Original: Other  serious nuclear and radiation accidents include the Mayak disaster, Soviet submarine K-431 accident, Soviet submarine K-19 accident, Three Mile Island accident, Costa Rica radiotherapy accident, Zaragoza radiotherapy accident, Goiania accident, Windscale fire, Church Rock Uranium Mill Spill and the SL-1 accident.
Simplified: Other serious nuclear accidents include Three Mile Island, the Windscale fire, the Mayak accident, and the SL-1 accident.