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Method for measuring content of 235U and 239Pu in U-Pu mixture

A mixture and content technology, which is applied in nuclear physics and nuclear engineering fields, can solve the problems of complex data processing and low accuracy of results, and achieve the effect of accurate content and fast measurement speed

Active Publication Date: 2013-12-04
CHINA INSTITUTE OF ATOMIC ENERGY
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0006] "Rapid determination of uranium and plutonium content in mixtures through measurement of the intensity-time curve of delayed neutrons" in "Nuclear Instruments and Methods in Physics Research B", Volume 215, pages 246-251 published in 2004 discloses a usable unit of quality 235 U and 239 The count rate of Pu delayed neutrons can be established to establish the equation for the U-Pu mixture 235 U and 239 Pu concentration, this method uses time points for analysis and calculation, the data processing is complicated, and the accuracy of the results is low

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  • Method for measuring content of 235U and 239Pu in U-Pu mixture

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Embodiment 1

[0019] Will contain 13.1μg 235 U, 11.9 μg 235 U+10.2μg 239 Pu and 10.2 μg 239 Three polyethylene boxes of Pu samples were placed in the running rabbit system, injected into the vertical channel of a 30kW micro-reactor (referred to as micro-reactor) and irradiated for 30s. After cooling for about 2s, the samples were sent back to the delayed neutron detector to measure the slow neutrons. The DSA-1000 digital spectrometer works in the multi-channel calibration (MCS) mode, the MCS interval is set to 1s, and the measurement is 100s. figure 1 yes 235 U 239 Characteristic map of delayed neutron decay time curves of Pu and its mixture samples.

[0020] The delayed neutron decay time curves of the three samples have the characteristics that the curves gradually change from divergence to convergence around 10s, so the delayed neutron counts per unit mass between 1-10s and 11-20s are selected as the mixture 235 U and 239 Pu quantification coefficient, assuming that the mixture ...

Embodiment 2

[0028] Will contain 13.1μg 235 U, 20.2μg 235 U+10.2μg 239 Pu and 10.2 μg 239 Three polyethylene boxes of Pu samples were placed in the running rabbit system, injected into the vertical channel of a 30kW micro-reactor (referred to as micro-reactor) and irradiated for 30s. After cooling for about 2s, the samples were sent back to the delayed neutron detector to measure the slow neutrons. The DSA-1000 digital spectrometer works in the multi-channel calibration (MCS) mode, the MCS interval is set to 1s, and the measurement is 100s. Select delayed neutron counts per unit mass between 2-8s and 11-17s as the mixture 235 U and 239 Pu quantification coefficient, assuming that the mixture 235 U has mass x1, 239 The mass of Pu is y1, establish a linear equation:

[0029]

[0030] Solve the equation to get: x1=5.0μg, y1=10.5μg

[0031] In the U-Pu mixture 235 U and 239 The Pu contents were 5.0 and 10.5 μg, and the relative uncertainties were 1.9% and 2.9%, respectively. Tab...

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Abstract

The invention discloses a method for measuring the content of 235U and 239Pu in a U-Pu mixture. The method carries out measuring in a delayed neutron mode and comprises the following steps that (1) a reactor is used for irradiating a 235U sample, a 239Pu sample and the mixture, and the count of a delayed neutron along with time is measured; (2) according to the count, measured in the step (1), of the delayed neutron along with time variation, an exponential damping function is used for carrying out fitting on a decay characteristic curve of the delayed neutron along with time variation; (3) according to the decay curve characteristic pattern, a time period before delayed neutron counting rate changing and a time period after delayed neutron counting rate changing are selected, wherein obvious change differences exist in the two time periods, and then unit mass delayed neutron counts of the two time periods are computed to be used as quantitative coefficients of the 235U and the 239Pu in the U-Pu mixture; (4) a system of linear equations is built, and the content of the 235U and the 239Pu is computed through the system of the linear equations. The method for measuring the content of the 235U and the 239Pu in the U-Pu mixture is accurate and rapid in measurement and wide in application range.

Description

technical field [0001] The invention relates to the technical fields of nuclear physics and nuclear engineering, in particular to a method for measuring the concentration of U-Pu in a mixture of U-Pu by using a delayed neutron counting method. 235 U and 239 Method of Pu content. [0002] Background technique [0003] Of the more than 550 incidents recorded in the IAEA's Illicit Trafficking and Trading Database between 1993 and 2001, about half involved nuclear materials. This illicit trafficking in nuclear material is a global problem, and stopping the illicit trafficking in nuclear material requires 235 U 239 Pu identification and quantitative detection. Nuclear warheads contain special nuclear materials, and the detection of nuclear warheads in the future deep nuclear disarmament will also require 235 U 239 Pu identification and quantitative detection. [0004] It is difficult to draw a definite conclusion by using the radioactivity of fissile material itself to id...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01T3/00
Inventor 肖才锦张贵英倪邦发刘存兄王平生
Owner CHINA INSTITUTE OF ATOMIC ENERGY