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

Abstract

Both reactions Nb‐93(n,n′)Nb‐93 m and Rh‐103(n,n′)Rh‐103 m are of particular importance for dosimetry in reactor, and the measurement of the activity of Nb and Rh dosimeters provides the basic data that can be traced back to the reactor operating information. These radionuclides emit only X‐rays of which emission intensities in recommended data are determined thanks to the γ‐ray transition probabilities and fluorescence yield values. In general, the knowledge of fluorescence yields is rather poor and based on old measurements. Nowadays, the use of tunable monochromatic X‐ray sources allows performing optimized measurements. In a first step, accurate values of the attenuation coefficients are measured at the metrology beam line of the SOLEIL synchrotron, using procedures such as optimized for similar measurements. In a second step, the fluorescence yields are determined using experimental approaches in a traditional experimental configuration. For both materials, several incident energies are used to get experimental spectra with energy‐dispersive spectrometer. The peaks of interest are processed using the COLEGRAM software, which allows detailed fitting of the peak shape. The K fluorescence yields are derived with about 2% relative uncertainty. Copyright © 2017 John Wiley & Sons, Ltd.