I haven’t actually checked into data sheets for silicon(e) coolant. But from what I’ve seen, none of the Borane family plays nice, either. The downside of pentaborane is that it reacts violently with air, which leads me to expect at least a double-walled fuel/valving design to keep it reasonably safe for highly trained servicing personnel. Probably nitrogen charged outer shell and pressure gauge.
But maybe a pressurized fuel system would only need an actual vacuum for the first shot of any run session.
