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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.”
Yue Guan, Fei Li, Mohammad Modarres
Nuclear Technology | Volume 133 | Number 3 | March 2001 | Pages 290-309
Technical Paper | Reactor Safety | doi.org/10.13182/NT01-A3175
Articles are hosted by Taylor and Francis Online.
A method of integrating traditional thermal-hydraulic (TH) analysis with probabilistic assessment (PA) (called the TH-PA method) has been developed. This method allows for an exhaustive search through a set of individually developed but subsequently linked logic models to screen and identify accident scenarios. The logic models consist of a probabilistic risk assessment (PRA) used for probabilistic screening purpose and an ensemble of integrated behavior logic diagrams (IBLDs). The PRA model represents the functional/logical relationships of the components and accident scenarios, the same way as is modeled in the conventional PRAs. The IBLDs hierarchically represent system interactions/dependencies due to TH phenomena and human actions. This hierarchy also shows causal factors and consequences of plant states, and identifies induced system failures. The TH-PA method relies on two types of scenario screening: probabilistic screening (PA screening) and TH screening. The PA screening eliminates scenarios with low frequencies (e.g., <10-10/reactor-yr). The traditional frequency-based screening method used in the PRAs has been adopted for PA screening. The TH screening eliminates scenarios that do not expect to result in core uncovery. For the TH screening, a simple accident trajectory approach has been devised. A trajectory represents the collapsed liquid volume fraction in the reactor primary system as a function of primary pressure. The trajectories are based on simple mass and energy conservation equations (if the TH-PA method is applied to a system where mechanical energy transfer is important, momentum conservation should also be considered). The roles of each plant system are then identified by indicating whether the system is a "source" or a "sink" for mass and energy at a given time during accident progression. Based on an input set that represents the plant system failures and the stage of the transient, the accident trajectory is developed. The accident trajectory allows for the evaluation of safety significance of scenarios. The trajectory also determines whether the core becomes uncovered, should the input conditions (i.e., conditions described by the input set) remain unchanged.