Good news, Bad news

Dear Reader,

I have been following the news and reading about the events in Japan, and I have noticed some things which I think I should comment on.

The fires in the spent fuel store are serious problems, while less of the shortlived but very toxic iodine-131 will be present in this older fuel this spent fuel could still pose a threat.

Plutonium has been discussed, it so happens that unit 3 was fueled with MOX. I am well aware that the public and nuclear workers are aware that plutonium can be a threat to health. On yahoo news it was said that plutonium once absorbed into the blood will linger for years in the bone marrow and the liver. This is true but might not be relevent.

Plutonium dioxide which is the chemical form of plutonium in nuclear fuel is very very insoluble in water, in fact it is very hard to dissolve it in acid. As a result it is unlikely to get into the blood of a worker or member of the public in a water soluble form. But in a paradoxical way the insolubility of plutonium dioxide makes it more dangerous, if plutonium dioxide is inhaled it can stick in the lungs and stay there for a very long time. This could lead to lung cancer. Overall I think that airborne insoluble plutonium is a greater threat to health than a water soluble form of plutonium.

Some of the plutonium dioxide will be cleared from the lungs by the action of the little hairs which sweep the dirt out of your lungs, this plutonium together with your phlegm will then be swallowed. The insoluble plutonium dioxide then will pass through the digestive system unchanged and come out at the other end. One of the classic ways to check a nuclear worker for exposure to airborne plutonium dioxide is to get a poo sample and then test it for plutonium.

Because plutonium dioxide is very insoluble it is unlikely to get into the public drinking water assuming that the Japanese water company filters the water before selling it.

On the other hand because plutonium dioxide is very insoluble and has a very high boiling point, it is unlikely to escape from the reactor if the reactor is just over heated. A mechanically violent event which is able to scatter fuel would be required for the plutonium to be ejected into the air from the reactor. So as long as no violent event occurs inside the reactor we are safe from the plutonium, currently I hold a view that the iodine, noble gases (krypton and xenon) and cesium from the reactor will be a greater threat right now.

If you do get plutonium dioxide into a cut then it would be able to deliver an alpha dose to the tissues where the powder ends up, if however you inhale, eat or inject a soluble form of plutonium into your body. Then things are rather different, what will happen is 10 % of the soluble plutonium will be lost in your urine rapidly while the rest of it is split equally between your liver and bones. In the liver it has a biological half life of about 40 years while in the bone the biological half life is about 100 years. This is much longer than the biological half lives of lead (circa 10 years) and cadmium (circa 30 years) in bone.

It is possible to prevent 90% of soluble plutonium entering the liver and bones but this requires rapid treatment with special drugs.

So the good news is that the plutonium is not likely to escape from a simply overheated reactor at an early stage. Also plutonium dioxide is not likely to invade ground water and then get into the drinking water supply.

While the bad news is if your inhale plutonium dust then it is very bad for your lungs.

Where to get news from

One important news source is the UN’s organisation which deals with nuclear technology. They are providing some updates on the state of the reactors and fuel in Japan.

http://www.iaea.org/newscenter/news/tsunamiupdate01.html

Nuclear update

Here is a link giving a recent update on the state on the nuclear plants in Japan

http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300273535P.pdf

The reactors in Japan can not explode like atom bombs

I am sure that all my readers will know that an atom bomb explosion near a populated area would have a very horrible effect. It would lead to countless deaths as a result of heat and blast.

It is important to understand that the reactors in Japan can not explode like an atom bomb with a nuclear detonation.

To create a nuclear detonation requires that the bomb design must satisfy a series of demands, the two most important ones here are.

1. The system must go from being subcritical to super prompt critical

Right now the reactors are subcritical and no fission reaction is occurring inside them. The addition of boric acid and the control rods should keep the reactors subcritical.

2. This change must occur very quickly, faster than the time between the spontaneous appearance of a neutron in the fuel

It would be impossible to remove the control rods at the speed which would be required. Also the removal of the boric acid would be very hard to do. Also the rate of neutron generation inside used power reactor fuel (either uranium dioxide or MOX) will be quite high. This fuel is close to the total opposite of a material which lend it’s self to building an atom bomb. 

The plutonium isotope signature is likely to be very bad for bomb making. The Pu-240 level in used MOX, used uranium dioxide fuel and reactor grade plutonium will be high. The Pu-240 is one of the key isotopes which makes it harder to build bombs out of plutonium than it is to make a uranium-235 based bomb.

So I think that a large explosion like one of the atom bombs dropped by the USAF on Japan at the end of world war two will not occur in the damaged reactors or in the spent fuel store in Japan.

Some good news about the reactor accident in Japan

There is something which is important to point out which may help with an understanding of the accident.

As a result of the radioactivity of the fuel inside the reactors heat is produced, this heat and not a nuclear fission reaction has been responsible for the damage to the nuclear reactors and much of the trouble in Japan. This heat production is known as decay heat.

This heat production inside the fuel is not going to last forever, with each hour and each day which goes by since the reactors were shut down the heat production inside the fuel will become smaller.

Understanding the nuclear accident scale

Some years ago to help people understand how big nuclear accidents are and to rapidly communicate with each other a scale was set up by the UN.

It ranges from zero (0) which is an event which has no safety significance, through to horrible major accidents such as Chernobyl (level seven). If you are confused by the scale then please go to the following link.

http://www.iaea.org/Publications/Factsheets/English/ines.pdf

News from Japan

If you want to know what the state of the reactors then I would suggest you go to this link, here it gives a summary of what is happening in different parts of the nuclear site.

http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300252224P.pdf

Cut out the middleman

Dear Reader,

Right now I guess that a lot of people are trying to understand what is happening in Japan with the nuclear reactors.

I know that a lot of people are having trouble finding a person or organisation which they can trust to give them a good and fair explanation of what is going on. One of the things which makes things more stressful and scary is a lack of knowledge and understanding of what is going on.

Even well educated people such as school teachers, medical doctors and other university graduates may be right now having trouble understanding what is going on. Rather than being a passive consumer of the news, I would encourage people to take an active approach and educate themselves to improve their understanding of the subject.

When you understand the subject more then while it may not change what is happening on your doorstep, it will give you one of the most important tools which is an understanding of what is happening.

I would like at this point to make a recommendation of a book which may help you quell the confusion in your mind. This book was originally written by a Czech Prof (Jiří Hála) who I know as an introduction to radioactivity and nuclear matters, after being used in the Czech Republic is was translated into English and is now in its second edition.

The later part of the book does explain about nuclear accidents and what happens when radioactivity is added to the environment by an accident, an atom bomb or by the disposal of radioactive waste.

The book is called “Radioactivity, Ionizing Radiation and Nuclear Energy”, it was written by Jiří Hála and James D. Navratil. The ISBN number of the first edition is 80-7302-053-X. It was published by Konvol in 2003.