# Space, energy and anisotropy effects on effective cross sections and diffusion coefficients in the resonance region

## Abstract

Present methods used in reactor analysis do not include adequately the effect of anisotropic scattering in the calculation of resonance effective cross sections. Also the assumption that the streaming term ..cap omega...del Phi is conserved when the total, absorption and transfer cross sections are conserved, is bad because the leakage from a heterogeneous cell will not be conserved and is strongly anisotropic. A third major consideration is the coupling between different regions in a multiregion reactor; currently this effect is being completely ignored. To assess the magnitude of these effects, a code based on integral transport formalism with linear anisotropic scattering was developed. Also, a more adequate formulation of the diffusion coefficient in a heterogeneous cell was derived. Two reactors, one fast, ZPR-6/5, and one thermal, TRX-3, were selected for the study. The study showed that, in general, the inclusion of linear scattering anisotropy increases the cell effective capture cross section of U-238. The increase was up to 2% in TRX-3 and 0.5% in ZPR-6/5. The effect on the multiplication factor was -0.003% ..delta..k/k for ZPR-6/5 and -0.05% ..delta..k/k for TRX-3. For the case of the diffusion coefficient, the combined effect of heterogeneity and linear anisotropy gave an increase ofmore »

- Authors:

- Publication Date:

- Research Org.:
- Georgia Inst. of Tech., Atlanta (USA)

- OSTI Identifier:
- 5517386

- Resource Type:
- Thesis/Dissertation

- Resource Relation:
- Other Information: Thesis (Ph. D.)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; THERMAL REACTORS; COMPUTERIZED SIMULATION; ZPR-6 REACTOR; ANISOTROPY; CROSS SECTIONS; DIFFUSION; REACTOR CELLS; RESONANCE; SCATTERING; URANIUM 238; ACTINIDE ISOTOPES; ACTINIDE NUCLEI; ALPHA DECAY RADIOISOTOPES; EPITHERMAL REACTORS; EVEN-EVEN NUCLEI; EXPERIMENTAL REACTORS; FAST REACTORS; HEAVY NUCLEI; ISOTOPES; NUCLEI; RADIOISOTOPES; REACTORS; RESEARCH AND TEST REACTORS; SIMULATION; URANIUM ISOTOPES; YEARS LIVING RADIOISOTOPES; ZERO POWER REACTORS; 220600* - Nuclear Reactor Technology- Research, Test & Experimental Reactors

### Citation Formats

```
Meftah, B.
```*Space, energy and anisotropy effects on effective cross sections and diffusion coefficients in the resonance region*. United States: N. p., 1982.
Web.

```
Meftah, B.
```*Space, energy and anisotropy effects on effective cross sections and diffusion coefficients in the resonance region*. United States.

```
Meftah, B. Fri .
"Space, energy and anisotropy effects on effective cross sections and diffusion coefficients in the resonance region". United States.
```

```
@article{osti_5517386,
```

title = {Space, energy and anisotropy effects on effective cross sections and diffusion coefficients in the resonance region},

author = {Meftah, B.},

abstractNote = {Present methods used in reactor analysis do not include adequately the effect of anisotropic scattering in the calculation of resonance effective cross sections. Also the assumption that the streaming term ..cap omega...del Phi is conserved when the total, absorption and transfer cross sections are conserved, is bad because the leakage from a heterogeneous cell will not be conserved and is strongly anisotropic. A third major consideration is the coupling between different regions in a multiregion reactor; currently this effect is being completely ignored. To assess the magnitude of these effects, a code based on integral transport formalism with linear anisotropic scattering was developed. Also, a more adequate formulation of the diffusion coefficient in a heterogeneous cell was derived. Two reactors, one fast, ZPR-6/5, and one thermal, TRX-3, were selected for the study. The study showed that, in general, the inclusion of linear scattering anisotropy increases the cell effective capture cross section of U-238. The increase was up to 2% in TRX-3 and 0.5% in ZPR-6/5. The effect on the multiplication factor was -0.003% ..delta..k/k for ZPR-6/5 and -0.05% ..delta..k/k for TRX-3. For the case of the diffusion coefficient, the combined effect of heterogeneity and linear anisotropy gave an increase of up to 29% in the parallel diffusion coefficient of TRX-3 and 5% in the parallel diffusion coefficient of ZPR-6/5. In contrast, the change in the perpendicular diffusion coefficient did not exceed 2% in both systems.},

doi = {},

journal = {},

number = ,

volume = ,

place = {United States},

year = {Fri Jan 01 00:00:00 EST 1982},

month = {Fri Jan 01 00:00:00 EST 1982}

}