The International Atomic Energy Agency (IAEA) reported on May 11 that "fluctuations" of enrichment levels at Iran's Natanz nuclear facility increased the fissile purity of uranium enriched there to up to 63 percent, citing environmental samples taken on April 22. Iran had begun enriching uranium to 60 percent purity in April. The IAEA report also noted that Iran was using a cascade of 27 IR-5 and 30 IR-6 centrifuges to enrich depleted uranium left over from that process to 5 percent purity. The Joint Comprehensive Plan of Action (JCPOA), the 2015 international agreement placing restrictions on Iran's nuclear program, requires that Iran enrich uranium to no more than 3.67 percent purity.