The cryocycling process developed by General Atomics is a method of demilitarization that involves subjecting solid propellants to repeated thermal cycles between ambient and cryogenic temperatures. During both the freezing and warming phases of the process, fractures develop in the propellant grain material, and, as these fractures intersect through repeated cycling, the bulk material is reduced to relatively uniform-sized rubble. The equipment to accomplish this includes a liquid-nitrogen supply system, cryocycling bins, warmup equipment, exhaust gas filtration system, a rubble classifier system, and a shipping container loading system. The cryocycling bins are fixed to carts that may be manually moved from station to station. The cryocycling and propellant classification operations may be performed unattended.
The developed process uses 11 bins for cryocycling and 11 workstations. Ten stations are for three-cycle cryocycling of the propellant grains and the 11th station is for recycling of oversize material from the prior day’s operations. Each bin contains three layers of propellant grains, each layer consisting of nine grains, for a total of 27 grains. Each station contains provisions for LN2 fill, vent, and air inlet. The stations interface with a remote programmable logic controller control system.
The bins are mounted on carts so they can be manually rolled to a dumping station. The dump station allows remote dumping of the contents from one bin into a classifier for an over/under separation process. The oversize material will discharge in the 11th bin for recycling during the next shift. The process also includes a gas cleanup system for the air and nitrogen leaving the propellant beds during the fill and warmup cycle to filter any possible propellant dust from the air and nitrogen that are exhausted to the atmosphere. The cryocycling process operations are sufficiently dust-free to eliminate any requirement for dust collection from the propellant handling systems.