A new monitor set for the determination of neutron flux parameters in short-time k(0)-NAA

作者：Kubesova, Marie^*; Kucera, Jan; Fikrle, Marek

来源：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment , 2011, 656(1): 61-64.

DOI：10.1016/j.nima.2011.07.050

• Short-time neutron activation analysis
• k(0) standardization
• Neutron flux parameters

Multipurpose research reactors such as LVR-15 in Rez require monitoring of the neutron flux parameters (f, alpha) in each batch of samples analyzed when k(0) standardization in NAA is to be used. The above parameters may change quite unpredictably, because experiments in channels adjacent to those used for NAA require an adjustment of the reactor operation parameters and/or active core configuration. For frequent monitoring of the neutron flux parameters the bare multi-monitor method is very convenient. The well-known Au-Zr tri-isotopic monitor set that provides a good tool for determining f and a after long-time irradiation is not optimal in case of short-time irradiation because only a low activity of the Zr-95 radionuclide is formed. Therefore, several elements forming radionuclides with suitable half-lives and Q(0) and (E) over bar (r) parameters in a wide range of values were tested, namely Au-198, Mn-56, Rb-88, I-128, Ba-139, and U-239. As a result, an optimal mixture was selected consisting of Au, Mn, and Rb to form a well suited monitor set for irradiation at a thermal neutron fluence rate of 3 x 10(17) m(-2) s(-1). The procedure of short-time INAA with the new monitor set for k(0) standardization was successfully validated using the synthetic reference material SMELS 1 and several matrix reference materials (RMs) representing matrices of sample types frequently analyzed in our laboratory. The results were obtained using the Kayzero for Windows program.

• 出版日期2011-11-11