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RISS 인기검색어
- 검색키워드
- 저자 : Lloyd Cody (검색결과 3 건)
- 무료
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Time Dependent Heat Transfer of Proliferation Resistant Plutonium
Cody Lloyd,Ravi Hadimani,Braden Goddard 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.2
Increasing proliferation resistance of plutonium by way of increased 238Pu content is of interest to thenuclear nonproliferation and international safeguards community. Considering the high alpha decay heatof 238Pu, increasing the isotopic fraction leads to a noticeably higher amount of heat generation withinthe plutonium. High heat generation is especially unattractive in the scenario of weaponization. Uponweaponization of the plutonium, the plutonium may generate enough heat to elevate the temperature inthe high explosives to above its self-explosion temperature, rendering the weapon useless. In addition,elevated temperatures will cause thermal expansion in the components of a nuclear explosive devicethat may produce thermal stresses high enough to produce failure in the materials, reducing theeffectiveness of the weapon. Understanding the technical limit of 238Pu required to reduce the possibilityof weaponization is key to reducing the current limit on safeguarded plutonium (greater than 80 at. %238Pu). The plutonium vector evaluated in this study was found by simulating public information onLightbridge’s fuel design for pressurized water reactors. This study explores the temperature profile andmaximum stress within a simple (first generation design) hypothetical nuclear explosive device of fourunique scenarios over time. Analyzing the transient development of both the temperature profile andmaximum stress not only establishes a technical limit on the 238Pu content, but also establishes a timelimit for which each scenario would be useable.
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Ability of non-destructive assay techniques to identify sophisticated material partial defects
Lloyd, Cody,Goddard, Braden Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.6
This study explores the ability of non-destructive assay techniques to detect a partial material defect in which 100 g of plutonium are diverted from the center of a 1000 g can of PuO<sub>2</sub> powder. Four safeguards measurements techniques: neutron multiplicity counting, calorimetry, gravimetry, and gamma ray spectroscopy are used in an attempt to detect the defect. Several materials are added to the partial defect PuO<sub>2</sub> can to replicate signatures of the diverted material. <sup>252</sup>Cf is used to compensate for the doubles neutron counts, <sup>241</sup>Am is used to compensate for the decay heat, and aluminum is used to compensate for the weight. Although, the doubles and triples difference before and after diversion are statistically indistinguishable with the AWCC in fast and thermal mode, the difference in the singles counts are statistically detectable in both modes. The relatively short half-life of <sup>252</sup>Cf leads to a decrease (three sigma uncertainty) in the doubles neutron counts after 161 days. Combining this with the precise quantity of <sup>241</sup>Am needed (10.7 g) to mimic the heat signature and the extreme precision in <sup>252</sup>Cf mass needed to defeat neutron multiplicity measurements gives reassurance in the International Atomic Energy Agency's ability to detect partial material defects.
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Novel homogeneous burnable poisons in pressurized water reactor ceramic fuel
Dodd, Brandon,Britt, Taylor,Lloyd, Cody,Shah, Manit,Goddard, Braden Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.12
Due to excess reactivity, fresh nuclear fuel often contains burnable poisons. This research looks at six different burnable poisons and their impacts on reactivity, material attractiveness, and waste management. An MCNP simulation of a PWR fuel pin was performed with a fuel burnup of 60 GWd/MTHM to determine when each burnable poison fuel type would decrease below a k<sub>∞</sub> of 1. For determining the plutonium material attractiveness in each burnable poison fuel type, the plutonium isotopic content of the used fuel was evaluated using Bathke's Figure of Merit formula. For the waste management analysis, the thermal output of each burnable poison fuel type was determined through ORIGEN decay simulations at 100 and 300 years after being discharged from the core. The performance of all six burnable poisons varied over the three criteria considered and no single burnable poison performed best in all three considerations.
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