Speculative upper-bound answer based on @JonCuster's comment: No more than 6.5 Kg / year$6.5 ~\frac{\mathrm{kg}}{\text{year}}$.
Suppose for exaggeration that Iran can use 5%$5\%$ of all Technetium used in the world (this circumvents the need to estimate things about dose policies, distribution of imaging scans etc.)
Suppose also that with HEU you need no more fuel than with LEU (this is a completely baseless assumption on my part, Physicists please correct me.)
Suppose that fuel use grows more-or-less linearly with reactor energy output.
@JonCuster reports that the two reactors which have so far provided the global Technetium needs were 135 MW$135 ~\mathrm{MW}$ and 60 MW$60 ~\mathrm{MW}$ respectively, and the smaller one used 40 Kg / year$40 ~\frac{\mathrm{kg}}{\text{year}}$ of Uranium.
By our assumptions, the two reactors together used (1+135/60)40 = 3.2540 = 130 Kg / year$\left( 1 + \frac{135}{60} \right) \cdot 40 ~\frac{\mathrm{kg}}{\text{year}} = 3.25 \cdot 40 ~\frac{\mathrm{kg}}{\text{year}} = 130 ~\frac{\mathrm{kg}}{\text{year}}$ of Uranium. 5%$5\%$ of this is 6.5 Kg / year$6.5 ~\frac{\mathrm{kg}}{\text{year}}$. So, under our assumptions, Iran should not need more than 6.5 Kg$6.5 ~\mathrm{kg}$ of 60%$60\%$-enriched Uranium each year for Technetium production.