The forward-problem approach in Safeguards verification: directly comparing simulated and measured observables

Volume: 54, June 2017, pages 70-74,

Authors: S.Vaccaro¹, I. Gauld², M. Vescovi³, H. Tagziria⁴, A. Smejkal¹, P. Schwalbach¹

¹_{European Commission, Directorate General Energy, Directorate Euratom Safeguards, Luxembourg,} ²_{Oak Ridge National Laboratory,} ³_{iScience, Milan,} ⁴_{European Commission, Directorate Joint Research Centre, Directorate Nuclear Safety & Security}

Abstract:

Physical verification by NDA in nuclear safeguards implies typically the adoption of an inverse-problem approach. This is, indeed, the definition of a problem, in which we use physical observables to deduct other physical quantities, which in our case are contained in the operator’s declaration. A typical example is the Plutonium mass, measured using Pu isotopics and neutron coincidence doubles counts, linked to the Pu 240 effective mass by a calibration.

An alternative approach has been recently proposed and is now close to the in-field deployment by the Euratom Safeguards Directorate of European Commission’s DG ENER. In fact, the detailed knowledge of the physical processes that are taking place in the sample and within the detector allows computing the amount of the measured observable, by modelling the physical system as it results from the operator’s declaration, in a forward-problem approach.

The present paper describes the first two examples of the forward-problem approach’s application to actual real-life safeguards verification. The first example deals with a Monte- Carlo-based modelling tool that has been developed to enable the inspectors to perform an improved verification of fresh fuel assemblies by neutron coincidence collar (NCC), taking into account the growing complexity of the fuel’s design. The second example shows how the verification of spent fuel is improved regarding the false alarm rate and the partial defect detection capability, by the integration of the automated review package iRAP and the modelling by the Oak Ridge transmutation code (ORIGEN).

The potential applications of the new approach are not limited to the two described in this article, which, however, represent relevant proofs of concept of the potential that a change of perspective in verification by NDA may generate.

Keywords:

NDA, Forward problem, Spent Fuel, Fresh Fuel, ORIGEN, Neutron Coincidence Collar

Reference guideline:

Vaccaro, S., Gauld, I., Vescovi, M., Tagziria, H., Smejkal, A., & Schwalbach, P. (2017). The forward-problem approach in Safeguards verification: directly comparing simulated and measured observables. ESARDA Bulletin - The International Journal of Nuclear Safeguards and Non-proliferation, 54, 70-74. https://doi.org/10.3011/ ESARDA.IJNSNP.2017.9