“3 April 1960 – Westmoreland County, Pennsylvania, United States

A core melt accident occurred at the Westinghouse Waltz Mill test reactor. From what information remains of the event, one fuel element melted, resulting in the disposition of 2 million gallons of contaminated water generated during the accident. At least a portion of the water was retained on site in lagoons, a condition which eventually led to detectable Sr-90 in ground water plus contaminated soil. The site is currently undergoing cleanup.”

Westinghouse’s 850 acre Waltz Mill facility is located in the rural community of Madison in Westmoreland County PA. The experimental reactor was one of the first privately owned test reactors to operate in the United States when it went on line in July 1959. The $7 million reactor produced heat but did not produce electric power and was much smaller than commercial reactors operating today. The reactor was 9 months old when a partial meltdown of a uranium-filled fuel rods in the reactor’s core caused radioactive krypton and xenon gases to billow into the air over rural Westmoreland County on April 3, 1960.

News reports

Melted down reactor moved

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1960 –  Westmoreland County, Pennsylvania – Westinghouse Waltz Mill Test Reactor Melts Down; via @AGreenRoad
http://agreenroad.blogspot.com/2014/04/1960-westmoreland-county-pennsylvania.html