Reply To: would nuclear energy really be accessible to all?

[Henning]

jamesr wrote:

I thought that with these very large currents the majority of the current flows on the outside of the electrode rather through the conductor anyway??

Exactly – that’s the problem. The current flows through a thin surface layer & hence all the resistive heating is concentrated there. Although it is the fast rise time (ie frequency) or the current flow that causes it to flow in the skin.

Isn’t only the charge located on the surface, being static? Why do I need on the other hand big copper wires to transport current over land lines? If that would be the case, a thin pipe of copper could replace solid copper lines, thus decreasing costs. Okay, they’re aluminium anyway…

Therefore I think the 20nm skin wouldn’t suffice. Correct me if I’m wrong. I’d love to be wrong here!

Okay, James quotes a different analysis here:

jamesr wrote:
I’m not sure I can go as far as percentages but here are a few figures from analysis done by Doug Olsen in 2003 (not verified):

For a copper anode, if the current is treated as a 1/4 sinusoidal rise to 600kA in 2us the skin depth is ~0.18mm. Integrating the current as a function of radius gives a maximum temperature rise of ~26C at the surface – for one shot. This diffuses into the bulk of the anode over time so after 40us or so the surface has dropped to 15C above its pre-shot temperature.