# REFLECTION OF FAST NEUTRONS FROM WATER

## Abstract

The backscattering of fast (0.3, 1, 3, 6, 9, and 14 Mev) neutrons from a semi-infinite water medium was calculated by the Monte Carlo method. The in= formation obtained includes the joint angular and spectral distribution of the reflected neutrons, the dependence of the number albedo and energy albedo on the source energy and obliquity, and the contributions to the albedo of successive orders of scattering. The spectra were calculated down to epithermal energies ( approximately 0.5 ev). The results for each case are based on the analysis of 3,000 neutron histories, generated wiih ihe use of an IBM-704 computer. In the random sampling, elastic scattering from hydrogen and oxygen, inelastic scattering from oxygen, and absorption due to n- alpha and n-p processes were taken into account. The cross sections for some of these interactions are not well known. Parallel calculations with different assumptions about the cross sections were made in order io estimate how sensitively the albedo depends on the cross sections. A self-contained description of the Monte Carlo method, its application to the calculation of radiation diffusion and in particular to the neutron albedo problem are included. Emphnsis is placed on the technique of correlated sampling which makesmore »

- Authors:

- Publication Date:

- Research Org.:
- Originating Research Org. not identified

- OSTI Identifier:
- 4197957

- NSA Number:
- NSA-14-000749

- Resource Type:
- Journal Article

- Journal Name:
- J. Research Natl. Bur. Standards

- Additional Journal Information:
- Journal Volume: Vol: 63A; Other Information: Orig. Receipt Date: 31-DEC-60

- Country of Publication:
- Country unknown/Code not available

- Language:
- English

- Subject:
- PHYSICS; ABSORPTION- ALBEDO- ALPHA PARTICLES- ANGULAR DISTRIBUTION- COMPUTERS- CROSS SECTIONS- DIFFUSION- ENERGY- ENERGY RANGE- EPITHERMAL NEUTRONS- ERRORS- FAST NEUTRONS- IBM 704- INTERACTIONS- MONTE CARLO METHOD- NEUTRON BEAMS- NUCLEAR REACTIONS- PROTONS- REFLECTION- SAMPLING- SCATTERING- SPECTRA- WATER; ALBEDO- ANGULAR DISTRIBUTION- COMPUTERS- CROSS SECTIONS- DIFFUSION- ELASTIC SCATTERING- ENERGY- ENERGY RANGE- EPITHERMAL NEUTRONS- ERRORS- FAST NEUTRONS- HYDROGEN- IBM 704- INELASTIC SCATTERING- INTERACTIONS- MONTE CARLO METHOD- OXYGEN- REFLECTION- SAMPLING- SCATTERING- SPECTRA- WATER

### Citation Formats

```
Berger, M J, and Cooper, J W.
```*REFLECTION OF FAST NEUTRONS FROM WATER*. Country unknown/Code not available: N. p., 1959.
Web. doi:10.6028/jres.063A.006.

```
Berger, M J, & Cooper, J W.
```*REFLECTION OF FAST NEUTRONS FROM WATER*. Country unknown/Code not available. doi:10.6028/jres.063A.006.

```
Berger, M J, and Cooper, J W. Tue .
"REFLECTION OF FAST NEUTRONS FROM WATER". Country unknown/Code not available. doi:10.6028/jres.063A.006.
```

```
@article{osti_4197957,
```

title = {REFLECTION OF FAST NEUTRONS FROM WATER},

author = {Berger, M J and Cooper, J W},

abstractNote = {The backscattering of fast (0.3, 1, 3, 6, 9, and 14 Mev) neutrons from a semi-infinite water medium was calculated by the Monte Carlo method. The in= formation obtained includes the joint angular and spectral distribution of the reflected neutrons, the dependence of the number albedo and energy albedo on the source energy and obliquity, and the contributions to the albedo of successive orders of scattering. The spectra were calculated down to epithermal energies ( approximately 0.5 ev). The results for each case are based on the analysis of 3,000 neutron histories, generated wiih ihe use of an IBM-704 computer. In the random sampling, elastic scattering from hydrogen and oxygen, inelastic scattering from oxygen, and absorption due to n- alpha and n-p processes were taken into account. The cross sections for some of these interactions are not well known. Parallel calculations with different assumptions about the cross sections were made in order io estimate how sensitively the albedo depends on the cross sections. A self-contained description of the Monte Carlo method, its application to the calculation of radiation diffusion and in particular to the neutron albedo problem are included. Emphnsis is placed on the technique of correlated sampling which makes possible an accarate estimate of albedo differences resulting from different assumptions about the cross sections. The random sampling computations were supplemented by analytical calculations of the single-scattering albedo. This was useful for an understanding of the Monte Carlo results because a considerable fraction of the reflected neutrons return after only one collision. (auth)},

doi = {10.6028/jres.063A.006},

journal = {J. Research Natl. Bur. Standards},

number = ,

volume = Vol: 63A,

place = {Country unknown/Code not available},

year = {1959},

month = {9}

}