Wolsong low- and intermediate-level radioactive waste disposal center : Progress and challenges - Cheong, Jae-Hak.; Choi, Jong-Soo.; Jeong, Chan-Woo.; Jung, Hae-Ryong.; Kim, Chang-Lak.; Kim, Geon-Young.; Kim, Kyun.; Kim, Kyung-Su.; Koh, Yong-Kwon.; Lee, Eun-Young.; Park, Jin-Beak.; Park, Kyung-Woo.