Chernobyl

hernobyl by Nicholas Lativy, on Flickr

I like to think that I was a little more aware of the Chernobyl nuclear disaster than other folks. I am a science nerd with a real Jones for the technology behind nuclear reactors and, at the time, I was dating a Soviet Studies major at U of M who had some real contacts that would share tidbits of “gossip”.

So 25 years ago today, we did not know there was anything going on, but it was only a day later that she told me that things on the border with the U.S.S.R. were getting weird and that she thought there might be some kind of accident in Ukraine.

We now know what happened. During an experiment designed to prevent a catastrophic loss of coolant flow during a loss of power from the power grid the reactor was pushed to an unstable configuration, where it was only the water in the reactor holding back the nuclear reaction. All the control rods had been withdrawn to deal with the production of xenon that had reduced the power levels in the reactor to very low levels.

The event they were actually testing for occurred while a planned shut down was in process. They lost power and had to go to the diesel backups. As feared these did not come on line fast enough to keep the water coolant flowing. Steam built up which reduced the ability of the water to moderate the reaction. At this point the operators attempted an emergency shut down. It would take about 20 seconds for the rods to be fully inserted in the core. Tragically the design of these rods forced the coolant out of the rod channels before they were inserted. This means the only thing holding back a run away reaction was withdrawn form the core.

As a result fuel rods fractured and fouled the control rod channels. Then there were the first of as series of steam explosions as the reactor started producing more and more intense nuclear reactions. It eventually blew the reactor vessel apart and started the fire in the roof of the building. Worse the graphite used as a moderator now had no cooling water around it and burst into flame throwing plumes of radioactive smoke into the sky and further reducing the ability to control the nuclear reaction of the fuel.

The world found out about Chernobyl two days later when workers at a Swedish nuclear plant began to have radiation alarms go off. The plume of radioactive smoke had reached from Ukraine to Sweden.

Chernobyl is a bad as it gets. It was the fire the spread the radioactive materials so far. Graphite burns hot and it took days to put the fire out. In that time radioactive cesium was lofted to the high level winds and spread in a classic fall out cloud. It brought low levels of radiation to all Europe west of the plant. There were even detectable levels of the radiation all the way to the United States.

Around the plant it was, obviously much worse. Large levels of radioactive iodine were released and exposed populations as far away as Kiev. The levels of thyroid cancer in that part of the world are 400 times the normal level. But radioactive iodine has a very short half live and is gone in a few weeks.

Of more concern is the cesium that was released. Most of it fell within 50 miles or so of the plant. Since that is a quarantine area, that has not been much of a problem. But it has not gone away by any means. It is in the soil or absorbed into the trees in the forest there.

Now Ukrainian forests are rather like the ones in the Western United States, they tend to grow then burn. There has been no major fire in the 25 years since Chernobyl. There also has been almost no forestry work there. This means that the forests around the plant are in the kind of shape where massive fires, the kind that last for months, can occur.

If one of these massive fires happens the trees which have absorbed the cesium will burn, and throw radioactive smoke, very similar to the smoke from the original accident, high into the air. Massive fires like that can create their own weather patterns, and that would mean that once again a plume of radioactivity will head west towards Moscow and the rest of Europe.

It would be dangerous to fight such a fire, again because of the level of radiation in the soil (which would dry and also loft) and the amount of cesium in the smoke. Inhaling that smoke would very bad for your health, to say the least.

This is the legacy of a major nuclear disaster. Buildings and areas can be quarantined but there is really very little that we can do to prevent the spread of long lived radioactive elements once they are in the environment.

The US Forest Service is helping the Ukrainian government with thinning plans, and the removal of downed trees. This will help to prevent a fire for a while, but as we have learned with our own Western States there is nothing in the world that can prevent a fire forever. In fact the act of fire prevention just makes the eventual fire worse, as we have disrupted the cycle where there are smaller trees interspersed with the larger ones to limit the heat and size of the fire.

One day, some time in the next couple of decades we will hear once again that the Chernobyl accident is spreading radiation as the forest burns. In one way we are lucky with the Fukishima accident. It is not in a heavily wooded area and, so far, there has not been the intense and wide spread release of fission byproducts like there was at Chernobyl. It is unlikely that we will have the same problems with clean up there, but there will be others that we have not thought of yet.

All of this leads to a single conclusion. We as a species really should not use nuclear fission for power generation. When it works it is great, it produces power and no greenhouse gases. The problem is that when it fails it is a flat nightmare. If the cost of world wide nuclear power generation is a disaster like Fukishima or Chernobyl every 25 years and the resultant decades or centuries of continued contamination for areas ranging from 50 miles to 500 is it really a viable option?

There are applications where it is appropriate. Space exploration, military applications and the like; however for civilian applications I have come to the conclusion that there is just too high a price to pay. Humans are fallible, running a reactor for decades; under private enterprise market rules is just a very, very bad combination.

So, as sad as the science nerd in me is, it is time that we put aside this type of power. It just sucks up resources that could be applied to the obvious solution to our electricity needs, wind and solar power.

In the end I think back 25 years to those brave folks who, completely unaware of the level of risk rushed to put out a burning nuclear power plant. I think about the operators and the technicians who did what they could to prevent their accident from being worse than it was and paid for it with their lives. I think about the people of Kiev, living with the knowledge that they were exposed to more radiation than anyone since the survivors of Nagasaki and Hiroshima and wondering what the next visit to the doctor might tell them.

I wonder what the next generation of Europeans will think when invisible particles of cesium once again fall from the skies, and expose them to a threat that was not their choice or fault. Will there still be a feeling that this type of power is worth the cost?

The floor is yours.