Archive for May, 2011

The Mysterious “Blue Glow” (part 4)

May 13, 2011

Tales from the Nuclear Age

Copyright © 2011 by Charles Glassmire


May 13, 2011

 The Mysterious “Blue Glow” (part 4)

 What’s the strange “Blue Glow” sighted  over Fukushima reactor 2?

          No, it’s not a flying saucer. Nor is it evidence the world is nearing its end or the reactor has “melted down”. It’s an effect often seen when reactor fission products encounter water – in fact some reactors are designed to be immersed in water. So it’s not an uncommon occurrence, and is familiar to operators of water cooled reactors everywhere.

          The phenomenon is called Cerenkov Radiation,  named after the Russian scientist who studied it. This effect is actually

Cerenkov Radiation

harmless light emitted in the blue region of visible light.  As the reactor operates, it generates usable electricity from Uranium nuclei breaking up into pieces (called fission products). These fragments often are radioactive. Some of them shoot off very fast electrons (called Beta particles) which often try to go faster than the speed of light in water. But as Einstein told us, nothing can travel faster than light in a vacuum. But light slows down when moving in a crowd of water molecules; so the speeding electrons have to slow down too, or Einstein would get mad (:-).

          These electrons try to move very rapidly through the water molecules, like a runner pushing his way through a crowd of slow moving people. Since they have a negative charge they pull on some water molecules as they pass by, which then oscillate and take some energy away from the electron. So the Beta particle slows down, leaving a trail of oscillating water molecules in its path. As those water molecules rock back and forth, they give off the energy they robbed from the Beta particle as a photon of light – blue light, as a matter of fact. So the blue glow that we see shining above reactor number 2 is just all those rocking water molecules giving off a blue light, testifying there is a lot of beta radiation slowing down in the water and becoming harmless.

 So what’s the future for the Fukushima reactor site?

          The situation is under control, but still not safe. Radiation levels in the reactors are still higher than allowable, but workers are now entering the buildings for short times. Reactors 5 and 6 seem to be undamaged and may in the future be restarted and become productive again. Numbers 1 to 4 have extensive damage. I suspect these reactors are beyond repair. The fissioning in the core must be seriously reduced, so no large quantities of damaging heat are emitted. Then I suspect the fuel rods will be removed and packed in fuel containment vessels, then stored underground.

          One major problem still remaining is the tons of contaminated seawater used to flood the cores. This material must be stored and where to put it seems still in question. The radiation released into the sea will ultimately be distributed in the Pacific Ocean and diluted back to background levels. Local seafood should be avoided for some time.

          The fission products deposited on the grounds must be bulldozed up and packed in closed containers for storage. Ultimately, reactors 1 to 4 will probably be filled with borated cement and sealed. This may take years. Remember that there were no deaths associated with this accident, despite many unfortunately killed from the Tsunami water damage …                    

(to be continued …)