Dose Rate Evaluation for the ES-3100 Package with HEU Content Using MCNP, ADVANTG, Monaco, and MAVRIC

Abstract

This paper presents a comparative study of dose rate calculations for the ES-3100 package with highly enriched uranium (HEU) content for different source configurations using the following computer codes: MCNP, Automated Variance Reduction Generator (ADVANTG)/MCNP, Monaco, and Monaco with Automated Variance Reduction using Importance Calculations (MAVRIC). The Model ES-3100 package was developed at the Y-12 National Security Complex for domestic and international transportation of Type B fissile radioactive material. In this study, six different source configurations (i.e., solid cylinder, cylindrical hemishell, cylindrical shell, rectangular plate, cylindrical rod, and cylindrical segment form) having 36 kg of HEU metal inside the package containment vessel (based on configurations in the ES-3100/HEU safety analysis report for packaging) are evaluated. Dose rates at 1 mm and 1 m from the package surfaces are calculated for these different source configurations. The MCNP and Monaco cases are run without any biasing options to accelerate the convergence. The Consistent Adjoint Driven Importance Sampling and the Forward-Weighted Consistent Adjoint Driven Importance Sampling (FW-CADIS) methods developed at the Oak Ridge National Laboratory are implemented in the ADVANTG/MCNP and MAVRIC codes to accelerate the convergence. ADVANTG generates variance reduction parameters using the Denovo code, and MCNP is used with the variance reduction parameters to accelerate the convergence. MAVRIC uses the Denovo code to construct an importance map and a biased source distribution that are supplied to Monaco to accelerate the Monte Carlo simulation. The FW-CADIS option in ADVANTG and MAVRIC is used to accelerate the convergence in this study. The accelerated convergence cases (ADVANTG/MCNP and MAVRIC) are about 100 times faster with 100 times less particle simulation than those cases run without biasing options (analog MCNP and analog Monaco). The MCNP, ADVANTG/MCNP, Monaco, and MAVRIC calculated dose rates at 1 mm and 1 m from the package surfaces for the different source configurations are compared and are found to be in general agreement.

Keywords:

• Monte Carlo calculation
• shielding evaluation
• ES-3100 package

Disclaimer

This work of authorship and those incorporated herein were prepared by Consolidated Nuclear Security, LLC (CNS) as accounts of work sponsored by an agency of the United States Government under Contract DE-NA0001942. Neither the United States Government nor any agency thereof, nor CNS, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility to any non-governmental recipient hereof for the accuracy, completeness, use made, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency or contractor thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency or contractor (other than the authors) thereof.

Acknowledgments

The author gratefully acknowledges the sincere support of Douglas E. Peplow (ORNL) in developing the Monaco and MAVRIC models. The author also acknowledges James J. Yugo (Y-12) and Scott W. Mosher (ORNL) for their support in preparing the ADVANTG input files and Richard W. Emmett (Y-12) for checking a select set of analog MCNP input/output files. Sincere acknowledgment goes to David A. Wilson (Navarro Research and Engineering) and Becky Williams (Y-12) for technical editing and manuscript preparation of this paper. The author acknowledges Samuel N. Cramer [ORNL (retired)] for exposing the author to shielding evaluation methodologies during the development of the ES-3100 package as well as introducing the capabilities of the MAVRIC and Monaco codes. The author also acknowledges Christopher J. Hurt (former University of Tennessee – Knoxville graduate student and currently ORNL employee) for his calculation support as a summer intern. The author also expresses his appreciation to Jeffrey G. Arbital (Y-12) and James C. Anderson (Y-12) for arranging funding for this work at Y-12 under contract DE-NA0001942.

This work of authorship and those incorporated herein were prepared by Consolidated Nuclear Security, LLC, as accounts of work sponsored by an agency of the United States Government under contract DE-NA0001942.

Notes

^a The Denovo, KENO-VI, MAVRIC, Monaco, and ORIGEN-S codes are part of SCALE.