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Spectroscopic Neutron Detector for Detection of Nuclear Materials


Low-background Spectroscopic Position-Sensitive Neutron Detector for Detection of Nuclear Materials in Cargo Containers

Tech Area / Field

  • FIR-INS/Nuclear Instrumentation/Fission Reactors
  • FIR-NSS/Nuclear Safety and Safeguarding/Fission Reactors
  • FIR-PSS/Physical Safety and Security at Facilities/Fission Reactors
  • INS-DET/Detection Devices/Instrumentation

8 Project completed

Registration date

Completion date

Senior Project Manager
Visser H

Leading Institute
Khlopin Radium Institute, Russia, St Petersburg


  • University of Padova / Department of Physics, Italy, Padova\nMassachusetts Institute of Technology (MIT) / Nuclear Engineering Department, USA, MA, Cambridge\nBubble Technology Industries Inc., Canada, ON, Chalk River\nKyoto University / Institute of Advanced Energy, Japan, Kyoto

Project summary

The main goal of the Project is to develop a new method for detection of nuclear materials (NM) in cargo containers and to build a detection device consisting of a pulsed neutron generator, low-background spectroscopic position-sensitive neutron detector, and electronic control and data acquisition system.

The Project is motivated by the increased importance of the development of technical means for cargo screening in order to prevent illegal trafficking of nuclear materials, including fissile materials (FM), which could be used by terrorists. At present there are no systems that can reliably detect fissile materials in cargo containers. Portals detecting spontaneous neutron and gamma radiation of NM are today the main tools for NM detection. However, gamma-rays spontaneously emitted by many nuclear materials cannot be detected, since they have very low energy and are absorbed by the material inside the container. Spontaneous neutron radiation is not emitted by some fissile materials at all. Therefore, new systems based on active nuclear methods using penetrating neutron radiation are presently being developed. However, use of active neutron methods is limited due to presence of neutron background: existing detection methods cannot distinguish background neutrons from fission neutrons produced in FM by the interrogating neutrons.

The proposed Project will result in the development and production of a new device – low-background spectroscopic position-sensitive neutron detector, which will be used for detection of fissile materials by detecting both fission neutrons and high-energy gamma-rays. The proposed detector will measure the energy of neutrons; this will significantly (3-5 times) decrease the neutron background counting rate due to selection of neutrons in the energy window that is specific for fission neutrons. At the same time the proposed detector will be a highly efficient γ-radiation scintillation detector capable of detecting spontaneous γ-radiation of NM, as well as high-energy (higher than 3 MeV) γ-radiation from induced fission. Using scintillators with neutron/gamma discrimination will allow one to distinguish high-energy γ-quanta from background neutrons.

The proposed detector will be an assembly of 3He counters of slow neutrons equipped with “active” neutron moderator consisting of the scintillation neutron detectors. Measurement of scintillation amplitudes triggered by the events in the 3He counters allows one to determine the energy of the detected neutron. Use of neutron spectrometry substantially decreases neutron background counting rate. Decrease of the neutron background allow one to decrease the detection threshold for fission neutrons. Spatial distribution of 3He counters and coincidences matrix between the counters and the surrounding scintillation detectors provides position sensitivity of the detector. The proposed detector system is in fact four detectors in one set-up: 3He-based detector of slow neutrons; scintillation detector of fast neutrons; scintillation detector of γ-quanta; spectrometric position-sensitive neutron detector.

The low-background spectroscopic position-sensitive neutron detector created in the course of the Project will be a universal tool for detection of illegal shipment of NM and FM in the following scenarios:

  1. Standoff detection of NM and FM using passive detection of spontaneous neutron/ gamma fission.
  2. Detection of FM (including shielded FM) inside containers by detecting delayed neutrons and high-energy fission gamma-quanta induced by external neutrons from pulsed neutron generator.

The following work will be carried out in the framework of the Project:
  1. Mathematic modeling of the device for NM and FM detection in cargo containers consisting of a pulsed neutron detector and low-background spectroscopic position-sensitive neutron detector in order to choose optimal operation mode and intensity of the neutron generator, scintillator type (plastic/liquid), and the geometry of the detector for minimal possible FM detection threshold;
  2. Production of low-background spectroscopic position-sensitive neutron detector based on 3He counters of slow neutrons and scintillation neutron detectors;
  3. Development and implementation of the detector control, data-acquisition, and decision-making systems;
  4. Assembling and tuning of the device consisting of a pulsed neutron generator, low-background spectroscopic position-sensitive neutron detector, detector control system, and data acquisition system;
  5. Laboratory testing of the device for detection of NM and FM sources/imitators:
    • detection of spontaneous fission neutron spectra;
    • detection of delayed fission neutrons induced in the FM imitator by neutrons from pulsed neutron generator;
    • detection of delayed high-energy fission gamma-quanta induced in the FM imitator by neutrons from pulsed neutron generator.
The results of the laboratory tests will be used to work out application principles for detector use in cargo screening systems.

Specialists from V.G. Khlopin Radium Institute have necessary qualification and experience in development of methods and equipment for detection of fissile materials. Among previous projects are IAEA project # 12600, NATO project # CP NR SFR 981003, and ISTC project # 3534. Scientists from KRI also have experience in modeling using MCNP4C2, MCNP5, MCNP-PoliMi codes applied to detection of NM and FM with passive and active neutron methods.


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