Characterisation of the IRSN CANEL/T400 facility producing realistic neutron fields for calibration and test purposes

Abstract

The new CANEL/T400 facility has been set-up at the Institute for Radiological Protection and Nuclear Safety (IRSN) to produce a realistic neutron field. The accurate characterisation of this neutron field is mandatory since this facility will be used as a reference neutron source. For this reason an international measuring campaign, involving four laboratories with extensive expertise in neutron metrology and spectrometry, was organised through a concerted EUROMET project. Measurements were performed with Bonner sphere (BS) systems to determine the energy distribution of the emitted neutrons over the whole energy range (from thermal energy up to a few MeV). Additional measurements were performed with proton recoil detectors to provide detailed information in the energy region above 90 keV. The results obtained by the four laboratories are in agreement with each other and are compared with a calculation performed with the MCNP4C Monte-Carlo code. As a conclusion of this exercise, a reliable characterisation of the CANEL/T400 neutron field is obtained.

Les installations de l’IRSN dédiées à la métrologie des neutrons

“…Les distributions en énergie de la fluence neutronique à ces positions ont été déterminées par simulation avec le code MCNP (Chartier et al, 1992 ;Lacoste et Gressier, 2004) et validées expérimentalement par des campagnes internationales de spectrométrie utilisant des détecteurs à protons de recul et des systèmes à sphères de Bonner (Thomas et al, 1997 ;Gressier et al, 2004b).…”

Evaluation of individual monitoring in mixed neutron/photon fields: mid-term results from the EVIDOS project

“…Two fields were used to irradiate the dosemeters: SIGMA (7) , where almost half of the ambient dose equivalent arises from thermal neutrons, and CANEL (8) with a maximum contribution to the dose equivalent of a few hundred keV and additional significant contributions of thermal and intermediate energy neutrons.…”

Individual neutron monitoring in workplaces with mixed neutron/photon radiation

“…Information on the direction distribution of the ®elds is also derived from PADC track-etch detectors mounted on different sides of the slab phantom and from analysis of the different detector readings for a novel design of neutron survey instrument (BAE SYSTEMS) (3) . In October 2002, prior to the campaigns in the workplaces, an intercomparison exercise was performed at the IRSN simulated workplace facility CANEL/T400 (13,14) and at the thermal neutron source SIGMA (15) . One or two additional campaigns are scheduled for the year 2004: at the BNFL plutonium re-processing plant and thermal oxide re-processing plant in Sella®eld (UK), and/or inside a pressurised water reactor building and around a transport cask in Ringhals, Sweden.…”

“…The neutron¯uence and ambient dose equivalent H Ã (10) as a function of the energy were determined using MCNP-4C and compared with experimental values derived from spectrometry in the framework of the EUROMET intercomparison (14) . The reference value used here is the experimental one, H Ã (10) 122.3 AE 6.1 pSv per monitor count.…”

“…Because of the complex irradiation conditions, dedicated computations of personal dose equivalent H p (10) are required, which are extremely time consuming and only preliminary results are available at present (13) . Thus, the reading of the personal dosemeters can only be compared with the personal dose equivalent value derived from the EUROMET spectrometry data (14) : H p (10) 126.5 pSv per monitor count, i.e. assuming a broad and parallel irradiation of the phantom.…”