Sunday, November 28, 2010

Nuclear Technology Basics: Introduction (Fun With Fission)

Well, I have just returned from Thanksgiving break. As promised, I will begin a series of posts concerning nuclear reactor technology and how different types of nuclear reactors differ from one another. In the near future, I will also include a glossary entry on my blog that people can reference at a later date in case they come across terminology that is not clear to them.

At the most basic level, all thermally-based power plants share the same mechanics of how they generate electrical energy. A heat source is used to generate steam, which causes a turbine to spin from the pressure provided by the steam which is being used as a working fluid. The action of the spinning turbine is connected to a generator which converts mechanical energy into electrical energy by the rotation of the turbine. Coal, oil, biomass and natural gas facilities use the combustion of these fuels to provide heat to create steam while solar thermal power stations use light from the sun and convert it into a source of heat. Geothermal energy is also thermally-based because it relies on heat from under the ground in geologically active regions in order to operate. Non-thermally based methods of electricity generation such as wind, hydroelectric, and wave energy turbines are directly spun by the movement of wind or water. Photoelectric solar stations generate electricity from solar cells using the photoelectric effect.

In the case of nuclear energy, heat is harnessed from a sustained nuclear chain reaction to drive a steam turbine. Nuclear reactions concern the interaction of an atom's nucleus with the nuclei of other atoms. Heat and subatomic particles are often produced as a result of a nuclear reaction, depending on what type of nuclear reaction it is and what elements are involved. A nuclear chain reaction is when the products of one nuclear reaction trigger additional nuclear reactions within a whole group of nearby atoms in a positive feedback loop. There are two main types of nuclear chain reactions, nuclear fission and nuclear fusion.

Nuclear fusion is when the nuclei of a pair or more of atoms become fused together. The fusion of the atoms releases large amounts of energy. Nuclear fusion is what powers stars in space and has also been achieved within a human laboratory. While nuclear fusion could hypothetically be used as a source of terrestrial power, this has proven to be quite difficult. Surrounding each atom is a positively charged field known as the electrostatic force that tends to repel other atoms away before a pair of atoms can become close enough for their nuclei to fuse. It requires massive amounts of energy to overcome the repulsion of the electrostatic forces between neighboring atoms. Although the development of a nuclear fusion reactor has been a high priority for many governments around the world for many decades, nuclear fusion reactions being carried out in a laboratory have yet to result in a sustainable fusion chain reaction as it seems to require more energy to cause atoms to fuse than what is actually released during the fusion process when attempted on Earth. Because of this, it is likely that a working fusion reactor is still many years away from being a reality.

Nuclear fission is the second type of nuclear chain reaction. It is basically the process of causing atomic nuclei to fragment by ramming them with subatomic particles, which in turn causes the subatomic particles that result from the fragmented nuclei to crash into the nuclei of other atoms and repeat the process. Fission reactions produce heat and other forms of radiation depending on what the products of the fission reaction are. Since the successful operation of the first fission reactor in 1942 at the University of Chicago, all reactors that have been built by humans have been fission-based. Interestingly enough, the existence of naturally occurring fission reactors has also been observed in nature such as the Oklo fossil reactors in Gabon, Africa where the isotopic ratio of uranium deposits within the area allowed nuclear fission to sustain itself. In addition, the georeactor theory in the geological field postulates that the Earth's magnetic field and the heat that is produced from its core might arise from the activities of a naturally occurring reactor in its interior similar to what has been seen at Oklo. However, the georeactor theory has little in the way of evidence that supports it at this time although this may change in the future.

That is enough for now, as I do not want to get too long-winded with each post. The next part of this series will be a look at the basics of nuclear fuel, reactor design, and the fuel cycle itself. Feel free to ask any questions that you might have.

Thursday, November 25, 2010

Thanksgiving Day Post

Today is Thanksgiving, which is an important holiday in the American calendar. Although Thanksgiving is said to commemorate the feast that the Native American tribes had with the early puritan colonists, the actual holiday itself was not established until 1863 by president Lincoln during his Thanksgiving proclamation. Up until then, many states scheduled their own "thanksgiving" events as an irregular observance, often during years when there was an especially bountiful harvest.

A magazine editor by the name of Sarah Josepha Hale wrote a series of letters to president Lincoln urging him to declare Thanksgiving as an official holiday. America was being torn apart by civil war and Mrs. Hale felt that nationalizing the custom of thanksgiving would help restore a feeling of unity throughout the US. The holiday was vaguely based on the Puritan harvest festival at Plymouth Plantation during 1621, which lasted three days from late September to early October. However, the idea behind Thanksgiving as set forth by Mrs. Hale was more of a celebration of "home and hearth" before the dead of winter rather than a specific historical event.

Since the Thanksgiving proclamation, Thanksgiving has been a national holiday that is celebrated on the last Thursday in November. Although the Puritans were more than likely eating venison at Plymouth, turkey is traditionally eaten on the holiday because West Point students were customarily served turkey during Thanksgiving, which had generally been a northeastern culinary tradition until then. Because of this, many West Point troops had been exposed to turkey, which helped cement its place on the Thanksgiving dinner table. After the end of World War II the famous Norman Rockwell image of a roast turkey serving as the symbol for "Freedom From Want" made turkey the national icon for Thanksgiving.

I myself had an enjoyable Thanksgiving today. The turkey was roasted upside-down to make sure that the breast area does not become desiccated during the cooking process. The dog, myself, and everybody else had plenty to eat and everybody seemed to have a good time. My favorite cut of a turkey is the leg or "drumstick" as I prefer dark meat to white meat when it comes to poultry flesh. The "white meat" on birds consists of fast-twitch muscle fibers, which are used for short bursts of intense activity, while the "dark meat" contains slow-twitch muscle fibers, which are mainly meant for sustained physical activity. Slow-twitch muscle fibers contain more myoglobin, which is a protein in muscle tissue that gives it a darker color.

I wish everybody an enjoyable Thanksgiving and I hope that they make sure they get enough to eat and that the company of their dinner guests is not too trying on their patience. The best part of Thanksgiving is often the leftover food the day after, as it is just as good if not better than the day before. Finally, one must not underestimate the remaining turkey skeleton, which is highly valuable for making soup stock out of after the last of the meat has been picked off by ravenous humans.

Happy feasting everybody!

Tuesday, November 23, 2010

All Fission Reactors Are Not Created Equal

For the next few days or so, I will be taking a look at the different types of nuclear reactors that have existed or have only been theorized about on paper. The reason being is that there are so many different potential reactor designs that it is often confusing to people outside of the field of nuclear engineering to determine how reactor designs differ and what the pros and cons of each design are. To make matters worse, the names of these reactors are often abbreviated to different acronyms making it even more difficult for laypeople to understand what the different terms mean.

This will be a bit of an undertaking, as there are literally hundreds of different reactor designs. Some have only existed on paper, others were only experimental prototypes, while others have been built but have since been decommissioned, either from age, lack of economic viability, or from politics. Although some reactor types are highly impractical or dangerous and have rightfully been consigned to the dustbin of history, there are some designs that would have been quite impressive from an economic and commercial standpoint.

At the moment, I am wondering how to proceed in terms of how I will talk about this. I am leaning towards a series of posts, with each post concerning a different "family" of reactor types based on what they use as their moderator materials. However, I am open to ideas from anybody who might offer suggestions.

Monday, November 22, 2010

Nuclear Energy in Asia is Going Full Steam Ahead

India has started construction of a new nuclear facility in Gujarat. It will be a pair pressurized heavy water reactors (PHWRs) that will generate 700 megawatts each. Planning started in January of this year after the site for the reactor was excavated within a short time frame of four months. Construction began today, and the reactor is expected to be online by 2015.

If India can do this, then why should it be so difficult to build new reactors in Europe and the US?

Possible New Reactor in Green River, Utah

The Emery County corporation has started to push the limits of its current energy infrastructure in Utah. Because of this, there has been a serious effort to construct a new nuclear facility near the town of Green River. The planned design would be a power plant with a pair of reactors that would generate 1,500 megawatts each. The nuclear powerplant would be a boon to the nearby community as well as the state of Utah with the positions that it would be able to offer people in its construction as well as its operation.

However, the plant has met opposition as opponents have attempted to prevent the facility from getting rights to water from the Green River that would be used for cooling. Most of the water that is circulated within a light water reactor is then returned to its source, while only a small amount of water is actually evaporated during the cooling process.

If this planned reactor goes forward, it would mark the first time since the 1970s that the construction of a new nuclear reactor was completed. If this project is successful, it might help revive nuclear energy in the US by encouraging the construction of new reactors in other locations. In any case, this is a promising sign that the "nuclear renaissance" will be more than just words.

Sunday, November 21, 2010

First New Uranium Mine in Years

Phase I of the South Texas Palanga uranium mining project has been completed by the UEC (Uranium Energy Corporation) under-budget and on schedule. Phases II and III are expected to be completed in 2011. This marks the first time in several years that uranium demand has allowed for the opening of a new mining facility. Mining operations will commence using in-situ leeching methods, where water that has been acidified with carbon dioxide gas will be pumped into the mining site. This is what allows the uranium to be extracted from the surrounding limestone as the uranium is dissolved in the water when it is pumped out again during mining operations.

The economic activities of the uranium mining industry have been depressed for years because of the lack of demand for nuclear energy in the US since the mid-1980s. In the early 2000s the price of uranium bottomed out and it has only been in the last three years that the uranium market has been showing signs of recovery. As the price of uranium has increased since then, there has been a renewed interest in re-opening old mines and prospecting for new sources of high-grade ore.

Many people raise fears that the world supply of uranium will peak in 80 years. One must keep in mind that this estimate is based on existing production rates of uranium ore and nuclear fuel fabrication. There are many mines across the world that have been forced to close either through political pressure, or because existing world uranium demand could be easily met by a smaller number of mines. The amount of uranium required by most reactor types is quite small, especially when compared to the fuel consumption rates of fossil-fuel generators like coal and natural gas. The fissile isotopes of uranium are extremely compact compared to other energy sources. A single fuel pellet like those used in a nuclear reactor is the equivalent of 1,780 pounds of coal from an energy standpoint. Although hundreds of these pellets are used to fabricate fuel rods in a light water reactor, the amount of uranium required to fuel a reactor is still a rather tiny amount.

In the event of a large build-out of new nuclear reactors, it would not be too difficult to increase the production of uranium ore to meet an increased demand since uranium is such a common element. However, up until now there has been little need to do so. In fact, should the easily recoverable sources of uranium ever run out like the most dire scenario erroneously predicts, existing stockpiles of spent fuel could easily be reprocessed for more fuel. Finally, uranium can be extracted from seawater. Although the cost of recovering uranium from using this method would be roughly ten times conventional mining methods, it would still be economically viable as the operational costs of nuclear electricity generation are relatively insensitive to price increases of fissile material.

Friday, November 19, 2010

N^4 Has Been Redesigned!

I thought that my layout for N^4 was getting a bit stale, so I overhauled it. It turned out better than I thought. The new options for Blogger also allowed me to get rid of that damn space between my blog articles and the sidebar that Firefox kept insisting on doing for some reason. As a bonus, I also put in a new header image.