The Big Picture

Perhaps no other area of energy policy has engendered more debate and controversy than nuclear power. The mere thought of a nuclear plant down the road spewing out dangerous radiation strikes fear in many people's minds due to Chernobyl, Three Mile Island, The China Syndrome, and our memories growing up of the horrible scenes from Hiroshima and Nagasaki. In reality, the nuclear energy technology is relatively safe compared to other technologies that we use every day, like automobiles. In fact, most of the radiation we are exposed to every day does not come from a nuclear power plant, but from nuclear medicine and x-rays done for medical purposes. For instance about the same amount of radioactivity comes from the smokestacks of coal-burning electrical power plants as comes from nuclear plants; both of these are lower than the dose the average person gets from doctor's x-rays in a year. Nuclear plants have not caused the death of anyone in this country of which we can be certain. One of the reasons people fear nuclear energy technology is that they do not understand the units of measurements for radiation, what a half-life is, what the different kinds of radiation are and what each of their biological effects are, how nuclear energy is produced, what the nuclear fuel cycle is, how much radiation is released normally from a nuclear plant, what we have learned from accidents at nuclear plants. In this chapter, the authors discuss each of these issues and the science underlying them. They also discuss the current thinking on how nuclear waste may be safely disposed of, and what the future of nuclear power is likely to be.

Frequently Asked Questions

• A neutron is used to split an atom's nucleus (usually uranium 235) into smaller nuclei (radioactive isotopes that are the breakdown products of U-235), which causes the release of energy and three neutrons.
• These neutrons break away from the nucleus and then each strikes another U-235 nucleus. Now these three U-235s are split, releasing 3 more neutrons each. These nine neutrons strike more U-235 nuclei and release 27 neutrons. This nuclear chain reaction, if unchecked, can proceed rapidly into a nuclear explosion (Figure 18.1)

• Fusion is the joining together of two molecules of hydrogen (H) to form helium (He). This fusion reaction would combine two atomic nuclei with one proton and one neutron each to form another atomic nuclei with two protons and two neutrons. This releases lots of energy. Helium is not a pollutant (Figure 18.6).
• This is the reaction that occurs on the sun. Although it has been a goal of some very high-tech research programs for some time, fusion has only been attained for a few seconds. These scientists contained the reaction in a magnetic field at extremely high temperatures.
• If this form of nuclear power could be achieved, it would be non-polluting and endless. But it has not been achieved yet on a commercial scale.
• Some scientists claimed to have done so in a low-tech set-up at room temperature a while ago ("cold fusion"), but they were misleading themselves and other scientists.

• A chemical element that spontaneously undergoes radioactive decay.

• These are the two isotopes in uranium ore. The normal ratio of the two in uranium ore is 99.3 % U-238 and 0.7 % U-235. This is too low a concentration of U-235 isotopes for the nuclear chain reaction to proceed on its own.
• With special purification and centrifugation procedures, the U-235 can be concentrated to 4 % of the sample. At this concentration of U-235, the fission reaction starts to accelerate rapidly on its own in a positive feedback loop.

• Radiation is the process that occurs when a radioactive isotope decays into another isotope and releases particles.
• There are three kinds of radiation particles:
• alpha particles - consist of two protons and two neutrons (a helium nucleus); this particle has the greatest mass, but it will not travel far (5-8 cm in air); little cell damage occurs due to this type of radiation. Toxic if ingested.
• beta particles - these are electrons, and they have little mass (1/1840 the mass of a proton). They travel farther than alpha particles, but they can be stopped by wood or metal.
• gamma rays - This is the most harmful type of radiation. It consists of electromagnetic radiation, similar to an x-ray. This can penetrate thick shielding and human bodies, but is stopped by lead.
• None of these are visible or can be sensed in any way by humans, unless Geiger counters are used to monitor them.

• Curies (Ci) - unit of radioactive decay = 37 billion nuclear transformations/second
• Becquerel (Bq) - unit of radioactive decay = 1 radioactive decay per second = 1 trillionth of a curie
• rad (rd) = radiation absorbed dose
• 1 Gray = 100 rads (these are both units of the absorbed dose of radiation)
• rems = relative biological effectiveness of radiation* dose in rads
• 1 sievert = 100 rems (these are both units of effective radiation dose, after accounting for the biological effectiveness or damage that is caused by different types of radiation)
• roentgen = unit of gamma radiation in coulombs/kilogram ( a coulomb is a unit of electrical charge)

• 1.5 millisieverts/year (1.0 - 2.5 millisieverts/year) total. (1 sievert = 1000 millisieverts)
• The average person in the USA will receive the following doses from each source:
• Medical X-rays: 0.7 - 0.8 millisieverts/year
• nuclear power plants/weapons tests: 0.04 millisieverts/year
• coal, oil, natural gas burning: 0.03 millisieverts/year
• See radiation dose chart in text (Figure 18.10)

• A dose of 5000 millisieverts(5 sieverts) is lethal to 50 % of people
• A dose of 1000-2000 millisieverts (1 -2 sieverts) is damaging to human health (temporary sterility in males, aborted pregnancy, vomiting, fatigue, an other problems)
• The maximum permissible dose set by the US NRC for people is 5 millisieverts per year
• Workers that mine uranium have an elevated rate of lung cancer
• It is uncertain if low levels of radioactivity can cause cancer, because it depends whether a linear or non-linear dose response curve for radiation is used. Because it is not known for certain, it is best to assume the worst case and use a linear model. This means that no matter how low the dose is, some cells may become cancerous.
• Radioactive materials can biomagnify in the food chain (Figure 18.12)

• The rapid fission reaction can lead to a rapid release of energy that is used at the core of the nuclear energy generation procedure: this release of heat and energy is what is used to heat water in the nuclear reactor.
• The heated water is used to create superheated steam, which spins a steam turbine, and this turns a generator that makes electricity.
• The intensity of the nuclear fission reaction is controlled by lowering control rods in a nuclear reactor, which stop the neutrons from continuing the chain reaction.
• This is similar in principle to a coal burning plant, except that the water is boiled using a nuclear fission reaction, not burning a fossil fuel (Figure 18.4).

• This is the location in the nuclear facility where the nuclear fission reaction is contained (Figure 18.5).
• The main components of a reactor are the core (fuel and moderator), control rods, coolant, and reactor vessel.
• The core of the reactor is enclosed in a stainless steel reactor vessel; the reactor vessel is contained within a reinforced concrete building.

• This is a nuclear reactor that consumes more fuel than it produces.
• This is the most common type of reactor in nuclear plants.

• Two major accidents have occurred, with many more minor incidents.
• Three-Mile Island accident, Harrisburg, PA, 28 Mar 1979
• Malfunctioning pumps caused a partial meltdown in the reactor core
• Releases of radioactive isotopes were allowed into the environment
• 1 millisievert was released (a low amount of radioactivity), and average exposure was 0.012 millisieverts in the entire area around the plant; some readings near the plant were as high as 12 millisieverts/hour. Thus, exposure to radiation was variable.
• There is a possibility that some people were exposed to higher levels than others and that some excess deaths from cancer may have occurred, be we cannot separate the victims from cancer cases caused by other things.
• Chernobyl, near Kiev, USSR, 26 Apr 1986
• This was the most serious nuclear accident ever. At first it was not announced by the Russians, only to be discovered by Swedish nuclear monitors 2 days later and some distance away.
• It has been suggested that the cooling system of this plant failed, which caused a complete meltdown of the graphite-core reactor. A fire broke out in the reactor core, blowing the roof off the building.
• This facility had a different design than the nuclear plants in the USA. It used a graphite core, which can lead to the problems descried above if a coolant system fails.
• More than 3 billion people in Europe and North America were exposed to some level of radiation from this event; the most significant exposures for human health occurred within 20 miles of the plant. This area has been evacuated by humans.
• 31 people died and 237 people suffered from radiation sickness
• Leukemia and other cancers may increase in the future among the people exposed to high levels within 20 miles of the plant. Already, 653 thyroid cancer cases have been described in children around the plant. It has been projected that in the future there may be as many as 16,000 deaths from cancer attributed to this event.
• Vegetation was killed or severely damaged within a 7-km radius of the plant.
• The population of animals (voles, otters, moose, waterfowl and wild boars) have increased since the accident in the evacuation zone. This increase is puzzling, because the rodents tested have shown an increase in mutation rates, yet their populations are greater than before. The increase is likely to be due to the lack of humans in the area, and the radiation is not great enough a dose to kill them immediately.

• This is how the nuclear fuels are mined, processed to become fissionable, reprocessed after use in a reactor, and finally stored or disposed of (Figure 18.8).
• Radioactive releases can occur at any point in this cycle, but are especially common at the mining, disposal, and decommissioning stages.
• Decommissioning nuclear plants after 30 years of operation (the useful lifetime) will be an expensive part of the cycle, and one that we have little experience with.

• We may run out in 100 years if all the plants that are supposed to be built are built.
• Breeder reactors can extend this time, because they make more fuel and use uranium more efficiently than burner reactors.

• There are two kinds of radioactive waste: low-level and high-level waste.
• Low-level waste is currently disposed of by burial at two remaining low level sites (in WA and SC)
• High level waste is temporarily stored in pools of water on the site where it is produced.
• There are about 29,000 tons of radioactive waste and spent fuel rods currently in temporary storage.

• Permanent storage of high-level waste produced in the USA will occur in an underground storage site at Yucca Mountain , NV.
• This site is planned, not yet functional.

• The decommissioning issue and radioactive waste disposal issue is unresolved.
• In order to achieve sizable reductions in the release of CO₂ from coal plants, nuclear power industry would have to expand tremendously their electric generation capacity and this goal would not be reached for more than 50 years. In that time, solar-electric could become economical.
• New nuclear plants are expensive because of safety concerns.
• Politically, nuclear power is very unpopular.

• It does not pollute the air or cause acid rain like fossil fuels do.
• It does not produce CO₂ or contribute to global warming.
• If breeder reactors are developed, they will extend the available fuel supply, making it inexhaustible.
• It is safer than other forms of energy for people; with the exception of the two major accidents outlined above, no one is thought to have died from this activity.

Ecology In Your Backyard

• Where is the closest nuclear power plant to your home or school?
• After reading this chapter, has your opinion about nuclear power changed?
• Would you allow a low-level radioactive waste dump to be built in your community?
• Would you allow high-level radioactive waste to be transported through your community?
• Please respond to these questions or send your thoughtful comments to:

Hardcopy Links In The Library

• Craxton, R. S. et al. 1986. Progress in laser fusion. Scientific American 255(2): 68
• Goldsmith, E. et al. 1986. Chernobyl: the end of nuclear power? The Economist 16(4/5): 138-209.
• Hatele, W. 1990. Energy from nuclear power. Scientific American 263(3):
• Lester, R. K. 1986. Rethinking nuclear power. Scientific American. 254(3): 31.

Ecolinks On The Web

• http://www.ncf.carleton.ca/~cz725/ - Frequently Asked Questions about Nuclear Power in Canada (unofficial). Mostly about the CANDU (a registered trademark) stands for "Canada Deuterium Uranium". It is a pressurized-heavy-water, natural-uranium power reactor designed first in the 1960's by a consortium of Canadian government and private industry.

• http://www-formal.stanford.edu/jmc/progress/nuclear-faq.html - Frequently asked questions about nuclear energy. A personal home page by John McCarthy, who is admittedly "...not a doomster." He is a computer scientist at Stanford University.

• http://www.cannon.net/~gonyeau/nuclear/index.htm - The Virtual Nuclear Tourist. Joseph Gonyeau's personal web page, with links to 200+ pages he has compiled about nuclear energy, nuclear accidents, and radiation safety.

• http://www.eia.doe.gov/fuelnuclear.html - The Department of Energy's website for electronic information about nuclear power and nuclear wastes. Check out the document entitled: "Spent Nuclear Fuel Discharges from U.S. Reactors 1994". This publication provides current statistical data on fuel assemblies irradiated at commercial nuclear reactors operating in the United States. This year's report provides data on the current inventories and storage capacities at these reactors. A good graphical depiction of energy use in the USA is shown here: http://www.eia.doe.gov/fueloverview.html

• http://www.nrc.gov/ - United States Nuclear Regulatory Commission. An official US Government site about nuclear power and its regulation. Go to the "watch list" link. Here the Nuclear Regulatory Commission evaluates the performance of the operating nuclear power plants in the United States and identifies those which require additional regulatory oversight because of declining performance. Once placed on the "watch list" a plant must demonstrate consistent improved performance before it is removed from the list. Also visit: U.S. Low-Level Radioactive Waste Disposal description and U.S. High-Level Radioactive Waste Disposal.

• http://www.nei.org/ - Nuclear Energy Institute (NEI) Home Page. This is the nuclear power industry-sponsored web site that lists the benefits of nuclear power, such as: "Because nuclear power plants do not burn anything, they are non-polluting and kind to the environment. Unlike coal-, gas- and oil-fired power plants, nuclear power plants do not emit carbon dioxide and other harmful greenhouse gases into the atmosphere." This is true. But what about the waste disposal issue? They also discuss that here. This is a very well made and informative site.

• Note: If any of these links are not working, please see if alternative links are available at the Ecolink Update Site.

Ecotest Online

1. How many uranium 235 atoms will be split by the neutrons arising from each collision in the nuclear chain reaction?

a. 1

b. 2

c. 3

d. 4

e. 5

2. What is the difference between nuclear fusion and nuclear fission?

a. In fusion, hydrogen atoms are split; in fission, helium atoms are fused.

b. In fusion, hydrogen atoms are fused; in fission, uranium-235 atoms are split.

c. In fusion, helium atoms are fused; in fission, uranium-235 atoms are split.

d. In fusion, uranium-235 atoms are fused; in fission, helium atoms are split.

3. Which type of radiation particle is most harmful to humans?

a. alpha

b. beta

c. gamma

d. delta

4. The radiation dose that will kill 50 % of humans exposed to it is 5000 millisieverts/year (we know this from the atomic blasts at Hiroshima and Nagasaki). What is the dose of radiation that the average person is exposed to annually from all sources (including nuclear power plants)?

a. 10,000 - 20,000 millisieverts/year

b. 1000 - 2000 millisieverts/year

c. 100 - 200 millisieverts/year

d. 10 - 20 millisieverts/year

e. 1 - 2 millisieverts/year

5. How do a coal-burning and a nuclear power plant differ?

a. The coal plant releases CO2 and no radiation, whereas the nuclear plant releases radiation and CO2.

b. The coal plant releases no radiation, but the nuclear plant does.

c. The coal plant boils water with a coal fire, the nuclear plant boils water with the heat from a nuclear fission reaction.

d. all of these are correct

6. Which of these was associated with the Chernobyl nuclear accident?

a. A fire broke out in the reactor core, causing a steam explosion that blew the roof off the building, releasing radioactivity into the environment, and killing 31 people.

b. There was a partial meltdown of the reactor core due to malfunctioning pumps.

c. 1 millisievert of radiation was released.

d. All of these are correct.

e. None of these are correct.

7. In the USA, high-level nuclear waste is currently stored in ____________________________.

a. Washington, DC

b. Pools of water at each nuclear power generating facility

c. South Carolina

d. Washington State

e. Yucca Mountain, Nevada

8. Which of the following is a disadvantage associated with nuclear power?

a. We will run out of uranium in 10 years.

b. Nuclear waste generates the precursors to acid rain.

c. Excessive CO2 is produced, which causes global warming.

d. The decommissioning of nuclear power plants and the safe disposal of nuclear waste are unresolved.

e. all of these are disadvantages.

9. Which of the following are advantages associated with nuclear power?

a. It does not pollute the air with particulates, sulfur and nitrogen compounds like fossil fuel plants.

b. It does not produce CO2 like fossil-fuel burning plants do.

c. It is safer than other sources of energy production.

d. It is less costly at present than other forms of energy that do not generate CO2.

e. All of these are correct.

10. A_________________ reactor produces more fuel than it uses.

a. nuclear fission

b. burner

c. nuclear fusion

d. breeder

e. none of these are correct

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