I don't know enough about energy production to speculate, but here's an example. The smallest nuclear plant in the US (located in Nebraska) can produce 502MW per hour. So, in a day, that's 12,048 MWh of power energy. Even if every single bitcoin miner on the planet was powered by this single facility, it would only consume 2.9% 70% of the facility's capacity.
You need to fix your units. There is confusion about the difference between power and energy, and the units used to represent them.
Power is the rate at which you can generate or expend energy. The units of power are watts (W). Units of energy are Watt-hour (Wh) and joules (J). 1 watt-hour is 1 watt for 1 hour (as well as ½ W for 2 hours or 2 W for ½ hour).
There is no such thing as 502 MW per hour, unless you are talking about changes to power. You meant to write just "502 MW" and "12,048 MWh of energy". A 502 MW power plant outputs 502 MWh each hour, or 12048 MWh per day.
Finally, 350 MW is 70% of 502 MW.