Looking at comment sections of news regarding our pilot plant to be built in Salmisaari, people seem to be overly confident in the capabilities of numerical CFD calculations. However, unlike reactor physics, which is an exact science, reactor thermal-hydraulic modeling always includes many parameters that need to be experimentally tuned to match the real world. Particularly in a natural-circulation system where driving forces are weaker and uncertainties consequently larger than in a forced-circulation system.
The purpose of the pilot plant is not to "test whether electricity can heat water". That we already know. But we must be absolutely certain that natural circulation with no pumps is strong enough to cool a shut-down reactor in every scenario. Without experiments, you can't honestly say you are.
