I upgrade into the newest version, and upon entering my test creative world. the game crash. here the logs http://pastebin.com/jFEbjx9b

Update: I fixed it by re installing it but i get this issue every now and then, but i do want to ask how does the waste and enrichment mechanic work?

Hi, this issue occurs when Optifine is installed. Big Reactors has a known conflict with Optifine, unfortunately.

The fertilization mechanic is complicated. Each fuel rod will emit radiation in the cardinal directions (N/E/S/W) periodically. This radiation will travel through the reactor's interior and, if it strikes another fuel rod, it will add to an internal "fertility" value in the struck fuel rod.

Fuel rods that have been fertilized will produce additional heat and radiation, but this extra heat and radiation costs 75% less fuel than normal.

As for waste, that's relatively simple. As your reactor's fuel decays, it generates waste. When 1000mB of waste has collected in the reactor, the reactor will (by default) eject it was an ingot into your access ports. You can then store it or reprocess it into other types of fuel using a cyanite reprocessor.