Neither of these are true. These are technologies which allow large amounts of power to be stored for long periods of time at low cost, that's the whole reason they aren't built on traditional battery technology, which cannot achieve this.
The constraint for these technologies is storage area.
Estimates put storage costs at around 2-4c per kWh. Comparitive lithium battery storage is 25-30c/kWh. It's really not expensive storage in anyone's measure
While the pilot tested the technology for up to 18 hours of storage, Sage Geosystems is confident it could operate on a weekly cycle, or even provide seasonal storage, CEO Cindy Taff said.
www.utilitydive.com
It's interesting that the point being driven here is cost. Of all of the generation sources, nuclear costs have been increasing faster than any other fuel source:
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I agree that a multi-source mix makes sense, and nuclear should be a part of that mix. But the boogeyman BS that renewables will blow up your appliances is just silly. You can have both and be just fine, just ask China who generated 4.98% of their energy from Nuclear and 34% from renewables
in 2022. No metrics on the number of exploding toasters though, sorry