This document consists of 4 AY Copy No. _of_ 15 5 pages Series, AEC-A —g-E-eENCLOSURE I UNIVERSITY OF CALIFORNIA LOS ALAMOS SCIENTIFIC LABORATORY (Contract W-7#05-ENG-36 ) P, O. BOX 1663 LOS ALAMOS, NEW MEXICO April 15, 1955 In Reply Refer To: Dir-~-1037 Brig. General K, E. Fields Director of Military Application U. S, Atomic Energy Commission Washington 25, D. Dear General C, Fields: Your letter of April 8, 1955 inquires as to the status of our present understanding and Prospects with respect to so-called "elean" weapons, . & “Enviro ‘ the fission debris would, of course, be accompanied by other material made radioactive by neutron capture, but unless the materials surrounding the bomb were rather carefully chosen for the purpose, the fission debris would still constitute the major source of residual radioactivity. RESTRICTED DATA This document contains restricted data as defined in the Atomic Energy Act of 1954, Its transmittal or the disclosure of its contents in any manner to an unauthorized person is prohibited. -~l- Enclosure I

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