This thermophotovoltaic cell is tuned to operate with radiant energy from a body heated to between 1900 and 2400 degrees Celsius. That is much hotter than any current reactor core. It wouldn't work with a traditional nuclear plant; it would require (at a minimum) developing reactors that operate at a much higher temperature. The most common power reactor design, the pressurized light water reactor, heats water to around 315 degrees Celsius:

https://en.wikipedia.org/wiki/Pressurized_water_reactor#Cool...

> The most common power reactor design, the pressurized light water reactor, heats water to around 315 degrees Celsius

Can’t it just heat something else than water? E.g. something that’s liquid at 2000C?

Could this maybe be used as part of a fusion reactor?

I think the problem isn't that we can't achieve 2000 degrees with fission, but the entire design would need to be re-thought to handle such temperatures.

You need a completely different sort of materials and need to consider new types of risks for a reactor that's supposed to operate at such temperatures.

Most semiconductors don't like ionizing radiation. In addition, the bottom-end of the operating range for this (1900C) is well above what google suggests is the typical coolant temperature (300C).