Editing Hanford Site (section)

===Production activities===
[[File:224-T Transfer lines.jpg|thumb|right|The 224-T plant under construction, showing the transfer pipes]]
Although the reactors could be shut down in two-and-a-half seconds, they would still generate heat due to the decay of fission products. It was therefore vital that the flow of water should not cease.{{sfn|Manhattan District|1947c|p=2.12}}{{sfn|Manhattan District|1947e|pp=5.63–5.65}} If the power failed, the steam pumps would automatically cut in and continue to deliver water at full capacity for long enough to allow an orderly shutdown.{{sfn|Manhattan District|1947c|p=5.69}} This occurred on March 10, 1945, when a Japanese [[Fu-Go balloon bomb|balloon bomb]] struck a high-tension line between Grand Coulee and Bonneville. This caused an electrical surge in the lines to the reactors. A [[scram]] was automatically initiated and the safety devices shut the reactors down. The bomb failed to explode and the transmission line was not badly damaged.{{sfn|Jones|1985|p=267}}<ref>{{cite web |title=Japanese Balloon Attack Almost Interrupted Building First Atomic Bombs |publisher=Inside Science |date=March 21, 2016 |first=Joel |last=Shurkin |url=https://www.insidescience.org/news/japanese-balloon-attack-almost-interrupted-building-first-atomic-bombs |access-date=October 26, 2022}}</ref> The Hanford Engineer Works was the only U.S. nuclear facility to come under enemy attack.{{sfn|Carlisle|Zenzen|2019|pp=41–42}}

Hanford provided the plutonium for the bomb used in the 1945 [[Trinity (nuclear test)|Trinity nuclear test]].{{sfn|Marceau|Harvey|Stapp|Cannon|2002|p=1.27}}  Throughout this period, the Manhattan Project maintained a top-secret classification. Fewer than one percent of Hanford's workers knew they were working on a nuclear weapons project.{{sfn|Marceau|Harvey|Stapp|Cannon|2002|p=1.22}} Groves noted in his memoirs that "We made certain that each member of the project thoroughly understood his part in the total effort; that, and nothing more."{{sfn|Groves|1983|p=xv}} The existence and purpose of Hanford was publicly revealed through press releases on August 7 and 9, 1945, after the [[bombing of Hiroshima]] but before Hanford plutonium was used (in a [[Fat Man]]) during the [[bombing of Nagasaki]] on August 9.{{sfn|Gerber|2007|p=295}}

Matthias was succeeded as area engineer by Colonel [[Frederick J. Clarke]] in January 1946.{{sfn|Cullum|1950|p=897}}{{sfn|Jones|1985|p=584}} DuPont would soon be gone too. Carpenter asked to be released from the contract.{{sfn|Hewlett|Anderson|1962|p=629}}{{sfn|Jones|1985|pp=591–592}} Groves informed [[Robert P. Patterson]], who had succeeded Stimson as Secretary of War on September 21, 1945,{{sfn|Hewlett|Anderson|1962|p=420}} Groves's choice of replacement was [[General Electric]] (GE),{{sfn|Carlisle|Zenzen|2019|p=54}} which took over operations at Hanford on September 1, 1946, and accepted a formal control on September 30.{{sfn|Hewlett|Anderson|1962|p=629}}{{sfn|Jones|1985|pp=591–592}} On December 31, 1946, the Manhattan Project ended and control of the Hanford Site passed to the [[United States Atomic Energy Commission|Atomic Energy Commission]] (AEC).{{sfn|Jones|1985|pp=599–600}} The total cost of the Hanford Engineer Works up to that time was {{inflation|US|348,101,240|orig=yes|1946|fmt=eq}}.{{sfn|Manhattan District|1947e|pp=11.4, B56}}