# Validating the performance of correlated fission multiplicity implementation in radiation transport codes with subcritical neutron multiplication benchmark experiments

## Abstract

Historically, radiation transport codes have uncorrelated fission emissions. In reality, the particles emitted by both spontaneous and induced fissions are correlated in time, energy, angle, and multiplicity. This work validates the performance of various current Monte Carlo codes that take into account the underlying correlated physics of fission neutrons, specifically neutron multiplicity distributions. The performance of 4 Monte Carlo codes - MCNP®6.2, MCNP®6.2/FREYA, MCNP®6.2/CGMF, and PoliMi - was assessed using neutron multiplicity benchmark experiments. In addition, MCNP®6.2 simulations were run using JEFF-3.2 and JENDL-4.0, rather than ENDF/B-VII.1, data for ^{239}Pu and ^{240}Pu. The sensitive benchmark parameters that in this work represent the performance of each correlated fission multiplicity Monte Carlo code include the singles rate, the doubles rate, leakage multiplication, and Feynman histograms. Although it is difficult to determine which radiation transport code shows the best overall performance in simulating subcritical neutron multiplication inference benchmark measurements, it is clear that correlations exist between the underlying nuclear data utilized by (or generated by) the various codes, and the correlated neutron observables of interest. This could prove useful in nuclear data validation and evaluation applications, in which a particular moment of the neutron multiplicity distribution is of more interest than the othermore »

- Authors:

- Publication Date:

- Research Org.:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

- Sponsoring Org.:
- USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation

- OSTI Identifier:
- 1564315

- Alternate Identifier(s):
- OSTI ID: 1457278

- Report Number(s):
- LA-UR-17-31332

Journal ID: ISSN 0306-4549; S0306454918302883; PII: S0306454918302883

- Grant/Contract Number:
- NA0002576; AC52-06NA25396

- Resource Type:
- Published Article

- Journal Name:
- Annals of Nuclear Energy (Oxford)

- Additional Journal Information:
- Journal Name: Annals of Nuclear Energy (Oxford) Journal Volume: 120 Journal Issue: C; Journal ID: ISSN 0306-4549

- Publisher:
- Elsevier

- Country of Publication:
- United Kingdom

- Language:
- English

- Subject:
- 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; fission multiplicity; radiation transport; subcritical benchmark; neutron multiplication

### Citation Formats

```
Arthur, Jennifer, Bahran, Rian, Hutchinson, Jesson, Sood, Avneet, Rising, Michael, and Pozzi, Sara A. Validating the performance of correlated fission multiplicity implementation in radiation transport codes with subcritical neutron multiplication benchmark experiments. United Kingdom: N. p., 2018.
Web. doi:10.1016/j.anucene.2018.05.051.
```

```
Arthur, Jennifer, Bahran, Rian, Hutchinson, Jesson, Sood, Avneet, Rising, Michael, & Pozzi, Sara A. Validating the performance of correlated fission multiplicity implementation in radiation transport codes with subcritical neutron multiplication benchmark experiments. United Kingdom. doi:10.1016/j.anucene.2018.05.051.
```

```
Arthur, Jennifer, Bahran, Rian, Hutchinson, Jesson, Sood, Avneet, Rising, Michael, and Pozzi, Sara A. Mon .
"Validating the performance of correlated fission multiplicity implementation in radiation transport codes with subcritical neutron multiplication benchmark experiments". United Kingdom. doi:10.1016/j.anucene.2018.05.051.
```

```
@article{osti_1564315,
```

title = {Validating the performance of correlated fission multiplicity implementation in radiation transport codes with subcritical neutron multiplication benchmark experiments},

author = {Arthur, Jennifer and Bahran, Rian and Hutchinson, Jesson and Sood, Avneet and Rising, Michael and Pozzi, Sara A.},

abstractNote = {Historically, radiation transport codes have uncorrelated fission emissions. In reality, the particles emitted by both spontaneous and induced fissions are correlated in time, energy, angle, and multiplicity. This work validates the performance of various current Monte Carlo codes that take into account the underlying correlated physics of fission neutrons, specifically neutron multiplicity distributions. The performance of 4 Monte Carlo codes - MCNP®6.2, MCNP®6.2/FREYA, MCNP®6.2/CGMF, and PoliMi - was assessed using neutron multiplicity benchmark experiments. In addition, MCNP®6.2 simulations were run using JEFF-3.2 and JENDL-4.0, rather than ENDF/B-VII.1, data for 239Pu and 240Pu. The sensitive benchmark parameters that in this work represent the performance of each correlated fission multiplicity Monte Carlo code include the singles rate, the doubles rate, leakage multiplication, and Feynman histograms. Although it is difficult to determine which radiation transport code shows the best overall performance in simulating subcritical neutron multiplication inference benchmark measurements, it is clear that correlations exist between the underlying nuclear data utilized by (or generated by) the various codes, and the correlated neutron observables of interest. This could prove useful in nuclear data validation and evaluation applications, in which a particular moment of the neutron multiplicity distribution is of more interest than the other moments. It is also quite clear that, because transport is handled by MCNP®6.2 in 3 of the 4 codes, with the 4th code (PoliMi) being based on an older version of MCNP®, the differences in correlated neutron observables of interest are most likely due to the treatment of fission event generation in each of the different codes, as opposed to the radiation transport.},

doi = {10.1016/j.anucene.2018.05.051},

journal = {Annals of Nuclear Energy (Oxford)},

number = C,

volume = 120,

place = {United Kingdom},

year = {2018},

month = {10}

}

DOI: 10.1016/j.anucene.2018.05.051

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Works referencing / citing this record:

##
Results of Three Neutron Diagnosed Subcritical Experiments

journal, December 2018

- Gomez, J. A.; Koehler, P. E.; Cutler, T. E.
- Nuclear Science and Engineering, Vol. 193, Issue 5