Re: How would they clean up plutonium in the ocean?

Hello Melissa

You have asked some very good questions. I am going to give you some answers as well as some web sites where you can look up the documents I used as reference sources. However, I am going to answer the questions in reverse order to how they were asked, since I think it will make more sense that way.

"What does plutonium do on a satellite, and if it's so bad why don't satellite makers use something else?"

http://www.aiaa.org/policy/space-nuclear.html
http://www.jpl.nasa.gov/cassini/MoreInfo/spacepwr.html

It is very expensive both to build a satellite, and to get it up into space. In addition, once it is in space, it is difficult to repair or maintain it, so it is built to keep itself going for many years. In the case of a satellite that is sent away from the earth, it must be completely self-contained. If a satellite were just an inert chunk of whatever, it wouldn't matter. But a satellite is usually a collection of various instruments and equipment; which usually require electricity, and sometimes also require heat, to operate.

How do satellites get electrical energy and heat? Sometimes they use solar panels. This can be a problem if the satellite accidently turns away from the sun, and then has no energy to turn back. If the satellite is being sent away from the sun, then solar panels would have to be so large that you couldn't even launch or manuever them. Batteries are very large and heavy, and because they are a chemical reaction, don't do as well when they get cold. Also, because they are a chemical reaction, they stop working fairly soon.

There is a material which creates heat at a constant rate for at least 25 years, and then very slowly reduces its heat output over the next 50 years. It is an isotope of plutonium called plutonium-238. It has a half-life of 87 years, and is used both for generating electricity as well as heat. The following web site has information about a satellite that is going to Saturn, with details about the heat and electrical generators going aboard.

http://nis-www.lanl.gov/nis-projects/caps/

Now, don't start imagining that they just take chunks of plutonium and glue them into place in the satellite. Each pellet is encased in a durable and corrosion resistant metal shells. There are a number of pellets used, each one separately encased. These are designed to withstand accidental impacts as well as the heat of reentering the earth's atmosphere. It is almost eery to look at one of the larger pellets, because it glows red hot. There is a picture of one in the web page above. I am giving you another web page that describes some of the tests that were done on heat sources, to make sure they would not break open easily.

http://www.lanl.gov/Internal/organizations/divisions/NMT/nmtdo/AQarchive/94-95winter/surveillance.html

"How would they clean it up? Would it wash onto any beaches and if it did would people be hurt by it?"

http://www-emtd.lanl.gov/td/Analysis/SystemsIntegration.html

Now, the question about plutonium in the ocean. To begin with, there is already plutonium in the general environment. There is some naturally occurring plutonium, but that amount is very small. The majority of plutonium in the environment is mainly a result of atmospheric testing of nuclear weapons from the late 1940's to the early 1960's, with a small portion of that coming from the reprocessing of nuclear fuel and destruction of thermoelectric generators from satellites reentering the atmosphere. So what is this plutonium doing?

Most of it is an oxide, that is, combined with oxygen. Once it falls to the earth, it tends to stay there. Plutonium is very heavy, much heavier than lead. It can be moved around by the wind, but because it is heavy, it tends to stay in one place and sink down into the soil. Running water can move it, but it stays solid because it is an insoluble solid. Actually, it dissolves in water about as fast as quartz glass does. So what happens in the ocean? It doesn't dissolve, and it is very heavy. It will tend to drop to the ocean floor and from there it will be buried very deep in the sediment. It could be stirred up by something cataclysmic, like an earthquake, but would have the tendency to fall back to the bottom again, and be buried again.

So what are the dangers of having environmental plutonium around? One of the points made in the web page above is this: Let's mix one kilogram (which is an unreasonably large amount) of plutonium oxide in a city water supply. We have to assume that for some reason it doesn't just settle to the bottom. Remember, it dissolves about as well as quartz glass, and if you throw a kilogram of broken glass into water it just settles to the bottom. Now we have a person drink two liters of that water every day for seventy years. The increased risk of cancer death (that is, risk added to all other risks) is 0.01%, or 1 in 10,000. There is a much greater chance that a person will be injured or killed in a car accident just driving to and from school or work. And this is if you could get the kilogram to stay suspended in the water and not just settle to the bottom. The plutonium in satellites is in chunks that do not readily break apart.

It is my opinion that you are in no danger of being hurt by levels of plutonium in the environment, either by it being in water or on the ground. You are probably more in danger, statistically speaking, of being hit on the head by the satellite as it comes back down.

Thanks for giving me an opportunity to answer this.

Janice Aasen