Detection of Highly Enriched Uranium Using a Pulsed IEC Fusion Device

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1 Detection of Highly Enriched Uranium Using a Pulsed IEC Fusion Device R.F. Radel, R.P. Ashley, G.L. Kulcinski, and the UW-IEC Team US-Japan Workshop May 23, 2007

2 Outline Motivation for pulsed IEC research Description of HEU detection method Progress of pulsed IEC development HEU detection results Conclusions 2

3 Motivation for Pulsed IEC-based Fissile Material Detection Research There have been at least 150 incidents of nuclear smuggling in past decade, half involving special nuclear material (IAEA) As little as 16 kg of HEU or 6 kg of Pu can be used to produce a 20 kiloton weapon, even with low technology levels Developing technology for the detection of HEU has become a priority for the US Department of Homeland Security IEC technology can provide high fluxes of D-D or D-T neutrons for long lifetimes 3

4 IEC Fusion-Based HEU Detection Concept Shipping containers Neutron shielding Neutron sources Door Door Power Supply 3 He detector arrays Source: Greg Sviatoslavsky 4

5 IEC Fusion-Based HEU Detection Concept Shipping containers Neutron shielding Neutron sources Door Door Fissile material Power Supply 3 He detector arrays Source: Greg Sviatoslavsky 5

6 Pulsed Fusion Neutrons Induce Fissions within the Shipping Container Source: Greg Sviatoslavsky 6

7 Wisconsin Design Uses Ion Source to Generate Pulses 200 kv DC Power Supply 0.2 μf Filament Temp Supply Positive DC Bias Negative Pulse Generator 7

8 Significant Progress has been Made Over the Past Two Years 1.E+10 Pulsed IEC Neutron Production D-D Neutron Production (n/s) 1.E+09 1.E+08 1.E+07 Jun-05 Dec-05 Jun-06 Dec-06 Jun-07 Date 8

9 Fusion Cross-Sections Increase with Increased Ion Energy Neutron Rate vs. Cathode Voltage 1.E mtorr Pa D 22 Neutron Rate (n/s) 1.E+08 1.E+07 1.E+06 Pulsed-0.5 A, 0.5 ms, 10 Hz Steady State-30 ma Cathode Voltage (kv) 9

10 Shorter Pulse Widths Generate Higher Intensity Pulses Pulse Width Scan Pulse Current (A) kv Cathode, mtorr Pa D 2 D ms 0.25 ms 0.5 ms 0.75 ms 1 ms Time (ms) 10

11 Shorter Pulse Widths Generate Higher Intensity Pulses Neutron Rate vs. Pulse Width 2.0E kv (cathode), 3 Hz, Pa mtorr D 2 D 2 Neutron Rate (n/s) 1.5E E E E Pulse Width (ms) 11

12 Pulsed IEC Capability Has Reached Levels Sufficient for Near-Term Application Research Max Cathode Voltage: 120 kv Max Pulse Current: Deuterium: 6 Amps Max D-D Neutron Rate: 4.7x10 9 n/s (96 kv, 5 A, 0.33 Pa) (110μs pulse width, 5 Hz) 12

13 MCNP Model Accurately Predicts Time-Dependent Neutron Behavior Paraffin Wax IEC 11 g HEU (93% U-235) 50 cm 3 He Detector 13

14 MCNP Model Accurately Predicts Time-Dependent Neutron Behavior HEU Detector Simulation D-D point source-6x10 8 n/s, 11 grams of 93% enriched uranium (10 g U-235) 1.E+04 1.E+03 Cts/10 ms in 3 He Detectors 1.E+02 1.E+01 1.E+00 1.E-01 1.E-02 1.E-03 1.E Time (ms) 14

15 MCNP Model Accurately Predicts Time-Dependant Neutron Behavior Thermal Neutron Decay No HEU in system Counts per Time Bin Experiment MCNP Model Time (ms) 15

16 Neutron Detector Construction Optimized Delayed Neutron Detection 3 He Detector HEU Sample Lead-shielded Paraffin Wax Amplifier, HV Supply Pre-Amplifiers To MCA 16

17 Pulsed IEC Device has Generated Detectable Levels of Delayed Fission Neutrons Pulses 1000 Delayed Neutrons vs. Time (1x10 9 D-D n/s during 10, ms pulses at 10 Hz) HEU Counts/2.4 ms bin Pulse Decay No HEU Time After Fusion Pulse (ms) 17

18 Delayed Neutron Production Scaled Linearly with Fusion Neutron Rate HEU 50 cm from IEC center Detectors ~10 cm from HEU Delayed Neutrons Above Background (Integrated for 2000 pulses) Delayed Neutron Production (500 μs pulse width, 10 Hz) 0 0.0E E E E E+09 Pulsed Neutron Rate (n/s) 18

19 Conclusions Numerous improvements were made to the pulsed IEC device: Pulsing circuitry was operated at voltages up to 120 kv Pulsed D + currents in excess of 6 Amperes were achieved Pulse width studies revealed increased neutron production at shorter pulse widths Pulsed neutron production rates as high as 4.7x10 9 n/s were generated during 110 μs pulses at 5 Hz. 19

20 Conclusions (cont.) An MCNP model was developed that accurately models the time-dependent behavior of pulsed IEC neutron production and the associated HEU detection hardware. This model was able to predict the number of delayed neutron counts collected in the 3 He detectors to within approximately ±10%. Pulsed D-D neutron production rates as low as 4x10 8 n/s generated in the UW-IEC were used to detect the presence of a 10 gram sample of uranium-235. Delayed neutron production was found to increase linearly with fusion neutron rates. Signal-to-noise ratios as high as 6.2 were found to exist when 65 kv remained on the cathode between fusion pulses.

21 Recommendations for Future Work Expand HEU detection study to look at effects of geometry and shielding Investigate Differential Die-Away technique 1000 Neutron Counts No HEU HEU 1 ms 2 ms 3 ms 4 ms 5 ms Neutron Counts 21

22 Questions? Ross Radel University of Wisconsin (Sandia National Laboratory)

Current Directions for the University of Wisconsin IEC Research Program

Current Directions for the University of Wisconsin IEC Research Program G. Kulcinski, J. Santarius, R. Ashley, H. Schmitt, D. Boris, B. Cipiti, G. Piefer, R. Radel, S. Krupakar Murali, K. Tomiyasu*, A.