Nuclear Techniques ›› 2019, Vol. 42 ›› Issue (9): 90502-090502.doi: 10.11889/j.0253-3219.2019.hjs.42.090502


An inversion method of in-core neutron field based on ex-core neutron spectrum measurement

Quan CAO Pei HAO Lijuan SONG Jing LONG Pengcheng YU Shengpeng GAN,Bin SUN Guangyao WU Yican FDS Team WU   

  1. Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei 230031, China
  • Received:2019-05-20 Revised:2019-06-26 Online:2019-09-10 Published:2019-09-18
  • Supported by:
    Information Project of Chinese Academy of Sciences(XXH13506-104);the project of Hefei Institutes of Physical Science(KP-2017-19);Young Elite Scientists Sponsorship Program by CAST(2017QNRC001)

Abstract: Background

The self-powered detectors (SPD) are widely used in commercial reactor for the real-time measurement of neutron flux distribution, but neutron spectrum cannot be obtained by SPD. Meanwhile, due to the extreme condition of advanced reactor systems, the existing in-core measurement systems cannot meet the requirement of real-time measurement of neutron field in the core of advanced reactor.


This study aim to develop an inversion method of in-core neutron field based on ex-core neutron spectrum measurement.


First of all, Monte Carlo calculation method was employed to obtain the spectrum response matrix between adjacent truncated planes in the core by forward neutron transport calculation. Then, the in-core neutron field could be inversed. Finally, two simplified reactor models were used for method verification and validation.


For the neutron field in the pressure vessel, the average relative deviation between the inversion result and the Monte Carlo transport computation result was about 14%, and for the neutron field in the external fuel region, the average relative deviation was about 11%.


The inversion method of in-core neutron field proposed in this paper preliminarily demonstrated the feasibility of the method for neutron spectrum monitoring in the reactor core.

Key words: Neutron flux distribution, Ex-core neutron spectrum, Spectrum response matrix, Inversion, Advanced reactor system

CLC Number: 

  • TL329+.2