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Published:  2016-02-12 Views:  650
Author:  karelnel
Published in:  Technical/Tegnies
Nuclear Energy - Chernobyl

Chernobyl

 

We grew up thinking that the Russians are all bad people  We learned that they are all a bunch of communists and they are the worst enemy of all and that they threatened to take over the world. All feared their nuclear weapons and their massive numbers of battle tanks. But how few of us realized how vulnerable and human they are.

 

In the province of the Ukraine, 130 km north of the city of Kiev, you used to find the peaceful town of Prypyat, on the banks of the river after which it was named. About 49000 people dwelled there. Close nearby  , about 3 kms, was the site of the 4 Chernobyl Nuclear Power reactors, each delivering  1000MW of electricity to the Russian people. Another 12500 people lived in the town called , Chernobyl another 15 Km away

 

The reactor design is of the graphite-moderated, light water cooled boiling water type where steam from the  pressure tubes directly drives the turbines. The graphite moderator is a pile of graphite 7mX12m cooled with nitrogen gas. 4 Main coolant pumps circulate the water through the core. There was one design weakness - in the low power regime the reactor could become unstable, but for these occasions there were thorough safety precautions prescribed.

 

Late in April 1986 unit no 4 was due for shutdown and the management decided to do a safety related experiment. They planned to prove that they could drive the emergency cooling pumps by means of the electricity from the huge alternators as they were running down after shutdown, without  relying on the emergency diesel generators. Because they had problems in stabilizing the reactor the operators closed out several safety systems and  withdrew all but 9 of the control rods, where the absolute minimum were never to be 30. The operators tried to keep the power up by decreasing the feedwater to the reactor and this created a serious instability in the reactor, which created an overwhelming power surge, about 100 times the nominal power output  It was 23 minutes past 1  on the night of 26 April 1986. It ruptured the fuel and the hot fuel reacted with the water which caused a steam explosion that destroyed the  core. A second explosion followed that added to the destruction of the core and also of a part of the building.

 

The explosion sent burning pieces of graphite into the air and massive volumes of radioactive materials were released into the  atmosphere. The burning graphite started fires on the rooftops of most of the adjacent buildings and the 100 or so firefighters that came in to extinguish the fire was walking into a virtual death-trap because of the extremely serious  radiation situation. They succeeded in extinguishing the fires by 05:00 the next morning, but by then the serious graphite fire in the reactor core started which for 20 days continued to spew deadly radioactive-isotopes into the environment - an estimated 50 tons of it!  The heavier radio-active particles in the air was deposited in the vicinity of the reactor, but the lighter elements were carried by the air currents far beyond the borders of Russia and was first detected in Sweden. Eventually all of the Northern hemisphere was effected in some way or another.

 

When radiation levels reach very high levels in Pripyat, at 11h00 on 27 April the authorities started to evacuate the 135000 people. It only took them 2.5 hours , using 1200 buses. How sad that these people had to leave behind everything they owned , never able to return. During the next week another 80000 people were removed from the area. In the meantime the Authorities were desperately trying to cover the  burning reactor by depositing about 5000 tons of Boron carbide, Dolomite, clay and lead into the damaged building by means of 1800  helicopter-sorties. Unfortunately the covering acted as a thermal shield as well which led to a further increase in the temperature of the mass and a further yielding of the structures and a core meltdown, with the release of even more radionuclides. In 15 days 400 workers tunneled extensively under the building and built a massive water cooled  concrete slab which was meant to prevent the melted core of burning its way through into the environmental waters.

 

One person died of the explosion, one died of a heart attack on site and another died the next morning of thermal burns. The most tragic however are the 30 odd people or liquidators that came to extinguish the fire and received lethal doses of radioactivity. The high intensity radiation interacts with living tissue and  destroys so much thereof that the body cannot repair itself. The people soon  (15 - 30 minutes) started vomiting, having fever and diarrhea and they became desperately ill. Mucous membranes were severely effected and became swollen, dry and ulcerated, making breathing and swallowing extremely painful. Blood cell and platelet counts fell dramatically indicating extreme damage to the marrow, which made it impossible for the patients to fight infections, and interfered with the clotting capabilities of the blood. Excessive burns complicated the treatment, and almost all of these patients died, in spite of all the specialized treatment.

 

But the human drama was much wider than this. Time however does not allow  me to elaborate. More or less 800000 other people were used to clean up the environment, all receiving significant doses. The population was severely traumatized  because of the lack of information and unpreparedness of the authorities. Throughout the years there was a constant and significant rise in the incidence of thyroid cancers, especially in young children that were in the area at the time. Although the official figure of casualties is  still at 33, some sources put it as high as 10000 (USA Today, April 4) Today, still 4 million people live in contaminated environments, and no-one knows what will the final outcome be.

 

This tragedy befell the Russian people. They were fathers & mothers just like we are, and had children just like us. They also struggled  for a foothold in life - as we do. But their destiny was irrevocably changed  - and perhaps the results will be evident only in the generations to come.

 

Friends - let us pause for a moment right here in our busy day and reflect on the preciousness of life as we  experience it. Let us refrain from grumbling and being discontent. Let us be  thankful for our privileges and for the grace we are  enjoying. Although we may not be in a position to do something for the people of Chernobyl, we can all extend our hand to a  child or a friend in need, and so make a contribution to life.

---000---

KPJ Nel

2016-02-12

 


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