Denuclearization is a process and not a single event, that requires political decision, bilateral or multilateral consultations and agreements, technical process for removal/disposal of nuclear explosive device (NED) and nuclear material, dismantlement /disablement of nuclear weapon facility and nuclear fuel cycle facility, technical process to verify denuclearization. To improve preparedness of future denuclearization, series of study to achieve effective and efficient denuclearization have been performed in ISCN. The study includes two phases, (1) lessons learned from past denuclearization experiences and (2) possible future dismantlement and verification options. (1) Lessons learned from past denuclearization experiences This phase of study covered past and ongoing denuclearization efforts, such as South Africa, Libya, Iraq, 3 states of former Soviet Union (Ukraine, Kazakhstan, and Belarus), Iran and DPRK. This study was performed from April 2018 to March 2020. (2) Possible future dismantlement and verification options This phase of study focusses on dismantlement of three key nuclear fuel cycle facilities, uranium enrichment, nuclear reactor, reprocessing facilities and quantitative evaluation of effectiveness and efficiency of future dismantlement and verification. This study has been performed since April 2020. As part of this (2) study, this paper focus on dismantlement and verification of potential uranium enrichment facility and potential nuclear material in the uranium enrichment facility, considering (a) peaceful use operation, (b) freeze, (c) disablement, (d) dismantlement, (e) removal from the state as potential options. Quantitative evaluation of effectiveness (irreversibility) and resources requirement including resources for verification of each option were performed and summarized in this paper.