Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

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1 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions Robert McElroy, Stephen Croft, Angela Lousteau, Ram Venkataraman, Presented at the Novel Technologies, Techniques, and Methods for Safeguards and Arms Control Verification Workshop, Albuquerque, NM, 29 August 2017 ORNL is managed by UT-Battelle for the US Department of Energy

2 Introduction The development and refinement of novel technologies, techniques and methods for nuclear material characterization and assay, as practical approaches that can be usefully applied to nuclear safeguards, is a continual process. The transformative impact is often only truly realized by the widespread adoption of numerous incremental improvements that show competitive advantage over the long run. At Oak Ridge National Laboratory, a key focus area for safeguards technology development is on identifying and honing measurement solutions which can be fielded and provide this kind of effective long-term benefit into the safeguards and arms control community. 2 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

3 Current Work A Brief Selection High-resolution gamma-ray spectrometry of used fuel pins for spent fuel characterization and inventory code verification; Advanced algorithms for Hybrid K-Edge Densitometry with superior accuracy and robustness for dissolved fuel sample assay; The replacement of radionuclide sources in traditional active neutron assay systems; The use of list mode data acquisition for more complete and flexible neutron detector system characterization to provide new approaches to item-specific enquiry; The re-imagining of shuffler and differential die-away techniques using multi-energy interrogation to determine U enrichment as well as mass; and methods to enhance the assessment of swipe samples. 3 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

4 Hybrid K-Edge Densitometry Addressing the evolving fuel cycle Physics Based Spectral Fitting Approach to Multi-elemental K-Edge Transmission X-Ray Fluorescence Incorporates Bremsstrahlung Source Term Chamber, sample and detector scattering effects Matrix effects Elemental Interference Full multi-elemental analysis Improved Measurement Precision by use of full spectrum. Calibration Free does not require representative standards. Accuracy limited by nuclear data (XCOM cross-sections) 4 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

Applicability to Arbitrary Actinide Mixtures The revised algorithms, allow determination of the conversion factors R U:Am, R U:Np, and R U:Cm without the need for calibration but The U and Pu

5 Applicability to Arbitrary Actinide Mixtures The revised algorithms, allow determination of the conversion factors R U:Am, R U:Np, and R U:Cm without the need for calibration but The U and Pu concentrations values, as well as the X-ray generator specific parameters (E 0 and x) necessary to calculate the conversion factors, are determined by fitting of the KED spectra acquired concurrently with the XRF spectrum. The actinide library can be adjusted to incorporate other elements such as Th. 5 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

6 Application to Minor Actinides The traditional ROI analysis would not be able to extract the minor actinide concentrations due to interferences from the U and Pu lines. 6 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

The DD Generator in Safeguards Am(Li) was, for >30 years, the neutron

Current policies and lack of availability necessitate the replacement of the

The obvious replacement candidate is the commercial off the shelf (COTS) neutron

The DD neutron generator is preferred over the DT generator because The neutron

7 The DD Generator in Safeguards Am(Li) was, for >30 years, the neutron interrogation source of choice in Safeguards systems for the quantitative mass assay of bulk uranium items. The AWCC and UNCL systems are key measurement systems in any safeguards program. Current policies and lack of availability necessitate the replacement of the Am(Li) with a non-isotopic source. The obvious replacement candidate is the commercial off the shelf (COTS) neutron generator. The DD neutron generator is preferred over the DT generator because The neutron energy (2.5 vs 14 MeV) emphasizes 235 U fission over 238 U fission. Inherent safety: The yield from a typical DD generator is only 1/100 th that of a DT generator simplifying both ALARA and shielding concerns 7 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

8 DD-AWCC Performance The DD generator may be operated in steady-state mode mimicking the traditional Am(Li)- based coincidence measurement with similar accuracy but with a loss of precision due to the large size of the generator. Operating the generator in pulsed mode provides an analog to the 252 Cf shuffler measurement with accuracy similar to the Am(Li)-based measurement but with improved measurement precision. MCNP simulations and measurements demonstrate an measureable but readily correctable enrichment dependence. 8 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

9 Extension to the Point Model Collaborative Efforts between ORNL and LANL Determining 252 Cf source strength by absolute passive neutron correlation counting S. Croft, D. Henzlova Point model equations for neutron correlation counting: Extension of Böhnel's equations to any order. Andrea Favalli a,n, StephenCroft b, PeterSanti a Extension of the Dytlewski-style dead time correction formalism for neutron multiplicity counting to any order Stephen Croft a,*, Andrea Favalli b 9 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

10 Extension of the Point Model (example) A Two-Energy Point-Model for Neutron Correlation Counting Stephen Croft, Andrea Favalli, Robert D. McElroy Jr., and Peter A. Santi Necessary to accommodate the difference in the induced fission events caused by (alpha,n) and spontaneous fission events for high alpha scrap items. Incorporated into direct multiplication measurement analysis. 10 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

11 Dual Energy Neutron Interrogation for Enrichment Measurement of Bulk Uranium Takes advantage of the difference in the fission cross-sections between 235 U and 238 U to provide a penetrating enrichment measurement Penetration is 10 s cm versus a few mm for HRGS Ratio of delayed neutron count rates is linearly related to the uranium enrichment. Proof of principle measurements performed using ORNL s 252 Cf drum shuffler and an assortment of NBL, NBS and other objects of varying enrichment. A pulsed DT neutron generator was installed in the shuffler to allow interrogation using both DT and 252 Cf neutrons. MCNP and Measured Rates tracked well. Dr. Angela Lousteau s PhD thesis from UT (received August 2017). 11 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

Direct Multiplication Measurement (DMM) Goal: Minimize the need for high performance multiplicity counters (typically used for Pu scrap assay) reducing the need for 3 He.

12 Direct Multiplication Measurement (DMM) Goal: Minimize the need for high performance multiplicity counters (typically used for Pu scrap assay) reducing the need for 3 He. An Add-A-Source (AAS) type measurement using 252 Cf provides the multiplication (assumes material is dry). By measuring multiplication directly, the triples rates, which drive the need for high performance counters, are no longer required. In principle the HLNCC (ε=18%) can provide the same performance as the ENMC (ε=63%) but using only 18 L of 3 He instead of 500 L. Status: Proof of concept measurements have been completed successfully. 12 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

Measurements of Spent Fuel Pins Sister Rods Spent Nuclear Fuel project has 25 individual

Acquire high resolution spectra over the full-length of each Sister Rod at ~4.

Compare gamma spectrum analysis with inventory calculations Make spectra available for

13 Measurements of Spent Fuel Pins Sister Rods Spent Nuclear Fuel project has 25 individual PWR rods with varying burnup, irradiation history, cooling time, and fuel cladding. Acquire high resolution spectra over the full-length of each Sister Rod at ~4.4 mm intervals. Compare gamma spectrum analysis with inventory calculations Make spectra available for simulation benchmarking Fork Detector Studies Linearity Sensitivity Evaluation of alternate neutron detectors 13 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

14 Conclusion We have examined a number of mature non-destructive assay applications that are key components of international safeguards programs. We have found that by re-imagining these techniques, in some cases starting from scratch, they can be adapted or extended to encompass greater swathes of safeguards measurement space, provide improved measurement performance, and potentially supplanting other established techniques. These advances have come not from new detectors, and only in part from today s more powerful computers, but in large part from doing what we physicists do best, by applying an understanding of the underlying processes to the problem and questioning why we have done these measurements in the historical manner. 14 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

15 Acknowledgements: This work sponsored in whole or in part by: U.S. Department of Energy, National Nuclear Security Administration, NA-22 Office of Defense Nuclear Nonproliferation Research and Development U.S. Department of Energy, National Nuclear Security Administration, NA-24 Office of Defense Nuclear Nonproliferation and International Security 15 Emerging Capabilities for Advanced Nuclear Safeguards Measurement Solutions

Uncertainty Quantification for Safeguards Measurements

Uncertainty Quantification for Safeguards Measurements Stephen Croft1, Tom Burr2, Ken Jarman3, Robert McElroy1, Andrew Nicholson1, and Adam Shephard1 1Oak Ridge National Laboratory, 2Los Alamos National