钍俘获反应率离线伽马测量方法

Thorium capture ratio determination through γ-ray off-line method

为了测定聚变-裂变反应堆模型钍包层中的钍俘获率以及钍–铀转化率,探索了一种新的钍活化离线γ测量法.利用测量232Th俘获反应产物233Th衰变链中233Pa衰变放出的311.98keV特征γ射线,来反推计算并最终确定232Th(n,γ)233Th的反应率,测试实验中不确定度约6%(233Th/232Th量级为1017情况下).详细介绍了此方法的背景和原理方法,并进行简单的校验实验,证明其能够较好地得到模拟装置中的俘获率.与瞬发γ测量法以及质谱分析法进行对比,本方法更适合用于聚变-裂变反应堆模型钍包层中的钍俘获率以及钍-铀转化率测量,并有望进一步测量其他相关参数.

To determine the thorium capture ratio and thorium-uranium conversion ratio in the thorium cladding of the fusion-fission reactor model, a new approach, activated thorium sample decay γ-ray off-line measurement, is introduced in this paper. This method is based on the measurement of the 311.98 keV characteristic decayγ-ray emitted by 233Pa which is produced through decay of 233Th, the capture product of 232Th. Then some reverse mathematic approach is brought in and finally the 232Th （n,γ） 233Th reaction ratio is determined, with an uncertainty of 6%in the test experiment （233Th/232Th under the order of magnitude 10-17）. In the paper, we introduce the detail of the approach including the background, principle and the result of a simple test experiment which shows that this approach can work well in thorium capture ratio determination. Compared with promptγ-ray method and mass spectrometer method, this decayγ-ray off-line method has many advantages in determining the thorium capture ratio and thorium-uranium conversion ratio in the thorium cladding. It is also promising in the measurement of other relevant parameters.