Film Badge Dosimetry in Atmospheric Nuclear Tests (1989) / Chapter Skim
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4 Use of Film Badges in Atmospheric Nuclear Testing
4 Use of Film Badges in Atmospheric Nuclear Testing
Pages 35-60
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From page 35... ...
. The selection of an appropriate calibration source, representing field expo sure conditions, with which to produce the characteristic response curve relating density and exposure.
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From page 36... ...
Because the abundance of lowenergy photons was small and variable, the true effect of changing lead thicknesses should be negligible in the presence of all the other factors known to influence film response. As implied above, determination of the characteristic curve of exposure versus film density underneath the photon filter can be accomplished with any radionuclide that emits high-energy photons.
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From page 37... ...
B BETA PARTICLE MONITORING Personnel film badge dosimeters were used for beta radiation monitoring during underground nuclear testing operations at the NTS from 1966 until 1987
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From page 38... ...
The response of Du Pont 502 double-coated emulsion in a paper wrapper (a typical low-range film component used during atmospheric testing) changes for maximum beta-particle energies between 0.5 and 3 MeV by almost a factor of ten (Hine and Brownell 1956~.
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From page 39... ...
At the other extreme, it may be the result of only beta radiation. The fast attempt to monitor beta exposures with personnel film badges during atmospheric nuclear testing was at Operation CROSSROADS in 1946 at Bikini Atoll in the Pacific.
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From page 40... ...
There is no evidence in the records that beta dosimetry was performed during WIGWAM. The final attempt to evaluate and report beta exposure with film badges during atmospheric testing was at Camp Desert Rock, outside NTS, during Operation PLUMBBOB in 1957.
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From page 41... ...
Either the firm badge used did not have the capabilities for monitoring beta dose, or procedures used for evaluating beta exposures were incorrect. Thus, betaparticle monitoring with personnel film badges was not successful during atmospheric nuclear testing series.
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From page 42... ...
Figure 4-2 shows typical calibration curves for the upper range of the 508 component and the lower range of the 1290 component. Calibration data show that the useful upper limit of the Type 508 exposure range was 10 R
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From page 43... ...
. A typical low-range bum component used for film badging during atmospheric test series was the Du Pont Type 502, which had a maximum useful exposure range of about 10 R
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From page 44... ...
Secondly, at least one additional higher range film component was included with the Type 502 in the fUm packet during each test series when the Type 502 was used. The additional film usually had a useful exposure range that began at about the maximum exposure measurable with the more sensitive film component (see Section 4.D)
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From page 45... ...
If a film was exposed beyond its range, the first indication of reversal would be the dots, which had a greater optical density to begin with. Thus, impression dots lighter than the remaining film indicated an exposure between the maximum usable range of the film component and the minimum required for reversal.
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From page 46... ...
This section identifies those differences between field and laboratory conditions which may require consideration of additional uncertainties in interpreting exposures of film badges worn in the field. Conversion of the OD of an exposed film to exposure is accomplished by comparison with ODs of films exposed to known amounts of radiation.
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From page 47... ...
Based on calibration techniques used during atmospheric weapons tests, results in terms of exposure to personnel film badges worn by individuals might be overstated. No evidence exists that corrections for backscatter were made.
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From page 48... ...
This technique was used in most of the later test series. Gross variations between batches could be identified in these earlier tests through the use of unexposed control films; however, unexposed films are not as sensitive as calibrated film for indicating changes during develop~ng.
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From page 49... ...
A variety of such environments was encountered during atmospheric testing. High temperatures and humidities along with salt water spray characterized the Pacific tests, while very dry, hot, and physically abusive conditions were found in the Nevada desert.
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From page 50... ...
For unprotected film badges worn for intervals greater than a week in relative humidities exceeding 70%, some fading can be postulated. The amount of fading depends on the time between radiation exposure and development.
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From page 51... ...
Better protection was afforded by coating the badges in ceresin wax or encasing them in sealed plastic cases. The latter technique, while successful in one test series, required a saw to open the case, and this led to light leaks in another test series.
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From page 52... ...
H FILM BADGE EXPOSURE VERSUS DOSE This section presents a brief summary of the basic quantities used in the measurement of ionizing radiation and the units in which these quantities were expressed throughout the atmospheric test series period.
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From page 53... ...
Because absorption of photons is a complex function of the atomic number of the absorber and the photon energy, the measurement of exposure or exposure rate at a given point in air provides only the first step in the determination of how much radiation energy would be absorbed by an object placed at that point in the radiation field. The absorbed dose, D, is the amount of energy absorbed from any kind of ionizing radiation per unit mass of absorbing material at a specified point.
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From page 54... ...
Therefore for these radiations the dose equivalent is numerically the same as the absorbed dose. In this report, the traditional units are used throughout because the SI units were not in use during the time period of atmospheric testing.
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From page 55... ...
Such refinements, if made, are likely to reduce the estimated dose even further. Thus the error made by using exposure as a substitute for absorbed dose to a critical organ is of little consequence when the exposure values are low (less than the allowable exposure limits)
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From page 56... ...
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From page 57... ...
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From page 60... ...
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