Can someone explain this pic to me? Already did some research but couldn't quite get a comprehensive answer on the graphite tipped rod thingy (why the core exploded when the graphite tips of the control rods were lowered) Pic is from:
http://accidont.ru/ENG/rodes.html

Why is there not a neutron flux spike in a) in the middle of the rods, shouldn't it be highest there because there is nothing but graphite for 2 meters on each side? Why does the bottom of the fuel rods seem to react so much stronger to the graphite rods than any other part?