Safety assessment of second-phase disposal facility in Gyeongju low- and intermediate-level radioactive waste (LILW) repository using RESRAD-OFFSITE code

A safety assessment was performed on the second-phase disposal facility of the Gyeongju low - and intermediate-level radioactive waste repository using the RESRAD-OFFSITE code. On the basis of the acceptance criteria of the repository, 13 radionuclides and gross alpha were selected as the radionuclides to be evaluated. In addition, the thermodynamic database of Japan Atomic Energy Agency and natural groundwater data that reflect the operational condition of the disposal facility were applied to derive the solubility by using the PHREEQC computational code. The distribution coefficient was derived for the component of disposal facility based on the sorption database of Japan Atomic Energy Agency. In addition to the solubility and distribution coefficient for various radionuclides, the data of the disposal facility and repository site were analyzed and applied to the RESRAD-OFFSITE code for the safety assessment modeling. The result of the safety assessment calculation revealed the exposure dose corresponding to 3.8% of the exposure dose limit (0.1 mSv/yr). Moreover, additional sensitivity analysis for the exposure dose was conducted by varying the geochemical parameters. Although the exposure dose changed as the geochemical parameters were varied, the result of the sensitivity analysis confirmed that the exposure dose limit was still satisfied.