## Shutdown Dose Rate Analysis Using the Multi-Step CADIS Method

## Abstract

The Multi-Step Consistent Adjoint Driven Importance Sampling (MS-CADIS) hybrid Monte Carlo (MC)/deterministic radiation transport method was proposed to speed up the shutdown dose rate (SDDR) neutron MC calculation using an importance function that represents the neutron importance to the final SDDR. This work applied the MS-CADIS method to the ITER SDDR benchmark problem. The MS-CADIS method was also used to calculate the SDDR uncertainty resulting from uncertainties in the MC neutron calculation and to determine the degree of undersampling in SDDR calculations because of the limited ability of the MC method to tally detailed spatial and energy distributions. The analysis that used the ITER benchmark problem compared the efficiency of the MS-CADIS method to the traditional approach of using global MC variance reduction techniques for speeding up SDDR neutron MC calculation. Compared to the standard Forward-Weighted-CADIS (FW-CADIS) method, the MS-CADIS method increased the efficiency of the SDDR neutron MC calculation by 69%. The MS-CADIS method also increased the fraction of nonzero scoring mesh tally elements in the space-energy regions of high importance to the final SDDR.

- Authors:

- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

- Publication Date:

- Research Org.:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

- Sponsoring Org.:
- USDOE

- OSTI Identifier:
- 1214480

- Grant/Contract Number:
- AC05-00OR22725

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Fusion Science and Technology

- Additional Journal Information:
- Journal Volume: 68; Journal Issue: 3; Journal ID: ISSN 1536-1055

- Publisher:
- American Nuclear Society

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY

### Citation Formats

```
Ibrahim, Ahmad M., Peplow, Douglas E., Peterson, Joshua L., and Grove, Robert E. Shutdown Dose Rate Analysis Using the Multi-Step CADIS Method. United States: N. p., 2015.
Web. doi:10.13182/FST15-123.
```

```
Ibrahim, Ahmad M., Peplow, Douglas E., Peterson, Joshua L., & Grove, Robert E. Shutdown Dose Rate Analysis Using the Multi-Step CADIS Method. United States. doi:10.13182/FST15-123.
```

```
Ibrahim, Ahmad M., Peplow, Douglas E., Peterson, Joshua L., and Grove, Robert E. Thu .
"Shutdown Dose Rate Analysis Using the Multi-Step CADIS Method". United States. doi:10.13182/FST15-123. https://www.osti.gov/servlets/purl/1214480.
```

```
@article{osti_1214480,
```

title = {Shutdown Dose Rate Analysis Using the Multi-Step CADIS Method},

author = {Ibrahim, Ahmad M. and Peplow, Douglas E. and Peterson, Joshua L. and Grove, Robert E.},

abstractNote = {The Multi-Step Consistent Adjoint Driven Importance Sampling (MS-CADIS) hybrid Monte Carlo (MC)/deterministic radiation transport method was proposed to speed up the shutdown dose rate (SDDR) neutron MC calculation using an importance function that represents the neutron importance to the final SDDR. This work applied the MS-CADIS method to the ITER SDDR benchmark problem. The MS-CADIS method was also used to calculate the SDDR uncertainty resulting from uncertainties in the MC neutron calculation and to determine the degree of undersampling in SDDR calculations because of the limited ability of the MC method to tally detailed spatial and energy distributions. The analysis that used the ITER benchmark problem compared the efficiency of the MS-CADIS method to the traditional approach of using global MC variance reduction techniques for speeding up SDDR neutron MC calculation. Compared to the standard Forward-Weighted-CADIS (FW-CADIS) method, the MS-CADIS method increased the efficiency of the SDDR neutron MC calculation by 69%. The MS-CADIS method also increased the fraction of nonzero scoring mesh tally elements in the space-energy regions of high importance to the final SDDR.},

doi = {10.13182/FST15-123},

journal = {Fusion Science and Technology},

number = 3,

volume = 68,

place = {United States},

year = {2015},

month = {1}

}