Neutron Shielding Near Compute
The D-3He burn is low-neutron at 5.44%, not aneutronic; that small but real neutron flux sets a bounded shielding envelope that must protect nearby compute and people.
Low-neutron, not no-neutron
The burner's dominant D-³He reaction produces mostly charged particles, but side reactions make it low-neutron, not aneutronic: about 5.44% of the fusion power leaves as neutrons. That fraction is small compared with a D-T machine, but it is not zero, and neutrons must be shielded — especially when the plant sits near sensitive compute and occupied halls.
The low neutron fraction is what makes the shielding envelope bounded rather than sprawling, and therefore what makes co-location near a campus feasible at all. A D-T source would demand far heavier shielding and a larger exclusion zone; the D-³He burn's 5.44% keeps the shield and standoff distances within what a developed site can accommodate.
The engineering task is real and stated plainly. Neutrons cause activation of nearby materials and can affect electronics, so the shielding must protect the compute from flux, keep activation within limits, and maintain safe access for operators. This is a well-understood radiation-protection problem, scaled down by the low neutron fraction, not eliminated by it.
The honest framing: 5.44% is a genuine advantage that bounds the shielding and enables urban-adjacent siting, but it is not a claim of aneutronic operation, and the safety envelope is a first-class part of any MetroVolt site.
- D-3He is low-neutron (5.44%), not aneutronic
- Neutrons require shielding even at low fraction
- Low fraction bounds the shield and enables co-location
- Activation and electronics protection are real design tasks