text: In urging for greater alarm about this event, Roger Mattson used the phrase "horse race" and argued his theory of an explosion with Victor Stello.
full_question: In urging for greater alarm about this event, Roger Mattson used the phrase "horse race" and argued his theory of an explosion with Victor Stello. This event resulted in the mass cancellation of orders of a device made by Babcock and Wilcox, a company strongly criticized by Dartmouth's President John Kemeny afterwards. Governor Dick Thornburgh ordered that pregnant woman and preschoolers maintain a five mile radius from this event. Caused by a stuck open relief valve, it resulted in the partial contamination of the Susquehanna River. For 10 points, name this partial nuclear meltdown that occurred in 1979 in Pennsylvania.
first_sentence: In urging for greater alarm about this event, Roger Mattson used the phrase "horse race" and argued his theory of an explosion with Victor Stello.
raw_answer: Three Mile Island accident