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Lod dol * We een tae me ee ete fog agenee one SEE OSEAN Tie NE got ame to N “ . i ny ae ah ed ieee oor co ) ae... aoe at cs: wtinte cf wel ee toe fo of 42. Copies, Sories 7%: ee ateae en en ar Js UNITEO STATES eee chen pe we ween, - ATOMIC. ENERGY COMMISSION Dn penne ggg FF were ane iets e 1851 poe Dear Mre Hoover: eiabes ann ere nw Si, FL . Reference is is mate to, our Letter + pnd sumeary;gf information | dated June ge 950) oncerning Dongld Duart~MacZean_ and a ; Guy Francis Be “Yonc rgeus. You aeked that ve prepare a meee paper | ee “In some, detail th the extent. of. damage done -t Ls Maclean representing the British Eubassy during 1947 and 1948 co, ; on matters dealing with the polities) aspects of atomic energy alee and | through his work on the Combined Development Agency. The - we __ Boe, above would be assuming that MacLean was either a Soviet agent: 7 en ee oo . or has defected to the Soviet Unione . a enn ES . , . Tg Tea me - ifm 0 PNET Ft — In February 1947, ¥ MacLean was _Aosignated ty bie Government to, ie: Fem a -- act_ae the United Kingdom's Secretary_of the Combined Policy errs: aes Ogmmittee concerned with atomic energy matters, composed of — oo representatives of the United States, the United Kingdon ana~ a Ses ieee Canada. The ABO representation on the Combined Policy Committes en jn ioc. ' | began in September 2947. Maclean's duties involved the meotuine an on oes with his Canadian and American counterparts of those atomic aoe . Pe See energy matters of concern to hie Government which come under a oti meen the purview of the Combined Policy Committes. In connection with: - Ee oe | ,these duties, MacLean had opportunity to have access to the 902-3 - _ ... {information shered by the several countries in the fields of “~~ “7 * So ag patents, declassification matters, and the research and de pees “T. - /a ment relating to the procurement and deneficiation BAEBDWITE Tyg SERENE io fe ee 2 Jnoteriale from foreign sources by the Combined Developnent JEP Yr} . al = am 7 aa! . Late “In his os capecity as UK Secretary of the ope he took part in the — - i re negotiations which | resulted in the Modus Vivendi which governs, a fees >|) ne the atomic energy relations among the th “three gove: governments since. =. wort, ae Jamary 1948._ ng the course of these negotiations, Maclean -+~ sss... ~.' Jhaé access to. ja to information relating to the eatimtes made at that - ene lean wie time of ore supply available. to ‘the _thraa governments | through *. se ref nsa4 . a. 195¢:_requirements of uranium for the atomic energy programs j woe abe thin the three governments “@uring that periods and tha definin s fart tema ‘tion of scientific areas inwhich the three governments deemed 2 2. Pee ag hee ae echnical cooperation could be accomplished with mataal benefit. | teva Sew: h in woe need -9 Bann 4 0 08} nee ty