Correlations in Prompt Neutrons and Gamma Rays from Fission2015/09/10 · Consortium for Verification Technology: Workshop th- October 15th & 16 , 2015 Motivation 2 • Nuclear nonproliferation

Correlations in Prompt Neutrons and Gamma Rays from Fission

S. A. Pozzi1, M. J. Marcath1, T. H. Shin1, Angela Di Fulvio1 , S. D. Clarke1, E. W. Larsen1,

R. Vogt2,3, J. Randrup4, R. C. Haight5, P. Talou5, T. Kawano5, I. Stetcu5, E. Padovani6

1Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI, USA 2Lawrence Livermore National Laboratory, Livermore, CA, USA 3University of California, Davis, CA, USA 4Lawrence Berkeley National Laboratory, Berkeley, CA, USA 5Los Alamos National Laboratory, Los Alamos, NM, USA 6Department of Energy, Polytechnic of Milan, Milan, Italy

Consortium for Verification Technology: Workshop - October 15th & 16th, 2015

Motivation

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• Nuclear nonproliferation and safeguards applications require improved models for physics of nuclear fission and detector response.

• Specifically, the correlated neutron and gamma ray emission properties of important nuclear isotopes such as 235U and 239Pu are not well known. These data are important in nuclear safeguards and nonproliferation.

• The present work builds on that experience and includes correlated information.

• There is a need for a new set of measured data to compare to fission models.

• Key neutron and gamma ray quantities to measure – Detected multiplicity

– Energy spectra

– Relative angle of emission

http://www.nti.org/e_research/e3_special_nuctrafficking_slovakia_Nov2007.html


• Neutrons emitted in the direction of motion of the fission fragment (FF) have the FF momentum added to their energy

Nuclear Fission

3

Center of Mass Frame Lab Frame

Direction of motion


Nuclear Fission Modeling MCNPX-PoliMi

• The multiple variables associated with nuclear fission are sampled independently by most Monte Carlo codes.

• MCNPX-PoliMi spontaneous fission model samples neutrons and gamma rays from a full multiplicity distribution.

• Neutron multiplicity dependent energy spectra.

• Anisotropic neutron angular distribution.

4

0 1 2 3 4 5 6 7 8 90

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Neutrons Emitted

Pro

ba

bili

ty

Pu-240

Cf-252


Nuclear Fission Modeling CGMF and FREYA

• Theoretical research is underway to develop CGMF and FREYA models that exhibit fission-particle correlations.

• CGMF and FREYA are event-by-event Monte Carlo codes that follow the fission event from scission to de-excitation

• Active collaboration is underway to verify these models and PoliMi with measured data.

5


UMich and LANL ChiNu Array Cf-252 Experiments

• EJ-309 organic liquid scintillator

– 17.78Ø×5.08 cm active volume

– 12.7 cm Hamamatsu R4144

– 1.25 H:C

– 0.94 g/cm3

• Pulse shape discrimination capable

MCNPX-PoliMi simulated 17.78Ø×5.08 cm EJ-309 40 keVee threshold =~0.5 MeV deposition

17.78Ø×5.08 cm EJ-309

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UMich Cf-252 Experiment

• In the Fall of 2014, an inorganic and organic scintillator array sensitive to both gamma-ray and neutrons has been created to investigate Cf-252 spontaneous fission gamma-ray and neutron correlations.

• This array provides a range of correlated measureables – Time cross-correlation distributions – Detected neutron and detected

gamma-ray multiplicities – Neutron energy from photon TOF as

a function of the number of detected photons

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LANL ChiNu Array Cf-252 Experiment

• In the summer of 2015, a

measurement was made of neutrons and gamma rays from a Cf-252 fission chamber with the LANL ChiNu liquid organic scintillator array – Larger source-detector

distance of 1 m – factor 2

– Stronger source – factor 8

– Fission chamber – better timing resolution and trigger

– Larger solid angle coverage – factor 2

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ORNL designed Cf-252 fission chamber



• 3,000 cps/detector

• 125 MB/s

• 30 hours and 27 billion fissions later we have 13 TB of waveforms

• Post-processing time is significant

• Physical storage space becomes difficult with full waveforms

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Results for a time cross-correlation distribution between pair of EJ-309s

Pairs of EJ-309s

Count rate as a function of angle between detectors

• Double coincidences are analyzed, but higher order coincidences are the target measurable

• Constructing a detailed MCNPX model for fission model comparison

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UMich and LANL ChiNu Array Cf-252 Experiments Neutron Cross-Talk Characterization

• Scatter-based non-absorbing detectors are prone to neutron cross-talk – A single neutron can scatter into one or

more detectors subsequently registering multiple counts

– Adversely increases correlated counts

• Characterization of cross-talk and its effect on the total observed coincidence counts is significant when experimental systems utilize numerous detectors

• Need to measure isolated cross-talk neutrons from Cf-252 spontaneous fission source and validate MCNPX-PoliMi simulations

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Detector 3

Θ

1m

1m

Cf-252

Detector 1 t1

Detector 2 t2

Po

lyet

hyle

ne,

60 c

m

Detector-source-

detector angle


UMich and LANL ChiNu Array Cf-252 Experiments Neutron Cross-Talk Characterization

• Time cross-correlation distributions were compared to MCNPX-PoliMi simulations and show good agreement.

• Neutron cross-talk counts within a measurement system primarily dependent on:

– Detector-source-detector angle

– Detector-detector distance

– Detector light output threshold

• Relative effects of neutron cross-talk characterized by these parameters, see poster this afternoon.

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Detector-Source-Detector Angle Θ 10° 20° 30°

Measured Integrated Count Rate [counts/sec]

2.798 0.6954 0.3301

MCNPX-PoliMi Integrated Count Rate [counts/sec]

3.213 0.7313 0.3561

% Difference 12.91 % 4.901 % 7.292 %


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Future Work Induced-Fission Measurements at WNR Facility at LANSCE

WNR - fast

neutron source

Lujan center –

moderated

neutron source

Ultracold neutron source


Summary and Conclusions

• Measurements of correlated, prompt emissions from 252Cf have been performed and partially analyzed

• There is a need for a measured correlated-data set to compare with fission model simulations

• Accurate models are necessary in order to effectively design such systems

• Advanced verification system could rely on detailed correlated emissions from fission

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Acknowledgements

• Thanks to my mentors at LANL Robert Haight, Matthew Devlin, and Patrick Talou.

• This research was performed under appointment to the U.S. Department of Energy Nuclear Nonproliferation International Safeguards Graduate Fellowship Program sponsored by the National Nuclear Security Administration’s Office of Nonproliferation and International Security.

• This work was funded in-part by the Consortium for Verification Technology under Department of Energy National Nuclear Security Administration award number DE-NA0002534.

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Correlations in Prompt Neutrons and Gamma Rays from Fission S. A. Pozzi1, M. J. Marcath1, T. H. Shin1, Angela Di Fulvio1 , S. D. Clarke1, E. W. Larsen1,

R. Vogt2,3, J. Randrup4, R. C. Haight5, P. Talou5, T. Kawano5, I. Stetcu5, E. Padovani6

1Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI, USA 2Lawrence Livermore National Laboratory, Livermore, CA, USA 3University of California, Davis, CA, USA 4Lawrence Berkeley National Laboratory, Berkeley, CA, USA 5Los Alamos National Laboratory, Los Alamos, NM, USA 6Department of Energy, Polytechnic of Milan, Milan, Italy

Documents

Correlations in Prompt Neutrons and Gamma Rays from Fission2015/09/10 · Consortium for Verification Technology: Workshop th- October 15th & 16 , 2015 Motivation 2 • Nuclear nonproliferation