Israel and Iran agreed to a dramatic ceasefire on the 24th (local time), bringing an end to the clashes, but the whereabouts of Iran's high-enriched uranium, which sparked the war, remain elusive even after the U.S. airstrikes.
Rafael Grossi, Director General of the International Atomic Energy Agency (IAEA), reported to the international community that "there were no radiation leaks from all three targeted nuclear facilities."
The Saudi Arabian Nuclear Regulatory Commission also noted, "No radiation effects were detected in the Arab and Gulf regions after the U.S. military targeted Iranian nuclear facilities."
According to military experts and intelligence officials, Iran is suspected of having meticulously concealed weapon-grade uranium in deep underground bunkers and secret tunnel networks in the Zagros Mountains after transferring it prior to the airstrikes.
Foreign media outlets such as Bloomberg and The Guardian drew attention to "16 trucks" captured by satellites just before the airstrikes.
On the 24th, satellite photo analysis firm Maxar Technologies reported that on the 20th, two days prior to the U.S. airstrike, trucks appeared and then disappeared on the road leading to Iran's Fordow nuclear facility.
Experts speculated that these trucks were transporting the nuclear material hexafluoride (UF6) gas. Uranium enriched to 60% surprisingly has a small volume, and Iran could transport the equivalent of 10 nuclear weapons in special metal containers.
Jeffrey Lewis, a prominent nonproliferation expert at the Monterey Institute of International Studies, analyzed, "The trucks were clearly seen loading something out of the facility just before the airstrikes," adding that "it is very likely that the entire enriched uranium storage was moved."
There is a prediction that Iran, realizing the possibility of a preemptive strike by the U.S., made a preemptive move to divert the enriched uranium.
However, media reports indicated that the final destinations of these trucks could not be fully tracked by satellite imagery alone. The U.S. administration is aware of these circumstances as well.
David Albright, a former UN nuclear weapons inspector and director of the Institute for Science and International Security (ISIS), expressed concerns during a CNN interview on the 24th, stating, "U.S. intelligence agencies also recognize that Iran has moved some uranium and that they do not know where it is."
Experts identified the underground nuclear facilities constructed in the mountainous region 4 km south of the Natanz area, Iran's largest nuclear site, as a strong candidate for new uranium concealment.
This area, nicknamed Pickaxe Mountain, has a massive underground nuclear facility that was first revealed in 2023.
According to Bloomberg, this facility is located near a depth of 100 meters (330 feet), deeper than the existing Fordow facility (80-90 meters underground). Even the U.S.'s most powerful bunker buster bomb, the GBU-57, cannot guarantee destruction in a single strike at that depth.
Iran accumulated knowledge in constructing underground fortifications during the eight-year war with Iraq in the 1980s. Subsequently, it actively used this technology to protect its nuclear program. The Fordow facility is an example where the Islamic Revolutionary Guard Corps (IRGC) underground missile base was converted into a nuclear facility.
Experts speculated that Iran utilized the network of underground tunnels it has built like a spider's web over decades to implement a "multi-layered defense" strategy, dispersing uranium to various locations.
Underground tunnels near the Isfahan nuclear facility and secret military bases managed by the Revolutionary Guard disguised as civilian facilities are also considered additional hiding places. These facilities have regular truck traffic, making it difficult to predict the movements of enriched uranium.
U.S. Vice President J.D. Vance stated on Fox News on the 24th, "Where the uranium is located is no longer an important question. Our goal is to eliminate Iran's uranium enrichment capabilities."
However, it faced criticism for effectively admitting a failure to secure intelligence.
Experts expressed concern that Iran might embark on "stealth nuclear development" using the concealed 60% enriched uranium. According to Israeli claims, 60% enriched uranium can be quickly processed to achieve the 90% concentration needed for nuclear weapons.
The James Martin Center for Nonproliferation Studies warned, "There is a significant possibility that Iran could establish secret enrichment facilities in inconspicuous buildings like warehouses."