Radiation FAQ

What is radiation?

It’s an energetic particle or packet on energy that is released from the nucleus of an atom in order so that atom can become more stable. There can several forms of this radiation Alpha particle, beta particles, gamma rays, etc (see definitions)

Where is radiation?

EVERYWHERE… We get radiation from just about everywhere you can think of. There is radiation from outer space, dirt, rocks, water, air, food you eat, consumer products, and even your own body has radioactive elements in it.

What is radiation therapy?

Radiation can come from special machines or from radioactive substances. When radiation is used at high doses (many times those used for x-ray exams); it can be used to treat cancer and other illnesses. Special equipment is used to aim the radiation at tumors or areas of the body where there is disease. The radiation causes more of the cancer cells to die than the normal cells because cancer cells are more radiosensitive than normal cells. The use of high energy rays or particles to treat disease is called radiation therapy. Sometimes it's called radiotherapy, x-ray therapy, cobalt therapy, electron beam therapy, or irradiation.

How much extra radiation do we receive from flying?

Radiation exposure, from natural cosmic sources, increases with altitude, with peak dose at about 45,000 feet. Dose from cosmic radiation also varies with latitude; it is lowest near the equator and highest near the poles. Therefore, the extra radiation dose from flying depends on (a) the particular route, (b) the duration of the flight, and (c) the fraction of the trip spent below the flight's maximum altitude. A good reference flight would be from California to New York and back, is an extra dose of about 0.003 rem (3 milli-rems). Whole-body dose from all natural radiation combined---which is about 200-350 milli-rems per year of whole-body exposure in the USA.

How much extra radiation dose do I get from a smoke detector?

Very, very little. If you have the much more common "ionization" type, there is a radionuclide in it -- usually 1 micro-curie of Americium-241. A micro-curie is one-millionth of one curie. Americium-241 emits alpha particles, which are kept inside the case. It also emits some gamma radiation which can penetrate the case. The dose rate at 3 feet away from the smoke detector was well lost within the background radiation of the area and could not tell if it was there or not. If you have a photoelectric smoke detector, there is no radioactive substance in it. Remember the benefit received from the smoke detector, would it be worth its safety precaution even if there were more radiation coming out of the smoke detector.

What methods are used to detect radiation?

Because ionizing radiation does just that, ionizes, it is easy to see that using a medium like a gas, and a voltage, you can measure the amount of charge liberated in that medium. That is the most common method of measuring radiation. The infamous Geiger Counter is in reality a small volume of gas, with a voltage applied across it. As the radiation enters the gas, it causes electrons to be formed, which are collected and measured to determine the amount of initial radiation present. The processes used with radiation detection is called scintillation. Scintillation is the giving off of visible light after interaction with radiation. The light can be collected then and used as another measure of the radiation intensity and energy. But, there are many different ways of measuring radiation, using semiconductors, liquids, superheated bubbles, crystals and plastics.

How much electricity do we get from nuclear power?

In the U.S. we get about 20% of all the electricity from nuclear power. Other countries vary but can go as high as 75% for France.

How much radiation do I get from nuclear power plants?

Very little. From all sources, a person in the U.S. receives an average exposure to radiation of about 360 millirems per year. Most of this comes from the natural radiation in soil, water, rocks, building materials, and food. For example, potassium is a common, naturally occurring radioactive element found in many foods. Radiation exposure from all commercial nuclear energy power plants has averaged 0.01 millirem per person annually. Those who live near a nuclear power plant receive less than 5 millirems per year. The federal limit for people who work in nuclear power plants is a maximum of 5,000 millirems per year. Utilities themselves normally have set their own limits even lower than that.

How Does a Reactor Work?

Neutrons striking uranium atoms cause these atoms to fission. In the process of fissioning they produce heat in a chain reaction in a nuclear reactor. This heat is used to turn water into steam and then the steam turns turbines, which turn generators that produce electricity.

Most commercial nuclear reactors use water to remove the heat created by the fission process. We call these light water reactors. The greater the nuclear reaction, the more heat is produced. The increasing heat turns more water to steam, which slows down the nuclear reaction. So the water works like a brake. It prevents the nuclear reaction from running out of control. If the water is cut off, the fission process stops.

Water flowing in a closed, pressurized loop removes heat in a pressurized water reactor. The heat passes to a second water loop through a heat exchanger. The second loop stays at a lower pressure, allowing the water to boil and create steam. The steam turns the turbine generator and produces electricity. Afterward, the steam is condensed into water and returned to the heat exchanger.

In a boiling water reactor, water boils inside the reactor itself. Steam from the water goes directly to the turbine generator to produce electricity. Here, too, steam is condensed and reused.

Can a nuclear power plant explode like a bomb?

No. It's impossible for a nuclear plant to explode like an atomic bomb because of the low concentration of U-235—fissionable uranium—in the fuel. There is only about 3-5 percent of U-235—the type of uranium whose atoms can be split to release large amounts of heat—in commercial nuclear fuel. In contrast, there is 20-90 percent of U-235 in a nuclear bomb.

Is it safe to live near a nuclear power plant?

Yes. That's because the companies that run nuclear power plants—and the Nuclear Regulatory Commission, which regulates the use of radioactive materials—make sure the plants operate safely.

To protect the public from a release of radiation, the plant design takes advantage of natural processes and incorporates backup safety systems—safety in depth. Because plant designers assume that equipment will fail and that operators will make errors, nuclear power plants have multiple backup systems to cope with equipment failure and human error. The systems work automatically and immediately. The plants also use a series of physical barriers to prevent the escape of radioactive material.

How many power plants are there in the U.S. and in the world?

In 1997, there were 437 nuclear power plants—105 of them in the U.S.—operating around the world. But since then several plants in the U.S. have closed down and the number is around 96. No new power plants have been built in the U.S. for many years (since about 1986), but many plants are being built in other countries.

What are the emissions from a nuclear power plant vs. a coal plant?

Water Vapor is emitted from the cooling towers at a power plant. Nuclear energy supplies us with enough emission-free electricity each year to serve 60 million homes. Fossil-fueled plants emit carbon dioxide (the primary greenhouse gas), nitrogen oxide (the source of our ozone problems), and sulfur dioxide (the precursor to acid rain) and yes even radioactive particulates that were contained in the coal.

Here are the annual "savings" to our atmosphere from U.S. nuclear power plants:

147 million metric tons of carbon

2.5 million tons of nitrogen oxide

5.3 million tons of sulfur dioxide

What happened at Three Mile Island?

Short Answer

On March 28, 1979 near Harrisburg, Pa., the worst accident in the history of nuclear power in the United States occurred at the Three Mile Island unit 2 reactor. The accident was caused by a combination of equipment failure and an inability of plant operators to properly assess and understand the condition of the reactor. Equipment failure caused a gradual loss of cooling water to the reactor's heat-producing core, which resulted in the partial melting of the fuel rod cladding and the uranium fuel, and the release of a small amount of radioactive material. There were no injuries or deaths attributed to the accident. Experts officially stated that the amount of radiation released into the atmosphere was too small to impair the health of the population in the vicinity of the plant. In response to the accident, the Institute of Nuclear Power Operations was established to promote excellence in operator training, plant management and operation. Also the industry formed a center to study the accident.

Long Answer

The accident started at approximately 4:00AM, March 28, 1979 when the main feedwater pump stops due to a resin buildup. The temperature and pressure of the reactor increased as a result of the lack of coolant flow. A safety relief valve opened as the pressure raised and the reactor automatically shut down. The reactor core began losing pressure as steam escaped through the open safety relief valve. At this point, the incident should be a mild failure unworthy of news attention. However, the safety relief valve failed to shut properly, so the pressure continued to drop and too much cooling water was lost. This excessive loss of coolant caused the temperature of the reactor core to increase above its normal operating temperatures.

The reactor operators improperly assessed the problem at this point-- they incorrectly assumed that the safety valve had closed. The lost coolant was not replaced and the water eventually turned into steam as the pressure continued to drop. The operators still erroneously thought that the reactor was overpressurized so they shut down the emergency and standby feedwater pumps.

The pressure continued to drop which caused large steam bubbles to form and impede the effectiveness of the remaining coolant. The temperatures in the reactor core eventually rose above the melting point of the uranium fuel and fuel cladding. All the fuel was damaged or destroyed and approximately 700,000 gallons of radioactive cooling water were spilled onto the floor of the reactor building. To control the excessive quantity of water that spilled out of the reactor, 400,000 gallons of radioactive water were released into the Susquehanna River. In addition, some of the radioactive gasses that flowed through the open valve were emitted into the atmosphere and some radioactive materials managed to pass through the four-foot thick walls of the plant. The estimates of the actual levels of radiation leaked vary, but the state insists that they were too low to adversely affect the health of people that lived in the vicinity of the reactor. To ensure the safety of the people most susceptible to radiation, on March 30, 1979 the governor did recommend the evacuation of all pregnant women and preschool aged children. Schools were closed in the area and the governor ordered people to stay indoors. The decision to evacuate was controversial as many experts insisted that there was no threat to the public health and such evacuation orders would cause public panic.

What happened at Chernobyl?

As is usually the case in any accident, a number of things combined to cause this one at Chernobyl. Unlike power reactors operating in the U.S. and other nations, the Chernobyl RBMK reactor (which is a graphite rather than a light water system) has a built-in instability that occurs at low power, which is how the reactor was operating at the time of the accident. If some of the cooling water in this reactor converts to steam, the RBMK increases in power. This in turn causes more steam to form, which causes another increase in power. The power increase feature of the RBMK caused a rupture in the cooling system and a large steam explosion occurred. This caused the cooling system to fail and the outer covering (or cladding) of the fuel elements to increase in temperature. The cladding was hot enough to react with the steam, causing hydrogen to form. The hydrogen then caused a second explosion. The release of this energy set the graphite core on fire.

A second factor in the Chernobyl accident involved a safety experiment being conducted. It required that the reactor be run in a very unusual manner. Because of a series of operational problems, the operators found themselves running the reactor far outside its safety limits. In their efforts to finish the experiment anyway, the operators --in spite of running the reactor under unfamiliar conditions-- turned off seven of the safety systems in the reactor and its control systems. Any one of these seven automatic controls could have prevented the accident had it been on.

How are U.S. reactors different from the reactor at Chernobyl?

There are many differences, which include not only physical differences but philosophical ones as well. The key differences have already been noted in the previous answer. These physical differences were made worse by the totally different attitude toward safety between the two countries. The U.S. is cautious to the extreme by comparison. It took seven years to restart Three Mile Island Unit 1 following the accident in the Three Mile Island Unit 2 reactor in 1979, the results of, which were much less severe than in the Soviet Union. The Soviets restarted their other reactors (of the identical design) at Chernobyl in a matter of a few weeks.

How much nuclear waste is there?

Since the first commercial nuclear power plant began producing electricity in 1957, the total amount of accumulated spent fuel (classified as high-level waste) is 9000 tons. For comparison, the Environmental Protection Agency reported that in 1982, 46 million tons of poisonous waste (that is, not nuclear) were disposed of. In comparison the amount of nuclear waste is very small.

Nuclear wastes are, for the same power output, some 3.5 million times smaller in volume than the wastes from coal plants. High-level nuclear wastes can be disposed of by diluting them with twice their own volume of neutral materials as they are changed into glass or ceramic form. The reprocessed waste volume form a 1,000-megawatt nuclear power plant would fit easily under a typical dining room table. A coal plant of the same capacity (1,000 megawatts) produces some 10 tons of waste per minute

After changing it to stable form, the volume of all nuclear waste produced until the year 2000 (including low-level waste from the entire U.S nuclear power industry) would fit into a cube 250 feet on each side. The high-level waste portion would fit into a cube 50 feet on each side within the 250-foot block.

What is food irradiation?

This is the use of high levels of radiation exposure to kill all of the bacteria, fungus, and insect larva and eggs that cause food to get eaten or spoil and go bad. This would prevent the food poisonings that come from improperly handled or processed meat, seafood or chicken. Tens of thousands of people get sick each year and several hundred die due to food poisoning. This would also prevent the losses of food being transported to a far designation. Without the bacteria to make the food go bad the shelf life of truck life of foods, especially fruits and vegetables are greatly increased.

Does irradiation adversely affect the nutritional value of food?

Extensive research has shown that macronutrients, such as protein, carbohydrates, and fat, are relatively stable to radiation doses of up to 10 kilogray. Micronutrients, especially vitamins, may be sensitive to any food processing method, including irradiation. Different types of vitamins have varied sensitivity to irradiation and to some other food processing methods. For example, vitamins C and B-l (thiamine) are sensitive to irradiation as well as to heat processing. The Joint Expert Committee of the Food and Agriculture Organization (FAO), World Health Organization (WHO), and International Atomic Energy Agency (IAEA), which examined these and other issues, stated in its conclusions in 1980 that irradiation does not induce special nutritional problems in food.

The change in nutritional value caused by irradiation depends on a number of factors. They include the radiation dose to which the food has been exposed, the type of food, packaging, and processing conditions, such as temperature during irradiation and storage time. Most of these factors are also true for other food preservation technologies. For example, measurement of vitamin C content in three varieties of apples kept in cold storage for up to 1 year showed decreases of between 40% to 70%, depending on the variety of apple. Yet it has never been suggested that cold storage is an inappropriate technology for apples and should not be used.

Just as vitamins vary in their sensitivity to heat, so do they vary in their sensitivity to radiation. This sensitivity depends upon the conditions under which food is irradiated. Vitamins A,E,C,K and B-1 (thiamine) in foods are relatively sensitive to radiation, while some other B vitamins such as riboflavin, niacin, and vitamin D are much more stable. Losses are generally less if oxygen is excluded and if the temperature during irradiation is low. Under optimal conditions, vitamin losses in foods irradiated at doses up to 1 kilogray are considered to be insignificant. At higher doses the effect of irradiation will depend on the specific vitamin, temperature, dose, food, and packaging. All of the food that the astronauts eat have been irradiated.

Does it make the food radioactive?

NO! The food that is irradiated does not become radioactive. Its just like using your microwave oven the food does not become radioactive.

What are some other uses for radioactive material other than nuclear power?

LOTS !!!

Well there is food irradiation (see earlier question). There is sterilization of medical and dental equipment, radiation is used to sterilize baby powder, bandages, contact lens solution and many cosmetics, including false eyelashes and mascara. Industry uses it to measure density and level of materials in pipes and tanks as well as a thickness indicator.

They also use radiation to check the integrity of welds on bridges and other large structures. It is used to treat cancer (see earlier question). Not to mention all the medical applications; x-rays, cat scans, Pet scans, flouroscopies. About 50-66% of all people who enter a hospital has some sort of procedure that involves radiation. Smoke detectors (see earlier question) save thousands of lives each year. It is used to identify metals, enhance rubber tires, make frying pans ect.