Let's figure out the question in more detail. Power is somewhat a ambiguous term as it may mean average power or instantanious power. Your answer is exact for the former case but for the latter you may write:
1.p(t)=v(t)*i(t)
2.v(t)=R*i(t)
1 & 2->3.p(t)=((v(t))^2)/R
4.-V is peak...
Ok, your right about the Z-transform equivalent and recognizing that z^-1 means a unit time delay, you could realize it with a clock controlled D-Flip Flop. However I am not really sure about your mixed analog/discrete view so let me know about the results.
Whats the problem with using water in a fast reactor. I mean moderating neutrons in a fast reactor just increases the fission chance and that is not bad is it?
How shall diffusion of precursor atoms be treated if the core is in liquios state(as is MSR)[I mean regarding to its low volumetric density, shall we treat it as gas-liquid diffusion and is diffusion approximation or even transport theory valid for it anymore, what's the meaning of state space...