The Flying Shingle
Wallace’s World
Here come da nukes
by Mike Wallace
Monday, March 21, 2011

If you are brave enough – or foolish enough (pick the adjective of your choice) to allow your country to become dependent on nuclear power, it’s absolutely critical that you place many, many layers of protection between yourself and the deadly radioactivity that provides the power of a nuclear reactor.

Let’s back up a step and recall how a nuclear reactor produces power. A reactor is constructed so that reactive elements in the shape of “rods” are slowly brought into contact with a surrounding medium, causing a nuclear reaction which releases enormous amounts of heat. Power is controlled by sliding the “rods” in and out of a radioactive medium. Additional control is achieved by inserting various types of “damping” mechanisms to slow the reaction should it somehow run amok. (SEE www.nature.com/news/2011/110316/full/news.2011.164.html)

The danger has always been the inability to keep the reactors cool, and especially the possibility that a lack of cooling water would expose the fuel rods. When they are exposed the reaction speeds up. The problem is if it heats up too much there is a tipping point at which things start to melt.

The important thing to understand in all this is the element of control. The nuclear reaction must proceed at a precisely measured pace; too slow, and it will not be self-sustaining nor produce enough power, too fast, and it will run out of control, leading to a dangerous nuclear “meltdown”, producing fatal damage to the reactor and – most dangerous of all – a massive and dangerous release of radioactivity. (www.fukushimaaccident.com)

Reactor operators practice every possible means of preventing such catastrophes, but there’s only so far they can go; as one naval nuclear operator put it, “a reactor scram [emergency shutdown] is an exciting drill. because once you start it, it’s no longer an exercise” [Submariner’s Review, (declassified edition), v.12 no. 3, June 1991] 

Because loss of control accidents (LOCA) present the greatest danger to a reactor, the worst thing that can happen is any breach in one of the many containment vessels separating the reactor mechanism from the outside world. A crack or pinhole in one of the containment vessels could be enough to cause a dangerous radioactive release.(www.nature.com/news/2011/110315/full/471273a.html}

It follows that if the containment system does not maintain a careful pressure balance – that is to say, dangerous pressure differential builds up between the various cooling elements – there is a risk of a leak that could vent radioactivity into the environment. (www.nature.com/news/2011/110316/full/news.2011.164.html)  The Japanese earthquake set loose at least one – if not several – of these nightmare scenarios at the Fukushima nuclear power plant in northern Japan (SEE resources.nei.org/documents/japan/Used_Fuel_Pools_Key_Facts.pdf)

It seems the damage to the Fukushima plant is severe. I’ve received an email from a colleague in Japan (Dr. Tatsujiro Suzuki, Vice-Chairman of the Japan Atomic Energy Commission), who writes that the situation at Fukushima “doesn’t look good”, and that “at least one of the reactors (there are six reactors and they’re all behaving differently) may have lost cooling capability”  – precisely the nightmare scenario outlined above( SEE bravenewclimate.com) (SEE ALSO EXCELLENT DISCUSSION OF THE DANGERS OF FUEL STORAGE NEAR THE REACTOR: resources.nei.org/documents/japan/Used_Fuel_Pools_Key_Facts.pdf)

We know that there have been several explosions and radiation released – to the point where US naval ships have picked up traces of radioactivity as far as100 miles off the Japanese coast. However, the Japanese government has not been forthcoming with information, which makes it very hard to determine whether or not things are under control. The vehement suspicion – as they said in the Inquisition – is things are not out of control but we don’t know.

As of Friday at noon it is unknown whether there will be a catastrophe or whether the Japanese authorities will be able to bring the temperatures under control enough so that we can say it’s over. Until stable shut-down happens it is not under control.
The worst case scenario would be complete melt-down, with Northern Japan – and quite possibly much of North Asia –facing a nuclear disaster unparalleled since Chernobyl. The best case scenario would see the plants being shut down in something reassembling a normal way.

Whichever scenario comes to pass, we have been taught another salutary lesson in the dangers of nuclear power
Mike Wallace is an Emeritus Professor at UBC, is on the Executive Board of Canadian Pugwash Scientists, winner of  the 1995 Nobel Peace Prize.

Opinions expressed in this column will usually be those of the author and do not necessarily reflect those of The Shingle.

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