RESEARCH ON THE CROSS-SECTION GENERATING METHOD IN HTGR SIMULATOR BASED ON MACHINE LEARNING METHODS LI Zeguang, Jun Sun, Chunlin Wei, Zhe Sui and Xiaoye Qian EPJ Web Conf., 247 (2021) 02039 Published online: 22 February 2021 DOI: 10.1051/epjconf/202124702039