Sunday, March 20, 2011

Radiation Issues

One of the key concerns about Japan is no longer the tsunami or the aftershocks, but the radiation issue.  Here are some facts to help people understand the "real" threats vs "perceived" threats.  First from CNN:

"A U.S. radiation expert has said there's not much reason to worry despite restrictions on some food produced in two provinces around the Fukushima Daiichi nuclear power plant. Japan slapped on the restrictions after high levels of radioactivity turned up in spinach and milk.  Dr. James Cox, professor of radiation oncology at the M.D. Anderson Cancer Center in Houston, said the reported levels posed little or no health concerns."

One of our Blackbelt members who was in Japan with us, has created a "Nuclear Reactors 101" document so that we can better understand what this is all about.  With his expertise in healthcare, he provided us with an interesting document that provides insights about the whole issue:

Nuclear Reactor – Simplified Explanation


By: B. Barton

U238 (uranium) is a naturally occurring, radioactive element. It can be converted (enriched) to another form of uranium (it’s isotope), called U235. If a free neutron collides with a U235 nucleus, the nucleus will absorb the neutron, become unstable and split in two. When it splits (i.e., decays), energy is released in the form of heat, slow neutrons, beta rays, and gamma rays. The splitting of a U235 nucleus is called nuclear fission. The slow neutrons that are released go on to split more U235 nuclei and this chain reaction is called a nuclear reaction.

A nuclear reactor is made up of:
• fuel rods that contain pellets of U235,

• control rods that can be raised and lowered to block the neutrons, thus slowing down or speeding up the reaction,

• a moderator; water that absorbs the heat that is given off by the reaction,

• a reaction chamber that contains the fuel rods, control rods, and moderator,

• a containment vessel or shell made of steel and concrete that covers the reaction chamber to contain the radiation.

Water inside pipes that circulate through the water in the reactor core is heated and drives steam turbines which power a generator, producing electricity.

A pound of highly enriched uranium contains the energy equivalent of approximately one million gallons of gasoline.
Nuclear Reactors - In Japan Following the Earthquake

Following the earthquake, the nuclear reactors in Japan were automatically shut down by the control rods but even though the fission reactions stopped, the fuel rods remained hot and continued to heat the water in the core to the point where it partially evaporated. There are normally pipes that circulate cold water through the water in the core to prevent this, but in Japan there was no electricity to operate this cooling system so some of the moderator water evaporated, exposing the fuel rods to air. When this happened, the rods became so hot that they melted in places (partial meltdown). When the rods melted, they released radioactive U235 into the core. Operators pumped sea water into the core to try to cool the moderator water but as they did, it was instantly heated and evaporated faster than they could replace it.

The amount of radiation that was being detected at the Fukushima power plant on March 12th (the day after) was very low, approximately 1 mSv/hr (millisieverts are a unit that measures the absorbed dose of radiation.). In comparison:

Naturally occurring background radiation ~ 2 mSv/yr

Chest X-ray 0.1 mSv

Mammogram 0.4 mSv

Abdomen X-ray 1.2 mSv

Annual exposure to aircrew travelling from New York to Tokyo 9 mSv

Abdomen or Pelvic CT Scan 10 mSv

Nuclear Medicine Heart Scan 10 mSv

MRI Scan no ionizing radiation

Ultrasound Scan no ionizing radiation

Radiation sickness and nausea 1,000 mSv

LD 50/40 5,000 mSv

Death within hours of exposure 20,000 mSv

It is important to note, however, that the amount of radiation that one receives is governed by the inverse square law. In addition, if radioactive dust (fallout) were to travel as far as North America, it would be so dissipated by the time it arrived that the radiation exposure from it would be negligible.

Potassium Iodide for Radiation Protection

The thyroid gland takes up (absorbs) iodide, converts it to iodine and uses the iodine to make T3 (thiiodothyronine) and T4 (thyroxin), the hormones that regulate metabolism. The thyroid will take up only as much iodide as it can use so when its stores are full it won’t absorb any more.

I131, an isotope of iodine, is one of the products of uranium fission. To prevent the thyroid from absorbing radioactive I131, one can saturate the thyroid’s stores with potassium iodide and this is why some people are taking this supplement.

Potassium iodide pills are being advertised on the internet as “Nuke Pills” and “Radiation Pills” and this is misleading as this type of supplementation will not prevent radiation induced cancer in any organ other than the thyroid.

Iodide supplementation would only be of benefit to those who are being exposed to high doses of I131, and in North America this is not the case.

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