Activity measurement ¹⁰³Rh^m X-ray emitting radio-isotope: Application to experimental programs carried out in the CEA critical facilities

Abstract

International benchmarks for cross-sections qualification are very poor in experimental means able to provide information on the neutron spectrum around 1 MeV. To fill this vacancy, one possible solution is to use the activation of rhodium. The reaction of inelastic neutron scattering on this element, in the energy range of 0.5 MeV to 5 MeV, leads to the formation of 103 Rh m . The return to the ground level of this radionuclide emits X-rays of low energy. This paper describes a method for determining the activity of 103 Rh m taking into account the constraining characteristics of this radionuclide and proposes a computed to measured results comparison for an experiment irradiated in the French CEA critical facility EOLE. Index Terms-efficiency calibration, 103 Rh m , X-ray measurement, scattered rays, escape rays. K α Bump scattered Raie K α = 20,17 keV Raie K α1 = 20,22 keV Raie K α2 = 20,07 keV K β bump scattered Raie K β2 23,20 keV Raie K β1 22,81 keV Raie K β = 22,87 keV K α Bump scattered Raie K α = 20,17 keV Raie K α1 = 20,22 keV Raie K α2 = 20,07 keV K β bump scattered Raie K β2 23,20 keV Raie K β1 22,81 keV Raie K β = 22,87 keV

Improvement of the activity measurement method for solid dosimeters emitting X-rays

“…Traditionally used to measure gamma rays, this is a more complex method for measuring low-energy X-rays. Besides an exact knowledge of the measurement environment (Domergue et al, 2009), it requires controlling the characteristics of the measurement sample and the resulting correction factors. This method also poses problems relating to fluorescence corrections and the relative uncertainties of the emission intensities of 93m Nb and K X-ray lines of 103m Rh.…”

“…This method also involves self-attenuation corrections of between 20% and 50% depending on the thickness of the dosimeter, which must be controlled given their impact on the final result. An initial approach was conducted in 2009 (Domergue et al, 2009); this study will allow this correction to be validated experimentally.…”

“…This type of measurement is applied for the detection of 103m Rh (Domergue et al, 2009), (resp. 93 m Nb) produced in rhodium (resp.…”

Measurement of K fluorescence yields of niobium and rhodium using monochromatic radiation

“…[1][2][3][4] Rh are of particular importance, and the activities of niobium and rhodium dosimeters are the basic data that can allow tracing back the reactor operating information. The activity of these dosimeters is measured by X-ray spectrometry [3,4] , using spectrometers equipped with high purity germanium detectors, because 93m Nb [5] and 103m Rh [6] are radionuclides which emit only X-rays (Figs 1 and 2). Emission intensities of these X-rays in the recommended data [7] are determined from the γ-ray transition probabilities, internal conversion coefficients and fluorescence yield values.…”