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![242g Am isometric ratio in total 241 Am capture [12, 13]](profile/Shigetaka-Maeda/publication/231061517/figure/fig2/AS:376114032726017@1466683981960/g-Am-isometric-ratio-in-total-241-Am-capture-12-13.png)
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![Fig. 1 242g Am isometric ratio in total 241 Am capture [12, 13]](profile/Shigetaka-Maeda/publication/231061517/figure/fig2/AS:376114032726017@1466683981960/g-Am-isometric-ratio-in-total-241-Am-capture-12-13_Q320.jpg)
![Table 1 Am Transmutation Performance[13]](profile/Shigetaka-Maeda/publication/231061517/figure/tbl1/AS:667776591093763@1536221754365/Am-Transmutation-Performance13_Q320.jpg)
Americium is a key element to design the FBR based nuclear fuel cycle, because of its long-term high radiological toxicity as well as a resource of
even-mass-number plutonium by its transmutation in reactors, which contributes the enhancement of proliferation resistance. The present paper deals with the numerical analysis of the Am sample irradiat...
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The main tool for the investigation of advanced nuclear power installations to be operated in various energy systems is mathematical modelling. Various alternatives for nuclear energy development are compared by introducing the functional to characterize current expenses for the nuclear power system. The computer codes elaborated were used to deter...
Citations
The design consideration of depleted U and Am (DU-Am) oxide fuel pin was performed for Pu denaturing in the framework of the protected plutonium production based on the irradiation analyses of the DU samples irradiated in the environment of broad range of neutron energy in the experimental fast reactor Joyo. From the results of irradiation analyses of DU, it was confirmed that there is a strong dependence of transmutation behavior of DU on the ratio of neutron flux in the resonance region to the total neutron flux, namely resonance neutron ratio, even in a fast reactor. Also, it was confirmed that there is a strong effect of sample material form and shape on generated Pu nuclide inventory especially near the reflector area (>20% resonance neutron ratio), because of the intensive self-shielding of 238U, though less is expected for 241Am. Sensitivity study of hypothetical DU-Am oxide fuel pellet irradiation on neutron energy and burn-up was performed to evaluate significant gradient of radial 238Pu isotopic composition profile (e.g., from 12% to 18% distribution in 3% Am doping, in 30% resonance neutron ratio and in the neutron fluence of 4.0 × 1022 n/cm2 inside a large pellet with softened neutron spectrum), and vulnerability of the fuel pellet surface in terms of Pu denaturing was revealed. Design consideration of radial zoning of 241Am content was introduced to flatten the radial distribution of isotopic composition of Pu. The results of radial zoning of 241Am (4% and 3% Am in the outer and inner zone of DU-Am oxide fuel pellet) in hypothetical irradiation neutronics analysis showed the radial profile of produced Pu is over 15 at.% of 238Pu isotopic composition in any zone and meets the criterion of Kimura et al. based on decay heat of Pu to impede utilization to fission explosive devices.
The proliferation resistance of plutonium can be enhanced by isotopic denaturing and one of the features of Pu isotopic denaturing is increasing of the spontaneous fission neutron emission rate. A high spontaneous fission neutron emission rate causes “predetonation” in a nuclear explosive device, and it makes the designing and building of a nuclear explosive device more complicated. In this paper, the enhancement of Pu proliferation resistance by isotopic denaturing was evaluated based on spontaneous fission neutron emission rate using a simple nuclear explosive device model. The feature of spontaneous fission neutron was evaluated with probabilistic approach, and a new Pu categorization which makes enable to categorize plutonium by its isotopic compositions was proposed based on the evaluation results. The Pu categorization was applied to an evaluation of the proliferation resistance of plutonium produced in LWRs and FBRs using the evaluation function, “Attractiveness” for two types of plutonium; plutonium produced in typical LWRs and FBRs, and denatured plutonium produced by transmutation of MAs.
The present paper is prepared for the peaceful use of the nuclear energy. It is important to develop the methodology to evaluate the proliferation resistance of nuclear energy systems, and the concept of evaluation function “Attractiveness (ATTR)” has been proposed as a new evaluation function for one of the intrinsic features of proliferation resistance, fissile material characteristics based on its isotopic barriers. In the present paper, the improvement of the function ATTR to evaluate plutonium is examined and performed. The terms of the characteristics of potential explosive energy and the technical difficulty for fission explosive device use in the evaluation function ATTR are both improved to refer their physical nature. The effect of compression on Rossi-alpha is introduced to improve the term of the characteristics of potential explosive energy. A relation between Rossi-alpha and potential explosive energy is also studied theoretically for the improvement of the evaluation function ATTR. Radiation barrier of plutonium is also introduced as a new technical difficulty factor. The improved evaluation function ATTR is applied for the categorizations of plutonium produced in typical reactors.
Americium is a key element to design the FBR based nuclear fuel cycle, because of its long-term high radiological toxicity as well as a resource of even-mass-number plutonium by its transmutation in reactors, which contributes the enhancement of proliferation resistance. The present paper summarizes analysis of the individual Am and U samples irradiation in Joyo to re-evaluate the results of Pu isotopes in the measure of proliferation resistance, and to combine the results for the prediction of DU-Am irradiation especially in the production of Pu isotopes. By the prediction of DU-Am oxide fuel in fast reactor environment with detail fuel irradiation analysis, it was confirmed that neutron moderation and fuel size affects the produced Pu isotope and its vector due to the very high sensitivity of 238U resonance capture reaction, the larger diameter fuel is more preferable in the case of moderated neutron spectrum environment for denaturing Pu in fast reactor blanket. Finally proliferation resistance of all the Pu produced in U, Am sample irradiation and DU-Am fuel irradiation prediction were evaluated based on decay heat and spontaneous fission neutron rate, and it was confirmed 241Am produces un-attractive Pu to abuse from the beginning to the end of irradiation, and more than 2% of 241Am doping is required to enhance the proliferation resistance of Pu to MOX grade and Kessler’s proposal in moderated neutron spectrum environment in fast reactor.
