Beware long-pent-up radium.

A physicist with the Air Force Institute of Technology at Wright-Patterson Air Force Base near Dayton, Ohio, was about to order a new radium source for an experiment when he found an old one left by a predecessor. While he was attempting to open it, however, the top of the sealed glass vial unexpectedly "shot off like a bullet," recalls George John. His subsequent investigation shows that radiation-induced decomposition of water in the vial had, over 22 years, generated enough hydrogen to substantially increase the pressure in the void above the radium solution. He says that's why it exploded upon opening.

Alpha particle emitters, like radium, are most prone to this hydrogen buildup in sealed containers, according to John's calculations in the November HEALTH PHYSICS. So, he warns, "If you have odl radium samples--I'd say anything over five years old -- you had better be cautious" or risk contaiminating the environment with a jettisoned radioactive spray.