# Nuclear Science and Techniques

《核技术》(英文版) ISSN 1001-8042 CN 31-1559/TL     2019 Impact factor 1.556

Nuclear Science and Techniques ›› 2018, Vol. 29 ›› Issue (2): 29

• NUCLEAR ENERGY SCIENCE AND ENGINEERING •

### Measurement of keff by delayed neutron multiplication in subcritical systems

Bin Ye 1,2, Chao-Wen Yang 1, Chun Zheng 2

1. 1 College of Physical Science and Technology, Sichuan University, Chengdu 610064, China
2 Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China
• Contact: Chun Zheng E-mail:zhengchun@caep.cn
• Supported by:

This work was supported by the National Natural Science Foundation of China (Nos. 11175164 and 91326109).

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Bin Ye, Chao-Wen Yang, Chun Zheng. Measurement of keff by delayed neutron multiplication in subcritical systems.Nuclear Science and Techniques, 2018, 29(2): 29
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Abstract:

In this paper, we build on the concept of equivalent fundamental-mode source to propose using delayed neutrons as a neutron source in multiplication experiments to acquire the effective multiplication factor keff of subcritical systems, which is difficult to acquire directly from conventional neutron source multiplication method. We analyzed the difference between a fundamental- mode fission source and delayed neutron source, then adopted a factor to convert delayed neutron distribution to an equivalent fundamental-mode source distribution, and employed Monte Carlo code to acquire this factor. The delayed neutron multiplication measurement method was established for the first time, and corresponding experiments were conducted in subcritical systems. The multiplication of delayed neutrons was measured based on Chinese Fast Burst Reactor-II (CFBR-II) at subcritical states, and keff was acquired from delayed neutron multiplication successfully (0.9921 and 0.9969, respectively). The relative difference between keff obtained by the new method and previous values acquired by the positive period method is less than 1% for these two studied cases.