It’s a a 10kW research reactor designed by the Argentinian firm Invap SE.
https://neutronbytes.com/2019/04/07/much-ado-about-saudi-research-reactor-justified-or-not/
https://www.theguardian.com/world/2019/apr/04/saudi-arabias-first-nuclear-reactor-nearly-finished-sparking-fears-over-safeguards
https://www.aljazeera.com/ajimpact/arms-control-experts-concerned-saudi-nuclear-reactor-push-200521155658787.html
So it’s not a nuclear plant.