After Fukushima

Istvan Gorog

Contents

• Introduction
• Discussion
• References

Introduction

In a White Paper I wrote in February 2011 and posted in March (Ref. 1), I established that Americans are routinely subjected to useless and costly excessive medical irradiation. The heightened public awareness of the harmful effects of (ionizing*) radiation on public health following the Fukushima reactor accidents provides an excellent opportunity to put this excessive irradiation in the proper perspective: even a worst case reactor meltdown would result in only a fraction of the dose the average American receives in unnecessary medical diagnostics. If we eliminated excessive diagnostic radiation by emphasizing evidence based treatments focusing on cures of illness, instead of searching for things that will provide opportunities for fee for service treatments (Ref 2), the financial benefit could be trillions of dollars over the next couple of decades. Such savings would go a long way toward balancing the Federal Budget.

After Fukushima we know that accidents that are possible though unlikely, are nevertheless disasters waiting to happen. In my previous White Paper I argued that post Chernobyl, post 9/11, a major nuclear reactor accident is not likely to happen. Clearly an earthquake and a tsunami on March 11, 2011 in Japan demonstrated that unlikely but possible natural disasters, possibly combined with human errors, do still happen. In the following, I will estimate the global impact of the radiation fall out from a truly major meltdown, one that is very unlikely, nevertheless possible, and much bigger than any that has happened thus far, and show that worldwide  the average radioactive exposure resulting from such an accident would still be a small fraction of what the average American receives (and pays for) in unnecessary medical diagnostics. My focus is on the potential savings available from properly managed healthcare; I am not arguing here either for, or against, nuclear power; I am only using nuclear power as a measure to demonstrate the insanity of our current fee for service health care system. I wish to contribute some arguments to how to fix it.

It the following discussion I demonstrate that the radiation dose Americans now receive in useless, harmful, and expensive medical diagnostic tests exceeds  about fifty times what a worst case scenario nuclear reactor accident would produce.

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*Ionizing radiation includes radioactive, cosmic, and X-ray radiation.

Discussion

How big a reactor accident could we possibly have? A good way to visualize

what lurks behind possible accidents is to first state that nuclear power and atomic bombs of the Hiroshima kind both release energy by splitting, or “fissioning” in the language of physics, heavy atoms into lighter pieces that have a total mass less than what the original heavy atom had. The mass difference via Einstein’s famous E=mc^2 is the energy produced. In a bomb the rapid release of this energy results in a fire bomb and mushroom cloud. In a reactor the controlled release of this energy is used to generate steam which in turn runs turbines that make electricity. The most basic reactors use a form of the metal Uranium, known as the isotope U-235. Upon splitting U-235 releases not only energy immediately (“prompt energy”) but also delayed energy emitted as the lighter fragment pieces go through radioactive decay. Whether an atom (or a gram or a ton) of U-235 is split in a bomb or in a reactor, the energies released are essentially the same for the same amount of material fissioned and the radioactive pieces are very similar. The delayed energy is about 5% of the total fission energy release (Ref. 3). From a bomb these radioactive fragments of fission are spread out through the atmosphere and result in the illness-causing fall out that ultimately led to the atmospheric test ban treaty in 1963. From a normal nuclear reactor operation these fragments are the principal radioactive components of the nuclear waste.  The waste is normally contained, cooled for many years to dissipate its radioactive energy and stored in a safe location for centuries. The energy released by the radioactive fragments in reactors after shut down is known as the decay heat. The post shut down problems, at Three Mile Island in 1979, Chernobyl in 1986, and Fukushima in 2011, were all the result of the loss of cooling and thus overheating of the reactor by the decay heat.

Much of the total of 5% delayed energy content of the radioactive pieces decays rapidly and contributes to the normal operating power of the reactor. Only a small fraction of it contributes to the decay heat after reactor shut down. The decay heat depends on the reactor power, its operating time, and the time since shut down.  In the following we will consider a typical “reference” U-235 reactor, producing 1 GW electrical power and that is shut down after one year of full power operation. The total decay heat energy at the time of shut down is about 0.25 % of the total fission energy produced in the reactor, equal to 0.0075 GW-years or one full day of operation (Ref. 4). Normally, this waste heat energy would be managed as part of the waste treatment, as discussed above. Under a worst nightmare scenario, a complete meltdown explosion could put all this radioactive energy into the atmosphere, where it would be spread globally, eventually contaminating soil and water.

To illustrate the environmental impact of a worst case scenario accident it is useful to compare the energetics of bombs and reactors. The fission energy released in one year of full power operation by a typical 1 GW electrical output nuclear power plant is equivalent to that released by 1,500 Hiroshima-size (15 kTon) atomic bombs. The explosions of a nuclear power plant and a nuclear bomb are very different. There are fundamental physical differences such that a reactor releases its prompt energy from its fissionable fuel at a much slower rate than does a bomb. Nevertheless the delayed energy releases after a few days follow similar patterns and their magnitude is proportional to the total fission fuel consumed and fission energy released. The initial spreading of the radioactive fragments from the two explosions would be very different and so would be the environmental impacts in the immediate vicinity of the explosions. The long term, few years to a few hundred years, global health impact in both cases would be primarily from an approximately uniform worldwide distribution of radioactive Cesium-137 and Strontium-90. The amount of radioactivity would be about the same from bombs and reactors for equal amounts of fuel fissioned. Thus, the long term environmental contamination from a worst case scenario reactor accident would be equal to what the radioactive fall out from about fifteen-hundred Hiroshima-size bombs would produce. From the basic physics of fission, we calculate that after a worst case accident at our “reference” reactor, the Cesium-137 and Strontium-90 radioactivity would each be about 5 million Curies.

To calculate global per person effective annual dose from a known amount of radioactivity released, we need measured data. I do not have access to any data that allows direct computation of the effective annual per person worldwide average dose from a given amount of radioactivity released into the atmosphere at a selected location. Thus we need to resort to rough estimates. Using data available for the long term residual radioactivity from nuclear weapons tests (Refs. 5 and 6), we estimate that 5 million Curies of Sr-90 thrown into the atmosphere results in less than about 0.01 mSv annual average global dose per person. The energy released from a decaying Cs-137  is less than one-half of that from Sr-90; thus we estimate that the total combined Cs-137 and Sr-90 worldwide annual average dose produced by the worst case reactor accident would be under 0.02 mSv per person. Here we assumed that the average person lives far from the accident location so that the effects of short decay radioactive products can be neglected. Also the estimate is for the first few decades after the accident and it will diminish with a half-time of about 30 years,  (As a cross check, I estimated what the worst case impact would be in Europe, using and scaling data from the Chernobyl disaster (Ref. 7). This is an over-estimate for a global long term exposure because the data includes only Europe, most of which is within about 1,000 miles from the accident and fast decay fission fragments that are highly active for a few days may have contributed to the exposures reported. Thus assuming that the worst case accident occurred in the Chernobyl location, I estimated that the European annual dose would be about 0.05 mSv per person.)

The average American in 2006 received 3 mSv annually in medical diagnostic tests, out of which more than 1 mSv was useless, harmful, and at best a wasted expense. Thus, average costly and unnecessary medical diagnostic exposure in 2006 was about fifty times what the long term global health impact of a worst case scenario reactor accident would be.

References

(1) “From Sr-90 Radiation hazard to Balancing the Budget”, Istvan Gorog, White Paper, Posted March 1,2011 at http://igorog.blogspot.com/

(2) “Overdiagnosed, Making People Sick in the Pursuit of Health”, Dr. H. Gilbert Welch, Beacon press, Boston, 2011

(3) “DOE Fundamentals Handbook Nuclear Physics and Reactor Theory”, Volumes 1 and 2, January 1993

4) Calculations based on web posted materials from University of Illinois at Urbana-Champaign,

https://netfiles.uiuc.edu/mragheb/www/NPRE%20457%20CSE%20462%20Safety%20Analysis%20of%20Nuclear%20Reactor%20Systems/Decay%20Heat%20generation%20in%20Fission%20Reactors.pdf

(5)             “Radiation protection and the “Tooth Fairy” Issue”, U.S.NRC Backgrounder Office of Public Affairs, on NRC web site, December 2004

(6) “Sources and Effects of Ionizing Radiation”, United nations Scientific Committee on the Effects of atomic Radiation, UNSCEAR 2008, United Nations, New York,2010, Volume I

(7) “Sources and Effects of Ionizing Radiation”, United nations Scientific Committee on the Effects of atomic Radiation, UNSCEAR 2008, United Nations, New York,2011, Volume II