Server crashes when you try to wrench any Reactor component. It did work in singleplayer. Since I'm not server owner, I do not have crashlog...

If it works on single player it is most likely some kind of conflict on SMP. If you can find a log, I'll take a look.

i have referenced the issue to CrazyPants as well, so all 3 of you have been linked https://github.com/CoFH/Feedback/issues/365

Just spoke with him - we both are very sure we are not to blame. I doubt it is EnderIO as well.

gah, then how can this be fixed?

Please re-open this issue, i have the crash reports.
Crash Report: http://pastebin.com/gVMZ4ErR
Also, asking you to re-open issue #2397

Regarding issue #2397 this is what KingLemming had to say https://github.com/CoFH/Feedback/issues/365

he says the crash is your side

Finding all the bugs on my server xD

Fixed the first crash :)
I'm confident the second issue is not on my end, however.

well maybe try talking to KingLemming, because your both going back and forth xD and my players cant play because of this crash, they cannot login.

KingLemming says its something about your chunkloading messing with fastcraft and CoFH, but i would reply and talk to him, so maybe you can figure something out, he also mentions that it could be a problem with EnderIO V364 but im not sure, everyone is pointing fingers so maybe all 3 get together?

I'd suggest making a copy of the world to tinker with, and then forcefully removing the object in question, and see if that solves it. If it does, try rebuilding the solar evap plant from scratch to see if you can replicate it. If removing it doesn't fix your problem, then it's something elsewhere (and you just got unlucky that it happened at the same time/place as the solar evap plant)

or all of the mods (Mekanism, COFH, and EnderIO (which recently updated))could add a debug thing to show if it actually is on their side when the server crashes, pretty much it shows more of what is happening?
would that help?

The problem is it's often not as simple as "If my mod fucked up, throw this error". Most mods do already include error handling for their own code.
The issue is caused by an interaction between two or more mods, and is likely not a straight forward error.

they are already working on this issue in another ticket