According to the ROK-IAEA Comprehensive Safeguards Agreement (CSA), the ROK submits inventory change reports (ICRs), physical inventory lists (PILs), and material balance reports (MBRs). Suppose inventory changes occur in each material balance area (MBA). In that case, the facility operators prepare ICRs monthly, conduct physical inventory taking (PIT) every 12 to 18 months, and submit PILs and MBRs to KINAC. KINAC reviews ICR presented by the facility operators, submits it to the IAEA, and reports it to the Nuclear Safety and Security Commission (NSSC). Various methods have been prepared and implemented to minimize errors in reviewing the accounting reports submitted by the facility operators. Accordingly, this paper analyzes the mistakes in the accounting reports that occurred over the past two years and proposed methods to improve them. The basis for carrying out the accounting reports is stipulated mainly in the CSA and the Nuclear Safety Act. First, Article 63 of the CSA describes the rationale for submitting the accounting reports, and the details are described in detail in the subsidiary arrangement. Article 98 of the Nuclear Safety Act stipulates information related to accounting reports, and details are described in the regulations on reporting internationally regulated materials, etc., of the NSSC Notice No. 2017-84. Among the accounting reports submitted in 2021, a total of 36 errors were confirmed. There were ten errors related to inventory changes, followed by six errors in the material balance period (MBP) in the header information. There were four cases of spacing, weight mismatch, and overdue errors, and the rest were related to grammar errors. There were a total of 30 errors in the accounting reports identified in 2022. MBP errors of header information, which occurred the second most in 2021, was the highest with nine, followed by six inventory change errors and five weight mismatch and overdue errors, respectively. Compared to 2021, the total number of errors has decreased by about six, which is interpreted as the result of outreach activities through accounting reporting workshops and nuclear control education conducted by KINAC. Accounting reporting is the most critical part of the Nuclear Material Accounting and Control (NMAC) system. Efforts to check errors in accounting reports and improve report quality through outreach activities could be confirmed by the statistics of the two years analyzed earlier. In the future, if the reporting program used by the facility operators is improved to minimize errors and manage the accounting reporting system through continuous maintenance work, the quality of the accounting reports will be upgraded to the next level.

• Chul Heo(Korea Institute of Nuclear Nonproliferation and Control (KINAC))