Discovering your believed correct model is wrong is a scientific breakthrough, as is discovering how to fix it.

Ok, I thought "breaktrough" brings you closer to something.

Eg. saying that "switch to Heliocentric worldview was a major breakthrough for Geocentric theory" sounds really weird to me.

The breakthrough would be more like saying, "the switch to heliocentric worldview was a major breakthrough for solar system modeling."

1) The reactors have been failing to generate sustained plasma due to specific failures.

2) The simulation models of the reactors did not correctly predict those failures.

3) The new model correctly predicts those failures.

4) Now you can iterate designs using the model with the expectation that these particular failures can be identified before building a full reactor.

5) Breakthrough.

Better understanding does bring you closer to making something tangible happen.

The heliocentric theory was a breakthrough for a variety of technologies. We certainly would have found going into space much more difficult if we still followed the geocentric theory.

The step is that they figured out _why_ reality wasn't as good as the model.

Another way to put it is that they improved the model.

That _does_ bring us closer to improving actual reactors.

We already know the current designs "don't work". If it weren't for turbulence, JET would have broken even a long time ago. Now there are better tools to predict when they won't work.