Pat, Jim clearly understands doses of ionizing radiation better than I do. Perhaps this will help until he answers. Neither the gray or the sievert is a "space dose" like the watts per square meter used for radio waves. The units are joules per kilogram and represent energy absorption in a sensor that simulates a human. The difference is that the gray measures the energy actually absorbed. The sievert is an "equivalent dose" and uses quality factors to approximate the damage done by the absorbed dose of different types of radiation. Beta particles, x and gamma rays have QF of 1. Alpha particles (internal only) have QF of 20. Random energy neutrons and protons have QF of 10, (or neutrons can have differing QFs for different energies, if you have the data)
--- On Tue, 3/15/11, Pat Naughtin <[email protected]> wrote: From: Pat Naughtin <[email protected]> Subject: [USMA:50030] Re: Putting radiation levels in perspective To: "U.S. Metric Association" <[email protected]> Cc: "U.S. Metric Association" <[email protected]> Date: Tuesday, March 15, 2011, 3:21 PM Dear Jim, At http://ireport.cnn.com/docs/DOC-572031?ref=feeds%2Flatest they seem to measure "Rate of space dose" in "(nGy/h)". Could you explain the quantity, "Rate of space dose", and the unit, "(nGy/h)", to me please? Thanks, Pat Naughtin Geelong, Australia On 2011/03/16, at 02:54 , James R. Frysinger wrote: > USMA Colleagues, > > I sent this out to my family and friends last night. > > Jim > > Folks, > > The reporters are going crazy and hyping the radiation from the failing > nuclear power plants in Japan. Meanwhile, coverage of the shortages in food, > water, fuel, shelter, and electricity and coverage of the tremendous loss of > life are being under-reported by comparison. That's because the reporters do > not understand radioactivity, nuclear reactors, radiation limits, or > radiation calculations. It's not that hard to do and I'll show you here how > to do it. > > There are a lot of adjectives being used in the media. Hard data is hard to > find but I heard one value stated today on TV and this site provides current > hard data. > > Actual radiation levels in Japan: > http://ireport.cnn.com/docs/DOC-572031?ref=feeds%2Flatest > > For your reference, the limits specified in the U.S. are listed at the bottom > of this email There are two groups presented here -- essentially for power > plant workers and for the folks on the streets. The latter is the one > officials are concerned about, but note that nuclear power plant workers are > deemed safe at about 50 times those levels! > > Now you can do your own calculations. Note that 1 mSv = 1 000 µSv = 1 000 000 > nSv. So, assume a conservative QF of 20 and an exposure limit of 0.02 mSv/h = > 20 µSv/h. That limits you to 1 µGy/h since 20 × 1 µGy/h = 20 µSv/h. And 1 > µGy/h = 1 000 nGy/h. > > From the data posted at the link above for 2011/03/15 03:20, it appears that > all the radiation levels are one-sixth or less of the U.S. limit for exposure > of members of the public to radiation from a nuclear power plant. There may > have been a brief spike near one plant today, but I do not have that figure. > > Please keep these facts in mind: > 1. Nuclear power plants are physically incapable of undergoing nuclear > explosion. The explosions you hear about are hydrogen explosions, rather like > natural gas explosions. > 2. Radiation exists around you naturally. > 3. Exposure limits are always much lower than natural radiation levels to > which you are exposed in your everyday lives. > 4. Low level radiation is just that -- low level. If it's low enough, there > is nothing to be concerned about. You, the ground you walk on, the banana in > your breakfast cereal, and many other things contain low level radiation. > Yes, you yourself are a low level radiation source! > 5. Reactor plants generally are designed to contain reactor cores even if the > cores melt down. I do not know for a fact, but the Japanese plants are > probably designed for events like that, too. The Russian nuclear reactor at > Chernobyl definitely was an exception to that rule, which is why nations kept > after the Russians for years not to operate plants of that design. > 6. Airborne radiation is diluted as it spreads out. Our west coast is in no > grave danger! > > The largest problems facing the Japanese right now do not include radiation, > despite the hyperventilating you hear or read in the news. The natural > radiation levels there seem to be much larger than those caused by the > failure of those nuclear powered plants. > > Jim > > 10CFR20 radiation limits in the U.S. > Exposure limits for occupational workers > annual > whole body 50 mSv (5 rem) > lens 150 mSV > skin 500 mSv > > Exposure limits for members of the public > annual 1 mSv > acute 0.02 mSv/h > > Multiply radiation levels in grays (Gy) by the appropriate quality factor > (QF) to determine estimated dosage in sieverts (Sv). > QF exposure > 1 x, gamma, or beta rays > 20 fission products, alpha rays (internalized) > > -- > James R. Frysinger > 632 Stony Point Mountain Road > Doyle, TN 38559-3030 > > (C) 931.212.0267 > (H) 931.657.3107 > (F) 931.657.3108 > Pat Naughtin LCAMS Author of the ebook, Metrication Leaders Guide, see http://metricationmatters.com/MetricationLeadersGuideInfo.html Hear Pat speak at: http://www.youtube.com/watch?v=_lshRAPvPZY PO Box 305 Belmont 3216, Geelong, Australia Phone: 61 3 5241 2008 Metric system consultant, writer, and speaker, Pat Naughtin, has helped thousands of people and hundreds of companies upgrade to the modern metric system smoothly, quickly, and so economically that they now save thousands each year when buying, processing, or selling for their businesses. Pat provides services and resources for many different trades, crafts, and professions for commercial, industrial and government metrication leaders in Asia, Europe, and in the USA. Pat's clients include the Australian Government, Google, NASA, NIST, and the metric associations of Canada, the UK, and the USA. See http://www.metricationmatters.com for more metrication information, contact Pat at [email protected] or to get the free 'Metrication matters' newsletter go to: http://www.metricationmatters.com/newsletter to subscribe.
