Nuclear Power & Radiation Q&A

Nuclear Power & Radiation Q&A
*provided by the NBC Universal Information Center

1. What is radiation?

Radiation is energy that travels in the form of waves or high-speed particles. It occurs naturally in sunlight and sound waves. Man-made radiation is used in x-rays, nuclear weapons, nuclear power plants and cancer treatment.

Source: NIH (National Institutes of Health): Radiation Exposure

2. What is the difference between ionizing and nonionizing radiation?



Source: NIH: MedlinePlus-Radiation Sickness

3. What happens if you are exposed to radiation?

If you are exposed to small amounts of radiation over a long time, it raises your risk of cancer. It can also cause mutations in your genes, which you could pass on to any children you have after the exposure.

A lot of radiation over a short period, such as from a radiation emergency, can cause burns or radiation sickness.

Source: NIH (National Institutes of Health): Radiation Exposure

4. What is radiation sickness?

Radiation sickness is damage to your body caused by a very large dose

Source: Mayo Clinic

5. What are other names for radiation sickness?

Radiation sickness is also called acute radiation sickness, acute radiation syndrome or radiation poisoning. Common exposures to low-dose radiation, such as X-ray or CT examinations, do not cause radiation sickness.

Source: Mayo Clinic

6. What are the differences between "chronic" exposure and "acute" exposure to radiation?

Chronic Exposure
Stochastic effects are associated with long-term, low-level (chronic) exposure to radiation. ("Stochastic" refers to the likelihood that something will happen.) Increased levels of exposure make these health effects more likely to occur, but do not influence the type or severity of the effect.

Acute exposure
Non-stochastic effects appear in cases of exposure to high levels of radiation, and become more severe as the exposure increases. Short-term, high-level exposure is referred to as 'acute' exposure. Many non-cancerous health effects of radiation are non-stochastic.  Unlike cancer, health effects from 'acute' exposure to radiation usually appear quickly. Acute health effects include burns and radiation sickness. Radiation sickness is also called 'radiation poisoning.' It can cause premature aging or even death. If the dose is fatal, death usually occurs within two months. The symptoms of radiation sickness include: nausea, weakness, hair loss, skin burns or diminished organ function.

Source: EPA: Radiation Protection

7. What are the symptoms of acute radiation exposure?

Bleeding from the nose, mouth, gums, and rectum
Bloody stool
Hair loss
Mouth ulcers
Nausea and vomiting
Open sores on the skin
Skin burns (redness, blistering)
Sloughing of skin
Ulcers in the esophagus, stomach or intestines
Vomiting blood

Source: NIH: MedlinePlus-Radiation Sickness

8. How is exposure from x-rays or gamma rays measured?

Total body exposure of 100 roentgens (or 1 Gy) causes radiation sickness.
Total body exposure of 400 roentgens (or 4 Gy) causes radiation sickness and death in half the individuals. Without medical treatment, nearly everyone who receives more than this amount of radiation will die within 30 days.

100,000 rads causes almost immediate unconsciousness and death within an hour

Source: NIH: MedlinePlus-Radiation Sickness

9. Is fallout from a nuclear bomb the same as fallout from a nuclear plant accident?

No. Due to differences in nuclear fuels and the resultant reactions that take place when a reactor accident occurs, the radioactive elements of this fallout (called isotopes) from a nuclear power plant accident are not the same as those found in fallout from the detonation of a nuclear device.

Source: US Dept of State: Radiological and Nuclear Incidents Fact Sheet

10. How can I determine the severity of exposure to radiation?

The severity of symptoms and illness (acute radiation sickness)


Source: NIH: MedlinePlus-Radiation Sickness

11. Is any amount of radiation safe?

There is no firm basis for setting a "safe" level of exposure above background for stochastic effects ....However, there do appear to be threshold exposures for the various non-stochastic effects. (Please note that the acute affects in the following table are cumulative. For example, a dose that produces damage to bone marrow will have produced changes in blood chemistry and be accompanied by nausea.)

Source: EPA: Radiation Protection

12. How can I calculate my radiation dose?

The Environmental Protection Agency provides a calculator that enables you to calculate your total yearly dose in mrem.

Source: EPA: Understanding Radiation-Calculate your Dose

13. What is the usual "rate of exposure" for the average person?

Most people receive about 3 tenths of a rem (300 mrem) every year from natural background sources of radiation (mostly radon).

Source: EPA: Radiation Protection

Who is protecting us from the dangers of radiation exposure?

State and local authorities maintain off-site emergency response plans, which are closely coordinated with the plant's on-site emergency response plan. They also conduct off-site radiological emergency preparedness exercises at each commercial nuclear power station every two years.

U.S. Nuclear Regulatory Commission (NRC) issues licenses and policies governing safe operation of nuclear reactors and the commercial use of radioactive materials. NRC also performs inspections and oversees emergency response programs for licensees.

U.S. Environmental Protection Agency (EPA) In 1989 under the Clean Air Act, EPA published standards limiting radionuclide emissions from all federal and industrial facilities. EPA also sets environmental standards for offsite radiation due to the disposal of spent nuclear fuel and high-level radioactive waste.

Department of Homeland Security (DHS), Federal Emergency Management Agency (FEMA) FEMA evaluates both the state and local off-site emergency response plans and the off-site radiological emergency preparedness exercises that are conducted at each commercial nuclear power station every two years.

U.S. Department of Energy (DOE) is responsible for the development and implementation of the disposal system for spent nuclear fuel from the nation’s nuclear power plants. This activity is totally funded by a tax paid by the users of nuclear-generated electricity.

Source: EPA: Nuclear Power Plants

What limits does EPA set on exposure to radiation?

Health physicists generally agree on limiting a person's exposure beyond background radiation to about 100 mrem per year from all sources. Exceptions are occupational, medical or accidental exposures. (Medical X-rays generally deliver less than 10 mrem).

EPA and other regulatory agencies generally limit exposures from specific source to the public to levels well under 100 mrem. This is far below the exposure levels that cause acute health effects.

Source: EPA: Radiation Protection

16. What is the difference between radiation exposure and radioactive contamination?

A person exposed to radiation is not necessarily contaminated with radioactive material. A person who has been exposed to radiation has had radioactive waves or particles penetrate the body, like having an x-ray. For a person to be contaminated, radioactive material must be on or inside of his or her body. A contaminated person is exposed to radiation released by the radioactive material on or inside the body. An uncontaminated person can be exposed by being too close to radioactive material or a contaminated person, place, or thing.

Radiation exposure occurs when a person is near a radiation source. Persons exposed to a radiation source do not become radioactive. For example, an x-ray machine is a source of radiation exposure. However, you do not become radioactive when you have an x-ray taken.

Radioactive Contamination results when loose particles of radioactive material settle on surfaces, skin, or clothing. Internal contamination may result if these loose particles are inhaled, ingested, or lodged in an open wound. Contaminated people are radioactive and should be decontaminated as quickly as possible. However, the level of radioactive contamination is unlikely to cause a health risk to another individual.

Source: NY Department of Health: Radiological Terrorism Rapid Response Card and CDC: Radiation Emergencies

17. What are the different routes, or pathways, by which people can be exposed...and what are the effects of each?

The various methods of exposure to radiation are Inhalation, Ingestion, and Direct (External Exposure)

Source: EPA: Radiation Protection-Exposure Pathways

Inhalation: what are the causes and effects?
Exposure by the inhalation pathway occurs when people breathe radioactive materials into the lungs.

The chief concerns are radioactively contaminated dust, smoke, or gaseous radionuclides such as radon.

What happens to inhaled radioactive materials?
Radioactive particles can lodge in the lungs and remain for a long time. As long as it remains and continues to decay, the exposure continues. For radionuclides that decay slowly, the exposure continues over a very long time.

Inhalation is of most concern for radionuclides that are alpha or beta particle emitters. Alpha and beta particles can transfer large amounts of energy to surrounding tissue, damaging DNA or other cellular material. This damage can eventually lead to cancer or other diseases and mutations.

Source: EPA: Radiation Protection-Exposure Pathways-Inhalation

Ingestion: what are the causes and effects?
Exposure by the ingestion pathway occurs when someone swallows radioactive materials.

Alpha and beta emitting radionuclides are of most concern for ingested radioactive materials. They release large amounts of energy directly to tissue, causing DNA and other cell damage.

What happens to ingested radioactive materials?
Ingested radionuclides can expose the entire digestive system.
Some radionuclides can also be absorbed and expose the kidneys and other organs, as well as the bones. Radionuclides that are eliminated by the body fairly quickly are of limited concern. These radionuclides have a short biological half-life.

Source: EPA: Radiation Protection-Exposure Pathways-Ingestion

Direct (External Exposure): what are the causes and effects?

The third pathway of concern is direct or external exposure from radioactive material. The concern about exposure to different kinds of radiation varies:

Limited concern about alpha particles. They cannot penetrate the outer layer of skin, but if you have any open wounds you may be at risk.
Greater concern about beta particles. They can burn the skin in some cases, or damage eyes.

Greatest concern is about gamma radiation. Different radionuclides emit gamma rays of different strength, but gamma rays can travel long distances and penetrate entirely through the body.

Gamma rays can be slowed by dense material (shielding), such as lead, and can be stopped if the material is thick enough. Examples of shielding are containers; protective clothing, such as a lead apron; and soil covering buried radioactive materials.

Source: EPA: Radiation Protection-Exposure Pathways-Direct (External Exposure)

18. How do we know radiation causes cancer?

...we have learned through observation. When people first began working with radioactive materials ....scientists began to notice patterns in the illnesses. People working with radioactive materials and x-rays developed particular types of uncommon medical conditions. For example, scientists recognized as early at 1910 that radiation caused skin cancer. Scientists began to keep track of the health effects, and soon set up careful scientific studies of groups of people who had been exposed.

Among the best-known long-term studies are those of Japanese atomic bomb blast survivors, other populations exposed to nuclear testing fallout (for example, natives of the Marshall Islands), and uranium miners.

Source: EPA: Radiation Protection

19. What are the risks of other long-term health effects [other than cancer]?

Other than cancer, the most prominent long-term health effects are:
Teratogenic mutations

Teratogenic mutations result from the exposure of fetuses (unborn children) to radiation. They can include smaller head or brain size, poorly formed eyes, abnormally slow growth, and mental retardation. Studies indicate that fetuses are most sensitive between about eight to fifteen weeks after conception. They remain somewhat less sensitive between six and twenty-five weeks old.

The relationship between dose and mental retardation is not known exactly. However, scientists estimate that if 1,000 fetuses that were between eight and fifteen weeks old were exposed to one rem, four fetuses would become mentally retarded. If the fetuses were between sixteen and twenty-five weeks old, it is estimated that one of them would be mentally retarded.

Genetic mutations
Genetic effects are those that can be passed from parent to child. Health physicists estimate that about fifty severe hereditary effects will occur in a group of one million live-born children whose parents were both exposed to one rem. About one hundred twenty severe hereditary effects would occur in all descendants.

In comparison, all other causes of genetic effects result in as many as 100,000 severe hereditary effects in one million live-born children. These genetic effects include those that occur spontaneously ("just happen") as well as those that have non-radioactive causes.

Source: EPA: Radiation Protection

20. Are children more sensitive to radiation than adults?

Yes, because children are growing more rapidly, there are more cells dividing and a greater opportunity for radiation to disrupt the process. EPA's radiation protection standards take into account the differences in the sensitivity due to age and gender.

Fetuses are also highly sensitive to radiation. The resulting effects depend on which systems are developing at the time of exposure.

Source: EPA: Radiation Protection

21. What is the cancer risk from radiation? How does it compare to the risk of cancer from other sources?

Each radionuclide represents a somewhat different health risk. However, health physicists currently estimate that overall, if each person in a group of 10,000 people exposed to 1 rem of ionizing radiation, in small doses over a life time, we would expect 5 or 6 more people to die of cancer than would otherwise.

In this group of 10,000 people, we can expect about 2,000 to die of cancer from all non-radiation causes. The accumulated exposure to 1 rem of radiation, would increase that number to about 2005 or 2006.

Source: EPA: Radiation Protection

22. Can radiation exposure before birth can increase a person's risk of getting cancer later in life?

Unborn babies are especially sensitive to the cancer-causing effects of radiation. However, the increased risks depend on the amount of radiation to which the baby was exposed and the amount of time that it was exposed. For example, if the radiation dose to the fetus was roughly equivalent to 500 chest x-rays at one time, the increase in lifetime cancer risk would be less than 2% (above the normal lifetime cancer risk of 40 to 50%).

Source: CDC: Radiation and Pregnancy

23. What additional health risks are there for a fetus exposed to radiation?

Health effects other than cancer from radiation exposure are not likely when the dose to the fetus is very low.

Most researchers agree that babies who receive a small dose of radiation (equal to 500 chest x-rays or less) at any time during pregnancy do not have an increased risk for birth defects.

The only increased risk to these babies is a slightly higher chance of having cancer later in life (less than 2% higher than the normal expected cancer risk of 40 to 50%).

For health risks during specific stages of pregnancy (weeks 1-2, 2-15,
16-25, 25+) see CDC outline.

Source: CDC: Radiation and Pregnancy

24. Why do nuclear power plants work?


Source: FEMA: Nuclear Power Plant Emergency

25. How much of our power is generated by nuclear plants in the U.S.?

Nuclear power accounted for about 20% of the total net electricity generated in the United States in 2008, about as much as the electricity used in California, Texas, and New York, the three States with the most people.

Source: EIA Energy Kids-Uranium (Nuclear)

26. How many nuclear power plants are there in the United States?

In 2008, there were 66 nuclear power plants (composed of 104 licensed nuclear reactors) throughout the United States. Most of the reactors are east of the Mississippi. Worldwide, over 400 reactors provide 17% of the world’s electricity.

Source: EIA Energy Kids-Uranium (Nuclear) and EPA: Nuclear Power Plants

27. How many Americans live near power plants?

Nuclear power plants operate in most states in the country. Nearly 3 million Americans live within 10 miles of an operating nuclear power plant.

Source: FEMA: Nuclear Power Plant Emergency

28. How can I found out if there are any plants near me?

The U.S. Nuclear Regulatory Committee website provides a map showing locations of operating nuclear reactors.

Source: NRC Facility Info Finder

29. What danger do nuclear power plants pose?


Source: FEMA: Nuclear Power Plant Emergency

30. What happened in Japan?

The Washington Post has an excellent feature showing how the emergency in Japan unfolded, along with a timeline and graphics explaining normal operations of the reactors and what damage has occurred in each.

Source: Washington Post: Japans Nuclear Emergency

31. Who will help me if there is a nuclear power accident at a plant near me?

Local and state governments, federal agencies, and the electric utilities have emergency response plans in the event of a nuclear power plant incident.

Source: FEMA: Nuclear Power Plant Emergency

32. What area around the plant is most at risk for being affected?

Emergency response planners define two “emergency planning zones.”
One zone covers an area within a 10-mile radius of the plant, where it is possible that people could be harmed by direct radiation exposure. This is considered to be the plume exposure pathway, or the path for airborne radioactive material in the plume. The plume would commonly contain radioactive noble gases and might also contain radioiodines and radioactive particulate materials. Many of these materials emit gamma radiation and can expose people nearby as the plume passes.

The second zone covers a broader area, usually up to a 50-mile radius from the plant, where radioactive materials could contaminate water supplies, food crops, and livestock. This is considered to be the ingestion exposure pathway and has been defined as the most likely area where radioactive material would settle out from the plume and fall to earth.

Source: FEMA: Nuclear Power Plant Emergency and FEMA Training: Intro to Nuclear Reactors

33. Which nuclear plants are in seismic zones?

The Washington Post has provided a map of the world showing the locations of these reactors and the likelihood of seismic activity.

Source: Washington Post: Nuclear Power Plants in Seismic Zones

34. How can I minimize my exposure just before an accident occurs?

Put distance between yourself and the source of the radiation, either by evacuation or remaining indoors.

Shield yourself with heavy, dense material (such as concrete). It should be between you and the source of the radiation.

Most radioactivity loses its strength fairly quickly.

Source: FEMA: Before a Nuclear Power Plant Emergency

35. What should I do during a nuclear power emergency?

• Keep a battery-powered radio with you at all times and listen to the radio for specific instructions.

• If you are told to evacuate, keep car windows and vents closed; use re-circulating air.

• If you are advised to remain indoors:

• Close and lock doors and windows.

• Turn off the air conditioner, ventilation fans, furnace, and other air intakes.

• Go to a basement or other underground area, if possible.

• Do not use the telephone unless absolutely necessary.

• If you expect you have been exposed to nuclear radiation:

• Change clothes and shoes.

• Put exposed clothing in a plastic bag.

• Seal the bag and place it out of the way.

• Take a thorough shower.

• Keep food in covered containers or in the refrigerator. Food not previously covered should be washed before being put in to containers.

Source: FEMA: During a Nuclear Power Emergency

36. What takes place during a nuclear accident?

When a reactor is operating, the fuel gets very hot. The fuel is immersed in water, and the heat produces steam, which is used to drive a turbine to produce electricity. The water also keeps the fuel from overheating, and is continuously circulated through the reactor core to carry away excess heat. Even if the reactor shuts down, the fuel will remain hot for a long time, so must still be cooled.

Fuel Damage
If the pumps that circulate the cooling water are not operating, the water in the reactor vessel will heat up and evaporate, and the fuel can become uncovered inside the reactor vessel.

Radioactivity Release Pathways
The radioactive material released from damaged fuel into the reactor vessel can get into the primary containment. To protect the reactor vessel and attached piping from rupturing due to high pressure, relief valves automatically open to discharge steam—and the radioactive material along with it—into the primary containment structure. Workers may also manually open the relief valves to prevent high pressure in the reactor vessel from impeding the flow of makeup water, such as the sea water

Partial Meltdown
If the fuel is uncovered by water and exposed for a period of hours, it will start to melt. This makes cooling more difficult as the melted fuel clogs the spaces between the fuel rods. The melted fuel will start to collect on the bottom of the steel reactor vessel (sometimes called the lower head). The molten fuel will begin to burn its way through the reactor vessel.

Complete Meltdown
If the water level is low enough, essentially all the fuel in the core can melt and will fall to the bottom of the reactor vessel. It will be a matter of hours before the fuel melts through the steel reactor vessel and onto the concrete floor of the primary containment. The containment is designed to contain the melted fuel and its radioactive emissions, but there are ways in which the primary containment can fail in the event of a meltdown; this has been a concern with the Mark I containment, which the affected Japanese reactors use. The emissions will generate increasing pressure over a period of days and weeks, which can lead to collapse of the primary containment if it is not relieved.

Source: Union of Concerned Scientists: Nuclear Accident ABCs