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National Museum of Nuclear Science & History

John R. Leary, Jr.

Shift Supervisor, Research ChemistOak Ridge, TN

X-10 Graphite Reactor
Manhattan Project VeteranScientist

John R. Leary Jr. was an American chemical engineer. He worked as a Shift Supervisor at the X-10 Plant, and as a research chemist in Building 205, at Oak Ridge. His wife and two sons lived with him at Oak Ridge.

A native of Pennsylvania, Leary and family arrived in Oak Ridge in August of 1943. Shortly after arriving, he and his wife Catherine and son John (III) moved in at Tucker Road on the Oak Ridge reservation. His son Edward was born in the Oak Ridge Hospital in 1944.

Earlier he had worked as a chemical engineer for several years for DuPont, living near Wilmington DE, and Tulsa, OK. At Oak Ridge, DuPont assigned him to Clinton Labs to work at the site’s X-10 plant on the graphite reactor. Here he was one of five “Shift Engineering Supervisors.” After the reactor went critical, he was assigned as a Research Chemist at a more classified Clinton Labs facility at Oak Ridge. 

In May 1945, he was transferred to Indiana Ordnance Works (IOW) in Charleston IN. In mid-July 1945 according to his wife, Catherine, he took a “short trip west to ‘Sunflower’” and returned home sick. After a short stay at Baptist Hospital in Louisville, KY, he was moved to hospital in Philadelphia PA, where he died on Jan 10, 1946. His death certificate records his illness as “bacterial-endocarditis” and the cause as an “Abdominal Aortic Aneurism.” He was 27. 

The AAA cause of Leary’s death sets a record for mortality tables. When he passed away in 1946, he may have been the first Clinton Labs Chemical Engineer to die after working on the Oak Ridge graphite reactor. His death is not testimony to hormesis. ORNL has lost his records, but the Clinton Labs phone book, and the eye-witness accounts by O.R. Volk and John H. Gillette, as well as the birth certificate of his son, Edward, establish that he was there.

Information provided by Leary son’s John Leary III.

John R. Leary, Jr.'s Timeline
1918 Jun 2nd Born in Harrisburg, PA.
1940 Jun Received a B.S. in Chemical Engineering (Honors) from Villanova University. (Phi Kappa Epsilon).
1943 Aug Arrived at the X-10 plant at Oak Ridge.
1945 May Transferred by DuPont to Indiana Ordnance Works (IOW) in Charleston IN.
1946 Jan 10th Died in Philadelphia PA of an AAA caused by bacterial-endocarditis
Manhattan Project Certificate-John R. Leary, Jr.
Manhattan Project Award Pin-John R. Leary, Jr.
"Exhibit A" Page 1
"Exhibit A" Page 2
"Exhibit B" Page 1
"Exhibit B" Page 2

Oak Ridge Chapel

The X-10 Graphite Reactor at Oak Ridge

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