### Numerical convergence and validation of the DIMP inverse particle transport model

The data integration with modeled predictions (DIMP) model is a promising inverse radiation transport method for solving the special nuclear material (SNM) holdup problem. Unlike previous methods, DIMP is a completely passive nondestructive assay technique that requires no initial assumptions regarding the source distribution or active measurement time. DIMP predicts the most probable source location and distribution through Bayesian inference and quasi-Newtonian optimization of predicted detector re-sponses (using the adjoint transport solution) with measured responses. DIMP performs well with for-ward hemispherical collimation and unshielded measurements, but several considerations are required when using narrow-view collimated detectors. DIMP converged well to the correct source distribution as the number of synthetic responses increased. DIMP also performed well for the first experimental validation exercise after applying a collimation factor, and sufficiently reducing the source search vol-ume's extent to prevent the optimizer from getting stuck in local minima. DIMP's simple point detector response function (DRF) is being improved to address coplanar false positive/negative responses, and an angular DRF is being considered for integration with the next version of DIMP to account for highly collimated responses. Overall, DIMP shows promise for solving the SNM holdup inverse problem, especially once an improved optimization algorithm is implemented.

- Publication Date:

- Grant/Contract Number:
- NA0002576; 127981

- Type:
- Accepted Manuscript

- Journal Name:
- Nuclear Engineering and Technology

- Additional Journal Information:
- Journal Volume: 49; Journal Issue: 6; Journal ID: ISSN 1738-5733

- Publisher:
- Korean Nuclear Society

- Research Org:
- North Carolina State Univ., Raleigh, NC (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

- Sponsoring Org:
- USDOE National Nuclear Security Administration (NNSA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 42 ENGINEERING

- OSTI Identifier:
- 1426201

- Alternate Identifier(s):
- OSTI ID: 1438026

```
Nelson, Noel, and Azmy, Yousry.
```*Numerical convergence and validation of the DIMP inverse particle transport model*. United States: N. p.,
Web. doi:10.1016/j.net.2017.07.009.

```
Nelson, Noel, & Azmy, Yousry.
```*Numerical convergence and validation of the DIMP inverse particle transport model*. United States. doi:10.1016/j.net.2017.07.009.

```
Nelson, Noel, and Azmy, Yousry. 2017.
"Numerical convergence and validation of the DIMP inverse particle transport model". United States.
doi:10.1016/j.net.2017.07.009. https://www.osti.gov/servlets/purl/1426201.
```

```
@article{osti_1426201,
```

title = {Numerical convergence and validation of the DIMP inverse particle transport model},

author = {Nelson, Noel and Azmy, Yousry},

abstractNote = {The data integration with modeled predictions (DIMP) model is a promising inverse radiation transport method for solving the special nuclear material (SNM) holdup problem. Unlike previous methods, DIMP is a completely passive nondestructive assay technique that requires no initial assumptions regarding the source distribution or active measurement time. DIMP predicts the most probable source location and distribution through Bayesian inference and quasi-Newtonian optimization of predicted detector re-sponses (using the adjoint transport solution) with measured responses. DIMP performs well with for-ward hemispherical collimation and unshielded measurements, but several considerations are required when using narrow-view collimated detectors. DIMP converged well to the correct source distribution as the number of synthetic responses increased. DIMP also performed well for the first experimental validation exercise after applying a collimation factor, and sufficiently reducing the source search vol-ume's extent to prevent the optimizer from getting stuck in local minima. DIMP's simple point detector response function (DRF) is being improved to address coplanar false positive/negative responses, and an angular DRF is being considered for integration with the next version of DIMP to account for highly collimated responses. Overall, DIMP shows promise for solving the SNM holdup inverse problem, especially once an improved optimization algorithm is implemented.},

doi = {10.1016/j.net.2017.07.009},

journal = {Nuclear Engineering and Technology},

number = 6,

volume = 49,

place = {United States},

year = {2017},

month = {9}

}