# The Chain-Length Distribution in Subcritical Systems

## Abstract

The individual fission chains that appear in any neutron multiplying system provide a means, via neutron noise analysis, to unlock a wealth of information regarding the nature of the system. This work begins by determining the probability density distributions for fission chain lengths in zero-dimensional systems over a range of prompt neutron multiplication constant (K) values. This section is followed by showing how the integral representation of the chain-length distribution can be used to obtain an estimate of the system's subcritical prompt multiplication (MP). The lifetime of the chains is then used to provide a basis for determining whether a neutron noise analysis will be successful in assessing the neutron multiplication constant, k, of the system in the presence of a strong intrinsic source. A Monte Carlo transport code, MC++, is used to model the evolution of the individual fission chains and to determine how they are influenced by spatial effects. The dissertation concludes by demonstrating how experimental validation of certain global system parameters by neutron noise analysis may be precluded in situations in which the system K is relatively low and in which realistic detector efficiencies are simulated.

- Authors:

- Texas A & M Univ., College Station, TX (United States)

- Publication Date:

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

- Sponsoring Org.:
- USDOE Office of Defense Programs (DP)

- OSTI Identifier:
- 766762

- Report Number(s):
- LA-13721-T

TRN: US0005308

- DOE Contract Number:
- W-7405-ENG-36

- Resource Type:
- Thesis/Dissertation

- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); Submitted to Texas A and M Univ., College Station, TX (US); PBD: 1 Jun 2000

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; CHAINS; DISTRIBUTION; FISSION; LIFETIME; NEUTRONS; PROBABILITY; PROMPT NEUTRONS; TRANSPORT; VALIDATION

### Citation Formats

```
Nolen, Steven Douglas.
```*The Chain-Length Distribution in Subcritical Systems*. United States: N. p., 2000.
Web. doi:10.2172/766762.

```
Nolen, Steven Douglas.
```*The Chain-Length Distribution in Subcritical Systems*. United States. doi:10.2172/766762.

```
Nolen, Steven Douglas. Thu .
"The Chain-Length Distribution in Subcritical Systems". United States. doi:10.2172/766762. https://www.osti.gov/servlets/purl/766762.
```

```
@article{osti_766762,
```

title = {The Chain-Length Distribution in Subcritical Systems},

author = {Nolen, Steven Douglas},

abstractNote = {The individual fission chains that appear in any neutron multiplying system provide a means, via neutron noise analysis, to unlock a wealth of information regarding the nature of the system. This work begins by determining the probability density distributions for fission chain lengths in zero-dimensional systems over a range of prompt neutron multiplication constant (K) values. This section is followed by showing how the integral representation of the chain-length distribution can be used to obtain an estimate of the system's subcritical prompt multiplication (MP). The lifetime of the chains is then used to provide a basis for determining whether a neutron noise analysis will be successful in assessing the neutron multiplication constant, k, of the system in the presence of a strong intrinsic source. A Monte Carlo transport code, MC++, is used to model the evolution of the individual fission chains and to determine how they are influenced by spatial effects. The dissertation concludes by demonstrating how experimental validation of certain global system parameters by neutron noise analysis may be precluded in situations in which the system K is relatively low and in which realistic detector efficiencies are simulated.},

doi = {10.2172/766762},

journal = {},

number = ,

volume = ,

place = {United States},

year = {2000},

month = {6}

}