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# Sensitivity of neutron observables to the model input in simulations of ${}^{252}\mathrm{Cf}\left(\mathrm{sf}\right)$

## Abstract

Within the framework of $FREYA$ event-by-event fission simulations, we study the sensitivity of various neutron observables to the input yield function $Y$ ($A,Z,$TKE) on which the fission event sampling is based. We first perform a statistical analysis of the available fission data in order to determine the distribution of possible yield functions $Y$ ($A,Z$,TKE) and we then construct a sample of 15,000 such yield functions. For each of these, $FREYA$ is used to generate one million fission events, leading to a corresponding ensemble of fission observables, including the neutron multiplicity distribution and its factorial moments, the neutron energy spectrum, and the neutron-neutron angular correlation. This procedure allows us to study the sensitivity of those neutron observables to the uncertainty in the experimental data. Particular attention is given to the pronounced anticorrelation between the mean neutron multiplicity $$\bar{v}$$ and the mean total fragment kinetic energy TKE. Because the former observable is very well determined experimentally, it is possible to exploit that inherent anticorrelation to derive a significantly stricter tolerance on TKE. In addition, we study the sensitivity to the various $FREYA$ parameters and we introduce a method for determining a A-dependent x parameter, $x$($A$), based on the measured A-dependent neutron multiplicity, ($A$).

- Authors:

- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Nuclear Science Div.; ; Univ. of California, Berkeley, CA (United States). Nuclear Engineering Dept.
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Nuclear Theory Group and X-Computational Physics Div.
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Physics Div.; ; Univ. of California, Davis, CA (United States). Physics Dept.

- Publication Date:

- Research Org.:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

- Sponsoring Org.:
- USDOE National Nuclear Security Administration (NNSA)

- OSTI Identifier:
- 1560105

- Alternate Identifier(s):
- OSTI ID: 1515102

- Report Number(s):
- LLNL-JRNL-767159

Journal ID: ISSN 2469-9985; PRVCAN; 957515

- Grant/Contract Number:
- AC52-07NA27344; AC02-05CH11231; DEAC52-06NA25396

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Physical Review C

- Additional Journal Information:
- Journal Volume: 99; Journal Issue: 5; Journal ID: ISSN 2469-9985

- Publisher:
- American Physical Society (APS)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 73 NUCLEAR PHYSICS AND RADIATION PHYSICS

### Citation Formats

```
Randrup, J., Talou, P., and Vogt, R. Sensitivity of neutron observables to the model input in simulations of 252Cf(sf). United States: N. p., 2019.
Web. doi:10.1103/PhysRevC.99.054619.
```

```
Randrup, J., Talou, P., & Vogt, R. Sensitivity of neutron observables to the model input in simulations of 252Cf(sf). United States. doi:10.1103/PhysRevC.99.054619.
```

```
Randrup, J., Talou, P., and Vogt, R. Wed .
"Sensitivity of neutron observables to the model input in simulations of 252Cf(sf)". United States. doi:10.1103/PhysRevC.99.054619.
```

```
@article{osti_1560105,
```

title = {Sensitivity of neutron observables to the model input in simulations of 252Cf(sf)},

author = {Randrup, J. and Talou, P. and Vogt, R.},

abstractNote = {Within the framework of $FREYA$ event-by-event fission simulations, we study the sensitivity of various neutron observables to the input yield function $Y$ ($A,Z,$TKE) on which the fission event sampling is based. We first perform a statistical analysis of the available fission data in order to determine the distribution of possible yield functions $Y$ ($A,Z$,TKE) and we then construct a sample of 15,000 such yield functions. For each of these, $FREYA$ is used to generate one million fission events, leading to a corresponding ensemble of fission observables, including the neutron multiplicity distribution and its factorial moments, the neutron energy spectrum, and the neutron-neutron angular correlation. This procedure allows us to study the sensitivity of those neutron observables to the uncertainty in the experimental data. Particular attention is given to the pronounced anticorrelation between the mean neutron multiplicity $\bar{v}$ and the mean total fragment kinetic energy TKE. Because the former observable is very well determined experimentally, it is possible to exploit that inherent anticorrelation to derive a significantly stricter tolerance on TKE. In addition, we study the sensitivity to the various $FREYA$ parameters and we introduce a method for determining a A-dependent x parameter, $x$($A$), based on the measured A-dependent neutron multiplicity, ($A$).},

doi = {10.1103/PhysRevC.99.054619},

journal = {Physical Review C},

number = 5,

volume = 99,

place = {United States},

year = {2019},

month = {5}

}

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