MCNP6 simulation validation of fast neutron coincidence detection system for nuclear security and safeguards applications

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1 MCNP6 simulation validation of fast neutron coincidence detection system for nuclear security and safeguards applications Débora M. Trombetta 1, Bo Cederwall 1, Kåre Axell1 2 1 Department of Physics, KTH Royal Institute of Technology 2 Swedish Radiation Safety Authority

org/newscenter/news/world-authorities-nuclear-safeguards-review-global-picture timing background sensitivity Reilly, Ensslin, Smith,

2 INTRODUCTION Nuclear Safeguards and Security: - Detection, Identification and Mass prediction of SNM Organic Scintillators as substitutors for H-3 detectors H and C based composition Efficient detection of fast neutrons timing background sensitivity Reilly, Ensslin, Smith, Kreiner, Passive Nondestructive Assay Manual - PANDA, Los Alamos, NM: Safeguards Science and Technology Group at LANL,

COMPUTATIONAL SIMULATIONS of correlations event-by-event DT1 Optimize experiment, detector development Validation (comparison with experiment) - GEANT - LLNL

Time-Analysis Quantities) - Implemented some correlated models (IPOL(1)=1, IPOL(1)=10) for Cf-252 systems - Integrated CGMF and FREYA into local research

3 COMPUTATIONAL SIMULATIONS of correlations event-by-event DT1 Optimize experiment, detector development Validation (comparison with experiment) - GEANT - LLNL Fission Library & FREYA (only locally integrated, not in the open community) - MCNPX-PoliMi (Monte Carlo N-Particle Transport Code System To Simulate Time-Analysis Quantities) - Implemented some correlated models (IPOL(1)=1, IPOL(1)=10) for Cf-252 systems - Integrated CGMF and FREYA into local research version DT2 - MCNP6 * FMULT CARD - METHOD=5 - LLNL Fission Library spontaneous, neutron-induced and photo-fission for most fissionable systems. * PTRAC card d1 Report: LA-UR

4 Slide 3 DT1 DT2 d1 PoliMi was developed from MCNP code for special use in safeguards experiments that rely o the detection of coincident neutrons and gammas from fission. Providing tallies in a even-by-event basis. Débora Trombetta, MCNP6 is a merge betwen MCNP5 and MCNPX. Using the PTRAC card we should be able to get the same results that PoliMi gives. the new features from MCNP6 that we are interested on are the capability of spontaneous neutron and the new model applied for correlated prompt secondary particle production. Débora Trombetta, Note: Prior to the inclusion of the LLNL Fission Library, all photons produced from all neutron reaction channels were sampled prior to the selection of the neutron reaction, meaning that gamma rays could not be correlated with specific neutron reactions actually taking place in the simulation dtrombetta,

EXPERIMENTAL SETUP AND ANALYSIS 70-3120KeVee ( 650-6600keV) Nuclear Instruments and Methods in Physics Research A 763, 565-574 (2014) m( 240

67m( 242 Pu) PSD discrimination line for 200,000 waveforms from PuO 2 (35 photons per neutron) Sample ID 1 2 3 4 Isotope Unit (g) 238 Pu 0.

138 0.278 240 Pu eff 0.42 1.00 1.56 2.30 Total mass 6.716 6.787 6.816 6.719 The sixteen-detector FNMC setup at the JRC facility in Ispra.

5 EXPERIMENTAL SETUP AND ANALYSIS KeVee ( keV) Nuclear Instruments and Methods in Physics Research A 763, (2014) m( 240 Pu eff ) = m( 240 Pu) m( 238 Pu) m( 242 Pu) PSD discrimination line for 200,000 waveforms from PuO 2 (35 photons per neutron) Sample ID Isotope Unit (g) 238 Pu Pu Pu Pu Pu Pu eff Total mass The sixteen-detector FNMC setup at the JRC facility in Ispra. A sample is placed in the center of the system [3]. EJ-309 detectors (7.62cm diameter and 7.62cm height) Aluminum holding structure with a diameter = 34 cm Lead shield thickness of 1cm Two time-synchronized CAEN V1720, 12-bit, 250-MHz, 8-channel 4

COMPUTATIONAL MODELLING, SIMULATIONS AND ANALYSIS MCNP INPUT *Geometry setup * FMULT - METHOD=5 * Source - PAR=-SF SP * PTRAC MCNP OUTPUT PTRAC TABLE Type of Interaction Particle Energy Time

6 COMPUTATIONAL MODELLING, SIMULATIONS AND ANALYSIS MCNP INPUT *Geometry setup * FMULT - METHOD=5 * Source - PAR=-SF SP * PTRAC MCNP OUTPUT PTRAC TABLE Type of Interaction Particle Energy Time Momentum MATLAB Coincidence counting Energy Deposition Time of flight * MCNP6 modeling of experimental setup [3]. The sample was placed at the center of the setup and surrounded by 1 cm lead shielding. 5

7 RESULTS Single neutron and nn coincidence rates as function of 240 Pu eff mass Single neutron rate (s -1 ) Series1 Measured [3] Series2 PoliMi [3] Series3 MCNP6 nn coincidence rate (s -1 ) Series1 Measured [3] Series2 PoliMi [3] Series3 MCNP6 Ratio (Measured [3]/MCNP6) Sample ID single n nn coincidences 1 1,03± ,89± ,08± ,90± ,95± ,93± ,97± ,96± * 1,02± ,96± Pu eff mass (g) Pu eff mass (g) * Error bars from measured and PoliMi are included in the figures but are smaller than the data point symbols. *The reference [3] (Dolan et al., 2014) presents this point as a sum of samples 1,2 and 3 but the total 240 Pu mass doesn t match. The correct mix of samples for this point seems to be 1,3 and 4 according to the total mass reported. 6

8 RESULTS Calibration Curve to the prediction of 240 Pu eff mass - Linear fit to four of the total five sample points the sample 3 ( ) was considered unknown and used for systematic uncertainty analysis. - The true mass value for the sample 3 is 1.56g. Measurements prediction = 1.49±0.01g - systematic error = 4.71% MCNP6 prediction = 1.57±0.01g - systematic error = 0.60% *The reference [3] doenst present the uncertanty related to the slope * Error bars are included in the figures but are smaller than the data point symbols. 2.52* coincidences/g/s 2.68±0.003 coincidences/g/s 6% of difference Measurements Results from Dolan et al. [3] Simulation Results with MCNP6 14 Linear Fit 12 Calibration Points Investigated Points Neutron Doubles per Second Pu eff (g) 7

9 CONCLUSIONS An alternative simulation approach that makes use of MCNP version 6 and the PTRAC card for calculating particle coincidences rates on an event-by-event basis has been investigated; It was validated to quantify small amounts (ranging from 0.5g to 1.5g) of 240 Pu; The MCNP6 simulations were in good agreement with the experimental results presented by Dolan et al. [3] - with a maximum difference of 11% for the nn coincidence rates. The agreement was slightly better than the MCNPX PoliMi simulations reported in [3]; The present work demonstrates that MCNP6 is comparable to the MCNP-PoliMi code for the proposed problem when it makes use of the LLNL fission library and the PTRAC card, even without using the CAP option for neutrons; 8

10 REFERENCES 1 - Ensslin, N., Harker, W.C., Krick, M.S., Langner, D.G., Pickrell, M.M., Stewart, J.E., Application guide to neutron multiplicity counting, Los Alamos Report LA M, (1998). 2 - Pickrell, M.M., Lavietes, A.D., Gavron, V., Henzlova, D., Joyce, M. J., Kouzes, R. T., and Menlove, H.O., The IAEA Workshop on Requirements and Potential Technologies for Replacement of 3He Detectors in IAEA Safeguards Applications, Journal of Nuclear Material Management 41 (2), (2013). 3 - Dolan, J.L., Flaska, M., Poitrasson-Riviere, A., Enquvist, A., Peerani, P., Chichester, D.L., Pozzi, S.A., Plutonium measurements with a fast-neutron multiplicity counter for nuclear safeguards applications, Nuclear Instruments and Methods in Physics Research A 763, (2014). 4 -Paff, M.G., Ruch, M.L., Riviere, A.P., Sagadevan, A., Clarke, S.D., Pozzi, S.A., Organic liquid scintillaton detection for on-the-fly neutron/gamma alarming and radionuclide identification in a pedestrian radiation portal monitor, Nuclear Instruments and Methods in Physics Research A 789, (2015). 5 - Kaplan, A.C., Flaska, M., Enqvist, A., Dolan, J.L., Pozzi, S.A., EJ-309 pulse shape discrimination performance with a high gamma-ray-to-neutron ration and low threshold, Nuclear Instruments and Methods Physic Research Sect. A 729, , (2013). 6 Industries, Neutron Safeguards Systems CANBERRA, Model JCC-31High Level Neutron Coincidence Counter, 2009.Available at Accordion1=2 7 - Padovani, E., Pozzi, S.A., MCNP-PoliMi ver.1.0 user s manual, CESNEF , Library of Nuclear Engineering Department, Politecnico di Milano, November (2002). 8 - MCNP6 Users Manual - Code Version 6.1.1beta, LA-CP (June 2014). 9 - Eljen Technology, Neutron/gamma PSD liquid Scintillator EJ-301, EJ-309, (n.d.) < (accessed 17 November 2017) 10 -Evans, L.G., Schear, M.A., Hendricks, J.S., Swinhoe, M.T., Tobin, S.J., and Croft, S., A new MCNPX PTRAC coincidence capture file capability: a tool for neutron detector design, Conference Paper, Los Alamos National Laboratory (2011). 9

11 Thank you for your attention! 10

Fast Neutron Multiplicity Counter: Development of an active-mode counter UM-INL Collaboration

Fast Neutron Multiplicity Counter: Development of an active-mode counter UM-INL Collaboration T.H. Shin 1, A. Di Fulvio 1, D.L. Chichester 2, S.D. Clarke 1, S.A. Pozzi 1 * thshin@umich.edu 1 Department