International Target Values for Measurement Uncertainties in Safeguarding Nuclear Materials - 2022

The objective of nuclear material accountancy (NMA) and its keystone, material balance evaluation (MBE), is to detect and deter the diversion of nuclear material by evaluating the nuclear material balances established through the State’s systems of accounting for and control of nuclear material (SSAC) against the corresponding uncertainties and by verifying the correctness of the States’ declaration through independent measurements. The effectiveness of NMA thus strongly depends upon the quality of both the facility operator’s declarations and the inspector’s verification measurements. In order to assess and compare the quality of bulk measurements (weight, volume), non-destructive assays (NDA) and destructive analyses (DA), and in continuation of the pioneering work of the European Safeguards Research & Development Association (ESARDA), a set of international target values (ITV) was first issued by the International Atomic Energy Agency (IAEA) in 1993 and is regularly updated and expanded, in collaboration between the IAEA and international experts.

The IAEA maintains a unique database of verification measurements taken over more than 30 years, paired with State declared values from nuclear fuel cycle (NFC) facilities under safeguards over the world. The database records undergo exploratory and statistical analysis and the IAEA evaluators use them to calculate initial random and systematic measurement uncertainty estimates. Based on these estimates, a network of international consultants from State or regional safeguards authorities (SRA), safeguards laboratories and NFC facilities reach a consensus on a revised set of ITV, i.e. measurement uncertainties that should be achievable under nominal conditions by typical NFC facility laboratories or during safeguards inspections. The role of all international stakeholders in understanding the importance of ITV in safeguards and providing expertise is therefore fundamental to warrant their quality, representativeness and achievability. The current ITV review was conducted with a particular focus on the role of international subject matter experts (SME) with the extension of the international SME network and the creation of a collaborative virtual ITV platform