You are talking about energy, which is not the same thing as power. TWh == energy, GW == power.
The distinction is important, especially in the Netherlands, which has a capacity factor of only about 10%-15%, whereas most of the US will be at least 20%-25%, which is twice as high.
I'm not sure of the typical number of reactors in the Netherlands, but using the US average of 1.6/power plant may not be the most representative comparison.
The point is about instant power injected, not energy, the point is that keep an AC grid at the right frequency it's a tricky business because energy production and consumption must match.
Too much from production the frequency skyrocket, little production the frequency plunge.
Now classic grids are designed on large areas to average the load for big power plants, this way those plant see small instantaneous change in their output demand, let's say a 50MW power plant see 100-300kW instantaneous change, that's something they can handle quick enough. With massive p.v., eolic etc grid demand might change MUCH more for big power plant, like a 50MW P.P. need to scale back or power up of 10MW suddenly and that's way too much to sustain. When this happen if the demand is too much the frequency plunge, grid dispatcher operators have to cut off large areas to lower the demand (so called rolling blackouts), when the demand drop too quickly the frequency skyrocket and large PP can't scale back fast enough so they simply disconnect. Disconnecting the generation fall and the frequency stabilize, unfortunately most p.v. is grid tied, if a p.p. disconnect most p.v. inverters who have seen the frequency spike disconnect as well creating a cascading effect of quickly alternating too low and too high frequency causing vast area blackouts.
Long story short a potential attack is simply planting a command "at solar noon of 26 June stop injecting to the grid, keep not injecting till solar noon + 5'", with just "1 second or so" (due to eventual time sync issues) all inverters of a certain brand might stop injecting, making the generation fall, a bit of rolling blackouts and large pp compensate quickly. Than the 5' counter stop, all inverters restart injecting en-masse, while the large pp are full power as well, the frequency skyrocket, large pp disconnect causing most grid-tied inverter to follow them, there are large change an entire geographic segment of a grid fall. Interconnection operators in such little time do not know what to do and quickly the blackout might became even larger with almost all interconnection going down to protect active parts of the grid, causing more frequency instability and so more blackouts.
You are using both with your energy generated numbers. That's where they come from.
Your solar TWh comes from 25GW at ~15% capacity factor, and to get your nuclear numbers you're looking at 1.6GW for each of nuclear "plants" when each reactor is usually about 1GW or less. There are ~90 reactors in the US, at 54 plants. The article is assuming 1 reactor per plant for the Netherlands.
> The article is assuming 1 reactor per plant for the Netherlands.
Small addition that isn't mentioned in the English version of the article, but only in the original Dutch version: the article talks specifically about the Borssele power station [0] (which has a power output of 485MW).
The distinction is important, especially in the Netherlands, which has a capacity factor of only about 10%-15%, whereas most of the US will be at least 20%-25%, which is twice as high.
I'm not sure of the typical number of reactors in the Netherlands, but using the US average of 1.6/power plant may not be the most representative comparison.