It explains how the plants work in easy-to-understand terms and answers a whole slew of questions that your average Joe might have about them. The media's doing a horrible job of explaining all of this, preferring to fearmonger instead of actually doing their job, so I understand good information is hard to come by. But I can personally vouch that the information on that tumblr is good - this is the same stuff I've been doing for the majority of my adult life.
The only difference is that we call it a "negative co-efficient of reactivity" and not a "negative void co-efficient", but it's pretty obviously the same thing. We also use Rem in the DOD - DOE uses Sieverts and/or Grays. I can try to convert units for you, but my mind can really only process Rem.
If you have any questions, I'd be happy to answer them to the best of my ability.