In-Pile Qualification of the Fast-Neutron-Detection-System

Research output: Contribution to report/book/conference proceedingsIn-proceedings paperpeer-review


Institutes & Expert groups

  • CEA Saclay - Commissariat à l'énergie atomique
  • CEA Cadarache - Commissariat à l'Énergie Atomique

Documents & links


In order to improve measurement techniques for neutron flux assessment, a unique system for online measurement of fast neutron flux has been developed and recently qualified in-pile by the French Alternative Energies and Atomic Energy Commission (CEA) in cooperation with the Belgian Nuclear Research Centre (SCK•ECEN). The Fast-Neutron-Detection-System (FNDS) has been designed to monitor accurately high-energy neutrons flux (E > 1 MeV) in typical Material Testing Reactor conditions, where overall neutron flux level can be as high as 1015 and is generally dominated by thermal neutrons. Moreover, the neutron flux is coupled with a high gamma flux of typically a few 1015 γ.cm-2.s-1, which can be highly disturbing for the online measurement of neutron fluxes. The patented FNDS system is based on two detectors, including a miniature fission chamber with a special fissile material presenting an energy threshold near 1 MeV, which can be 242Pu for MTR conditions. Fission chambers are operated in Campbelling mode for an efficient gamma rejection. FNDS also includes a specific software that processes measurements to compensate online the fissile material depletion and to adjust the sensitivity of the detectors, in order to produce a precise evaluation of both thermal and fast neutron flux even after long term irradiation. FNDS has been validated through a two-step experimental program. A first set of tests was performed at BR2 reactor operated by SCK•CEN in Belgium. Then a second test was recently completed at ISIS reactor operated by CEA in France. FNDS proved its ability to measure online the fast neutron flux with an overall accuracy better than 5%.


Original languageEnglish
Title of host publicationEPJ Web of Conferences
Subtitle of host publication5th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications - ANIMMA 2017
Number of pages3
Publication statusPublished - 10 Jan 2018
Event2017 - ANIMMA - Advancements in Nuclear Instrumentation Measurement Methods and their Applications: International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications - Palais des Congrès, Liège, Belgium
Duration: 19 Jun 201723 Jun 2017

Publication series

NameEPJ Web of Conferences
PublisherEDP Sciences
ISSN (Print)2100-014X


Conference2017 - ANIMMA - Advancements in Nuclear Instrumentation Measurement Methods and their Applications
OtherAdvancements in Nuclear Instrumentation Measurement Methods and their Applications. Application fields: Fundamental physics; Fusion diagnostics and technology; Advanced Nuclear Energy Systems; Research reactors; Nuclear fuel cycle; Decommissioning, dismantling and remote handling; Safeguards, homeland security; Severe accident monitoring; Environmental and medical sciences; Education, training and outreach
Internet address


  • Nuclear Measurements, Fission Chamber, Reactor Instrumentation

ID: 6776687