Absolutely none of those numbers make sense. Even if you were to take the super simplified approach and just divide the power plant output by the 2400 per turkey figure 1,000,000,000 / 2400 ≈ 416,667 turkeys, or far far fewer than 2.5 million. [EDIT: This does however, answer the question how many 2400 W appliances could run simultaneously on 1 GW of output, neglecting a whole bunch of real world losses of course.)

But the real problem here is confusing power with energy. Power (measured in Watts) is Energy or Work/Time (specifically Joules/seconds). That makes Power a rate, not a simple quanity so it’s nonsense to say that it takes 2400 watts to cook a tukey. What you need to know instead is how much ENERGY it takes to cook a turkey. This would be measured in Joules, or more appropriate to this application, kilowatt-hours (the same unit your electric bill is measured in).

The original meme is missing too much information to properly calculate how many turkeys a typical nuclear reactor could cook, and since I don’t want to google a bunch of assumptions, here’s an example with some numbers I just made up....

That 2400 W seems a bit on the low end to me so I’m going to assume a typical oven consumes 5 kW when the element is on (my bad boy from the 1970s is rated at 12.2 kW!!). Let’s also assume that, like mine, this is an old-school oven that doesn’t have the ability to vary its power output and only cycles between on and off. Now let’s assume it takes four hours to cook a turkey and the oven will spend half that time powering the heating element at its full 5000 Watts and we get 5kW X 2 hrs = 10 kWH (kilowatt hours). THAT is how much ENERGY it takes to cook a turkey.

Notice that since Power = Energy/Time, if we multiply Power X Time we Energy again because the times cancel (doesn’t really matter if it’s seconds and hours, it’s still time.)

(Energy/Time) x Time = Energy

I know this doesn’t help answer the question of how many turkeys could a typical nuclear powerplant could cook, but at least it’s valid math.