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Nuclear Nonproliferation Policy
The mission of the Nuclear Nonproliferation Policy Division (NNPD) is to promote the peaceful use of nuclear technology while simultaneously preventing the diversion and misuse of nuclear material and technology through appropriate safeguards and security, and promotion of nuclear nonproliferation policies. To achieve this mission, the objectives of the NNPD are to: Promote policy that discourages the proliferation of nuclear technology and material to inappropriate entities. Provide information to ANS members, the technical community at large, opinion leaders, and decision makers to improve their understanding of nuclear nonproliferation issues. Become a recognized technical resource on nuclear nonproliferation, safeguards, and security issues. Serve as the integration and coordination body for nuclear nonproliferation activities for the ANS. Work cooperatively with other ANS divisions to achieve these objective nonproliferation policies.
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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.”
C.-K. Chris Wang, Thomas E. Blue, Reinhard Gahbauer
Nuclear Technology | Volume 84 | Number 1 | January 1989 | Pages 93-107
Technical Paper | Radioisotopes and Isotope Separation | doi.org/10.13182/NT89-A34199
Articles are hosted by Taylor and Francis Online.
A neutronic study of an accelerator-based neutron irradiation facility (ANIF) for boron neutron capture therapy (BNCT) was performed using three-dimensional Monte Carlo transport calculations. The major components of the ANIF are a radio-frequency quad-rupole proton accelerator, a 7Li target, and a moderator assembly. Neutrons are generated by bombarding the 7Li target with 2.5-MeV protons. The neutrons emerging from the 7Li target are too energetic to be used for BNCT and must therefore be moderated. Calculations show that, among all materials for the ANIF, beryllia (BeO) and heavy water (D2O) are the best moderators. Between them, beryllia provides better neutron spectra, but D2O gives higher neutron intensities. Adding alumina (Al2O3) to D2O improves the neutron spectra, but it also increases gamma-ray contamination. The overall performance of an ANIF was evaluated for a moderator assembly composed of a 20.0-cm-high x 12.5-cm-radius beryllia cylinder reflected by 30.0 cm of alumina. Calculations show that the addition of the alumina reflector doubles the epithermal neutron intensity at the irradiation port. A 0.05 g/cm2 thick layer of 6Li was placed between the beryllia moderator and the alumina reflector to reduce the number of thermal neutrons escaping from the beryllia to the alumina, and therefore the capture gamma rays produced by aluminum in the reflector. Also, a 0.025 g/cm2 thick layer of 6Li was placed at the irradiation port of the moderator assembly to remove thermal neutrons from the field. Finally, a neutron shield of 10.0-cm-thick D2O wrapped with 6LiF was placed around the moderator assembly except at the irradiation port. The useful neutron flux (which is the flux of neutrons with energies greater than ∼1 eV) at the irradiation point, which is in front of the moderator assembly, is 4.87 x 108 n/cm2.s for a 10-mA proton beam. The corresponding total absorbed dose rates for neutron and gamma rays are 1.9 and 0.64 cGy/min, respectively. The ratio of the total neutron absorbed dose rate to the useful neutron flux is 6.5 x 10-11 cGy/n·cm-2, which is slightly higher than, but comparable to, the value of this ratio that has been estimated for moderated reactor neutron fields. The maximum usable depth (MUD) in a head phantom is calculated to be ∼7.5 cm assuming that the 10B concentration is 30 µg/g in tumor and 10 µg/g in blood, and the singlesession treatment time is 1.6 h. If the beryllia cylinder in the moderator assembly were replaced by a 15.0-cm-high x 12.5-cm-radius cylinder of heavy water, the treatment time would be reduced to 30 min, at the price of a higher entrance neutron dose to normal tissue and thus lower therapeutic gains and MUD.
