1. Institute of Nuclear and New Energy Technology of Tsinghua University, The Key Laboratory of Advanced Reactor Engineering and Safety, Ministry of Education, Beijing 100084, P. R. China
2. Beijing Institute of Spacecraft Environment Engineering, Beijing 100094, P. R. China
3. Science and Technology on Reliability and Environmental Engineering Laboratory, Beijing 100094, P. R. China
4. Advanced Materials Laboratory, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China