# Comparison of Experimental Methods for Estimating Matrix Diffusion Coefficients for Contaminant Transport Modeling

## Abstract

Diffusion cell and diffusion wafer experiments were conducted to compare methods for estimating matrix diffusion coefficients in rock core samples from Pahute Mesa at the Nevada Nuclear Security Site (NNSS). A diffusion wafer method, in which a solute diffuses out of a rock matrix that is pre-saturated with water containing the solute, is presented as a simpler alternative to the traditional through-diffusion (diffusion cell) method. Both methods yielded estimates of matrix diffusion coefficients that were within the range of values previously reported for NNSS volcanic rocks. The difference between the estimates of the two methods ranged from 14 to 30%, and there was no systematic high or low bias of one method relative to the other. From a transport modeling perspective, these differences are relatively minor when one considers that other variables (e.g., fracture apertures, fracture spacings) influence matrix diffusion to a greater degree and tend to have greater uncertainty than diffusion coefficients. For the same relative random errors in concentration measurements, the diffusion cell method yields diffusion coefficient estimates that have less uncertainty than the wafer method. However, the wafer method is easier and less costly to implement and yields estimates more quickly, thus allowing a greater number ofmore »

- Authors:

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

- Publication Date:

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

- Sponsoring Org.:
- USDOE Office of Environmental Management (EM)

- OSTI Identifier:
- 1407916

- Report Number(s):
- LA-UR-17-30221

- DOE Contract Number:
- AC52-06NA25396

- Resource Type:
- Technical Report

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION; Diffusion coefficients

### Citation Formats

```
Telfeyan, Katherine Christina, Ware, Stuart Douglas, Reimus, Paul William, and Birdsell, Kay Hanson.
```*Comparison of Experimental Methods for Estimating Matrix Diffusion Coefficients for Contaminant Transport Modeling*. United States: N. p., 2017.
Web. doi:10.2172/1407916.

```
Telfeyan, Katherine Christina, Ware, Stuart Douglas, Reimus, Paul William, & Birdsell, Kay Hanson.
```*Comparison of Experimental Methods for Estimating Matrix Diffusion Coefficients for Contaminant Transport Modeling*. United States. doi:10.2172/1407916.

```
Telfeyan, Katherine Christina, Ware, Stuart Douglas, Reimus, Paul William, and Birdsell, Kay Hanson. Mon .
"Comparison of Experimental Methods for Estimating Matrix Diffusion Coefficients for Contaminant Transport Modeling". United States.
doi:10.2172/1407916. https://www.osti.gov/servlets/purl/1407916.
```

```
@article{osti_1407916,
```

title = {Comparison of Experimental Methods for Estimating Matrix Diffusion Coefficients for Contaminant Transport Modeling},

author = {Telfeyan, Katherine Christina and Ware, Stuart Douglas and Reimus, Paul William and Birdsell, Kay Hanson},

abstractNote = {Diffusion cell and diffusion wafer experiments were conducted to compare methods for estimating matrix diffusion coefficients in rock core samples from Pahute Mesa at the Nevada Nuclear Security Site (NNSS). A diffusion wafer method, in which a solute diffuses out of a rock matrix that is pre-saturated with water containing the solute, is presented as a simpler alternative to the traditional through-diffusion (diffusion cell) method. Both methods yielded estimates of matrix diffusion coefficients that were within the range of values previously reported for NNSS volcanic rocks. The difference between the estimates of the two methods ranged from 14 to 30%, and there was no systematic high or low bias of one method relative to the other. From a transport modeling perspective, these differences are relatively minor when one considers that other variables (e.g., fracture apertures, fracture spacings) influence matrix diffusion to a greater degree and tend to have greater uncertainty than diffusion coefficients. For the same relative random errors in concentration measurements, the diffusion cell method yields diffusion coefficient estimates that have less uncertainty than the wafer method. However, the wafer method is easier and less costly to implement and yields estimates more quickly, thus allowing a greater number of samples to be analyzed for the same cost and time. Given the relatively good agreement between the methods, and the lack of any apparent bias between the methods, the diffusion wafer method appears to offer advantages over the diffusion cell method if better statistical representation of a given set of rock samples is desired.},

doi = {10.2172/1407916},

journal = {},

number = ,

volume = ,

place = {United States},

year = {Mon Nov 06 00:00:00 EST 2017},

month = {Mon Nov 06 00:00:00 EST 2017}

}