A method for calculating the velocity and argument cosine of heavy nuclei in the process of epithermal neutron scattering

A computational method, a technique for thermal neutrons

Inactive Publication Date: 2018-12-18
SOUTH CHINA UNIV OF TECH
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Problems solved by technology

But for those with obvious resonant elastic scattering properties such as 238 For heavy nuclei

Method used

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  • A method for calculating the velocity and argument cosine of heavy nuclei in the process of epithermal neutron scattering
  • A method for calculating the velocity and argument cosine of heavy nuclei in the process of epithermal neutron scattering
  • A method for calculating the velocity and argument cosine of heavy nuclei in the process of epithermal neutron scattering

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Embodiment

[0027] The existing constant scattering cross-section free gas model assumes that the heavy nuclei are unbound and their velocity distribution conforms to the Maxwell distribution, and assumes that the microscopic elastic scattering cross-section of the nuclide at absolute zero is constant, and P(V,μ|v) represents the relationship with the velocity v The conditional probability distribution function for heavy nuclei that collide elastically with neutrons is as follows:

[0028]

[0029] In the formula:

[0030]

[0031] P 2 =1-P 1

[0032]

[0033]

[0034]

[0035] Among them, P(V,μ|v)dVdμ is the probability distribution function of the velocity of heavy nuclei; D is the ratio of the elastic scattering cross section at absolute zero to the effective elastic scattering cross section; P 1 ,P 2 Respectively, the sampling probability value, f 1 (V), f 2 (V) are functions related to the velocity of heavy nuclei under the corresponding probability; V is the vel...

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Abstract

The invention discloses a method for calculating the velocity and argument cosine of heavy nuclei in the process of epithermal neutron scattering. In fission reactors, the maximum elastic scattering cross section method based on the energy range of heavy nuclei in the superheated region is used to simulate the neutron elastic scattering process; when the neutrons in the superheated region with energies from 0.4 eV to 210 eV scatter resonantly and elastically with the heavy nuclei in the nuclear reactor, at first, the velocity and argument cosine of heavy nuclei are sampled with a certain probability, then the velocity and argument cosine are accepted with a certain probability, or the velocity and argument cosine are discarded with a certain probability, so that the final velocity and argument cosine of heavy nuclei are obtained. The invention optimizes and improves the sampling of the velocity and the argument cosine of the heavy nucleus in the resonance elastic scattering process ofthe traditional neutron and the heavy nucleus, and at the same time, the elastic scattering cross section of heavy nuclei scattered by neutrons in the energy range of superheated region is also takeninto account, which enables the model to calculate the elastic scattering process of the neutrons and heavy nuclei more accurately.

Description

technical field [0001] The invention relates to the field of nuclear reactor neutron scattering, in particular to a method for calculating the velocity and argument cosine of heavy nuclei during the scattering process when neutrons in an epithermal zone collide with heavy nuclei by elastic scattering. Background technique [0002] During neutron scattering in the epithermal region, the Monte Carlo program uses a free gas model to account for the effect of the thermal motion of heavy nuclei on neutron scattering. Existing free gas models assume that heavy nuclei are unbound and their velocity distribution conforms to the Maxwell distribution, and assume that the microscopic elastic scattering cross section of nuclides at absolute zero is constant. But for those with obvious resonant elastic scattering properties such as 238 For heavy nuclei such as U, the assumption of a constant elastic scattering cross section is obviously not valid. In order to overcome the defects of th...

Claims

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Application Information

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IPC IPC(8): G06F17/18G06F17/15
CPCG06F17/15G06F17/18
Inventor 蔡杰进李志峰刘荣
Owner SOUTH CHINA UNIV OF TECH
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