It took me forever to figure out how to get my fission reactor to drain, unfortunately there is little to no in sight in this around the internet. So I am sharing my discovery with those of you who are having difficulty draining the toxic waste from your fission reactor. You know that little block called "reactor drain"? Don't use it. There's a couple reasons why
Number one you don't need it
Number two its a waste of space
Number three I don't even know how its properly used.
Anyway, here's what you'll need.
A properly set up Dynamic tank
So here's a secret, if you have your fission reactor submerged under one block of water and at least two blocks of water around it, it will never over heat. So now you can utilize the space under your reactor. So hook your mechanical pipe up on the bottom of your reactor, use the configurator on the piece that's connected to the reactor, so that piece is red. Now run the ye pipe to your dynamic tank and presto, your now draining that nasty toxic waste into your dynamic tank. It will fill quick, so buckets are now your new bff. I have my reactor set up to an ME network, so its auto fed fission rods. I reccomend this, because than you can set up steam funnels and have a closed reactor and double efficiency. Also consider hook in your pistons up to a daylight sensor, with steam funnels, your reactor turbine will coast through the day and the pisons will drop at night. This is the most efficient set up I've found