Establishment Of The Evaluation Criteria For Swipe Environmental Samples From Nuclear Facilities

The International Atomic Energy Agency (IAEA) monitors undeclared nuclear activities in member states by environmental sampling program. The Republic of Korea (ROK), as a member state of the IAEA, has also been operating domestic environmental sampling program. The environmental sampling program in the ROK includes the collection, screening and particle analysis of cotton swipe samples. However, there is no evaluation criteria for the analysis results to verify undeclared nuclear activities. Therefore, we intended to establish evaluation criteria using a reference spent fuel assembly and the MCNP and Origen-Arp code. The reference spent fuel assembly has the following characteristics: PLUS7 type assembly (ce 16x16), 4.5wt% enrichment, 45 GWd/MTU discharge burnup and 30 years passed after discharge. The spent nuclear fuel was divided into 10 sections in the axial direction to obtain the average neutron flux for each section using MCNP. The discharged burnup for each section was estimated based on the neutron flux. The isotopic ratio of each section was calculated using Origen-Arp. We then calculated the range of isotopic ratio using the simulation results. As a result, we have established the evaluation criteria of swipe samples from a spent fuel assembly and will use it as irradiation information is given.