Is Plutonium Release the Real Danger at the Damaged Japan Fukushima Nuclear Reactor?

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Nuclear power plants are a source of electricity that does not use up oil, natural gas or coal supplies or increase the carbon dioxide levels in the atmosphere, but they come with their own risk as the disaster at the Japanese Fukushima Daiichi nuclear power plant is clearly showing us. Knowing how these reactors work can help you to stay safe when there is an accident like this and protect you and your loved ones from harm.

Power plants of this type are basically giant water boilers that use the heat generated by decay of radioactive 'fuel' to run generators to produce electricity. The fuel pellets contained in the reactor core of the Number 2 unit of the damaged Fukushima plant consist of a mixture of oxides of uranium and plutonium known as MOX. This fuel may be produced by processing spent uranium from other reactors in combination with plutonium from nuclear weapons. The extremely toxic plutonium in MOX is what makes the risk from meltdown of the reactor core of the Japanese plant much more serious.

Everyone knows that radiation, or at least too much radiation, is harmful to humans and can cause DNA damage. But not all radiation is the same in its potential for harming us. A CAT scan uses X-rays which are a form of radiation that allows details of internal organs to be visualized and diseases to be diagnosed with amazing accuracy. The X-rays are produced in a controlled way by the CAT scan machine and not by decay of radioisotopes as in a nuclear power plant. Uranium and plutonium are large elements that form what are known as radioisotopes, unstable variant forms differing in the number of neutrons in the nucleus.

Plutonium (the chemical symbol is 'Pu'—singularly appropriate) is one of the original heavy metals.A chunk of Pu feels warm to the touch because its atoms are continually 'decaying', which means they are spitting out an alpha particle—two protons plus two neutrons—and a small amount of energy. There are some 600 billion of these decays per second in Pu-238, so even though the energy released per decay is very small, altogether they add up to make a pretty good heat source.

Pu-239 is a different isotope of plutonium and is the one used in weapons because it is able to undergo a chain reaction similar to what happens with uranium in the atomic bomb. Pu239 is produced continuously from uranium-238 in nuclear reactors such as the Fukushima unit; but in these reactors, the mixed oxide or MOX pellets were enriched in Pu-239. When an atom of Pu-239 decays, it releases an alpha particle like Pu-238 and some weak gamma rays, which are similar to X-rays.

So, what makes plutonium so hazardous? To answer that question properly, we need to know what form the plutonium is in. A solid piece of Pu metal produces alpha particles from radioactive decays, and these energetic particles can damage cells—but they have to penetrate them to do that. Pick up a piece of plutonium. It feels warm because of the continuous alpha decays. The particles, however, are blocked by the outer layers of your skin. A single sheet of paper stops them almost completely.

The problems with Pu-239 begin when it gets inside your body. An exploding nuclear reactor core could release small particles of plutonium oxide into the air, which would be carried aloft by winds and transported to population centers where they could be inhaled into the lungs. Once lodged in the airways they would continue to release billions of alpha particles per second with a half-life of 24,000 years. The particles have enough energy to damage the cells' DNA and potentially cause mutations that can lead to cancer.

How can you protect yourself from Pu-239? The obvious answer is—get as far away from the source as possible. Externally, plutonium is not that harmful. What you do not want to do is breathe it in. The MOX fuel contains mixed oxides of uranium and plutonium and if particles of MOX enter and remain in the lungs, there is an increased risk of lung cancer. Covering your nose and mouth with a handkerchief will help in an emergency, but for best protection the N95 particle mask is recommended. These masks fit over the nose and mouth and block 95% of particles larger than 0.3 microns in diameter. They should be marked as certified by the National Institute for Occupational Safety and Health (NIOSH) and can be purchased on the Web from a number of different suppliers. In order to work effectively, they have to be carefully fitted around your nose, and if you have a beard you cannot get a good fit without shaving it off.

Accidents such as occurred when the combination of earthquake and tsunami shut off coolant water to reactors in the Japanese Fukushima power station are fortunately rare, but understanding the risks can help you protect yourself and your loved ones. Being prepared for any kind of natural disaster means making a plan ahead of time and being sure everyone in your family understands what to do. It can save your life.
 

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