Science and Technology Review, June 1999

The following two abstracts are for the 2 feature stories in this issue of ''Science and Technology Review''. (1) ''Forewarnings of Coming Hazards''--The Atmospheric Release Advisory Capability (ARAC) at Lawrence Livermore is an emergency response organization chartered to aid Department of Energy and Department of Defense sites when radioactive or toxic material is released into the atmosphere. Developed from studies beginning in the 1960s, it became a funded operational program in the late 1970s. Using an emergency response modeling system now in its third generation, ARAC scientists predict how atmospheric releases that could affect public health and safety will disperse. The ARAC system has evolved through experience gained during regular training exercises and in over 160 alerts and emergency responses to date. The work of ARAC scientists described in the article demonstrates the different modeling challenges they encounter in preparing for and responding to a variety of atmospheric emergencies. (2) ''Unraveling the Mystery of Detonation''--Laboratory experts in the detonation of high explosives are putting the computational power of the Accelerated Strategic Computing Initiative (ASCI) to the test. Their research centers on insensitive explosives, whose behavior during detonation is slower and more complex than that of sensitive explosives. The article features three research projects, which are exploring detonation from different angles: the initiation phase, the molecules produced during detonation, and further development of CHEETAH, a thermochemical detonation code. All research teams are using ASCI supercomputers, which have increased their ability to simulate the detonation process by a factor of 100,000.