There are safety-related limits (power modulation proportion, duration of a pause needed after each modulation, modulations frequency...), and the very combusti

There are safety-related limits (power modulation proportion, duration of a pause needed after each modulation, modulations frequency...), and the very combustible status is a major parameter. Pertinent document (French ahead!): https://new.sfen.org/rgn/expertise-nucleaire-francaise-suivi-charge-seduit-europe/ https://new.sfen.org/rgn/expertise-nucleaire-francaise-suivi... « un réacteur peut varier de 100 % à 20 % de puissance en une demi-heure, et remonter aussi vite après un palier d’au moins deux heures, et ce deux fois par jour » Proposed translation: "a reactor power output can vary from 100% to 20% in 30 minutes, then after 2 hours can go back to 100% at the same speed, and can cycle this way 2 times per day". This is quite a good performance when it comes to load-following (French engineers are very good at this), however it is insufficient in the real world (save any ridiculously expensive over-provision of nuclear reactor, most idling) and very weak compared to gas turbines performances.