Feedstock The process starts with uranium hexafluoride (UF₆) enriched to 60% U-235. Iran reportedly had around 400 kg, according to the NYT reporting cited by Faytuks.
Centrifuge Cascades To raise the enrichment from 60% to 90%, you’d need:
Fewer centrifuges than earlier stages.
Possibly 1–2 cascades of ~160–200 IR-6 machines could do the job in 2–3 weeks, depending on efficiency and operational runtime.
Product Output Assuming no material losses, you could produce around 25–35 kg of 90% enriched uranium—enough for at least one nuclear weapon, depending on the design and engineering.
Technical Considerations
The SWU cost for this enrichment step is modest: ~25–30 SWU per kg of 90% product.
The tails assay (waste enrichment level) would likely be adjusted to optimize throughput and limit material loss—typically ~10–20% in this phase.
Strategic Implication
This is precisely why 60% stockpiles set off alarm bells: once a country has this material, the technical and time barrier to weapons-grade material shrinks dramatically.
Key Points:
The SWU requirement for this enrichment step is ~25–30 per kg of 90% U-235.
Enrichment is most SWU-efficient at higher levels; fewer centrifuges are needed per unit gain.
Tails assay (leftover enrichment) is typically high in this final stage to reduce loss of valuable U-235, which is why most of the original 400 kg ends up in the tails.
The timeline is short: a few weeks or less, assuming operational centrifuge cascades.
The War Powers Resolution of 1973—passed over Nixon’s veto—does not require an imminent threat to the United States as a condition for the president to introduce U.S. forces into “hostilities.” Instead, the statutory language hinges on two key triggers: actual hostilities or situations where “imminent involvement in hostilities is clearly indicated by the circumstances”.
The relevant section, 50 U.S.C. § 1541(c), states that the president’s powers as Commander-in-Chief may only be exercised to introduce forces into hostilities under one of three conditions:
A declaration of war,
Specific statutory authorization, or
A national emergency created by an attack on the U.S., its territories, possessions, or armed forces.
That third clause is likely the source of the “imminent threat” interpretation—but it’s not a blanket requirement for all uses of force. Rather, it’s one of the exceptions that allows unilateral presidential action without prior congressional approval.
The phrase “hostilities” itself was deliberately left undefined in the statute, and the legislative history shows that Congress debated this ambiguity. Some members wanted a broader definition to include any use of force, while others feared that would unduly restrict the president. The final compromise left it vague—perhaps intentionally—so that future administrations and courts would have to interpret it case by case3.
Legislative history of the War Powers Resolution as passed by the 93rd Congress in 1973.
Origins and Intent The War Powers Resolution (H.J.Res. 542) was introduced by Rep. Clement Zablocki (D-WI) on May 3, 1973, in direct response to the Vietnam War and the perceived erosion of congressional authority over war-making. The House Foreign Affairs Committee reported it out with amendments on June 15, 1973, and it passed the House on July 18 by a vote of 244–170. The Senate followed on July 20, passing it with amendments 75–20. After resolving differences in conference, both chambers approved the final version in October. President Nixon vetoed it on October 24, but Congress overrode the veto on November 7, 1973.
Key Legislative Language The phrase you’re focused on—“hostilities or situations where imminent involvement in hostilities is clearly indicated by the circumstances”—was a compromise. Some members of Congress wanted a broader definition to include any deployment of armed forces, while others feared that would unduly restrict the president’s flexibility. The final language was intentionally ambiguous to allow for case-by-case interpretation.
The legislative record shows that Congress was particularly concerned with avoiding another situation like the Gulf of Tonkin Resolution, which had been used to justify a broad and prolonged military engagement without meaningful congressional oversight. The House and Senate debates reflect a desire to reassert congressional authority without completely tying the president’s hands in emergencies.
Committee Reports and Debates The House Report (H. Rept. 93-287) and the Senate debates contain rich discussions on the meaning of “hostilities.” Some legislators argued it should include any situation where U.S. forces are exchanging fire, while others suggested it should be limited to declared wars or large-scale combat. The ambiguity was seen as a feature, not a bug—intended to preserve flexibility while still requiring consultation and reporting.
Conclusion
I would argue that we have been engaged in hostilities with Iran since the revolutionary regime seized our embassy and held our diplomatic personnel. We have listed it as a State Sponsor of Terror since 1984 and the president would be authorized to use military force to address the ongoing threat that poses.
TimInHonolulu 