The latest buzzword on the crisis in Fukushima is recriticality. Sounds scary, and it is. But experts say it's also unlikely:
While spent fuel rods generate significantly less heat than newer ones, there are strong indications that some fuel rods have begun to melt and release extreme levels of radiation. Japanese workers struggled on Thursday to add more water to the storage pool at reactor No.3. It is unclear if that effort worked.
The
phenomena occurs when and if fuel pellets inside the fuel rods melt and conglomerate into a pool. When a big enough mass of radioactive substances which emit the right kind of radiation are in one small locale, the odds of a fleeing particle hitting another uranium atom and causing it to emit more particles, which in turn hit more ... becomes statistically likely. It's the origin of the term
critical mass and the fundamental principle behind both nuclear reactors and nuclear bombs. While such an event could produce a large, radioactive as hell explosion, the material in those rods is not what physicists call weapons grade. Which means even such an unlikely event won't produce a Little Boy or Fat Man type detonation. It would be more like a massive dirty bomb on steroids
- Scientific American has a timely article on advances in solar energy which argues that an analogue to Moore's law may be at work on solar cells:
If humanity could capture one tenth of one percent of the solar energy striking the earth – one part in one thousand - we would have access to six times as much energy as we consume in all forms today, with almost no greenhouse gas emissions.
- The NASA Messenger probe is cool. But look what will be out tonight: Super full moon!
- It's always lonely to be the skeptic in the room (H/T Pharyngula):