Those big ceramic cored wirewound resistors have a spectacular failure mode with HV, but, the typical rating is about a kV/cm of length.
One way to make a high power HV resistor is to use a bunch of smaller resistors in series. If you want, say 60K @ 150W, you could go out and get 120 2 Watt resistors at 500 ohms and string them in series.
Or you can make a water resistor (actually salt water in a tube), which, with the right tube material can dissipate a lot of power (water resistors are more common in impulse applications where they can take a huge impulse energy because of their large mass). http://home.earthlink.net/~jimlux/hv/rwater.htm has details.
Created on Saturday, March 24, 2001 9:17 AM EDT by James Lux