Assuming Astron will have around 200m shares on issue by the...

Assuming Astron will have around 200m shares on issue by the time they get the mine into production,
Phase 2 NPV is stated at AUD $2.2bn for the Donald mine. Astron will have sold half to Energy Fuels, retaining the other half meaning ATR's Donald mine NPV = $1.1bn for Phase 2. Divide by 200m shares and there's your $5/share.

Upon signing the agreement one would expect wages, consultants fees and project o'head will be equally shared by both partners. Hopefully this will limit too much further equity having to be raised by ATR. Perhaps they will sell down some Energy Fuels shares if necessary to fund those costs.

The NPV figure is independent of how much Energy Fuels paid for their half share. If we further assume that internal cashflows from Phase 1 will pay for the mine expansion, and the cash received now from Energy Fuels and debt to be raised will be sufficient to finance everything to production, then as investors we will need to see how well the joint venture can manage operational risk. If they can get on top of certain key variables, then the likely best case could even approach $10/share for Astron.

OTOH the stock could be close to worthless if it all turns pear-shaped.