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Title: Correlated Fission Simulations with MCNP6.2 and MCNPX-PoliMi

ORCiD logo [1]; ORCiD logo [1];  [2];  [1];  [2];  [2]
  1. Los Alamos National Laboratory
  2. Dept. of Nuclear Engineering and Radiological Sciences, University of Michigan
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Resource Relation:
Conference: IRRMA X - 10th International Topical Meeting on Industrial Radiation and Radioisotope Measurement Applications ; 2017-07-09 - 2017-07-13 ; Chicago, Illinois, United States
Country of Publication:
United States
Correlated fission, MCNP, DRiFT, MCNPX-PoliMi

Citation Formats

Rising, Michael Evan, Andrews, Madison Theresa, Marcath, Matthew, Sood, Avneet, Clarke, Shaun, and Pozzi, Sara. Correlated Fission Simulations with MCNP6.2 and MCNPX-PoliMi. United States: N. p., 2017. Web.
Rising, Michael Evan, Andrews, Madison Theresa, Marcath, Matthew, Sood, Avneet, Clarke, Shaun, & Pozzi, Sara. Correlated Fission Simulations with MCNP6.2 and MCNPX-PoliMi. United States.
Rising, Michael Evan, Andrews, Madison Theresa, Marcath, Matthew, Sood, Avneet, Clarke, Shaun, and Pozzi, Sara. 2017. "Correlated Fission Simulations with MCNP6.2 and MCNPX-PoliMi". United States. doi:.
title = {Correlated Fission Simulations with MCNP6.2 and MCNPX-PoliMi},
author = {Rising, Michael Evan and Andrews, Madison Theresa and Marcath, Matthew and Sood, Avneet and Clarke, Shaun and Pozzi, Sara},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2017,
month = 7

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  • We present new results on the measurement of correlated, outgoing neutrons from spontaneous fission events in a Cf-252 source. 16 EJ-309 liquid scintillation detectors are used to measure neutron-neutron correlations for various detector angles. Anisotropy in neutron emission is observed. The results are compared to MCNPX-PoliMi simulations and good agreement is observed.
  • Many safeguards measurement systems used at nuclear facilities, both domestically and internationally, rely on He-3 detectors and well established mathematical equations to interpret coincidence and multiplicity-type measurements for verifying quantities of special nuclear material. Due to resource shortages alternatives to these existing He-3 based systems are being sought. Work is also underway to broaden the capabilities of these types of measurement systems in order to improve current multiplicity analysis techniques. As a part of a Material Protection, Accounting, and Control Technology (MPACT) project within the U.S. Department of Energy's Fuel Cycle Technology Program we are designing a fast-neutron multiplicity countermore » with organic liquid scintillators to quantify important quantities such as plutonium mass. We are also examining the potential benefits of using fast-neutron detectors for multiplicity analysis of advanced fuels in comparison with He-3 detectors and testing the performance of such designs. The designs are being developed and optimized using the MCNPX-PoliMi transport code to study detector response. In the full paper, we will discuss validation measurements used to justify the use of the MCNPX-PoliMi code paired with the MPPost multiplicity routine to design a fast neutron multiplicity counter with liquid scintillators. This multiplicity counter will be designed with the end goal of safeguarding advanced nuclear fuels. With improved timing qualities associated with liquid scintillation detectors, we can design a system that is less limited by nuclear materials of high activities. Initial testing of the designed system with nuclear fuels will take place at Idaho National Laboratory in a later stage of this collaboration.« less
  • Organic liquid scintillation detectors are valuable for the detection of special nuclear material since they are capable of detecting both neutrons and gamma rays. Scintillators can also provide energy information which is helpful in identification and characterization of the source. In order to design scintillation based measurement systems appropriate simulation tools are needed. MCNPX-PoliMi is capable of simulating scintillation detector response; however, simulations have traditionally been run in analog mode which leads to long computation times. In this paper, non-analog MCNPX-PoliMi mode which uses variance reduction techniques is applied and tested. The non-analog MCNPX-PoliMi simulation test cases use source biasing,more » geometry splitting and a combination of both variance reduction techniques to efficiently simulate pulse height distribution and then time-of-flight for a heavily shielded case with a {sup 252}Cf source. An improvement factor (I), is calculated for distributions in each of the three cases above to analyze the effectiveness of the non-analog MCNPX-PoliMi simulations in reducing computation time. It is found that of the three cases, the last case which uses a combination of source biasing and geometry splitting shows the most improvement in simulation run time for the same desired variance. For pulse height distributions speedup ranging from a factor 5 to 25 is observed, while for time-of-flights the speedup factors range from 3 to 10. (authors)« less
  • Monte Carlo particle transport codes used to accurately model detector response are traditionally run in fully analog mode. Analog simulations of cross-correlation measurements with these codes are extremely time-consuming because the probability of correlated detection is extremely small, approximately equal to the product of the probabilities of a single detection in each detector. The new 'implicit correlation' method described here increases the number of correlation event scores thereby reducing variance and required computation times. The cost of the implicit correlation method is comparable to the cost of simulating single event detection for the lowest absolute detector efficiency in the problem.more » This method is especially useful in the nuclear non-proliferation and safeguards fields for simulating correlation measurements of shielded special nuclear material. The new method was implemented in MCNPX-PoliMi for neutron-neutron cross-correlations with a Cf-252 spontaneous fission source measured by two detectors of variable stand-offs. The method demonstrated good agreement with analog simulation results for multiple measurement geometries. Small differences between non-analog and analog cross-correlation distributions are attributed to known features of the specific problem simulated that will not be present in practical applications. (authors)« less