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Month: January 2013

Why don’t nuclear reactors go kaboom? A reactor kinetics primer part – 3

Water Dolphin

We have discussed the time behavior of the neutron flux and reactivity feedbacks. Now it is time for the the thermal side of things. The point kinetics model describes how much energy is produced in the fuel, but we also need a model for how the energy is transported within the fuel, through the fuel cladding and into the coolant. To figure it out we need models for heat conduction through the fuel and cladding, heat transfer to the fluid through convection, properties of the fluid at different temperatures and pressures and so on. This blog post will deal with the heat conduction in the pellet and through the cladding.

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För de som inte gillade Wechselmanns film…

…finns det hopp om en annan bild av kärnkraften på biodukarna. I dagarna har har Robert Stones film Pandora’s Promise premiär på Sundance Film Festival i Park City (Utah, USA), han gör i denna upp med de myter som tidigare legat till grund för hans kärnkraftsmotstånd. Vi får se om och när den lyckas leta sig över Atlanten till våra biosalonger.


Den bör givetvis granskas kritiskt, men vi har all anledning att tro att den kommer vara avsevärt mer saklig än Maj Wechselmanns Världens säkraste kärnkraftverk. Varför då då? Jo, han började ifrågasätta och faktakolla allt det han trott vara sant, och vågade komma fram till att han hade fel. Robert Stones egna ord:

Pandora’s Promise is without question the most personal and important film of my career.  I’ve learned that just about everything I thought I knew about energy turned out to be wrong.  And most of what I thought I knew about nuclear energy and its historical events has turned out to be precisely the opposite of what really happened.

Hatten av för Robert Stone…

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Why don’t nuclear reactors go kaboom? A reactor kinetics primer part – 2

Advanced test reactor Foto: Matt Howard, Source: Wikimedia Licens: Creative Commons Attribution-Share Alike 2.0 generic

Its time for some more fun with reactor kinetics, in the last post we ended by looking at the point kinetics equation with one group of delayed neutrons. In this post as I promised we will talk about reactivity feedbacks. To brush up your memory, reactivity is defined as:


Why don’t nuclear reactors go kaboom? A reactor kinetics primer part – 1

Nuclear reactors contain tons of fissile material and nuclear bombs contain only kilograms of fissile materials, so why does one of them explode with enough force to flatten a city but the other doesn’t? I will pull out some latex skillz and geek it out with equations to describe the physics behind whats in nuclear engineering is called reactivity excursions or RIA (Reactivity Insertion Accident). The level of these blog posts will be such that an interested and fairly math savy person can understand and calculate these kind of things on their own.

Castle Romeo photo: United States Department of Energy, Source: Wikimedia

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