equipment and structures, These activities are conducted under the Civil Effects Test Group, in which FCDA is a principal participant, (2) Training of specialists in various phases of nuclear defense activities, particularly in the radiological field. , \ (3) Indoctrination of key civil defense personnel and officials with civil defense responsibility and assisting Mm carrying out the civil defense responsibility for public education on nuclear weapons effects, These activities are largely conducted by the Joint Visitors Bureau, with civil defense having a large part in the justification, planning and conduct of "open" shots. In Operation Plumbbob, for the first time, there is participation by the civil defense organizations of other nations. Foreign civil defense represeritatives have been invited to open shots and French and German shelter designs are being tested, under FCDA sponsorship. FCDA has four large technical programs in Operation Plumbbob. Two of these programs are designed to furnish data for the Engineering Office and two are designed to furnish data and operational information to the Radiological Defense Division. Shelter Tests FCDA engineering programs are primarily concerned with obtaining criteria for the design of shelters -~ dome, dual purpose and family type. Shelters of various types were constructed on Frenchman Flat so they could be subjected to a nuclear explosion, This is the "proof testing"; in other words the taking of the final step in design by subjecting the design to actual nuclear detonation conditions. (For some things, such as shelters, engineers often believe the results are predictable. Even so, since human lives are involved, actual field tests must take place.) Two types of mass shelters were tested in Operation Plumbob. One is a dual-purpose shelter, designed for use either as a shelter or an underground garage -- a type of protection now being built exten- sively in the Scandinavian countries. The other is the "dome" shelter which has been advanced in engineering circles as an effective and economical means of providing mass shelters. Dome structures are much cheaper to construct than other types and FCDA technicians are anxious to study how they will react under the pressures of an atomic explosion. Tests were conducted on three reinforced concrete domes of 50 foot diameter and six inch constant shell thickness ; and on one full-scale dome type steel shelter door 83 by 103 feet installed ina reinforced concrete structure. - 68 -.