Ingen kan nog ha missat dokumentären ”Kärnkraftens återkomst” som visades på svt 1 i måndags. Det var en intressant dokumentär som till en början verkade lovande men som sen gav på tok för mycket utrymme till kärnkraftsmotståndares halvsanningar och rena lögner. Väldigt synd, jag tog iallafall tillfället i akt och skrev ett litet mail till producenten av programmet, Justin Pemberton. Här är en kopia av mailet

Dear Mr Pemberton,

Your show the nuclear comeback recently aired here in Sweden and I enjoyed it quite a bit! First I want to complement you for a show that gives both sides a moment to talk instead of it being a one sided show, very refreshing. However as a student of reactor physics I have a couple of comments about a few things said and not said during the show.

I think it would have been very enlightening to try and separate between what takes place during a meltdown in a regular light water reactor and the criticality accident that took place in the Chernobyl accident. The Three mile island accident is the ”perfect” demonstration of a light water reactor meltdown. The cooling fails and the fuel reaches its melting point and destroys the reactor itself. But there is never enough energy produced at any point to threaten the containment structure. In fact it takes a lot for a meltdown to even breach the reactor vessel itself. The TMI accident had zero impact on the outside.

A criticality accident as in Chernobyl is a completely different story because there the runaway chain reaction provides all the energy necessary to cause steam explosion that can spread radionuclides wide and far. But a criticality accident in a light water reactor is a impossibility since a loss of coolant automatically means loss of moderation, a chain reaction can not be sustained without moderated(i.e. slowed down) neutrons and thus the chain reaction naturally comes to a complete halt.

So even a meltdown doesn’t really present a danger to the surrounding unless in the most implausible scenarios. Since reactors that can suffer criticality accidents are illegal to even build in the west such a accident as Chernobyl need not be feared. Nothing on that scale can happen. In contrast chemical and other industrial accidents can have far larger death tolls than even Chernobyl, the Bhopal and Banqiao disaster has shown that. No nuclear accident in a western reactor can ever reach the same proportions as the Bhopal disaster, its hard to even imagine a scenario that would lead to a single death.

With some of the generation 4 designs like the pebble bed reactor the risk of meltdown is completely eliminated since the fuel has such a high melting point that even a total loss of coolant indefinitely cant produce the temperatures required to melt or even threaten the integrity of the fuel. This has been demonstrated in both Germany and China in research reactors of that type.

Regarding the waste its not quite true that there is no finished waste repository in the world. America has a repository for waste from the weapons program, WIPP – waste isolation pilot plant. The waste stored there is transuranic waste of the same kind as the long lived waste from civilian nuclear power. There is no reason, except political of course, that the method used in WIPP cant be used for civilian nuclear waste as well. The very thorough probabilistic safety assessments of WIPP has shown it will be safe without a doubt for the required time period.

Its hard to imagine a tougher target for terrorists than nuclear power plants. Regardless of what the terrorists can do inside the reactor it wont have a impact on the outside unless the containment structure is compromised. But it would take a extraordinary event to break the containment structure since its meter thick reinforced concrete. I love how you included the classic clip of a phantom fighter jet crashing into a piece of the containment, It really demonstrates how immensely sturdy they are!

If you happen to know what study the British Greenpeace representative was quoting when he mentioned that temperatures in a train tunnel fire can reach 8000 degrees I would be very grateful. Its hard to imagine a tunnel fire reaching temperatures 4 times as high as in a blast furnace. This is a interesting video clip showing the tests the transport caskets has gone through. http://www.youtube.com/v/1mHtOW-OBO4

Best regards
Johan Simu
Master of science student
Göteborg university