International key comparison of neutron fluence measurements in mono-energetic neutron fields: CCRI(III)-K10

Abstract

To ensure the validity of their national standards, National Metrology Institutes, NMIs, participate regularly in international comparisons. In the area of neutron metrology, Section III of the Consultative Committee for Ionizing Radiation is in charge of the organization of these comparisons. From September 2011 to October 2012, the eleventh key comparison, named CCRI(III)-K11, took place at the AMANDE facility of the LNE-IRSN, in France. Participants from nine NMIs came with their own primary reference instruments, or instruments traceable to primary standards, with the aim of determining the neutron fluence, at 1 m distance from the target in vacuum, per monitor count at four monoenergetic neutron fields: 27 keV, 565 keV, 2.5 MeV and 17 MeV. The key comparison reference values (KCRV) were evaluated as the weighted mean values of the results provided by seven participants. The uncertainties of each KCRV are between 0.9 % and 1.7 %. The degree of equivalence (DoE), defined as the deviation of the result reported by the laboratories for each energy from the corresponding KCRV, and the associated expanded uncertainty are also reported and discussed.

Development of a Compact Flat Response Neutron Detector

“…Monoenergetic neutrons were produced at 144 keV and 565 keV by the Li(p,n) Be reaction and at 5 MeV by the D(d,n) He reaction with a Van de Graaff accelerator and at 14.8 MeV by the T(d,n) He reaction with a Cockcroft-Walton accelerator [17]. The accuracy of the neutron fluences provided at 144 keV, 5 MeV, and 14.8 MeV were supported by the recent international comparison performed by the Consultative Committee for Ionizing Radiation (CCRI) of the International Bureau of Weights and Measures (BIPM) [18]. Pulse height spectra from the two He proportional counters showed that gamma rays were successfully rejected by pulse-height discrimination without sacrificing neutron detection efficiency.…”

Experimental and theoretical study of long counters on the departure of “point” assumption and scattering background influence

“…During the whole measurements, another calibrated long counter is used as a monitor settled in the side. The whole neutron field can be traced to the BIPM standard Mono-energy neutron fields (CCRI(III)eK10) Chen et al, 2007. Results are summarized in Table 3 with our calculated values. The background scattering counts stands for the counter's counts with shadow cone settle, and are normalized to one isotropic neutron emitted from the source.…”

Development of a compact flat response neutron detector

“…Monoenergetic neutrons were produced at 144 keV, 565 keV and 5 MeV with a Van de Graaff accelerator and at 14.8 MeV with a Cockcroft Walton accelerator [15]. The accuracy of the neutron fluences provided at 144 keV, 5 MeV and 14.8 MeV were supported by the recent international comparison organized by the Consultative Committee for Ionizing Radiation (CCRI) of the International Bureau of Weights and Measures (BIPM) [16]. To suppress room-return neutrons, neutron sources and measurement instruments were placed on an aluminumgrating floor supported at the mid-height of the irradiation room, 11.5 m wide, deep and high.…”