Reactor Accelerator Plutonium Destruction, and it could be used to destroy .8 metric tons of plutonium per year. The third and final advantage of the M.H.T.G.R. is the ability to supply freshwater.

In order to achieve this a Water Production Plant must be built, and added to the nuclear island.

“After the steam from the NI is used to produce electrical energy, it’s waste heat is sent to the WPP. This hot circulating water is the energy source for the WPP. About 20% of the salt-water can be desalinized into fresh water, while the rest is returned to the ocean in the form of concentrated brine. The seawater intake system is designed to take in 340,000 gpm of seawater, which corresponds to 68,000 gpm of fresh water produced.” (http://starfire.ne.uiuc.edu/~ne201/1996/pederson/link4.html)

Considering the need for freshwater this is an incredible advantage.

The need for an alternative form of energy is very real, and when the safety features of the M.H.T.G.R. are taken into account, the concept of nuclear energy being a solution to the energy crisis is a distinct possibility. MIT Nuclear Engineer Lawrence Lidsky states that “What is needed is a nuclear reactor that Dan Rather can shoot with a bazooka on-camera, and it shuts down without releasing radioactivity. That is what the M.H.T.G.R. is.” A presentation by Osman Chughtai and David Shannon states that “The worst case scenario, where the third world nations aspire to US consumption rates, means there are only 17 years left. Although this is a worst case, most best case scenarios offer a resource exhaustion time scale which is at most 3-4 times this value which is 50-70 years.” (http://www.umich.edu/~gs265/society/fossilfuels.htm) With this pressing crisis, and the pollution produced by fossil fuels, alternative energy is a must, and the need for alternative energy can best be answered by the M.H.T.G.R.