That just means for LWR applications you need to switch the storage media. Any thermal plant could implement heat storage if they identify a medium with a large

That just means for LWR applications you need to switch the storage media. Any thermal plant could implement heat storage if they identify a medium with a large latent heat of fusion that is around where you want to preheat your working fluid to. The salt used for energy storage is normally a eutectic mixture of ~60% sodium nitrate and ~40% potassium nitrate (not NaCl) and has a melting temperature of ~260 °C. The secondary on a PWR has a maximum temperature of 275 °C. So within the liquid range of typical thermal storage salts, though I suspect finer tuning of the salt composition would be used to reduce the melting temperature to closer to the feed water temperature of ~220 °C.