The SI unit for power (whether average or instantaneous) is Joules per second. Not Joules per second hours per year.
So are we talking about Power or are we talking about Energy?
The second is a unit of power because the silver isn't used up (it's made very very hard to recycle in the NPP, but it's still technically possible after a few decades), the issue is how much is occupied by the equipment.
If you can't understand the distinction between power and energy maybe we shouldn't consider your position on power and energy credible.