Fukushima Reactors (part 3)

Tales from the Nuclear Age

Copyright © 2011 by Charles Glassmire

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Apr. 26, 2011

Fukushima Reactors (part 3)

What about Plutonium found on the ground near the reactors?

          Plutonium is an element of concern, but it’s important to understand why that is. The principal Plutonium isotope made in power reactors (239Pu) has a half life of 24,000 years. So once created, it stays around for a very long time. When you run a Uranium fueled reactor, such as those BWR’s used at Fukushima, you manufacture Plutonium along with other fission products. So there are small amounts of Plutonium in the spent fuel rods stored in the rooms at the top of the reactors, and inside the reactor core containment. There are about 11,175 spent fuel rods stored for the six reactors on site. It seems that Japan does not have a geologically safe underground storage site for these used fuel rods. The United States has spent several Billion dollars building such a storage site in Nevada which is in a geologically stable salt formation under a mountain. The nuclear industry could look forward to shipping its spent fuel there for permanent safe storage. Sadly, President Obama has closed down the site and cancelled all future work as a payoff to Senator Harry Reid. Now all those fuel rods are sitting in the cooling pools at U.S. reactor sites with no where to go.

           Plutonium has a very odd history. This element is a metal not found in nature (except possibly from a few spontaneous fissions of Uranium in the Earth’s crust). It had to be created by man, specifically by Glenn Seaborg and his team at Berkeley during World War II. They bombarded a Uranium isotope (238) with a heavy Hydrogen nucleus. This created another new element called Neptunium which decayed within a few days to Plutonium 239. But they didn’t get very much. In fact the first amounts were invisible; only a few atoms. Indeed, they had to run the process for a whole year in a cyclotron to get a miniscule amount enough to even be weighed and measured! Then because of the secrecy of the atom bomb project, they couldn’t even publicize their discovery until after the War in 1946!

 Why go to all this trouble over Plutonium?

          The 239Pu isotope proved of great interest to the Manhattan Project. It turned out to be fissionable, releasing lots of usable energy when its nucleus split apart. When 239Pu fissions, it generates two new neutrons, and sometimes three. So you use one neutron to fission it and you get two new ones to go on and break up other nuclei. This multiplication factor means it’s a better candidate for a chain reaction weapon than even Uranium 235. So you need much less Plutonium to create a critical mass for a bomb. In fact, a softball sized sphere will do the trick. For this reason Plutonium is a great candidate for weapons mounted on Ballistic Missiles. Much less weight to carry, which means less rocket fuel etc.

          The Manhattan project immediately began two production facilities for Plutonium. One was located at Oak Ridge and another major one at Hanford in the north western U.S. They began design of a Plutonium bomb, which ultimately proved successful and was dropped at Nagasaki.

          The fuel rods in Fukushima number 3 are a special design using a mixture of Plutonium Oxide and Uranium Oxide. This mix is called MOX. So there are significant amounts of Plutonium in reactor 3, which carries over into the spent fuel rods stored in the number 3 fuel cooling pool. After the tsunami killed the pumps, these cooling pools were subjected to hundreds of tons of cooling water to keep the temperature down. This water filled tunnels under the site and drained into the ocean. It’s no surprise that small amounts of Plutonium are detected in the surrounding area.

          Oddly enough, Plutonium radiation is not a significant problem unless it’s inhaled or ingested. 239Pu radiates by releasing an alpha particle. This is a big low energy particle which can’t penetrate a sheet of paper, or even the skin thickness of a human being. If amounts are left on the skin for enough time however, a burn and skin lesions could occur. This may be prevented by simply washing with cold water and controlling the runoff water.

          However it is a serious problem in any quantity inside the body. The metal is a chemical poison if ingested or inhaled into the body. The symptoms which may occur in the event of ingestion or inhalation of Plutonium depends heavily on the amount taken in. In a heavy exposure the symptoms might include liver damage, increased risk of bone, liver or lung cancer, and increased risk of leukemia. Children and pregnant women would be especially susceptible to damage. 

          But we live in a radioactive world. In fact, those of us living in the United States all have trace amounts of Pu in our bodies left over from the atomic testing which went on in Nevada in the 50’s and 60’s. On the average, this probably gives us less exposure than we get from the Cosmic Rays which continually bombard the Earth on a daily basis, or the Radon gas collecting in our cellars…

  (to be continued …)

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One Response to “Fukushima Reactors (part 3)”

  1. Dorine Says:

    Hello, I log on to your new stuff on a regular basis. Your story-telling style is witty, keep up the good work!

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