<p>This photo shows the High Flux Isotope Reactor during routine refueling in July 2015. The blue glow comes from Cherenkov
radiation, caused when electrons emitted by the spent fuel travel through water faster than light does.
</p>
Image credit: Genevieve Martin, ORNL
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/37940997@N05">Oak Ridge National Laboratory</a>
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/oakridgelab/34300813941/">Beautiful refueling</a>