Determination of λf value has great importance for nuclear physics, especially for calculation of fission track age in geochronology. Many workers have been determining it over nearly 50 years. In this study, measure...Determination of λf value has great importance for nuclear physics, especially for calculation of fission track age in geochronology. Many workers have been determining it over nearly 50 years. In this study, measurements of λf value have been performed with comparison method of fission track and other dating of international standard age sample (i.e. the zircon sample of Fish Canyon Tuff, San Juan Mountains, Colorado, U.S.A.), and solid-state track detector (SSTD) method, in which detectors were moscovite or polycarbonate (Lexan) and fission sources were natural uranium ones of different contents. The international standard age samples were irradiated twice by thermal neutron fluences 7.83×1014n·cm-2 and 1.38×1015n·cm-2 respectively. Determined λf value is (6.82±0.58) × 10-17a-1. Using 8 fission sources of different uranium contents, determined λf value by SSTD method is (7.06±0.22)×10-17a-1. The mean of λf is (7.03 ± 0.21)×10-17a-1 for the two methods. The published results of λf determined with defferent methods are compared and factors influencing its measurement are discussed. λf value (7.03±0.21)×10-17a-1 is recommended as spontaneous fission decay constant of 238U for fission track age calculation.展开更多
基金Project supported by the National Natural Science Foundation of China.
文摘Determination of λf value has great importance for nuclear physics, especially for calculation of fission track age in geochronology. Many workers have been determining it over nearly 50 years. In this study, measurements of λf value have been performed with comparison method of fission track and other dating of international standard age sample (i.e. the zircon sample of Fish Canyon Tuff, San Juan Mountains, Colorado, U.S.A.), and solid-state track detector (SSTD) method, in which detectors were moscovite or polycarbonate (Lexan) and fission sources were natural uranium ones of different contents. The international standard age samples were irradiated twice by thermal neutron fluences 7.83×1014n·cm-2 and 1.38×1015n·cm-2 respectively. Determined λf value is (6.82±0.58) × 10-17a-1. Using 8 fission sources of different uranium contents, determined λf value by SSTD method is (7.06±0.22)×10-17a-1. The mean of λf is (7.03 ± 0.21)×10-17a-1 for the two methods. The published results of λf determined with defferent methods are compared and factors influencing its measurement are discussed. λf value (7.03±0.21)×10-17a-1 is recommended as spontaneous fission decay constant of 238U for fission track age calculation.
