# Implementation of Chord Length Sampling for Transport Through a Binary Stochastic Mixture

## Abstract

Neutron transport through a special case stochastic mixture is examined, in which spheres of constant radius are uniformly mixed in a matrix material. A Monte Carlo algorithm previously proposed and examined in 2-D has been implemented in a test version of MCNP. The Limited Chord Length Sampling (LCLS) technique provides a means for modeling a binary stochastic mixture as a cell in MCNP. When inside a matrix cell, LCLS uses chord-length sampling to sample the distance to the next stochastic sphere. After a surface crossing into a stochastic sphere, transport is treated explicitly until the particle exits or is killed. Results were computed for a simple model with two different fixed neutron source distributions and three sets of material number densities. Stochastic spheres were modeled as black absorbers and varying degrees of scattering were introduced in the matrix material. Tallies were computed using the LCLS capability and by averaging results obtained from multiple realizations of the random geometry. Results were compared for accuracy and figures of merit were compared to indicate the efficiency gain of the LCLS method over the benchmark method. Results show that LCLS provides very good accuracy if the scattering optical thickness of the matrix is smallmore »

- Authors:

- Publication Date:

- Research Org.:
- Lockheed Martin Inc., Schenectady, NY 12301-1072 (US)

- Sponsoring Org.:
- US Department of Energy (US)

- OSTI Identifier:
- 820722

- Report Number(s):
- LM-02K132

TRN: US200405%%130

- DOE Contract Number:
- AC12-00SN39357

- Resource Type:
- Technical Report

- Resource Relation:
- Other Information: PBD: 18 Nov 2002

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; ACCURACY; ALGORITHMS; BENCHMARKS; EFFICIENCY; GEOMETRY; IMPLEMENTATION; MATRIX MATERIALS; MIXTURES; NEUTRON SOURCES; NEUTRON TRANSPORT; SAMPLING; SCATTERING; SIMULATION; THICKNESS; STOCHASTIC MIXTURE; TRANSPORT; MONTE CARLO; MCNP

### Citation Formats

```
T.J. Donovan, T.M. Sutton, and Y. Danon.
```*Implementation of Chord Length Sampling for Transport Through a Binary Stochastic Mixture*. United States: N. p., 2002.
Web. doi:10.2172/820722.

```
T.J. Donovan, T.M. Sutton, & Y. Danon.
```*Implementation of Chord Length Sampling for Transport Through a Binary Stochastic Mixture*. United States. doi:10.2172/820722.

```
T.J. Donovan, T.M. Sutton, and Y. Danon. Mon .
"Implementation of Chord Length Sampling for Transport Through a Binary Stochastic Mixture". United States. doi:10.2172/820722. https://www.osti.gov/servlets/purl/820722.
```

```
@article{osti_820722,
```

title = {Implementation of Chord Length Sampling for Transport Through a Binary Stochastic Mixture},

author = {T.J. Donovan and T.M. Sutton and Y. Danon},

abstractNote = {Neutron transport through a special case stochastic mixture is examined, in which spheres of constant radius are uniformly mixed in a matrix material. A Monte Carlo algorithm previously proposed and examined in 2-D has been implemented in a test version of MCNP. The Limited Chord Length Sampling (LCLS) technique provides a means for modeling a binary stochastic mixture as a cell in MCNP. When inside a matrix cell, LCLS uses chord-length sampling to sample the distance to the next stochastic sphere. After a surface crossing into a stochastic sphere, transport is treated explicitly until the particle exits or is killed. Results were computed for a simple model with two different fixed neutron source distributions and three sets of material number densities. Stochastic spheres were modeled as black absorbers and varying degrees of scattering were introduced in the matrix material. Tallies were computed using the LCLS capability and by averaging results obtained from multiple realizations of the random geometry. Results were compared for accuracy and figures of merit were compared to indicate the efficiency gain of the LCLS method over the benchmark method. Results show that LCLS provides very good accuracy if the scattering optical thickness of the matrix is small ({le} 1). Comparisons of figures of merit show an advantage to LCLS varying between factors of 141 and 5. LCLS efficiency and accuracy relative to the benchmark both decrease as scattering is increased in the matrix.},

doi = {10.2172/820722},

journal = {},

number = ,

volume = ,

place = {United States},

year = {2002},

month = {11}

}