对加速器驱动中子发生器的数值模拟包括离子输运、聚变反应、中子输运等。由于核反应截面远低于带电粒子输运的库仑截面，且核反应平均自由程远大于靶厚度，直接蒙卡抽样难以抽到聚变反应。在MCNPX程序基础上，采用“强迫”聚变方法，即每个入射氘核必发生一次聚变反应，聚变反应处氘核的真实状态(位置、能量和方向)以抽样产生，并以此状态来确定聚变中子的出射状态，实现了氘核与聚变中子的耦合输运模拟计算。研究结果表明，该方法能够给出氘核输运对聚变中子能谱和角分布的影响，中子产额计算结果符合预期。

Deuteron ion transportation, fusion reaction sampling and neutron transportation simulation are included in the numerical calculation of accelerator driven neutron generator. As well known, the nuclear reaction cross section is much smaller than Coulomb cross section of charged particle transportation, and the mean free path of nuclear reaction is far longer than the depth of target, compared to deuteron ion transportation, the direct sampling efficiency of fusion reaction is almost zero. In this paper, a “forced” fusion arithmetic is introduced and embedded into MCNPX program. By the “forced” fusion arithmetic, fusion reaction must happen for every source deuteron ion. The position, energy and flight direction of deuteron ion that interact with tritium are sampled from all energy steps. The position, energy and flight direction of fusion source neutron are sampled according to that of deuteron ion. The deuteron ion and neutron coupling transportation can be calculated with the revised MCNPX.