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    Quick Primer on Contamination Control Measures

    by Dogs_In_A_Pile

    Thursday, March 17, 2011, 10:02 PM

This short primer was provided by ChrisMartenson.com member Dogs_In_A_Pile in the comments to our ongoing post covering the developments in Japan. We are featuring it here given the many questions readers are asking on this topic and the importance at this time of clearly understanding risks we do (and don’t) face. It is based on his expertise developed during his military service on nuclear-powered submarines. 

Radiation and contamination are used interchangeably and they are not the same thing, nor are treatment methods.  You can receive radiation exposure and not need any contamination control, and you can become contaminated and not need treatment for exposure to radiation.  NOTE – I am not saying that if you get contaminated you won’t receive any radiation exposure, because you will.  What I am saying is that you may be contaminated with such a low level of contaminated particles that there will be no need for radiation exposure treatments.  The difference is both subtle and vast. 

Here is a quick primer on contamination control measures.

  1. Know what the radionuclide is – Is it particulate or is it a gas?  There are some radionuclides that exist as a radioactive gas that decay to a radioactive particulate.  Just because a gas dissipates, it doesn’t mean you are safe if you are exposed to an area of particulate that may be stirred up and ingested.
  2. Absent knowledge of the specific radionuclide, don’t expose yourself to it if you don’t have to.  This may seem like stating the obvious, but it’s not.  Exposing yourself to contamination to treat an injured person or remove an injured person is probably the right call.  Exposing yourself to contamination to reach an injured pet is probably not the right call.  That said, in violation of my own advice, I wouldn’t hesitate to go get my 12-year-old golden retriever.
  3. If you do have to expose yourself to radioactive contamination, there are two things to differentiate:
    • General radiation level.  You can minimize exposure to radiation by utilizing the following, preferably in combination:
      • Time:  Minimize the time exposed.  Do what you need to do as rapidly as it can be done safely and effectively.
      • Distance:  Maximize the distance between the radiation source and yourself.  Exposure falls off as an inverse squared function.  A 10 millrem/hr source measured at 2 feet will drop to 2.5 mr/hr at 4 feet.  (http://www.wright.edu/admin/ehs/documents/EquationsforRadiationSafety.pdf)
      • Shielding:  Utilize whatever you can to put between you and the source.  Concrete, lead, steel, poly sheeting, or poly blocks are all effective to varying degrees against the different types of radiation you may encounter.
    • Contamination.  Contamination is the “dirt;” radiation is the energy coming off the dirt.
      • Breathing protection:  It may be suspended as particulates in the air if it is fine enough.  A simple mask that provides any degree of mechanical filtration is better than nothing.  Sealed forced air is best.  If you can see suspended motes, really think twice about entering the area without breathing protection.  You will exhale about 75-90% of inhaled particulate matter.  You run into trouble when the specific radionuclide is preferentially concentrated in the body, like I-131 is.
      • Protection against skin contamination:  Long-sleeved shirts, long pants, shoes, socks, a hood, gloves, etc.  Try to cover all exposed skin to the maximum extent possible.  Assume that the clothing is contaminated, and dispose of it after you have left the area that is potentially contaminated.  If you can, construct a staging area at the boundary of the contaminated area so you can strip down and step into the clean area and leave your contaminated clothing behind.  Important safety tip – make sure you are wearing undergarments.  (Unless you are either immodest or a show-off Surprised).
      • If you do have skin contamination or suspect you have skin contamination, there are several methods of removing it safely:
        • You can use a tape press.  Duct tape or packing tape will work.  Press the sticky side on to the affected area with enough force to contact the material, but light enough to not risk grinding it into the skin.  Discard the used tape, as it will be contaminated.
        • Wash and rinse with soap and water.  Use lukewarm water.  Hot water opens the pores and risk trapping the particulate inside.  Cold water closes the pores and will trap the particles.  A mild abrasive is okay to use if you don’t grind it into your skin.  If you suspect the particulate to be trapped in an abrasion or a cut, scrub vigorously, as it is already stuck in your skin.   A little bleeding from a mild abrasion (like a skinned elbow or knee) isn’t bad since the blood flow will in some cases help push the particulate away from the skin, where it can be rinsed away.  The risk is pushing it down into a large enough blood vessel or capillary that it could get picked up by your circulatory system, but the risk is low if you are careful.  Collect the rinse water, since it will be contaminated, and keep it separated.
        • If you have an open wound with serious bleeding and you suspect there is contamination present, you must treat the wound first.  Sealing some amount of contamination in a wound to stabilize severe bleeding for further treatment is far better than bleeding to death.  Collect and dispose of the medical waste assuming that it is contaminated.
        • Skin contamination in and of itself is not a big deal if the associated dose rate is relatively low and you remove it as quickly as possible.

Regarding the unfolding situation in Japan,, it is important to understand the real nature of the risk associated with a release of a radioactive plume from steam venting, a fire or some combination of both.  Understand the radionuclide composition of the plume and the type of radiation associated with each.  Alpha emitters, beta emitters, gamma emitters, and neutron emitters are all handled (figuratively) differently, and each poses different levels of risk. 

  • Alpha:  External alpha contamination isn’t that big of a deal, since the particles won’t penetrate dead skin.  Internal alpha contamination is a big risk – an alpha particle is a helium nucleus (4He2) and it is big and heavy.  Whatever it hits in a cell’s nucleus, it wrecks. 
  • Beta:  External beta contamination is not much of a risk (in reasonable quantities), since betas are easily shielded by clothing.  Internal beta contamination presents varying degrees of risk depending on the radionuclide, which defines half-life and energy level of the beta decay.  Some radionuclides decay rapidly and may pose a very minimal risk.  Longer half-lives increase the risk.  Some radionuclides are preferentially concentrated and the risk increases.  Knowledge of the isotope is key.
  • Gamma:  High energy and penetrating.  There is not much you can do except utilize the concept of Time/Distance/Shielding.  You want to minimize your exposure to a gamma emitter, regardless of whether it is from contamination or a fixed source.
  • Neutron:  High energy, very penetrating, very damaging.  You really don’t want to be exposed to neutron radiation, regardless of whether it is contamination or a radiation source.

 I hope this helps.  I’m sure I forgot something, so if there are any questions don’t hesitate to ask by commenting below.

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