The exact heat effects for reactors are:
100% maximum hull heat: BOOM!
85% maximum heat: Blocks within a 5x5x5 cube have a chance of burning or turning into lava ('moving' lava only, no source blocks).
70% maximum heat: Entities within a 7x7x7 cube will get hurt.
50% maximum heat: Water blocks within a 5x5x5 cube (both sources and flowing) will have a chance of evaporate.
40% maximum heat: Wood/Wool/Leaf blocks within a 5x5x5 cube have a chance of burning.
Didn't know that either...
I added it to the Nuclear Reactor wiki entry, since there's no mention of it there, either. 
Yeah, I discovered that as well when working with your 3-chamber MkII-1 EC design last night.
The Readtor Planner may not take that into account when calculating maximum operating temperature or how long a reactor can run. It would seem that the projected results are under the assumption that the specified amount of cooling water will remain in the chamber at all times, regardless of the hull temperature.
Fortunately, I was able to pull the cells, swap out the cooling components and apply ice to get it back down to a temperature where I could replace the water, so there was no incident. But it shows that even presumably "safe" designs can have unforeseen effect.
Yeah, I discovered that as well when working with your 3-chamber MkII-1 EC design last night.
The Readtor Planner may not take that into account when calculating maximum operating temperature or how long a reactor can run. It would seem that the projected results are under the assumption that the specified amount of cooling water will remain in the chamber at all times, regardless of the hull temperature.
Fortunately, I was able to pull the cells, swap out the cooling components and apply ice to get it back down to a temperature where I could replace the water, so there was no incident. But it shows that even presumably "safe" designs can have unforeseen effect.
I think accepted best practice is to put the water source block up above the reactor out of evaporation range. Then the flowing water around the reactor can evaporate, but gets immediately replaced.
Indeed, that's a good idea. I will certainly keep that in mind for future builds. I can pretty well visualize how I'd set it up.
Still, it helps to keep in mind that any design that's cooled by surrounding water, that gets above that threshold, will need such a means of constantly replenishing the water or it will overheat.
I've been fortunate that none of my "lessons learned" have come at the cost of a meltdown or explosion.
one time i forgot running reactor in 3x3x3 hole with water around. when i come back i found a 5x5x5 hole and reactor in center. luckily uranium burn out just before it explode.
That sounds like my first one - used Rick's "budget plan" but didn't realize it relied on immersion. Just set the reactor core up right in the middle of my workshop and paid it no attention...
...until it started to emit smoke and flames! Fortunately, I was present when it happened, and not off on an excursion.
That sounds like my first one - used Rick's "budget plan" but didn't realize it relied on immersion. Just set the reactor core up right in the middle of my workshop and paid it no attention...
...until it started to emit smoke and flames! Fortunately, I was present when it happened, and not off on an excursion.
damn, if you were doing something outside, comeback and see big crater that would be very very bad day.
That's when you abort and rollback to your last backup. You -do- keep backups, at least of your test worlds, yes?
The crater left behind by my very first failure was... spectacular.
I am extreamly paranoid of this. I created my entire first reactor on a backup world, backed up THAT world to test my design, then backed up AGAIN to see if my container would contain the explosion.
