Syria's Nuclear Issue Takes Center Stage: What Is the Story Behind "Site 99"?

“Site 99” in Syria has returned to the forefront, after US officials revealed that the International Atomic Energy Agency (IAEA) will soon remove nuclear materials stored in a secret location within Syria, following understandings reached between the administration of US President Donald Trump and Syria and Tel Aviv. According to the US Axios website, efforts to reach an agreement to secure the nuclear materials were part of broader attempts to contain a crisis that risked escalating into a confrontation involving Israel, Syria, and possibly Turkey, due to the site’s sensitivity.

The regime of ousted President Bashar al-Assad developed a secret nuclear program centered on the “Al Kibar reactor,” which was bombed by Israel in 2007, largely destroying Syria’s nuclear program. However, several sites designated for research, development, and storage remained in place, most of them inactive.

Axios reported that Israel had closely monitored “Site 99” over the past two years, where the Assad regime had stored nuclear materials that were part of the Al Kibar reactor project. According to a US official, the nuclear materials stored at the site included “yellowcake,” along with other residues and byproducts from the Al Kibar facility.

Axios noted that the materials present cannot be used to manufacture a nuclear weapon, but could potentially be used to create a “dirty bomb”—a conventional explosive device designed to disperse radioactive material to contaminate an area rather than produce a nuclear explosion.

An Israeli official revealed that Israel bombed the entrances to the secret site shortly after the fall of the Assad regime in late 2024, to prevent access. Axios quoted a US official as saying that discussions between the United States and Israel had continued for more than a year to find the best possible approach to dealing with the secret “Site 99,” before agreeing that the optimal strategy involved obtaining the consent of the Syrian government and involving it in the removal process.