A performance estimate for the detection of undeclared nuclear-fuel reprocessing by atmospheric ⁸⁵Kr

To test the sensitivity of using atmospheric ⁸⁵Kr to detect undeclared separation of plutonium from irradiated nuclear-reactor fuel, measurements of atmospheric ⁸⁵Kr taken in Tsukuba, Japan are analyzed to determine: (1) a lower limit of detection for discovering anthropogenic ⁸⁵Kr emissions, (2) the probability of detecting plutonium separation at the Tokai Reprocessing Plant, and (3) the extent to which these results can be generalized to other sites. A LLD of at least 3.4σ = 0.14 Bq/m³ with a theoretical false-positive rate of 0.05% is recommended for safeguards' purposes. At this threshold, the continuous separation of 100, 300, and 900 g equivalent weapon-grade plutonium per day was found to correspond to 10%, 50%, and 80% probability of detection, respectively. The smallest detected concentration was for the continuous separation of 45 g/day, with a probability of detection of about 0.6%. It was found that the detection rate is determined predominately by the weather