I explained in another comment the details and challenges of production. In short, scaling up is difficult and requires either special rods that produce 1.2 grams per 10-foot rod per 500 days of irradiation in a light-water reactor or else heavy water reactors that can create up to 130 grams per 700 MW reactor per year. It's extremely inefficient either way.

Lithium blankets are being researched, but they're not yet proven.