The lunar exosphere is too skimpy to trap or spread the Sun’s energy, so differences between sunlit and shadowed areas on the Moon are extreme. Temperatures near the Moon’s equator can spike to 250°F (121°C) in daylight, then plummet after nightfall to -208°F (-133°C).
Only at night.
https://science.nasa.gov/moon/weather-on-the-moon/
Which sounds like a pretty big challenge for a nuclear reactor. Maybe they only plan to put them on the poles?