If we know the halving thickness, then multiply it by 10 for PF of about 1000 (1024). Radiation shielding materials are commonly categorized by their ‘halving thickness’, which is the thickness of that material required to block half of the incoming gamma rays. For example, a shield that only lets 1/1,000 (one one-thousandth) of the gamma rays through, has a protection factor of PF1000 (the modern day standard). And so on.Ī radiation shield is characterized by its total ‘protection factor’. Another layer of ‘halving thickness’ brings it down to 1/8, or PF 8. If you add another ‘halving thickness’, the material will block half of the remaining gamma rays, leaving 1/4. A halving thickness has a protection factor (PF) of 2. How do we apply all this in order to get an approximate idea about gamma radiation shielding for various materials?Ī halving thickness is the amount of material that will block half the gamma radiation passing through it. Gamma Radiation Shielding For Various Materials Permanent shelters built specifically to protect against nuclear weapon effects should have PF values much higher than PF 40. In heavy fallout areas a sizable fraction of the occupants of PF 40 shelters will receive radiation doses large enough to incapacitate or kill them later. Shelters constructed of the right materials can give a much greater protective factor than this.Īccording to FEMA TR-87, Standards for Fallout Shelters, “The minimum level of protection for public fallout shelters is PF 40”.ĬAUTION: Permanent home fallout and blast shelters described in widely available FEMA pamphlets have protection factors in line with the PF 40 minimum standard for public shelters in buildings. Or protective factor.Ī typical house will reduce the power of the radiation to one fifteenth of that outside – this is called a protective factor of 15. This brings us to radiation protection factor. See radiation halving thickness materials chart below. Two inches will cut the radiation to 25%, 3 inches to 12.5%, and so forth. So if the halving thickness of a material is 1 inch, then a 1 inch thick sheet will cut the radiation to 50%. However, the material you use matters significantly some materials reduce the intensity of radiation more than others… Radiation Halving ThicknessĮvery material has a “halving thickness.” This is the thickness required to reduce the radiation intensity by half.
Therefore, to help protect yourself from radiation you use shielding. ShieldingĪs ionizing radiation passes through matter, the intensity of the radiation is diminished. This means that the further away you are from the source of the radiation, the less radiation you’ll be exposed to. Radiation decreases with distance in accordance with the inverse square law. The less time you spend exposed to radiation the lower your dose. To protect yourself from gamma radiation resulting from a nuclear explosion, there are three things to consider: Time Nuclear Radiation Shielding – Gamma & X-ray Gamma radiation though travels at the speed of light. It is carried by the wind currents (fallout) and eventually falls to the ground and ‘decays’. It can be stopped by a single piece of paper, or an air filter (think of it as a heavy dust particle). The ‘Alpha’ particle (another type of radiation from a nuclear explosion) is also dangerous, but is hardly penetrable. In other words, Gamma and X-ray radiation are of primary concern. “Gamma or X radiation constitutes the principal casualty producing form of ionizing electromagnetic radiation associated with nuclear explosions”. the total thickness of the material used, based on radiation halving thickness valuesĭifferent types of radiation behave in different ways:Īccording to the NATO Handbook On The Medical Aspects Of NBC Defensive Operations,.properties of the shielding material (density is important).the type of radiation itself and the energy thereof.The effectiveness of the material depends on: Radiation shielding is a mass of absorbing material placed between yourself and the source of radiation in order to reduce the radiation to a level that is safer for humans.
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