186 THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD Detectable contamination was noted on fallout trays located at distances of 50 miles All air sampling stations, at some period during the tests, have indicated plutonium concentrations in (he air. The highest single daily exposure within the Nevada Test Site occurred at Gate 385 and amounted to 154 disintegrations per minute per cubic meter. The highest single exposure beyond the confines of the Nevada Test Site limits occurred at Indian Springs, Nevada, and amounted to 5.3 disintegrations per minute per cubie meter. Detectable plutonium was found on air sample filters at distances of 100 miles and these results were confirmed by chemical analysis. The pattern of contamination was the same for all air samples at all locations. Depending on the distance from the point of detonation, there was a sharp rise in alpha counts on air filters on shot dayor the day following. This persisted for 3 to 4 days with decreasing intensity, with a return to background levels on the fourth orfifth day. After an area has been contaminated, surface monitoring readings are inadequate to measure the hazard to work parties in this area. A mobile trailer mounted air sampler which could collect’ the dust stirred up by the towing vehicle was used to simulate working conditions. There is little correlation between PLUTONIUM CONTAMINATION FOUND OFF-SITE a relatively large aren of the Nevada Test Site consisted of removal of tapsail in theareas of highest contamination and harrowing, wetting, compacting andstabilizing the balance of the arcainvolved, DISCUSSION Mr. Placak. This, of course, is a problem that has been rather dear to our hearts for some time now with regard to the possibilities of contamination from such detonations. Certainly the process of harrowing a piece of land and thereby mixing the plutonium with a greater amount of inert material is very comparable to the old, old trick of painting a laboratory surface with a coat of paint in order to remove plutonium contamination from the zone where it could become a potential health hazard. So these the surface with one centimeter of the upper earth’s surface to produce a dilution factor of 1 105. Do we have any other comments on this ment increases with time. This is under- by plutonium, it would seem quite straight- up the alpha contamination and to render it undetectable by survey instrument monitoring. There is continuous redeposition of plutonium due to wind action, butthis appears to represent relatively minor concentrations, that is less than one disintegration per minute per cubic meter on air filters. A workable method for decontamination of They will go all the way from 500 counts per All one has to do is to mix the plutonium at due to rain and wind erosion tends to cover standable when one considers that weathering something similar. We found during this survey that if you take on the same surface an arca of concrete about the size of that platform which was in the fallout pattern and presumably should have been uniformly contaminated—if we monitor that very carefully --we will find a wide range of monitoring results. regard to the decontamination of the area inquired about during the first day of this symposium and which it was indicated had never been made before. If there are particular were 1,000 counts per minute, 14 counts per minute and 7 counts per minute. The discrepancy between the two types of measure- and determine the type of information you are asking for, because practically the only menitoring instruments we have are Peewees, or to me seem to be very sound practices with the same air concentration of about 200 disintegrations per minute per cubic meter was obtained in areas where the Pee Wee readings For example, patterns? Some measurements which were buildings or structures in the area contaminated forward to make detailed measurements around these structures to indicate some measure of the variations in intensity of the fallout in close to large buildings, the snow fence effects, and things of this sort. J wonder if any measurements of this type have been made by the health monitoring people? However,it may be very difficult to monitor significantly particular topic? Dr. Wrekxorr (Bureau of Standards). May I suggest that this seems to be a testsituation which offers a unique opportunity for making measurements of the fine structure of fallout these twa types of readings. supposed to go the other way. What did go into the proving ground went into an area that has only one real building, and thatis the old 1953 civil defense house. We didn't make the measurements that you indicate. M. W. Carter and 0. R. Placak Dr. Lancaam. Thank you Mr. Praca. Obviously we did not intend to put anything on the proving ground. It was 448029 O—58-——_13 187 minutes (o 1,500 counts per ‘ite, depending, T suppose, on small nonuniformities in the sur- face, how much dustis on the top of the material or various otherfactors. It is really difficult. to monitor for this stuff. Unless we do it as we attempted to do it by establishing an artificial surface, a fallout tray covered with an alkyl resin, and then make a verydesirable monitoring surface, 1 don’t know how youcan do it. Have [ answered your question atall? Dr. Lancuam. I think what this amounts to is that the short range of the alpha makesit so unusuallydifficult to detect that the methods thatare easy for making such measurements are not sufficiently sensitive to give the detail you would like to have. objection to it, I think. This is the principal