Monday, October 20, 2008

Natural Radiation

by Marcel F. Williams

Humans exist on a planet and within a universe that is naturally radioactive. In fact, humans and all other plant and animal species that live and breed on Earth are also inherently radioactive.

Since the birth of the cosmos, the earth has been subjected to an endless hailstorm of cosmic radiation. These potentially deleterious ionizing particles consist of highly accelerated protons, electrons, and neutrons originating mostly from other stars in our galaxy.

Our planet of evolutionary origin is also radioactive due to naturally occurring radioactive elements in the earth's crust such as: potassium-40, uranium-238, thorium-232, and rubidinum-87, and radium-226. In fact, the radioactive decay from uranium, thorium, and potassium may be responsible for 45 to 90% of the earth's internal heat source which is the source of earthquakes, volcanoes, mountain building, hot springs, and continental drift.

On average, humans receive 0.4 mSv (40 millirems) of cosmic radiation. People also receive about 0.5 mSv (50 millirems) of terrestrial radiation. We also inhale about 1.2 mSV (120 millirems) of radiation from radon gas annually.

The human species is also internally radioactive due to the potassium in our bones which exposes our tissues to 0.4 mSv (40 millirems) of ionizing radiation. So being in constant proximity to other human beings increases one's exposure to ionizing radiation.

So if you lived with at least one other person in your house, you would receive 0.4 (40 millirems). That's more than ten times as much radiation as you would receive by living near a nuclear facility. If you lived in California and moved to Colorado, you would receive 45 times as much ionizing radiation as you would living next to a nuclear power facility.

Ionizing Radiation Levels (annual):

0.39 (mSv) Annual human internal radiation due to radioactive potassium

0.35 mSv Annual exposure to cosmic radiation in the state of Louisiana

1.20 mSv Annual exposure to cosmic radiation in the state of Colorado

0.30 mSv Annual exposure to terrestrial radiation in the state of Texas

1.15 mSV Annual exposure to terrestrial radiation in the state of South Dakota

0.07 mSv Annual radiation exposure to while living in a stone, brick, or concrete building

0.03 mSv Annual radiation exposure while living near the gate of a nuclear power plant

0.01 mSv Annual USA dose from nuclear fuel and nuclear power plants

1.15 mSv Annual radiation exposure while working at a nuclear power plant

2.0 mSv Annual human internal radiation due to radon

1.0 mSv Annual Limit of dose from all DOE facilities to a member of the public who is not a radiation worker

5.0 mSv Annual USA NRC limit for visitors

20 mSv Annual (averaged over 5 years) is the limit for radiological personnel such as employees in the nuclear industry, uranium or mineral sands miners and hospital workers

50 mSv Annual highest dose which is allowed by regulation of occupational exposure. Doses greater than 50 mSv annually arise from natural background levels in several regions of the world but do not cause any discernible harm to local populations.

500 mSv Annual USA NRC occupational whole skin, limb skin, or single organ exposure limit

Ionizing Radiation Levels (acute):

0.o5 mSV One round-trip to Paris-New York

0.46 mSv off-site exposure to the Three Mile Island core meltdown accident

2.2 mSv Average dose from upper gastrointestinal diagnostic X-ray series

50 mSv Lowest dose at which there is any evidence of cancer being caused in adults

100 mSv USA EPA acute dose level estimated to increase cancer risk 0.8%

500-1000 mSv Low-level radiation sickness due to short-term exposure

Persons working at a nuclear facility are normally exposed to 1.15 mSv (115 millirems) annually. This would be the equivalent of living in the state of Ohio where Americans there are exposed to an equivalent amount of cosmic and terrestrial radiation and below that of states like Colorado, Wyoming, and Utah where one receives a lot more background radiation.

If you lived near the gate of a nuclear reactor and never left the house, you would be exposed to 0.03 mSv (3 millirems) of radiation annually from that nuclear facility. However, you would receive 0.07 mSv (7 millirems) of radiation if you were living in a stone, brick, or concrete building. So you would receive more radiation from your house than from living near the gate of a nuclear facility.

But what about a nuclear meltdown?

Thanks to the fact that US reactors are housed in huge protective containment structures, the nuclear meltdown at Three Mile Island exposed nearby residents to only 0.46 mSv of acute radiation. That's nearly five times lower than receiving a gastrointestinal medical X-Ray and more than 100 times below the level of cancer causing radiation. But the new generation of nuclear reactors such as the AP1000 and GE's ESBWR have core damage frequencies at least 100 to 1000 times lower than current reactors such as the LWR at Three Mile Island. But, again, even if a meltdown did occur, the public would be protected by the containment structures which are also designed to withstand an impact from a jet plane.

Americans are exposed to natural radiation from cosmic and terrestrial radiation ranging from as low as 0.75 mSv (75 millirems) to as high as 2.25 mSv (225 millirems). And Americans are exposed to an additional 2.0 mSv (200 millirems) of radon gas on average. Yet living near the gate of nuclear power facility would only expose them to 0.03 mSv (3 millirems) of radiation. And even consistent contact with a family member would expose you to another 0.4 mSv (40 millirems) of radiation annually. So the idea that a dramatic increase in nuclear power would expose humans to a dramatic increase in ionizing radiation is clearly not supported by the scientific evidence.

References and Links

1. G. Olah, A. Goeppert, and G. Prakash, (2006) Beyond Oil and Gas: The Methanol Economy, Wiley-VCH Verlang, Weinheim, Germany

2. Ionizing radiation (Wikipedia)

3. Economic Simplified Boiling Water Reactor

4. Martin D. Ecker, and Norton J. Bramesco (1981) Radiation: All you need t know about to stop worrying...or to start, Vintage Books, New York

5. Radiation and Life

A New Papyrus Publication


Jason Ribeiro said...

Again you write a very well crafted essay Marcel. I think you could make another article just on the subject of the chances of a nuclear accident especially with the new designs. As I figure it, your chances of winning the lotto are about a 1000 times better than an AP1000 meltdown.

Marcel F. Williams said...

Thanks for the comments Jason.

Even though containment structures have a 95% chance of containing a meltdown, the frequency of meltdowns was still too high, IMO, for any major global expansion of nuclear power.

That's why I thought the pebble bed reactors might be the ultimate answer to nuclear safety.

However, with the extremely low core damage frequencies of the latest generation of LWR and BWR reactors, the entire planet could be totally powered by nuclear energy with very little worry about meltdowns for several hundred years and any breach of containment for several thousand years.

Of course, when large amounts of radiation did escape from a nuclear reactor (Chernobyl), less than 50 people died.

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