启明星1#次临界装置的裂变率分布

启明星1#次临界装置是我国为开展加速器驱动的次临界系统(ADS)研究而建立的国际上第1个具有快-热耦合结构的次临界反应堆实验装置。启明星1#次临界装置在确定的装载下、由不同能量的外中子源作用时,利用MCNP程序分别对装置快中子能谱区、热中子能谱区燃料元件的径向及轴向裂变率分布进行模拟计算,所使用外中子源的中子能量分别为2.5、5、14MeV。计算结果表明:在外中子源源强相同的情况下,源中子能量越高,裂变率越大;在源中子能量相同的情况下,次临界反应堆的轴向裂变率分布为中间高、两端低,径向裂变率分布在快中子能谱区先减小后增大,而热中子能谱区则是先增大后减小,然后,随着接近反射层又逐渐增大。该裂变率分布计算结果为后续实验测量和探测器布置提供了参考。

Fission Rate Distribution for Venus 1# Sub-critical Assembly

Venus 1# sub-criticality assembly, which consists of both fast and thermal neutron spectra zones for accelerator driven sub-critical system (ADS) research in China, is a sub-critical system. The loaded assembly is driven by external neutron source with different neutron energy. The fission rate distributions on radial and axial aspect for fast and thermal neutron spectra zones’ fuel element were calculated by using MCNP code. The neutron energies of the external neutron sources were 2.5, 5, 14 MeV, respectively. The result shows that if the source strength is the same, the higher the neutron energy is, the larger the area of function is and the greater the fission rate is. On the other hand, if the neutron energy is the same, the fission rate distribution of the axis is lower on the both side and higher in the middle, while the radial fission rate distribution first decreases and then increases for fast neutron spectra zone and initially increases and then decreases and increases again when approching the reflector for the area of thermal neutron spectra zone. The calculating fission rate distributions provide a reference for follow up experimental measurements and detectors arrangement.