Still having a hard time getting used to the fact that the is allowed to go slightly positive at times........
Im tryin hard to think this through, but I dont get it. Reactivity of the fuel rises, but what does that have to do with temp coeff? Fuel burns hotter, temp goes up, resonance absorption goes up??? It has to be really really small then. And they do more boron injection for more shut down margin then, wouldnt they?

He mentioned moderator coefficient, and you go off trying to reverse engineer Doppler!

(Yes, I'm too lazy to fetch yet another facepalm picture!)
Imagine: PWR, BOL, boron around 2500 ppm. Warm water stretches, fewer HBO
3s to steal those precious neutrons, so mo neutron flux per cm
2 . Fuel gets lucky like Britney Spears. Thus, warm reactor hottub water increases reactivity and is thus the shiznit.
- Apologies to anyone having learned Reactor Physics prior to the creation of Myspace -