as In addition to general information on the nature of radioactivity, and on the means for its detection and measurement, this manual eontains operating instructions to aid laboratory personnel in carrying out their duties. Considerable information giving a general packground in the field of radiological effects has been included to assist personnel in the performance of duties for which no adequate CS, instructions can be prepared. t) de - CRLR - 117 - THE CONTAMINATION OF A VEHICLE ENGINE (WC 54) WITH RADIOACTIVE SAND, AND ITS DECONTAMINATION. M. G. Gordon, H. A. Chambers, and L. A. Ford, 9 February 1953. CONFIDENTIAL bh we To determine the location and extent of radiological contamination of a running vehicle engine, fine sand tagged with aged (1-4 yr) fission-product solution was introduced into the engine intake-air through an air filter, Fifty grams of such contaminated dust was introduced into a special chamber surrounding the air filter, over an 8-hr period, at a rate corresponding to 0.025 g/cu ft of combustion air. This arrangement was effected by operating the engine at 1,300 rpm, equivalent to a speed of hr. 30 mi/hr. 0 mxternal monitoring gave no indication of the hazard involved in servicing contaminated vehicle engines. The metal and air shielding afforded by the engine and its location in the vehicle was such that contamination within the engine could not be traced externally. Radio- activity varied from (relatively) very high in the air filter, carburetor, and engine head to low in the exhaust system, valves, and pistons. 7. reduced criginal contamination readings ranging between 4,000 and 43,000 LE counts/min to residual readings of from 1,300 to 1,500 counts/min. CRLR ~ 120 - ; PRELIMINARY CALCULATIONS ON THE EFFECTIVENESS OF SMOKE AT OPERATION KNOTHOLE. Charles S. Brice, Jr., 24 March 1953. SECRET-RESTRICTED DATA On the basis of experimental data obtained by using a collimated ion oratory fects Con- taminaticn in the crankcase and the oil filter was found to depend on engine ccndition, with little contamination in these locations if piston rings were close-fitting. Decontamination was easily effected in most cases by simple techniques, such as wiping or brushing. These techniques ~ beam oF light, prediction is made of the degree of attenuation of thermal radiation by a white, oil-fog smoke, and of the temperature rise within a carbon smoke. 7O mmg/l. REST ATOMI Calculations were based on smoke concentrations up to - 1954 oe