Original sentence: In 1946 Canadian Manhattan Project physicist Louis Slotin performed a risky experiment known as "tickling the dragon's tail"  which involved two hemispheres of plutonium being brought together until separated only by a screwdriver.Slotin pushed the hemispheres apart with his bare hands to stop the reaction which saved several co-workers present in the room; however Slotin absorbed a lethal dose of the radiation and died during the following week.The screwdriver slipped, the hemispheres then touched and set off a chain reaction criticality accident filling the room with harmful radiation and a flash of blue light (caused by excited, ionized air particles returning to their unexcited states)
Edited sentence: In 1946 Canadian Manhattan Project physicist Louis Slotin performed a risky experiment known as "tickling the dragon's tail" which involved two hemispheres of plutonium being brought together until separated only by a screwdriver.On this unlucky day the screwdriver slipped, the hemispheres then touched and set off a chain reaction criticality accident filling the room with harmful radiation and a flash of blue light (caused by excited, ionized air particles returning to their unexcited states).Slotin absorbed a lethal dose of the radiation and died during the following week.Slotin heroically pushed the hemispheres apart with his bare hands to stop the reaction; his actions saved several other co-workers present in the room