在裂变径迹测定年代中准确测定中子通量

ACCURATE DETERMINATION OF NEUTRON FLUENCE IN FISSION TRACK DATING

用裂变径迹技术测定年代必须使用准确的中子积分通量和^(235)U的中子有效裂变截面值,通常是采用Au和Co活化监测器或用铀标准剂量玻璃的B值测定中子通量,一般这些方法测定的中子积分通量不能代表与^(235)U反应的实际通量,有时测定值和实际值之间的差异是不能忽略的。本文提出一种在裂变径迹年代中测定中子通量的新方法,这种方法是用裂变产物法测定照射积分中子通量与^(235)U有效裂变截面的乘积,同时我们得到了UG—5标准铀剂量玻璃的刻度系数b(b=ρ_i/σ.φ),它的平均值是(1.23±0.06)×10^(11)。这种方法避免了中子能谱变化和中子温度不同带来的影响,它是直接测定中子与^(235)U反应的效应,在探求^(238)U的λ_f值工作中是一种准确和可靠的测定中子积分通量的方法。

Age determination using the fission track technique depends upon accurate neutron fluence and fission cross-section value of ^(235)U. The neutron fluecne determined commonly from Au and Co monitors or the B value of dosimetric standard glasses usually does not represent the true fluence reacting with ^(235)U. Sometimes, the difference between determined and real values can not be neglected. A new methcd is presented for the determination of neuitron fluence in fission track dating in this paper. The method is used to determine the product of irradiation neutron fluence multiplied by the effective fission cross-section of ^(235)U by fission product method. In the meantime, we have obtained calibration constant b (b=ρi/σ·Φ) of UG-5 Standard Uranium Glass. The mean b value is (1.23±0.06)×10^(11).This method avoids the effect of neutron spectrum and neutron temperature variation on the accurate determination of neutron dosimetry in fission track dating. The method directly determines the effect of neutron reacting with ^(235)U. It is an accurate and reliable method in λ_1 of ^(238)U approach.