Two materials for two different problems
Rapid 3DShield comes in two materials because radiation isn't one thing. Photons (X-rays and gamma rays) and neutrons interact with matter in completely different ways, so each needs a different shield.
Tungsten for X-rays and gamma rays
Photons are stopped by dense, high-atomic-number material. Tungsten (Z = 74) is one of the densest metals there is. Rapid 3DShield Tungsten carries 88–94% tungsten, and the filament is 7.80–9.20 g/cc. Parts are used straight off the printer as a lead-free shield.
Boron carbide for neutrons
Neutrons carry no charge and pass through dense metals relatively easily. Boron-10 absorbs slow (thermal) neutrons very strongly, with a cross-section of about 3,840 barns. Rapid 3DShield Boron Carbide is 50–60% B₄C at 1.30–1.50 g/cc. At mid-spec loading, a few millimetres of fully dense print absorbs nearly all of a thermal-neutron beam (calculated; see the boron carbide guide).
Side by side
| Rapid 3DShield Tungsten | Rapid 3DShield Boron Carbide | |
|---|---|---|
| Stops | X-rays and gamma rays | Thermal neutrons |
| Loading | 88–94% tungsten | 50–60% boron carbide |
| Filament density | 7.80–9.20 g/cc | 1.30–1.50 g/cc |
| Binder | PLA-based; prints similar to PLA | PLA-based; prints similar to PLA |
| Nozzle | 0.8 mm hardened steel | 0.6 mm hardened steel |
| Drying | Do not dry (degrades the binder) | Do not dry (degrades the binder) |
| Sintering | None. Used as printed | None. Used as printed |
| Formats | 1.75 / 2.85 mm; 0.5, 1, 3, 5 kg spools; 1, 3, 5 kg pellets | 1.75 / 2.85 mm; 0.25, 0.5 kg spools; 1 kg pellets |
Mixed fields
Where both are present, put boron carbide on the neutron side and tungsten behind it. The tungsten also absorbs the 0.48 MeV gamma ray that boron-10 gives off in most captures. Fast neutrons need a hydrogen-rich moderator first; boron works best once neutrons are slow.
Working on a shielding program or ordering by PO? Email [email protected]. · Tungsten filament · Boron carbide filament