 In 1953 , they made their first attempts using one of the large reactors at the <unk> nuclear site in what is now known as the Cowan – Reines neutrino experiment . Their detector now included 300 litres ( 66 imp gal ; 79 US gal ) of <unk> fluid and 90 <unk> tubes , but the effort was frustrated by background noise from cosmic rays . With encouragement from John A. Wheeler , they tried again in 1955 , this time using one of the newer , larger 700 MW reactors at the Savannah River Site that emitted a high neutrino flux of 1 @.@ 2 x 1012 / <unk> <unk> . They also had a convenient , well @-@ shielded location 11 metres ( 36 ft ) from the reactor and 12 metres ( 39 ft ) underground . On June 14 , 1956 , they were able to send <unk> a telegram announcing that the neutrino had been found . When Bethe was informed that he had been proven wrong , he said , " Well , you shouldn ’ t believe everything you read in the papers . " 
