Radiation-induced damage in tungsten (W) and W alloys has been considered as one of the most important issues in fusion research, because radiation-produced defects not only degrade the mechanical property but also change the behaviours of H and He in W significantly, such as the retention of H. Nano-structured W has been developed to reduce accumulation of defects within grains and further mitigate radiation-induced damage. However, the fundamental role of a grain boundary (GB) in healing radiation damage in W is not yet well understood. Using molecular dynamics and statics, we evaluate energetically and kinetically the role of a GB in defect evolution (vacancy and interstitial segregation and their annihilation) near the GB in W, by calculating the vacancy (interstitial) formation energy, segregation energy, diffusion barrier, vacancy–interstitial annihilation barrier near the GB and the corresponding influence range of the GB. We find that, as reported and expected, interstitials are preferentially trapped into GBs over vacancies during irradiation, with vacancies dominant near the GB and interstitials highly localized at the GB. On the one hand, the GB serves as a sink both for vacancies and interstitials near itself by reducing their formation energy and diffusion barrier. The formation energy of the vacancy decreases only by ∼0.86 eV, but 7.5 eV is reduced for the formation energy of the interstitial in the GB core, indicating that the sink is unexpectedly stronger for interstitials than vacancies. The average barrier of vacancy diffusion is 0.98 eV much less than 1.8 eV in the bulk; the interstitial migrates into the GB via a barrier-free process. On the other hand, the GB acts as a catalyst for the vacancy–interstitial recombination at the GB by lowering the annihilation barrier. The annihilation with the average barrier as low as 0.31 eV works even at a low temperature of 121 K; besides, the annihilation of a close vacancy–interstitial pair is spontaneous. Meanwhile, the annihilation mechanism near the GB is modified due to the exceptionally large reduction in the interstitial formation energy. The influence range of the GB is small (1–1.5 nm), leading to a small volume fraction of the GB region working as the sink and the catalyst. This indicates that GBs in fine W grains may play a limited role in improving radiation performance.

No abstract

As a multi-ethnic country, China is concerned with the protection and reservation of the rights and freedoms of ethnic minorities. The rights of ethnic minorities to self-determination are guaranteed in China through the establishment of ethnic regional autonomies, which corresponds to China's domestic strategic interests. China's ethnic policy is aimed at maintaining political stability and the country's territorial integrity, at achieving the integration of Chinese society and the harmonious development of ethnic relations. The object of research is the problem of enforcement of the right to national self-determination in the Chinese Communist Party's theory and policy. The research methodology is represented with historical, structural and functional, systemic approaches, and the analysis of literature sources. The historiography of the research is represented with the books by the Chinese and Russian scholars (T.V. Lazareva, V.A. Manko, M.Kh. Farukshin) considering different views on the development of ethnic regional autonomy and self-government principles. In China, the enforcement of the right to self-determination by ethnic minorities is divided into two stages. The establishment of the right to self-determination was the first stage (from 1922 to 1949), and the process of improving the system of regional ethnic autonomy has been the second stage (from 1949 to the present). The system of regional ethnic autonomy in China is an effective way to solve ethnic problems.

No abstract