Complex sentence: An engineering team conceives a plan to rig a makeshift coolant system; because Polenin has discovered that the submarine was supplied with chemical, not nuclear, suits, teams are instructed to work in 10-minute shifts to limit radiation exposure.
Split into simpler sentences: An engineering team conceives a plan to rig a makeshift coolant system, but Polenin discovers the submarine has been supplied with chemical suits rather than radiation suits. Teams are instructed to work in 10-minute shifts to limit radiation exposure.