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Time-dependent multiplicity for Cf-252 neutron source.

Xiaobo Liu¹, Yaru Shi¹, Jiansheng Li¹

¹Institute of Nuclear Physics and Chemistry, CAEP, Mianyang, 621900 , China.

Applied Radiation and Isotopes : Including Data, Instrumentation and Methods for Use in Agriculture, Industry and Medicine

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Summary

Californium-252 (Cf-252) neutron sources decay over time, affecting their strength and neutron multiplicity. This study provides equations to predict these changes, crucial for accurate calibration of neutron counters.

Keywords:

Cf-250 Cf-252 neutron source Cm-248 Decay model Neutron multiplicity correction Neutron multiplicity counting Neutron strength correction

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Published on: December 8, 2016

Area of Science:

Nuclear Physics
Applied Nuclear Science

Background:

Californium-252 (Cf-252) is a key neutron source for calibrating neutron multiplicity counters.
Understanding the time-dependent behavior of Cf-252 sources is essential for accurate measurements.

Purpose of the Study:

To develop equations for calculating the time-dependent strength and neutron multiplicity of Cf-252 sources.
To analyze the impact of decay on Cf-252 source characteristics over time.

Main Methods:

Derived general equations based on the decay models of Cf-252, Cf-250, Cm-248, and Cm-246.
Utilized nuclear data for these nuclides to model a long-aged Cf-252 source (>40 years).
Performed neutron multiplicity counting experiments using a thermal neutron multiplicity counter for verification.

Main Results:

Calculations showed a significant decrease in the 1st, 2nd, and 3rd moment factorials of neutron multiplicity for aged Cf-252 sources compared to pure Cf-252.
Experimental measurements for two Cf-252 sources (one aged, one with 17.1 years service life) were consistent with the derived equations.
The study quantifies the time-dependent variations in Cf-252 source strength and multiplicity.

Conclusions:

The developed equations accurately predict the time-dependent changes in Cf-252 neutron source attributes.
These findings are vital for applying appropriate corrections in neutron counter calibration.
Accurate calibration ensures reliable results in applications relying on neutron multiplicity measurements.