# Advances in the computation of the Sjöstrand, Rossi, and Feynman distributions

## Abstract

This study illustrates recent computational advances in the application of the Sjöstrand (area), Rossi, and Feynman methods to estimate the effective multiplication factor of a subcritical system driven by an external neutron source. The methodologies introduced in this study have been validated with the experimental results from the KUKA facility of Japan by Monte Carlo (MCNP6 and MCNPX) and deterministic (ERANOS, VARIANT, and PARTISN) codes. When the assembly is driven by a pulsed neutron source generated by a particle accelerator and delayed neutrons are at equilibrium, the Sjöstrand method becomes extremely fast if the integral of the reaction rate from a single pulse is split into two parts. These two integrals distinguish between the neutron counts during and after the pulse period. To conclude, when the facility is driven by a spontaneous fission neutron source, the timestamps of the detector neutron counts can be obtained up to the nanosecond precision using MCNP6, which allows obtaining the Rossi and Feynman distributions.

- Authors:

- Argonne National Lab. (ANL), Lemont, IL (United States)
- Karlsruhe Inst. of Technology (KIT) (Germany)
- Kyoto Univ. (Japan)

- Publication Date:

- Research Org.:
- Argonne National Lab. (ANL), Argonne, IL (United States)

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

- OSTI Identifier:
- 1422765

- Grant/Contract Number:
- AC02-06CH11357

- Resource Type:
- Journal Article: Accepted Manuscript

- Journal Name:
- Progress in Nuclear Energy

- Additional Journal Information:
- Journal Volume: 101; Journal Issue: PC; Journal ID: ISSN 0149-1970

- Publisher:
- Elsevier

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 97 MATHEMATICS AND COMPUTING; ECCO; ERANOS; Feynman; KUKA; MCNP; PARTISN; Rossi; Sjöstrand; Subcritical; VARIANT

### Citation Formats

```
Talamo, A., Gohar, Y., Gabrielli, F., Rineiski, A., and Pyeon, C. H.
```*Advances in the computation of the Sjöstrand, Rossi, and Feynman distributions*. United States: N. p., 2017.
Web. doi:10.1016/j.pnucene.2017.01.006.

```
Talamo, A., Gohar, Y., Gabrielli, F., Rineiski, A., & Pyeon, C. H.
```*Advances in the computation of the Sjöstrand, Rossi, and Feynman distributions*. United States. doi:10.1016/j.pnucene.2017.01.006.

```
Talamo, A., Gohar, Y., Gabrielli, F., Rineiski, A., and Pyeon, C. H. Wed .
"Advances in the computation of the Sjöstrand, Rossi, and Feynman distributions". United States.
doi:10.1016/j.pnucene.2017.01.006. https://www.osti.gov/servlets/purl/1422765.
```

```
@article{osti_1422765,
```

title = {Advances in the computation of the Sjöstrand, Rossi, and Feynman distributions},

author = {Talamo, A. and Gohar, Y. and Gabrielli, F. and Rineiski, A. and Pyeon, C. H.},

abstractNote = {This study illustrates recent computational advances in the application of the Sjöstrand (area), Rossi, and Feynman methods to estimate the effective multiplication factor of a subcritical system driven by an external neutron source. The methodologies introduced in this study have been validated with the experimental results from the KUKA facility of Japan by Monte Carlo (MCNP6 and MCNPX) and deterministic (ERANOS, VARIANT, and PARTISN) codes. When the assembly is driven by a pulsed neutron source generated by a particle accelerator and delayed neutrons are at equilibrium, the Sjöstrand method becomes extremely fast if the integral of the reaction rate from a single pulse is split into two parts. These two integrals distinguish between the neutron counts during and after the pulse period. To conclude, when the facility is driven by a spontaneous fission neutron source, the timestamps of the detector neutron counts can be obtained up to the nanosecond precision using MCNP6, which allows obtaining the Rossi and Feynman distributions.},

doi = {10.1016/j.pnucene.2017.01.006},

journal = {Progress in Nuclear Energy},

number = PC,

volume = 101,

place = {United States},

year = {Wed Feb 01 00:00:00 EST 2017},

month = {Wed Feb 01 00:00:00 EST 2017}

}