Evaluation of the Revised Sampling Planning Method for
National Safeguards Inspection

As the ROK adopted the state level approach (SLA) as the IAEA safeguards, the ROK’s Nuclear Safety and Security Commission (NSSC) amended domestic notification to strengthen national safeguards inspection. The notification requires an independent on-site inspection supporting program to verify the facilities’ declared information, which includes an optimized sampling method for on-site inspection. This research suggests a revised sampling method for national inspection from the conventional IAEA’s sampling planning method. The revised method minimizes assumptions for simplification in the conventional method to calculate the exact sample sizes for each verification type. The neglected assumptions in the conventional methods are the binomial assumption of the hypergeometric distribution and the parameter assumption using regression analysis. A previous study indicated that the revised method can reduce total sample size or sample size for more accurate verification types for each stratum, while maintaining the same non-detection probability (β) given to a target facility. This research then compares the feasibility of the revised method using a hypothetical physical inventory of a benchmark fuel fabrication plant and diversion scenarios to compare the detection capability of the two methods. The following four diversion scenarios are suggested and detection probabilities for each scenario are then compared to the non-detection probability given to the benchmark facility. The four diversion scenarios are 1) 1 SQ diversion in a single stratum with the gross defect, 2) 1 SQ diversion in a single stratum with the partial defect, 3) 1 SQ diversion in a single stratum with the bias defect, and 4) 1 SQ diversion in two strata with the gross defect. Results indicate that the revised method satisfies the detection probability while maintaining the small sample sizes. Therefore, the revised sampling planning method can be applied to the on-site inspection supporting program for national inspection. Future works will include the feasibility of applying the independent sampling plan for national inspection to demonstrate the feasibility.