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NRC Science 101 — Different Types of Radiation

Donald Cool
Senior Radiation Safety Advisor

science_101_squeakychalkIn earlier Science 101 posts, we talked about what makes up atoms, chemicals, matter and ionizing radiation. In this post, we will look at the different kinds of radiation.

There are four major types of radiation: alpha, beta, neutrons, and electromagnetic waves such as gamma rays. They differ in mass, energy and how deeply they penetrate people and objects.

The first is an alpha particle. These particles consist of two protons and two neutrons and are the heaviest type of radiation particle. Many of the naturally occurring radioactive materials in the earth, like uranium and thorium, emit alpha particles. An example most people are familiar with is the radon in our homes.

The second kind of radiation is a beta particle. It’s an electron that is not attached to an atom (see previous blog post). It has a small mass and a negative charge. Tritium, which is produced by cosmic radiation in the atmosphere and exists all around us, emits beta radiation. Carbon-14, used in carbon-dating of fossils and other artifacts, also emits beta particles. Carbon-dating simply makes use of the fact that carbon-14 is radioactive. If you measure the beta particles, it tells you how much carbon-14 is left in the fossil, which allows you to calculate how long ago the organism was alive.

The third is a neutron. This is a particle that doesn’t have any charge and is present in the nucleus of an atom. Neutrons are commonly seen when uranium atoms split, or fission, in a nuclear reactor. If it wasn’t for the neutrons, you wouldn’t be able to sustain the nuclear reaction used to generate power.

The last kind of radiation is electromagnetic radiation, like X-rays and gamma rays. They are probably the most familiar type of radiation because they are used widely in medical treatments. These rays are like sunlight, except they have more energy. Unlike the other kinds of radiation, there is no mass or charge. The amount of energy can range from very low, like in dental x-rays, to the very high levels seen in irradiators used to sterilize medical equipment.

fordoncools101As mentioned, these different kinds of radiation travel different distances and have different abilities to penetrate, depending on their mass and their energy. The figure (right) shows the differences.

Neutrons, because they don’t have any charge, don’t interact with materials very well and will go a very long way. The only way to stop them is with large quantities of water or other materials made of very light atoms.

On the other hand, an alpha particle, because it’s very heavy and has a very large charge, doesn’t go very far at all. This means an alpha particle can’t even get through a sheet of paper. An alpha particle outside your body won’t even penetrate the surface of your skin. But, if you inhale or ingest material that emits alpha particles, sensitive tissue like the lungs can be exposed. This is why high levels of radon are considered a problem in your home. The ability to stop alpha particles so easily is useful in smoke detectors, because a little smoke in the chamber is enough to stop the alpha particle and trigger the alarm.

Beta particles go a little farther than alpha particles. You could use a relatively small amount of shielding to stop them. They can get into your body but can’t go all the way through. To be useful in medical imaging, beta particles must be released by a material that is injected into the body. They can also be very useful in cancer therapy if you can put the radioactive material in a tumor.

Gamma rays and x-rays can penetrate through the body. This is why they are useful in medicine—to show whether bones are broken or where there is tooth decay, or to locate a tumor. Shielding with dense materials like concrete and lead is used to avoid exposing sensitive internal organs or the people who may be working with this type of radiation. For example, the technician who does my dental x-rays puts a lead apron over me before taking the picture. That apron stops the x-rays from getting to the rest of my body. The technician stands behind the wall, which usually has some lead in it, to protect him or herself.

Radiation is all around us, but that is not a reason to be afraid. Different types of radiation behave differently, and some forms can be very useful. For more information on radiation, please see our website.

Don Cool, who holds a Ph.D. in radiation biology, advises the NRC on radiation safety and for 30 years has been active on international radiation safety committees.

45 responses to “NRC Science 101 — Different Types of Radiation

  1. Pamela79 May 26, 2015 at 6:24 pm

    According to the National Radon Defense, radon is the second leading cause of lung cancer in the US; yet, few people know about it because it is a colorless, odorless, radioactive gas. Common indications of radon poisoning include persistent or recurring respiratory infections, cough, hoarseness, breathing difficulties. Although these symptoms do not guarantee long-term exposure to the carcinogen, they require medical attention.
    Interested can these links for more information on lung cancer:
    http://www.nationalradondefense.com/radon-information/radon-symptoms.html http://www.cancereffects.com/Lung-Cancer-%28Cancer-of-Lungs%29-Symptoms,-Screening,-Rates,-Treatment.html

  2. Ricky Ward May 6, 2014 at 6:48 am

    Hello, this article is surely informative. Whether from radioactive material or produced by devices like x-ray machines can be harmful. Radiation can kill cells in our body. Some of the cells can grow back fine but others are permanently damage and will not be able to function.

  3. Garry Morgan April 26, 2014 at 10:25 am

    The fuel pool inventory emits ionizing radiation and if uncovered will burn, thus emitting deadly levels of ionizing radiation into the air, land, water and atmosphere such as occurred at Fukushima.

    Is the NRC saying they do not know the amount in weight and radionuclide content of current radioactive material in the fuel pools which they are supposed to be regulating which is contained in spent fuel pools and in dry storage at the various nuclear power plants across the nation? Could you please explain where the current weight and radionuclide inventory of each fuel pool and dry storage may be found, link etc. Again, the key word is current inventory.

    The info document you listed is from 1992, it is appreciated but surely there is a current listing of fuel pool weight and radionuclide inventory which you track as our regulator? Help us out here please.

    • Moderator May 1, 2014 at 4:59 pm

      The NRC requires licensees that possess nuclear fuel to keep an accounting of their inventory and report to us on any changes. This information is sensitive and is not available to the public.

      Maureen Conley

      • Garry Morgan May 1, 2014 at 9:51 pm

        The NRC is hiding the fact that hundreds of thousands of pounds of deadly, highly radioactive used/spent nuclear trash, called spent nuclear fuel, is stored in defective GE Mark 1 fuel pools in unsafe containments with no overhead protection; as the song says, “Who do you think you are fool’n?”

        The public has a right to know how much dangerous, highly radioactive spent nuclear fuel is stored in fuel pools. The GE Mark 1 fuel pools are a serious health, and security threat to our nation. It is your responsibility NRC to keep the public accurately informed of the threat, regulate and offer protection as our regulator. You have failed, you appear to offer protection to the nuclear industry, not the citizens in regards to spent nuclear fuel.

        Inappropriate secrecy and deceit will not resolve the serious national problem of spent nuclear fuel. Particularly in the case of the lacking overhead containment in the GE Mark 1 nuclear facilities.

        The entire situation relating to spent nuclear fuel has been allowed to grow to a serious health and security threat.

  4. CaptD April 21, 2014 at 7:14 pm

    Attention NRC Moderators!

    If we have to wait so long to get normal comments posted then please explain why you allowed:
    Dan Williamson’s April 17, 2014 at 8:23 am (see above) comment to be posted at all, since “halitosis and warped floors.” has no place in this NRC blog…

    BTW if you delete the above comment you are welcome to delete this comment about it.

    • Moderator April 22, 2014 at 9:08 am

      The blog is checked multiple times a day so that comments are approved and posted frequently. As stated previously, we try to be liberal in our application of the comment guidelines so as to allow as much dialogue as possible, although at times we will remove direct, personal attack verbiage while still posting the remainder of the comment. We also try to limit our moving of topics to the Open Forum for the same reason.


    • stock April 22, 2014 at 12:01 pm

      It appears that those who attack any type of anti-radiation comment get free reign to use false arguments, ad hominems, and be generally rude. Since the NRC is tasked with promotion of the nuclear industry, I guess this is expected.

  5. stock April 21, 2014 at 1:07 pm

    Slightly off topic, but one I have spent a few hours trying to ferret out.

    Can Doc Cool or anyone here provide realistic radiation inventory data for spent fuel based on an average burn up rate? I am looking for not just the Ur, Pu and higher transuranics, but the fission products such as Cs, Sr, and all the usual suspects.


    • Moderator April 25, 2014 at 2:35 pm

      I was asked to respond to your question.

      The NRC does not track the isotopic inventory in each spent fuel assembly at nuclear power plants. The following is a link to a public document titled “Characteristics of Potential Repository Wastes”: http://curie.ornl.gov/system/files/documents/38/Part%201%20MOL.20100608.0018%20RW-0184R1%20Vol%201.pdf. It contains physical, isotopic, and thermal characteristics of all type of commercial spent nuclear fuel assemblies. For example, in the middle of Table 2.4.13 on Page 2.4.17, the most dominant (i.e., >1%) isotopes, in terms of curies/Metric Tons of Initial Heavy Metal (MTIHM), for a typical Pressurized Water Reactor (PWR) spent fuel assembly enriched up to 4.42%, burned up to 40,000 MWD/MTIHM, and cooled for 10 years are shown. These numbers are still valid to date. The number for each isotope should be multiplied by 0.45 MTIHM/assembly, which is a typical number for a PWR assembly, in order to obtain the isotopic inventory in a single PWR fuel assembly.

      Maureen Conley

      • stock April 25, 2014 at 2:49 pm

        thanks Maureeen, I will review the doc later. I had found some others where they list fission product, but like 22 years after the burn….would prefer to have data on the year of burn stoppage.

      • stock April 25, 2014 at 3:03 pm

        Maureen I did a review, and thank you so much, this is a great resource, and they do a simple list of the primay fission products 1 year after burn, and for various enrichments and degree of burn. Perfect for what I need to do.

        Sorry to ask another favor, but can you find a similar resource that would depict fission products and neutron production from various MOX mixes? Thanks!

      • Moderator April 28, 2014 at 5:12 pm

        We are not aware of any similar sources of radionuclide inventory data for MOX fuel. This report was prepared for the Department of Energy as part of its Yucca Mountain program to characterize materials that require geologic disposal. MOX fuel is not used in the U.S. for power production in commercial nuclear reactors.

        Maureen Conley

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