Radiation shielding provided by transportation vehicles and structures typical of where people live and work were estimated for cloud and fallout gamma-ray sources resulting from a hypothetical reactor accident. Dose reduction factors are recommended for a variety of situations for realistically I assessing the consequences of reactor accidents.

On 11 July 1970, an Athena missile was launched by the U.S. Air Force from Green River, Utah, as part of a routine testing program. The nose cone contained two WO sources of approximately 470 mCi each. The Athena operated abnormally resulting in an impact in Mexico. Through the USAEC, the EG&G Aerial Radiological Measuring System (ARMS) scientific team was asked to participate in the search for the 6 7 C~ using the ARMS gamma radiation detection system. In a period of 3 days, the impact crater was located and the ground recovery team was directed to the site. Various samples were returned to the EG&G Las Vegas laboratory for analysis and identification.

Environmental and fallout gamma radiation protection factors (PF's) were estimated for a variety of civilian transportation vehicles using measurements of the natural terrestrial radiation as a source. The PF values are below 2 in light vechicles, truck beds, or trailers; from 2.5 to 3 in the cabs of heavy trucks and in a railway guard car; and froni 3.0 to 3.5 in the engineer's seat of heavy locomotives. This information can be useful in planning the possible movement ofpersonnel from or through areas contaminated either by a wartime incident or a peacetime accident. The information may also be useful for studying the reduction of exposure to the natural terrestrial radiation environment provided by vehicles.