Hi,
I agree with Sceadwian in that a MOSFET would be a good choice.
Turning off an SCR that is conducting a dc current means shorting it out
with a low impedance device (like a MOSFET) anyway, for a time period
that allows the SCR to fully turn off, and then the rate of rise of voltage
has to be limited too once the low impedance device turns off. Too
much of a hassle if you ask me.
Also, you can get MOSFETs that will have lower voltage drop than an
SCR would have so that would mean higher efficiency too (provided
a good driver circuit is also used).