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The Attila suite has a GUI driven activation capability (Fornax) that tracks the population of isotopes created through neutron activation and decay processes, compatible with both SMP (attilasolver) and DMP (severian). Fornax provides users with the capability to use the Rigorous Two-Step (R2S) method with an Attila deterministic or Attila4MC (MCNP6) based workflow. With the Attila deterministic workflow, users will have the ability to run neutron flux and activation calculations on the tetrahedral mesh and then produce gamma sources at desired decay time steps with an appropriate neutron flux strength. The gamma sources will be produced on a mesh element wise basis, and the activation gamma calculations can then be run on the same tetrahedral mesh, making for an accurate, simple and fast workflow.

Users will have the flexibility to choose regions to burn and whether to include additional report data such as radioactive isotope inventories and activity data. The Attila4MC workflow will perform cell wise activation calculations on the tetrahedral mesh, generating cell wise activation gamma sources that can be run in MCNP. These workflows provide for a simple method for visualising activation gamma contours through the use of Tecplot in the Attila software suite.

Features of Fornax include:


  • Decay chains specified in a single XML file
  • Users can modify or add decay chain data for their applications
  • User specifies which CAD/mesh regions to activate
  • Creates a unique activation source in each tetrahedral element, providing a high spatial resolution
  • Eliminates the need for a user defined activation “grid”
  • Provides unrivaled solution precision
  • Fine resolution, body-fitted activation mesh
  • No spatial homogenization
  • Intuitive post processing visualization of calculated inventories
  • Optional output of region-wise activities for waste categorization

Activation and Depletion

Performed as a 2-step process (R2S):

Step One:
Calculate neutron flux field and activation source at desired timesteps

  • Run through regular Attila neutron calculation and Fornax/ASG
  • Activation gamma source can be created at every timestep

Step Two:
Compute activation dose rate field

  • Regular Attila gamma calculation using activation gamma source file

Generic Tokamak Case Study

  • Attila calculations performed using SFSW-FENDL31d-FG cross sections and SFSW-Fornax-r2 dataset
  • ~1.2 million tetrahedral mesh elements
  • Neutron flux calculation performed with 53 neutron groups
  • 2.0E+20 n/s over 1 day, and cooling time of 30 days after final “shot”
  • Activation calculation time 20 minutes
  • Gamma shut down dose rate (SDDR) calculation performed with 42 gamma groups, 1 hr 20 minutes run time
  • Activity inventory report produced for concrete walls

FNG Activation Benchmark

Benchmark 1 to validate accuracy of dose-rate calculations after shut-down in representative ITER shielding conditions (ITER Task T-426)

  • Neutron flux and activation calculations performed using SFSW-FENDL31d-FG cross sections and SFSW-Fornax-r2 dataset
  • ~220k tetrahedral mesh elements, 3.5 cm mesh for fine spatial resolution
  • Neutron calculation performed with 175 neutron groups, calculation time ~5 hrs
  • Activation calculation time 13 minutes
  • Shut down gamma calculations performed with Transpire94g cross section, 20-30 minutes depending on timestep

Results Summary Reactions and Plots

References

  1. P. BATISTONI, M. ANGELONE, M. PILLON, L. PETRIZZI, "SINBAD Abstract NEA-1553/55 FNG-ITER Dose Rate Experiment", ENEA, 2000-2001.

Attila® is a trademark of Silver Fir Software

MCNP® and Monte Carlo N-Particle® are registered trademarks owned by Triad National Security, LLC,

manager and operator of Los Alamos National Laboratory.

SpaceClaim® is a trademark of ANSYS, Inc. Tecplot 360® is a trademark of ANSYS, Inc.

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