Temporal radiation is an exotic form of energy first encountered by the crew of Enterprise NX-01 in 2152. It produces disorienting time-distortion effects which cause those exposed to it to relive the same moment repeatedly, while time outside the radiation's influence proceeds at a normal pace.
The radiation was being produced by a 31st century time travel pod, which Enterprise had discovered drifting in space. Examining the pod, Commander Charles Tucker and Lieutenant Malcolm Reed experienced the effects of the radiation firsthand, after removing a panel from the exterior of the pod. As they engaged in the same conversation over and over again, they soon began to realize what was happening. Upon examination by Doctor Phlox, they discovered that the particle density was too low to allow any lasting effects, but Captain Archer nevertheless ordered the launch bay sealed off.
Later, after coming under attack from Tholians, who sought to claim the pod for themselves, Archer and Reed attempted to load a warhead from a torpedo into the pod, with the intention of detonating it after the Tholians had gained possession of it. Their effort was hampered, however, by the effects of the temporal radiation, which caused them to experience the same events repeatedly as the Tholian attack on Enterprise continued. Archer and Reed were eventually successful, but the Tholians managed to deactivate the warhead before Reed could detonate it. Eventually, the pod was retrieved by temporal agents in the 31st century, and the Tholians withdrew. (ENT: "Future Tense")