Nuclear as a Energy Source

Nuclear power is similar to fossil fuel energy production in that it uses produced heat energy (thermal energy) to boil water to produce mechanical work which is then transformed into electricity. As a fuel source, it uses the uranium isotope 235. In a reactor, it releases enormous amounts of energy by fission splitting of the atoms. Nuclear power plants provide 13-14% of the world’s energy. According to the international atomic energy agency, there are 439 active plants, with many of them in the United States, France, and Japan.

Nuclear energy is among the most controversial of the non-renewable energy sources. On one hand it does not release carbon dioxide emissions in its operation process, which makes it a more publicly attractive energy sources. It also has relatively abundant fuel reserves and thus can be seen as a stable energy supply. On the other hand opponents have highlighted the threats it poses to the environment and to populations, and the fact that it cannot be considered sustainable since it uses a finite fuel supply and it produces dangerous wastes. The following sections will run through the most significant issues of nuclear energy production, followed by a future glimpse of nuclear energy with some of its positive opportunities.

Issues

waste storage: according to (Sovacool 2011), 10,000 metric tons of high-level (highly radioactive ) waste is produced every year. These includes isotopes of high atomic mass elements such as Neptunium, Plutonium, and Technetium, which have half-lives measured in the tens of thousands of years; thus representing the daunting task of proper storage and disposal.

Comparatively, nuclear energy produces little wasted by volume when compared to global industrial activity and fossil fuel power plants (especially coal).

Possibility of meltdowns: this occurs when the temperature of the plant’s core is not cooled fast enough, resulting in an exploded reactor with gaseous radioactive material being released. The Chernobyl accident has been the most devastating and widely cited nuclear energy meltdown. More recently there was the Fukushima type of Japan which released some radiation as a result of the diesel powered coolants being damaged by the March 2011 tsunami.

Conversely, it should be noted that, relative to other more common energy production methods, the amount of lives lost per terawatt hour produced is much lower. The highest is 161 for coal, with Hydro at 0.1 and nuclear at 0.04 (NBF, 2011). Due to the strictly managed power plants, the risk of a meltdown is extremely low, yet the elusive nature of radiation makes it a more fearful type of environmental disaster.

Impacts of mining uranium: as with acquiring any other type of underground mineral, mining uranium has its impacts on landscapes, water, habitats and it has its share of emissions. The Reasonable Assure Reserve of uranium at less than $130/Kg is sufficient for at least half a century. Additional harder to reach uranium is at abundant levels.

Carbon dioxide emissions: the process of converting uranium to energy does not produce directly carbon dioxide or other greenhouse gas emissions. This is one of the main arguments in favor of nuclear energy compared to other fuel based energies. However, a considerable amount arises from the construction of the plant, mining operations, enrichment of uranium, disposal of wastes, and decommissioning. Given these, the total CO 2 emitted per kilowatt hour of electricity produced is 3.3 grams; this is compared to 400 g for natural gas and 700 g for coal.

Water issues: the main use of water is for cooling purposes. Are according to (UCSUSA, 2007) a nuclear power reactor is about 33% efficient, which means that every 3 units of thermal energy produced by the reactor core, only one can be transformed into electricity for the energy grid. The remaining 2 units are considered waste heat and have the associated impacts to the environment in the form of thermal pollution.

Depending on the water availability of the region, a nuclear power plant will either use a once through system (water is used to cool then subsequently released to the environment), or a less effective close-cycle cooling system (the same volume of water is continuously being cycled as coolants).

Nuclear weapons proliferation: it is known that one of the original applications of an induced fission reaction of uranium was to produce the plutonium required for atomic bombs. Therefore, nuclear reactors, especially in more hostile countries such as Iran, pose the risk of nuclear weapon proliferation.

Massiveness of scale required: compared to other energy production methods, and especially renewal methods, the production energy requires massive infrastructure. This ranges from the machinery for the mining process, to uranium enrichment facilities, the reactors, and finally the coolant systems. This requires massive amount of construction costs and initial capital; which makes it infeasible for many developing countries, even those rich in Uranium deposits. Unfortunately, it is not cost competitive with coal and natural gas (especially if carbon emission credits are not considered).

Decommissioning: the amount of money and effort that has to be spent on the plant continues long after it has reached its usable life. Many parts of the facility have residual amounts of radioactivity, which therefore necessitates proper containment and burial.

Susceptibility to terrorist attacks: due to the massiveness of scale and importance in providing energy to a wide population, and to the fact that a meltdown has disastrous and long-lasting effects, opponents will highlight that a nuclear plant can be a attractive target for a terrorist attack.

Public perception: given these issues, the public perception of nuclear energy is mostly of a “not in my backyard” type of sentiment. This attests to the fact that radioactive substances are rather intangible and worrying to the public, and thus pose in inflated perceived risk.

Opportunities

Nuclear reaction and atomic energy is continuously being researched and developed. There are many aims, which includes more quicker and efficient fission reactions, safer and controlled reactions, higher fuel utilization, use of spent or depleted uranium fuel for further energy production, use of non-ideal or less enriched uranium isotopes, use of elements other than uranium, and better plant energy efficiencies. Of the many promising developments, two will be described: traveling wave reactors and the use of thorium.

Traveling wave reactors:

Conventional reactors must use enriched uranium as fuel, as this type of isotope (235) is most easily split in a fission reaction to produce energy. According to (Wald 2009):

Enriching the uranium for reactor fuel and opening the reactor periodically to refuel it are among the most cumbersome and expensive steps in running a nuclear plant.

A traveling wave reactor would serve to substantially minimize both those operations.

The operation of the traveling wave plant works to continuously converts non-fissile (un-splitable) material into usable fuel. It also can use the more abundant in nature 238 isotope of uranium (which there is billions of tons stockpiled around the world as a byproduct of 235 uranium production). The researchers that have developed it claimed that it can theoretically run indefinitely as the spent material is continuously being recycled.

Use of thorium:

According to a MSNBC news article (Niiler, 2007), thorium has the potential to replace uranium in nuclear energy production.

Supporters say thorium is more abundant, produces less waste and is less dangerous than uranium, while the same time a great source of energy that won’t add to greenhouse gas emissions.

There are several technological advantages of using thorium, one of which is that:

the technology does not require using cooling water under high pressure to transfer the heat of the reaction into steam to drive a turbine… The reactor core is less complex than a traditional uranium-fueled reactor.

Another advantage is that they can use salt as a coolant, lessening the dependency on water resources and thermal pollution. Other advantages highlighted are that thorium reactors are easier to decommission, and by-products of the plants cannot be used to produce nuclear weapons.

The reason thorium is not being used currently despite the clear advantages over uranium, is the fact that present infrastructure, from the mining operations to refine it and running the core, is suited for uranium only. Some say the only reason uranium was used to begin with is the fact that nuclear reactors were initially developed for atomic weapons.

Sources:

Benjamin K. Sovacool (2011). Contesting the Future of Nuclear Power: A Critical Global Assessment of Atomic Energy, World Scientific, p. 141

Niiler, Eric. (2011): “Is thorium the future of nuclear power?.” Innovation on MSNBC.com. http://www.msnbc.msn.com/id/44820498/ns/technology_and_science-innovation/t/thorium-future-nuclear-power/

Wald, Matthew. (2011) “TR10: Traveling-Wave Reactor.”Technological review: Published by MIT. http://www.technologyreview.com/energy/22114/

No Author. (2011) “Deaths per TWH per energy source.”Next Big Future. http://nextbigfuture.com/2011/03/deaths-per-twh-by-energy-source.html

No author. (2007) “Got Water? Nuclear Power Plant Cooling Water Needs” Union of Concerned Scientists. http://www.ucsusa.org/nuclear_power/nuclear_power_technology/got-water-nuclear-power.html