Category Archives: Nuclear Reactor Design

Nodal diffusion method

The finite difference method is widely used in the design calculation of fast reactors, the analysis of critical assembly experiments, and so on. For fast reactors, convergence of the outer iteration is fast due to the long mean free paths of neutrons, and moreover, the nuclear and thermal-hydraulic coupled core calculation is not needed. Hence, the computation speed required for […]

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Reactivity control by burnable poisons

As shown in Fig. 3.13, reactors in the beginning of the operation cycle are required to have an excess reactivity compensating for the reactivity variation due to consumption of fissile materials and accumulation of FPs with burnup. Since some fuel rods of fresh fuel assemblies include pellets containing several weight percent of burnable poisons (neutron absorbers), the excess reactivity necessary […]

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Doppler coefficient

The Doppler coefficient represents that reactivity is decreased by an increase in neutron resonance absorption (mainly by 238U and 240Pu) resulting from power and then fuel temperature rises. A reactivity variation to a 1 % power rise is referred to as the Doppler power coefficient, and a reactivity variation to a 1 ° C fuel temperature rise is referred to […]

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Design of fuel assembly

(1) Features of fast reactor fuel assembly A fast reactor fuel assembly consists of triangularly arranged fuel elements and a containing wrapper tube (cf. Fig. 4.3). Positions of the fuel elements are kept by the wire spacers or the grid spacers, so that the coolant channels are ensured. The upper shielding is contained in the upper part of the wrapper […]

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Nuclear Reactor Design

Nuclear reactor design is based on knowledge and data from many nuclear engi­neering fields including nuclear reactor physics, nuclear thermal hydraulics, and nuclear safety. In nuclear reactor design, reactor performance is evaluated by numerical anal­ysis for requirements of nuclear and thermal limitations, stability, controllability, and safety, referred to as conceptual design. To approximate reactor performance, the design then proceeds to […]

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Core Management [3, 26, 27]

[1] Summary of core management Core management technology is intended to secure reactor safety and to realize efficient and economic fuel burning. BWR core management can be divided into reload core design and operation management as shown in Fig. 3.27. In the reload core design, middle — and long-term fuel preparation plans are made and the fuel assembly arrangement and […]

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Axial Power Distribution Oscillation

For a constant core power, the difference in average moderator temperature between upper and lower core region is constant and independent of axial power distribution. Hence, axial power distribution oscillation cannot be expected to be suppressed by the moderator temperature coefficient and the Doppler effect will be expected instead. Since the axial power distri­bution becomes flatter with burnup from an […]

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