Development of laboratory standards for AMS measurement of 237Np

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 2010-06, Vol.268 (11), p.1949-1953
• Main Authors: Wang, Xianggao, Jiang, Shan, Dong, Kejun, He, Ming, He, Guozhu, Li, Chaoli, Li, Shizhuo, Gong, Jie, Lu, Liyuan
• Format: Article
• Language: English
• Subjects: 177Lu–U; 237Np; Accelerator mass spectrometry; Accelerators; Calibration; Cross sections; Decay rate; Fast neutrons; Monitors; Self-attenuation; Uranium
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/j.nimb.2010.02.106

A new method for the preparation of 237Np/ 238U laboratory standards for accelerator mass spectrometry (AMS) measurement was developed at China Institute of Atomic Energy (CIAE). 237Np was generated by β-decay (6.75 days) of 237U produced via fast neutron induced 238U(n,2n) 237U reaction. The 58Co(n,2n) 59Co and 93Nb(n,2n) 92mNb reactions were used to monitor the integral incident neutron flux. The cross-section of 238U(n,2n) 237U was determined by measuring the emission rate of 208.0 keV γ-rays from 237U decay with a calibrated HPGe γ-ray spectrometer at CIAE. In order to correct for the self-attenuation of 208.0 keV γ-ray in the U sample, a 177Lu–U method was introduced. The new correction method provided effective and high quality measurements of the cross-section for the 238U(n,2n) 237U reaction; and the 237Np/ 238U ratio. A series of AMS standards for 237Np/ 238U (10 −9–10 −13) can be obtained by successive dilution of the original standard sample.