Nuc Eng


Reference Info
-->Radiation
Radiation Information

A collection of information on Radiation.

  • From Gammas to Dose: Radiation dose is measured in Sieverts (Sv). Dose rate would be Sv per unit time, eg, Sv / hour or Sv / year. A Sv is a big quantity (about 8 Sv received in a short time would surely be fatal) and much smaller quantities are more typically encountered. So doses of milliSv or mSv (=0.001 Sv) and microSv or µSv (=0.000001 Sv) are used. An older unit still used in the USA is the Rem (100 Rem = 1 Sv, think cents and dollars). But how big is a Sv? Can it be related to something you might be more familiar with?
    • For radiation we measure the energy deposited in cells in joules per kilogram, a unit called the "Gray". If every kilogram of our bodies received a joule of energy, then we say we received a whole body dose of 1 Gray (abbreviated 1 Gy).  Not all radiation does an equal amount of damage. To compensate for this, when we talk about radiation exposure, we usually use the Sievert. For x-rays, gamma rays, and electrons, these are equivalent to Grays, ie, 1 Sievert = 1 Sv = 1 Gray (approximately) = 1 Gy = 1 joule/kg.
    • A typical gamma or beta might be about 0.5 Mev (million electron volts).  1 Mev = 1.6x10-13 joules so 0.5 Mev = 0.8x10-13 joules.  So it will take billions of these 0.5 Mev gammas to deposit a dose of 1 Sv.  Dividing 1 joule by 0.8x10-13 gives 1.25x10+13 gammas = 12.5 million million radiation hits.
    • Background radiation is of the order of 3 mSv per year = 0.003 Sv / year = 3.75x10+10 radiation hits per year = 1189 hits per second.  For a 75 kg person that is 89,000 hits per second in that person assuming 0.5Mev radiation.  That's what is received each and every second, day in, day out.  Obviously our bodies have some pretty aggressive and successful coping mechanisms.  There is no proven negative effects of acute (ie received in a short period) doses below 100 mSv (that's about 1.25 million million radiation hits) and many studies have shown a positive effect (hormesis). 
    • If there are about 50 trillion (5 x 10+10) cells in the human body and 3 mSv = 3.75x10+10 radiation hits, then a dose of about 4 mSv hits every cell in the body on average.
    • I am no expert on radiation detection devices such as Geiger counters but basically the detection end of the instrument is a gas filled chamber that gets ionized by the striking radiation.  The resulting electron flow gets amplified to generate an audible click and a meter reading.  From what I have seen, a sensitivity significantly less than background is common.  It is not hard technically to build an instrument to detect enough radiation to emit a signal. Perhaps a few 100 gamma or so. Compare that to the 89,000 gammas that hit your body every second due to background radiation.
    • By way of contrast, solar radiation on a sunny day is of the order of 300 joules per m2 per second. That probably works out to about 2 joule / kg per second for the average person laying prone on the ground (75 kg and 0.5 m2?) or 2 Sv per second if the sun's radiation were high energy gammas.  Luckily the sun's photons that reach us are of low energy compared to x-rays and gammas so the photons don't penetrate your body.  But wear sunscreen because your skin takes quite a pounding in direct sunlight. 
  • Radiation Dose Tables and Charts
    • A summary of the dose received for specific events
      Description Dose
      Reference
      Sleeping next to someone
      		0.05 µSv
      1
      Living within 50 miles of a nuclear power plant for 1 year
      		0.09 µSv
      1
      Eating one banana
      		 0.1 µSv
      1
      Living within 50 miles of a coal power plant for 1 year
      		0.3 µSv
      1
      One arm x-ray
      		1 µSv
      1
      Using a CRT monitor for 1 year
      		1 µSv
      1
      One day on Cororado plateau (high natural background
      		1.2 µSv
      1
      Dental or hand x-ray
      		5 µSv
      1
      Average background per day
      		10 µSv
      1
      One chest x-ray
      		20 µSv
      1
      EPA yearly release target for nuclear power plant 30 µSv
      1
      Airplane flight New York to LA
      		40 µSv
      1
      Living in a stone, brick or concrete bldg for 1 year 70 µSv
      1
      EPA yearly release limit for nuclear power plant 250 µSv
      1
      Yearly dose from natural potassium in the body
      		390 µSv
      1
      EPA yearly limit to single member of the public
      		1 mSv = 1,000 µSv
      1, 2
      Mammogram
      		 3 mSv
      1
      Normal yearly background dose
      		 3.65 mSv
      1
      Chest CT scan
      		5.8 mSv
      1
      Maximum yearly dose for US radiation workers
      		50 mSv
      1, 2
      Lowest one year dose clearly linked to cancer
      		100 mSv
      1, 2
      Dose causing symptoms if received in a short time
      		400 mSv
      1
      Severe radiation poisoning, sometimes fatal
      		2 Sv = 2,000 mSv
      1
      Fatal dose
      		8 Sv
      1
      References:
      1 http://xkcd.com/radiation/
      2 Canadian Nuclear Safety Commission
    • Rad Pro calculator - Rad Pro Calculator online performs many nuclear calculations that are useful to the health physicist, radiological researcher, radiochemist, radiation safety officer, health physics technician (HP) and other professionals in radiation physics and radiological engineering. It calculates, among other things, radioactivity units conversions (SI and US customary) and gamma emitter dose rate and activity.
    • Argonne National Labs - Radiation Fact Sheets for Selected Environmental Contaminants to Support Health Risk Analyses. Really nicely done. Just in case the link should disappear in the future, here is the pdf version (2.4Mb) of the chart.
    • Radiation Dose Chart from the American Nuclear Society - Our daily exposure to radiation comes from numerous sources within our environment. The annual dose to which we are subjected depends upon where and how we live, and what we eat, drink, and breathe. This easy-to-use chart shows how to estimate that dose. Just in case the link should disappear in the future, here is the pdf version (941 kb) of the chart.
    • Radiation Dose Chart (source http://xkcd.com/radiation/) - uses coloured squares to indicate the amount of radiation received for various activities. [local archive (pdf 419kb)]
  • Other Commentary and Papers
    • General
    • ANS Nuclear Cafe blog entry on the ANS President's Special Session - Low-Level Radiation and Its Implications for Fukushima Recovery containing links to good reference material including a 208 page report that contains a compendium of published reports and thus represents a great resource. [local archive pdf 54Mb Warning: huge file size)
      • From the Foreword: "This report from the ANS President’s Special Session at the 2012 Annual Meeting focuses on the LNT model and questions the validity of assumptions and discusses the science and policies that created the model. This report presents the information collected and discussed, and invites your review of the LNT model; it also suggests a more realistic approach to address the health effects, mitigate the hazards, and set appropriate limits to sensibly and realistically avoid the potentially adverse consequences of radiation exposure. The pessimism that now makes much noise in the global public about nuclear radiation can, in our time, be shown to be wrong. The information collected and discussed in this Special Session has, we are hopeful, opened the door to a change in our attitudes with the foundation of scientific evidence about radiation. It is dedicated to the residents surrounding the Fukushima site who are still unable to return to their homes due to the overreaction toward low-level radiation."
    • As posted on radsafe-bounces@agni.phys.iit.edu, Wednesday, March 23, 2011 7:32 PM by Bobby R. Scott, Senior Scientist, Lovelace Respiratory Research Institute, Albuquerque, NM, USA
      • He writes: "Calculations (Feinendegen L. Health Physics 100(3): 274-276, 2011) indicate that for each second it takes you to read these comments, your body is receiving more than 1,000,000 (not a typo) radiation energy deposition events (here called radiation hits) from natural radiation sources. Many advocates the linear-no-threshold (LNT) hypothesis think that just one extra beta radiation hit from an iodine-131 atom that was previously released among other atoms from the damaged Fukushima nuclear power facility in Japan could cause you to develop cancer. Please note that if the greater than 1,000,000 natural radiation hits to your body during the last second did not harm you (which is very likely the case), you have no reason to be concerned about one extra radiation hit from a stray iodine-131 atom before your next greater than 1,000,000 hits from natural radiation occur during the next second. Multiply 1 million radiation hits by (60 sec/min)x(60 min/hour)x(24 hours/day) and it can be seen that each day we are likely receiving more than 86 billion harmless radiation hits to our bodies from natural radiation. This has happened over millions of generations of mammals (humans included here) since first originating on the planet, thanks largely to a hierarchy of efficient natural defenses that have evolved [antioxidant defenses, selective apoptosis of aberrant cells, anticancer immunity (Feinendegen 2011, as cited above; Scott BR. Health Physics 100(3):337-339, 2011)]. In fact, a small amount of extra radiation can amplify our natural defenses (Scott 2011). The cited references are extended abstract that relate to a special issue of the Health Physics Journal that contains the "Proceedings of the Conference on Biological Consequences and Health Risks of Low-Level Exposure to Ionizing Radiation In Honor of Victor P. Bond" [Health Physics 100 (3): 2011]. It is well established that large amounts of radiation can cause harm. However, the harm after high doses at least in part relates to suppression of the body's natural defenses. Thus, biological responses after high and low radiation doses are not the same which invalidates high- to low-dose extrapolation of cancer risk based on the LNT hypothesis. The frequency assertion by so-called experts that "there is no safe dose of radiation" related to the Fukushima power plant in Japan should therefore be challenged by those reporting the news. Interestingly, those making the implicated LNT-related proclamation often reference the descriptive-risk-models-based BEIR VII report but appear to be unaware of the related biological-mechanisms-based French Academies Report that challenged the finding of the BEIR VII Report related to the claimed validity of the LNT hypothesis for radiation doses less than 100 mSv."
      • I realize that there is a discrepency between Bobby Scott's numbers (1,000,000 hits per sec) and mine (89,000 hits per sec). Perhaps the average energy of background radiation is more like 50 kev rather than my assumed 500 kev but from the spectrum shown here I think 500 kev is the better figure. The peak is at about 100 kev and the tail is long (note the semi-log scale). Dr. Bernard Cohen (see link below) did a similar calculation using 600 kev but with a background radiation level of 0.8 mSv per year compared to my assumption of 3 mSv per yr. He arrived at 15,000 hits per second. I figure 500 kev and 3 mSv per year are good enough figures for a ball park number to illustrate. The main point is that the number of hits per second is large enough to say with confidence that we are awash in radiation even at the lower more conservative value.
    • Nuclear Radiation and Health Effects - a good summary by the World Nuclear Association (WNA). Lots of great info there.
    • A Layman's Introduction to Radiation - by a Senior Reactor Operator at the Reed Research Reactor. Nicely done. [local archive pdf 142kb)]
    • Radiation info (introductory level) by Jeremy Whitlock, with permission (pdf 296kb).
    • H.J. Moe, Operational Health Physics Training - Covers Reactor Operations, Particle Accelerators, and X-Ray Devices as well as the basics. It's a "Must Read", apparently.
    • "Resolving the controversy over beneficial effects of ionizing radiation", overheads (pdf 44 kb) and text (pdf 33 kb) by Dr. Jerry M Cuttler, PEng, Atomic Energy of Canada Limited, presented at the conference on the Effects of Low and Very Low Doses of Ionizing Radiation on Health World Council of Nuclear Workers (WONUC), Versailles, France, 1999 June 16-18.
    • The LNT Hypothesis: Ethical Travesties (pdf 168kb), an article by Margaret N. Maxey, Ph.D., Professor, Biomedical Engineering, College of Engineering, The University of Texas at Austin, Wingspread Conference, Racine, WI, August 1997. - Slowly but inexorably, radiation scientists are recognizing that the LNT hypothesis -- at one time administratively useful in regulating radiation exposures during the infancy of radiation science -- has in its maturity become scientifically illegitimate and ethically indefensible.
    • It’s Time to Tell the Truth About the Health Benefits of Low-Dose Radiation, by James Muckerheide, 21st Century Science & Technology Magazine. [local archive (pdf 245kb)]
    • Ionizing Radiation in the 20th Century, by Zbigniew Jaworowski (pdf 1161kb)
    • Dr. Bernard Cohen, University of Pittsburgh - an authoritative source on nuclear energy. Links to a number of papers, his famous book, data, etc. particularly those disproving the LNT Linear No Threshold hypothesis.
    • The 3 R's; Radiation, Risk, and Reason (pdf 1.9Mb) found at ThreeMileIsland.org is excellent read on radiation. [Archival copy pdf 1.9Mb]
    • Learning About Energy - Much of What You Know Simply Isn't So, hosted by Ted Rockwell. Tons of great information here. See The Nucelar Power Safety Record for instance.
    • Scientific data on the effects of low doses of radiation, by Dr. Ron Mitchel - "High doses of radiation can cure cancer but low doses can prevent it. New research indicates that low doses of radiation Reduce the natural risks of cancer and birth defects. Most cancers and birth defects occur for natural reasons, and it is widely believed that any exposure to radiation increases that risk. However, there is no scientific evidence that this is true for the low doses that most people might receive from the environment, medical tests or the workplace. On the contrary, surprising new research indicates that low doses of radiation are actually beneficial and reduce these natural risks."
    • Presented at the 11th Pacific Basin Nuclear Conference (PBNC ’98), Banff, Canada, 1998 May 3-7:
      • Linear Versus Non-Linear: A Perspective from HEALTH Physics and Radiobiology (pdf 76kb) by N.E. Gentner and R.V. Osborne, Health & Environmental Sciences Division, Atomic Energy of Canada Limited, Chalk River, Ontario K0J 1J0, Canada. A well rounded paper that covers the topic well, including the implications for regulation. The following quote from the paper is the nub: The "problems with LNT theory" mainly relate to what are seen as excessive costs for protection against radiation versus other risks to human health. The issue as we see it is that the attention given to low doses of radiation is excessively high even if the LNT based risk coefficients were to be correct. This is the issue we have to continue to address and rectify. It is this cost of a theoretical cancer death prevented which is out of whack; public misperception and whatever leads to this misperception, not LNT, is to blame for this. To be effective, it is the perception issue that has to be addressed. "
      • Fear of Radiation is Killing People and Endangering the Planet Too (pdf 51kb) by Theodore Rockwell, MPR Associates, Inc., U.S.A. Abstract: We are permitting tens of thousands of real people to die needlessly each year because some people fear that the alternative might pose a hazard to hypothetical people from postulated events that have never happened. The real people are dying from food poisoning, from inhaling particulate matter from coal-fired power plants, from avoiding mammograms, x-rays, MRIs, and other life-saving technologies, from unwillingness to use smoke-detectors containing radioactivity, and many other such fears. In addition, the planet is threatened by global warming, acid rain, smog, toxic runoff, and shortages of drinking water. Use of nuclear technologies could ameliorate all these problems, but many people are afraid because we have told them that even the tiniest amounts of radiation are hazardous. This is simply not true, and we should start saying so. In fact, there is considerable evidence that therapeutic doses of low-level ionizing radiation would be beneficial for most people.
      • Molecular Biology, Epidemiology, and the Demise of the Linear No-Threshold Hypothesis (pdf 67kb) by Myron Pollycove, U.S. Nuclear Regulatory Commission, U.S.A.
      • The Research on the Health Effects of Low-Level Radiatio in Japan (pdf 219kb) by Sadao Hattori, Central Research Institute of the Electric Power Industry, Japan.
    • Can radiation have beneficial health effects? - a good, concise summary of the LNT / threshold / hormesis situationby R.V. Osborne, as posted on Jeremy Whitlock's Canadian NuclearFAQ.
    • High Background Radiation Areas of Ramsar, Iran by S. M. Javad Mortazavi where it is concluded that: "There are many other areas with high levels of background radiation around the world, and epidemiological studies have indicated that natural radiation in these areas is not harmful for the inhabitants. Results obtained in our study are consistent with the hypothesis that a threshold possibly separates the health effects of natural radiation from the harm of large doses. This threshold seems to be much higher than the greatest level of natural radiation." See also the paper Very High background Radiation Areas of Ramsar, Iran: Preliminary Biological studies (pdf 404kb), by M. Ghiassi-nejad et al.
    • UCS Science: How Many Cancers Did Airlines Really Cause? by Brian Mays, NEI Nuclear Notes, April 17, 2011: "There is a lot of confusion about how many excess cancer deaths will likely result from exposure to radiation at low-dose and low-dose-rates. [Using LNT] 79,000 and 40,000 are reasonable estimates of the number of excess cancers and cancer deaths attributable to the flying in the past decade." It seems that if you apply LNT for risk assessment then you arrive at the conclusion that flying is a bigger radiation risk than Chernobyl. The author does this deliberately of course to counter the scare tactics of the anti-nukes. Draw your own conclusions but it seems to me that the use of LNT for risk assessment leads us to conclude that the outside risk of the Chernobyl disaster is no worse than the outside CANCER risk of flying. Now while LNT should not be used for risk assessment in my opinion, if people insist on using LNT for risk assessment then for the sake of argument (and drawing them into making their own conclusions) we can go with that and follow the argument to a fitting end: a comparison of nuclear risk to risks we find socially acceptable. In short, it is the comparison that is germane, not the absolute numbers. In this way nuclear risks are still lower than the risks of many acceptable social activities. All we need is a fair comparison. [local archive (pdf 158kb)]
    • Lawrence Solomon: The fallout of the Nobel scam of 1946 - Scientist’s radiation cover-up might have cost thousands of lives. [local archive (pdf 26kb)]
    • Forbidden Science: Low Level Radiation and Cancer by Norman Rogers - "There is massive evidence that low levels of radiation rather than causing cancer, actually suppress cancer.  The reason is, probably, that radiation in small or moderate quantities stimulates cellular repair mechanisms.  This is not to negate the fact that large amounts of radiation can kill you or make you sick.  This protective effect of low levels of radiation is called radiation hormesis. The case of radiation hormesis provides yet more evidence that the scientific establishment and the EPA are lacking in objectivity when their interests are at stake." [local archive (pdf 40kb)]
    • Personal commentary: I think people are missing the obvious: Low dose effects of the order of background and probably below 100mSv or so are lost in the noise.  There may be some effects +/- but we can't be absolutely sure for any given individual what the effects are, +/-/ or nil (but my bet is on hormesis).   But the point is that it doesn't matter!   A dose of 4 mSv is about one radiation hit per cell.  Our bodies get hit about 89,000 times per second due to 3 mSv background.  We live in a sea of radiation.  Meanwhile, a person, usually a child, somewhere in this world dies every 3.5 seconds of hunger related causes.  It is well past time for people to get real. So I guess we should concentrate on comparative risk.  LNT is a valid admin tool for operational needs and is a valid tool for risk assessment for high doses and high dose rates.  But it should not be used for low dose risk assessments. For low dose risk assessments, the comparative risks are so tiny as to be negligible. It seems pretty unethical to me to obsess about low radiation levels; the resources spent avoiding that theoretical cancer death could surely be better spent elsewhere.