What is the voltage? Let me presume it is 240 volts, single phase. 10,000 watts divided by 240 is 41.6 amps. This is a "continuous load" so the wires must have an ampacity of 125% of 41.6 amps, which is 52 amps. I don't have my book handy, so I don't know if a #8 will suffice. I will say that you must have a wire with an ampacity of at least 52. You can use a 60 amp breaker on such a wire, since it is the next higher rated overcurrent device.
Welcome to the forum.
Charles E. Beck, P.E., Seattle
Comments based on 2008 NEC unless otherwise noted.