Issue description

Duplicate of #7587, but happening in 1.20.1. I am using D-T Fuel fusion reactor, used lasers to ignite it (last issue was more about "resistive heater ignited" fusion). Everything related to fusion is stored in a single chunk and all chunks are loaded by a dimensional stabilizer. Ran save-all command before stopping the server.

When the ignition stops, all reactor data is still stored inside (plasma and case heat etc), meaning just the ignition stops.

Steps to reproduce

1. Build a fusion reactor in a single chunk. Also make sure fuel is in the same chunk too.
2. Ignite the reactor with lasers.
3. Chunkload the chunk of the reactor via any way.
4. Restart the server.
5. Join the server, the fusion ignition will be gone but all the NBT data will be still there.

Minecraft version

1.20.1 (Latest)

(Neo)Forge version

Forge 47.2.14

Mekanism version

10.4.5 (Latest)

Other relevant versions

No response

If a (crash)log is relevant for this issue, link it here: (It's almost always relevant)

No response

Same issue. Spent 3 days trying to get this to work and researching every reason why it wouldn't.

Doesn't matter if I send D-T fuel, Deuterium and Tritium, or all of the above.

My reactor would ignite, but would not consume ANY fuel.

I can confirm this bug. It seems the multiblock has to re-form every time the server restarts, which can kill the ignition. With a high enough injection rate of deuterium and tritium, re-ignition happens automatically. With D-T fuel, re-ignition does not happen without inserting another hohlraum. Also, water cannot be inserted into the fusion reactor if only D-T fuel is used.

There is no workaround for the issues I have listed, as feeding deuterium and tritium vs D-T fuel are mutually exclusive upon (re)forming the multiblock and the water is removed. Same MC and Mek versions.

With an ultimate gas tank on reactor port normally this creates a buffer which gives time for AE2 to initialize. Since then, I no longer have any problems during a server restart. But it is known that ATM 8, 9 also had this "bug"

Unfortunately the issue occurs even with a full ultimate chemical tank feeding fuel to the reactor in the same chunk. So yes it is still a valid bug. We will see if 1.21 will have it, it probably will.

Can confrirm that, on ATM9 - to the sky modpack, builded setup below, after restarting world, reactor shutdowns

(user FTB chunk loader)

I solved this by putting a filled Hohlraum into a creative bin then piping them to the fusion reactor. Works great but you will need to cheat in a creative bin for it to work. I view the creative bin as making the fusion reactor function as it's supposed to work. If you have modular routers, you can even hide the whole setup.

Using a hohlraum source is just a workaround to reignite it immediately but definitely not the way to fix it

A workaround is needed while the bug exists if you want to run on D-T fuel.

Yes, just have to make a lot of hohlraums ready for ingition.

While not exactly sure, I think this bug was fixed at some point (either by accident or intentionally, as a side effect of code changes in the mod) because the bug doesn’t seem to occur in 1.21 at all.