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  General Kenneth Nichols and the Manhattan Project
  Nichols
  The Oak Ridger has published the latest in a series of articles about General Kenneth D. Nichols, the Manhattan Project, and the 1954 Atomic Energy Act. The series has been produced by Nichols’ grandniece Barbara Rogers Scollin and Oak Ridge (Tenn.) city historian David Ray Smith. Gen. Nichols (1907–2000) was the district engineer for the Manhattan Engineer District during the Manhattan Project.
  As Smith and Scollin explain, Nichols “had supervision of the research and development connected with, and the design, construction, and operation of, all plants required to produce plutonium-239 and uranium-235, including the construction of the towns of Oak Ridge, Tennessee, and Richland, Washington. The responsibility of his position was massive as he oversaw a workforce of both military and civilian personnel of approximately 125,000; his Oak Ridge office became the center of the wartime atomic energy’s activities.”
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Radionuclide release from an engineered barrier in a low- and intermediate-level waste repository is evaluated. The results of experimental studies conducted to determine the radionuclide diffusion coefficients and the hydraulic conductivities of calcium bentonite and crushed granite mixtures are presented. The hydraulic conductivity of the mixture is relatively low even at low dry density and clay content, and the principal mechanism of radionuclide migration through the mixture is diffusion. The measured values of apparent diffusion coefficients in calcium bentonite with a dry density of 1.4 Mg/m³ are of the order of 10^-13 to 10^-12 m²/s for cations and 10^-11 m²/s for iodine. These values are similar to those in sodium bentonite. The radionuclide release rates from the engineered barrier composed of the concrete structure and the clay-based backfill were calculated. Carbon-14 and ⁹⁹Tc are the important nuclides; however, their maximum release rates are <10^-5 GBq/yr. To quantify the effect of uncertainties of input parameters on the radionuclide release rates, Latin Hypercube sampling was used, and the ranges of release rates were estimated statistically with a confidence level of 95%. The uncertainties of the assessment results of the radionuclide release rate are larger in the case of the sorbing nuclides such as ¹³⁷Cs. Finally, the sensitivity of the input parameter to release rate is also evaluated.