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DTRA’s advancements in nuclear and radiological detection
A new, more complex nuclear age has begun. Echoing the tensions of the Cold War amid rapidly evolving nuclear and radiological threats, preparedness in the modern age is a contest of scientific innovation. The Research and Development Directorate (RD) at the Defense Threat Reduction Agency (DTRA) is charged with winning this contest.
Y. Harima, S. Tanaka
Nuclear Science and Engineering | Volume 90 | Number 2 | June 1985 | Pages 165-173
Technical Paper | doi.org/10.13182/NSE85-A17674
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Exposure buildup factors for plane isotropic, point isotropic, and plane normal sources have been calculated using a discrete ordinates direct integration code, PALLAS-PL, SP-Br, in infinite and finite water shields in the 0.06- to 0.1-MeV range. The values of the attenuation kernel, Be-µr, are greater than unity at distances up to a few mean-free-paths in an infinite medium. The maximum value of Be-µr depends on the incident energy, and this effect reaches a maximum for a 0.08-MeV source. The implication that the dose rate with a shield is greater than without a shield should be noticed. Results of this study show, however, that the large degree of scattering in a low-z material, such as water, produces this effect. Buildup factors, energy spectra, and angular distributions were analyzed for three source geometries in the comparisons of scattered gamma-ray transport in infinite and finite water shields.