On single player, it seems when I log off the server and then return, the fusion reactor just stops producing power. It will have a full supply, empty products, full power and temp in the >1500 MK. The RF/t is initially saved upon log on, but will quickly drop to zero with no explanation on why. If gone unnoticed it will then wipe out my power storage. The only way I found to fix it is to break the reactor and replace it.
Nuclearcraft version 2.10p 1.12.2 on modpack ATM3.

Deuterium and tritium

Which fuels are you using?

Yeh, thought so - what's happening is that you're overshooting the efficiency curve. The optimal temperature for D-T is ~816.5 MK, so once your reactor continues to heat up past that point, the efficiency goes down and down. You want to use a comparator or active cooling to keep your reactor at near-max efficiency.

I cant find anything on any tutorial about comparator being on heat or efficiency. I guess I need to know how to control that because temperature just keeps rising no matter what I do.
Also, why would the reactor explode if I use 15 redstone? It exploded twice and hasnt exploded since I changed the length, but I came up with this new issue.
I guess there needs to be better tutorials on this. I have watched your videos and cant find anything to help me.

I am using a comparator. What I've found, if I follow your suggestions and use the max 15 redstone the reactor explodes, so I am using 13 redstone line hoping to keep temperature down. It doesn't explode now but it does this now.

It still should not explode with a full signal - is the comparator reading efficiency or heat?

In the reactor GUI, there is a button laballed efficiency/heat comparator - the blue colour represents efficiency and the other is heat. If you want to use the comparator to keep the reactor at a decent efficiency, you want the former setting.

Could I perhaos get a picture of your core comparator setup?

Yeh, the tutorial is a little outdated now - need to update it!

I had left the reactor in the default setting, which was efficiency, since i did not understand the interface, but still have a problem.

Ah, ok - the problem is that the comparator and redstone signal must be at the base of the core, i.e. on the bottom level.

Is that why? Guess I need to reroute everything then

Ok, that was the issue. thank you. I guess the tutorial you made on this did not explain this or how important inputs/output locations are. Did not think it was important, as long as it was set up