a CRLR - 297 - ATTENUATION OF 1.2 MEV GAMMA RADIATION BY SOVIET AND U. S. MILITARY VEHICLES AND U. S. RAIL EQUIPMENT. Robert P. Beckelheimer and Ralph E. Rexroad, 1 August 1953. CONFIDENTIAL The object of the work described in this report was to determine e amount of shielding from gamma radiation afforded by certain Soviet and U. S. military vehicles and U. S. rail equipment, when operated in areas contaminated with Co©0 (gamma energies of 1.17 and 1.33 Mev). Under the conditions of the test, practical attenuation factors (the dose rate inside the vehicle divided by the dose rate 3 ft above the center of the road outside) for gamma radiation from a 20-ft roadway when the vehicles were located at the center of the road ranged from 0.02 to 0.44. The attenuation factors for vehicles traveling along the shoulder of the road ranged from 0.005 to 0.29. Sandbags over the floor boards and mitual shielding by personnel riding in the bed of the truck have negligible effect on the dose rate. to personnel in the cab. The load of a cargo truck offers little shielding Practical attenuation factors for gamma radiation from a level field with the vehicles located at the center varied from 0.025 to 0.75. Decontamination of a 16-ft wide strip through the field reduced the dosage rate by 30% when the contaminant was merely swept aside, and by 50% when the contaminant was removed for personnel walking through the field. These factors are increased as the mode of conveyance changed from walking or riding in a jeep to riding in larger vehicles. Practical attenuation factors for gamma radiation from a level field with rail equipment located at the center ranged from 0.15 to 0.55. CRLR - 298 - PROTECTION AFFORDED BY OPERATIONAL SMOKE SCREENS AGAINST THERMAL RADIATION (WI-768). (Operation KNOTHOLE) Eimer H. Engqvist and Charles W. Forsthoff, 7 December 1953. CONFIDENTIAL The original objective of Project 8.4-1 was to evaluate the attenuaticn, by an operational fog-oil smoke screen, of thermal radiation resulting from the detonation of a nuclear device, and to secure data to verify theoretical calculations on the above currently being developed under contract to the Chemical Corps. WNAQ '