I was reading on an aqua/hydroponics site that recommended using hydrogen peroxide for cleaning LECA.
I've also heard of people microwaving damp LECA for quite some time. That said, I share Merlyn's concern about it exploding in there!
If you were being paranoid, a pressure cooker makes a fairly good "home autoclave" that will kill pretty much everything.
Obviously, Ray has used LECA more than pretty much anyone else, so I imagine his method works well.
If I'm using Bleach, I go with about a cup per gallon; about an ounce or two per gallon if Physan.
I usually soak it a couple of days to clean the bleach out afterwards, with about 50% of the volume LECA in the drum. If there is more water, it's faster.
Chryss, the stuff is too porous to trap steam and explode.