My buddy and I found a "fix" that seems to be working for the following error code, try at your own risk.
Problem: Placing thermal reacter (item number 192) next to a nuclear reactor causes crash.
OS: win7 64bit
Java Version: Version 7 Update 9 (build 1.7.0_09-b05)
Tekkit Version: 3.1.3
Fix: Turn your crashed server off. Go to your server folder. Go to mods folder. Delete your zip folder (mod_IC2NuclearControl-1.1.10b-mcpc-r1)
Restart your server. Join your server, then exit your server. Save, then stop your Tekkit server.
Go to your original (Tekkit_Server_3.1.3) folder that you downloaded from the Tekkit Website. Go to mods folder, find the (mod_IC2NuclearControl-1.1.10b-mcpc-r1.zip).
Copy and Paste it back in to your server mods folder.
Start your server back up, and join.
Warning: This is just to recover you map and make it playable. If you try to place a thermal reactor next to a nuclear reactor, it will crash again.
Just remember not to use it.
Error Code:
[sEVERE] java.lang.RuntimeException: java.lang.NoSuchMethodException: ic2.common.TileEntityNuclearReactor.tickRate()
2012-12-16 00:49:22 [sEVERE]at nuclearcontrol.NuclearHelper.getReactorTickRate(NuclearHelper.java:304)
2012-12-16 00:49:22 [sEVERE]at nuclearcontrol.TileEntityIC2Thermo.checkStatus(TileEntityIC2Thermo.java:190)
2012-12-16 00:49:22 [sEVERE]at nuclearcontrol.TileEntityIC2Thermo.q_(TileEntityIC2Thermo.java:244)
2012-12-16 00:49:22 [sEVERE]at net.minecraft.server.World.tickEntities(World.java:1189)
2012-12-16 00:49:22 [sEVERE]at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:559)
2012-12-16 00:49:22 [sEVERE]at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:457)
2012-12-16 00:49:22 [sEVERE]at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
2012-12-16 00:49:22 [sEVERE] Caused by: java.lang.NoSuchMethodException: ic2.common.TileEntityNuclearReactor.tickRate()
2012-12-16 00:49:22 [sEVERE]at java.lang.Class.getMethod(Unknown Source)
2012-12-16 00:49:22 [sEVERE]at nuclearcontrol.NuclearHelper.getTickRateMethod(NuclearHelper.java:128)
2012-12-16 00:49:22 [sEVERE]at nuclearcontrol.NuclearHelper.getReactorTickRate(NuclearHelper.java:300)
2012-12-16 00:49:22 [sEVERE]... 6 more
2012-12-16 00:49:22 [sEVERE] Unexpected exception
java.lang.RuntimeException: java.lang.NoSuchMethodException: ic2.common.TileEntityNuclearReactor.tickRate()
at nuclearcontrol.NuclearHelper.getReactorTickRate(NuclearHelper.java:304)
at nuclearcontrol.TileEntityIC2Thermo.checkStatus(TileEntityIC2Thermo.java:190)
at nuclearcontrol.TileEntityIC2Thermo.q_(TileEntityIC2Thermo.java:244)
at net.minecraft.server.World.tickEntities(World.java:1189)
at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:559)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:457)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
Caused by: java.lang.NoSuchMethodException: ic2.common.TileEntityNuclearReactor.tickRate()
at java.lang.Class.getMethod(Unknown Source)
at nuclearcontrol.NuclearHelper.getTickRateMethod(NuclearHelper.java:128)
at nuclearcontrol.NuclearHelper.getReactorTickRate(NuclearHelper.java:300)
... 6 more