In 1997, someone taking a picture of an embedded controller board at the Haddam Neck nuclear plant set off the fire protection systems in the control room, causing everyone to evacuate the control room for an hour.

http://www.nrc.gov/reading-rm/doc-collections/gen-comm/info-...

And the conclusion?

"They also confirmed that the light from the Canon flash and the Polaroid flashbulb could be effectively blocked by "black bagging" the flash, or by blocking the EPROM window with "tin foil" held in place by clear cellulose tape, or by blocking the EPROM window with "standard electrical tape."