ques CRLIR - 61 - MAXIMUM ALLOWABLE CONCENTRATIONS OF FISSION PRODUCTS IN THE AIR AS A FUNCTION OF EXPOSURE TIME AND TIME AFTER DETONATION. Robert L. Harvey, 16 January 1952. UNCLASSIFIED (u) - This report supersedes CRLIR 64, in which were described the calculation and determination of fission-product concentrations, higher than those published by the Subcommittee on Internal Dose of the National Committee on Radiation Protection, which are permissible for relatively shorttime exposure. 2 aor In this report, some of the previous assumptions have been modified, calculations have been refined, and the presence of plutonium has been considered. The calculations of this paper result in a lower estimate ie oe of the per cent of Sr which is absorbed and retained in the human body for a given concentration in air. The outcome of this work was the setting ae of permissible airborne concentrations up to 50 times those established in aes CRLIR, 64. The author points out that his calculations are based on an assumption that all ingested radioactivity will be deposited in the bones; no corputation has been made of the dose resulting from material accumlated “ in the lungs. cd 2 3 CRLIR - 94 - EXPERIMENTAL TESTS OF SHIELDING AND ATTENUATION OF GAMMA RADIATION FROM RADICACTIVE TANTULUM VERSUS INFINITE PLANE THEORY. Jerry J. Mahoney and Robert B. Price, 4 January 1952. SECRET-RESTRICTED DATA wer This report deals with the shielding afforded by walls, roofs, ard floors of structures against radioactive contaminant, and with the atteruation of radicactivity by structural materials, air, and earth at varying ors eo heights above a contaminated plane. a ine ee-- Attenuation factors were determined for a concrete roof and for concrete-block and tile-block buildings at varying heights above floor level. No difference was found in dose rates at positions having the same geometric relation to vertical and horizontal planes of the same size ard shape uniformly contaminated with the same amount of radioactive material. The effects of air scattering and ground reflection were observed at various heights above contaminated ground. Roughness of terrain was found to increase total attemation, particularly at lower altitudes. Dose rate was found to increase with height above contaminated land of "infinite" area, where the contaminant was buried in a uwsiform pattern and at a unifcrn depth below the surface, due to decreasing earth attenuation as the metering height increased. . m= (RES RATA° NRE yt