NRIC Virtual Test Bed: tritium in a divertor monoblock during pulsed operation (TMAP8).

A transient 2D finite-element demonstration published in the NRIC Virtual Test Bed: coupled heat conduction and tritium transport with trapping and release through three solid materials over up to fifty 1,600 s plasma cycles, reproducing figures from a 2024 Fusion Engineering and Design paper. It is tagged as a demonstration, intended as a safety-analysis input rather than a validated prediction.

Relationship to fusion

Magnetic-confinement fusion: an ITER-like tokamak divertor monoblock under pulsed heat and tritium flux. For an inertial-fusion chamber this is analogous only, not validating: the shared physics is hydrogen-isotope diffusion, trapping and permeation in metals under cyclic thermal loads, but geometry, materials, plasma-contact mechanism, flux magnitudes and time scales differ.

1. One TMAP8 input file (divertor_monoblock.i) with the mesh generated in-file: 36 sectors, radii 6, 7.5 and 8.5 mm, 28 mm pitch, half domain with symmetry
2. Plasma cycle: 100 s ramp-up, 400 s flat-top, 100 s ramp-down, 1,000 s dwell; end time 8.0e4 s
3. Heat flux 10 MW/m2 at flat-top on the plasma-facing surface; coolant wall temperature 552 K at flat-top and 300 K in dwell
4. Tritium surface flux of 5.0e20 m-2 s-1 entering the first mesh layer (0.1 % of the incident flux)
5. Material diffusivities, solubilities, trap densities and detrapping energies for tungsten, copper and CuCrZr
6. Run per the VTB instructions: tmap8-opt -i divertor_monoblock.i

• Time histories of mobile, trapped and total tritium inventory in each material
• Tritium permeation flux through the coolant-tube wall and release flux at the plasma-facing surface
• Temperature at the top surface and at the tube wall; field output at selected cycle times
• Figures reproducing the 2024 paper's temperature, inventory and field plots

• 2D cross-section with mirror symmetry; coolant replaced by a prescribed wall temperature and near-zero tritium concentration
• Plasma implantation and surface recombination simplified to a fixed surface flux into the first mesh layer
• One trap population per material with constant density; relatively low detrapping energies chosen to keep run time down
• Chemical-potential equilibrium at material interfaces; no neutron damage, transmutation or thermomechanics
• The VTB page notes a mismatch between some documented detrapping energies and the active input values

TMAP8

devel branch (no tagged releases) · Must be built separately; the Virtual Test Bed does not vendor it as a submodule. github.com ↗

MOOSE

Virtual Test Bed submodule · Heat transfer module required; PETSc and MPI through MOOSE. github.com ↗

Virtual Test Bed repository

devel HEAD 33898f60853e49773cd119cf93140e1b31a690c6 (2026-10-08) github.com ↗