Zirconium alloys used in nuclear reactors undergo irradiation creep, which consists of a visco-plastic deformation activated by irradiation occurring under constant load. However, the fundamental underlying mechanisms have not been unraveled yet. A new high-stress irradiation creep mechanism for recrystallized Zircaloy-4 has recently been proposed based on in situ ion irradiation deformation experiments. A displacement cascade is assumed to induce a direct unpinning of a dislocation from an irradiation defect if the cascade occurs within an effective volume around the pinning point. In the present work, a systematic molecular dynamics study was performed to investigate the effect of a 20 keV cascade occurring near <a>-screw dislocation pinned on an interstitial <a>-loop. The direct release of dislocations by displacement cascades is predicted by the simulations. This release is more likely around the pinning points and with increasing stress, in agreement with experimental observations. The effective volume is roughly estimated for three stress levels equal to $0.89{\tau }_c$, $0.93{\tau }_c$ and $0.97{\tau }_c$, with ${\tau }_c$ being the critical stress for unpinning (without irradiation). A mechanism is proposed suggesting that unpinning occurs when the displacement cascade encompasses, at its peak of damage, the two pinning points of the dislocation. A methodology requiring acceptable computation time has been implemented to estimate the effective volume for various cascade energies and loop characteristics, faithfully reproducing the MD results. The mean pinning lifetime calculated using the model provides values of the same order of magnitudes as in the in situ deformation experiments under ion irradiation at high stress levels.

核反应堆中使用的锆合金会经历辐射蠕变，辐射蠕变由在恒定载荷下发生的辐射激活的粘塑性变形组成。但是，尚未阐明基本的基本机制。基于原位离子辐照变形实验，最近提出了一种用于重结晶Zircaloy-4的新的高应力辐照蠕变机理。如果位移级联发生在钉扎点周围的有效体积内，则认为位移级联会导致位错直接从辐照缺陷中脱出。在目前的工作中，进行了系统的分子动力学研究，以研究20keV级联发生在钉在间隙<a>环上的<a>螺旋位错附近。模拟预测了位移级联直接释放位错。与实验观察结果一致，这种释放更有可能在固定点附近并随着应力的增加而增加。对于三个等于$0。89{\tau }_C$， $0。93{\tau }_C$ 和 $0。97{\tau }_C$，带有 ${\tau }_C$是松开（无辐射）的临界应力。提出了一种机制，当位移级联在其破坏的峰值处包含位错的两个钉扎点时，就会发生松脱。已经实现了一种需要可接受计算时间的方法，以估算各种级联能量和回路特性的有效体积，从而忠实地再现MD结果。使用该模型计算的平均钉扎寿命可提供与在高应力水平下离子辐照下的原位变形实验中相同数量级的值。