Dynamical Damage Processes of Neutron-Irradiated Meterials

在用中子照射的材料中，产生高能量的初级撞击原子。随后形成位移损伤级联。材料损伤结构的演化过程包括级联损伤叠加、高温热振动引起的结构弛豫、嬗变核反应产生的气体原子引起的空洞和气泡以及合金中的沉淀物等。本文对增殖反应堆和聚变反应堆中最重要和最严重的缺陷空洞形成的原子学进行了研究。1.利用纯铜和纯镍的多体势，用分子动力学计算机模拟研究了空洞形成的原子学。这两种材料对于纯铜具有低堆垛层错能，而对于纯镍具有高堆垛层错能。这些反映了松弛（塌陷）堆垛层错四水在铜和镍位错环的形成。当氢原子被困在 ...更多信息 在小的空位团中，氢原子在空位表面周围移动，阻止空位团的坍塌。这导致在辐照金属中形成空隙。氦原子在空胚中不可能运动得这么快。因此，氦原子作为空穴形成的有效气体原子值得怀疑.为了验证计算机模拟结果的可靠性，在美国西北太平洋实验室的FFTF增殖堆中，对铜和镍进行了聚变堆内的高注量辐照。标本有两种。一个是从制造商那里收到的。另一种方法是在超高真空中熔化排气，以除去原始试样中溶解的残余气体。只有一个胶囊被成功辐照。在辐照后的试样中，可以观察到孔洞数密度的显著差异。脱气试样显示出低密度的空隙，而我们观察到高密度的空隙在接收试样。许多其他胶囊显示钠泄漏或气体泄漏。在这些情况下，空隙密度的差异不能被忽略.人们普遍认为，氦原子对空洞的形成贡献更大。我们通过计算机MD模拟对其进行了研究。少

In materials which are irradiated with neutrons, primary knock-on atoms of high energy are generated. Subsequently displacement damage cascades are formed. Damage structure in materials evolves with cascade damage overlapping, structural relaxation due to thermal vibration at high temperature, formation of voids and bubbles due to gas atoms generated by transmutation nuclear reactions and precipitates formation in alloys. In the present work of this year, atomistics of void formation are studied which are the most important and serious defect in breeder and fusion reactors.1.Utilizing eam many body potential of pure copper and pure nickel, atomistics of void formation was examined by molecular dynamics computer-simulation. These two materials have low stacking fault energy for pure copper and high stacking fault energy for pure nickel. These reflect the formation of relaxed (collapsed) stacking fault tetrahydra in copper and dislocation loops in nickel. When hydrogen atoms are trapped … More in small vacancy clusters, hydrogen atoms move around surface of voids and prevent the collapsing of vacancy clusters. This leads to the formation of voids in irradiated metals. Helium atoms could not move so fast in void embryo. Therefore, helium atoms are questionable to be effective gas atom on the formation of voids.2. To test reliability of the results of computer-simulation, copper and nickel were irradiated in fusion reactor to heavy high fluence at FFTF breeder reactor in Pacific Northwest Laboratory in the united state. Specimens are two kinds. One is as-received from the manufacture. Another is out-gassed by melting in ultra-high vacuum in order to remove the residual gas dissolved in as-received specimens. Only one capsule was success-fully irradiated. We could observe the remarkable difference of void number density in irradiated specimens. Out-gassed specimen shows low density of voids, while we observed high density of void in as-received specimens. Many other capsules show either sodium leakage or gas-leakage. In these cases, difference of void density could not be observed.3. It is widely believed that helium atoms contribute more seriously on the formation of voids. We examined its by computer MD simulations. Less