SIR: The authors read with interest the comments of Mr. Kalmon and appreciate the opportunity to discuss the issues he has raised. Mr. Kalmon’s remarks pertaining to the conversion of radioactivity units to mass units is well-taken and recognized by the authors. Admittedly, a direct conversion requires knowledge of the isotopic composition of the sample. Although the authors were certainly receptive t o any information which would clearly define the uranium levels existing near such facilities, precise isotopic data was not available. However, with respect to the uranium concentrations cited for the Paducah, K Y and Piketon, OH gaseous diffusion plants, the values listed were included primarily to provide a comparison (order of magnitude) with levels found in the New York State survey, and were in no way a n attempt to single out specific uranium sources or that of the nuclear industry in general. I n regard t o the asserted incorrect assumptions made by the authors pertaining t o the uranium assay of samples taken near the above sites, the Piketon plant concentration of 300 ng U/m3 cited is based on a n average alpha activity of 0.1 pCi/m3 listed on p 216 of the April 1970 issue (Vol. 11, No. 4) of Radiological Health Data and Reports put out by HEW. This data, references to have been provided by Mr. Kalmon himself, follows a short paragraph which specifically states, “Natural uranium and thorium-234 are the most likely radionuclides t o be released t o the environment by the Portsmouth area gaseous diffusion plant.” Based on this clearly stated information, a direct conversion was made to arrive a t the 300 ng U / m 3 figure. We might add that there was n o attempt on the author’s part to exaggerate the levels of uranium near these sites, for if such were the case i.he 2.4 pCi/m3 level (-7200 ng/m3) recorded and listed in the July-December 1970 report could have been cited. With respect t o the 90 ng U/m3 level cited for the Paducah, K Y plant, this figure was calculated from Table 6, p 214 of the above report which listed a mean uranium alpha radioactivity of 0.03 pCi/m3. The conversion to mass units in this case was based o n superscript b of this table which states that the alpha radioactivity concentrations listrd were calculated using the NBS Handbook 69 definition that “a microcurie of recently extracted normal uranium corresponds to 7.57 X
I O 4 alpha dis/sec.” This information indicated that the uranium concentrations found in the outdoor air samples had a n isotopic assay representative of natural uranium. Granted that gaseous diffusion plants enrich uranium isotopes having high specific activities, it follows that such plants, whose feed is primarily natural uranium must likewise show a material balance whereby the integrated loss of uranium to the environment would have a n assay representative of the feed, unless it is suggested by Mr. Kalmon that only the highly enriched material is preferentially lost. It would seem more likely that special precautions are taken to prevent loss of this valuable portion of the process, with less attention afforded the feed and depleted material streams. The authors d o not pretend to know the intricate operations of a gaseous diffusion plant. However, it is common knowledge that the total rate of flow of low enriched material in the plant is on the order of IO7 times larger than the finalproduct (-94z U Z 3 9flow rate. The inference, therefore, made by Kalmon that because such plants produce enriched uranium, the alpha activity recorded in the local environs would be due primarily to highly enriched uranium, is very misleading. The radioactivity from the overwhelming quantities of UZ3*present in such plant operations would predominate over the combined activities of the other uranium isotopes present in any significant amounts. Consequently, the authors contend that the figures of 300 and 90 ng U/m3 cited, although not analytically precise, are representative of levels near such plants, and are definitely not two orders of magnitude high, as suggested by Kalmon. If there is data to the contrary, it should be made available. The authors suspect that such information does not exist, and would like to emphasize that it was one of the objectives of the subject uranium survey to stress the need to make isotopic assays of environmental samples to prevent misinterpretation of data. The determination of gross alpha and beta activity can no longer be considered sufficient in describing the effluents from nuclear industrial sources.
Willard G . Myers Department of Nuclear Science Rensselaer Polytechnic Institute Troy, N Y 12181
Volume 6, Number 4, April 1972 369
