Basically the EU+3 group agreed to be a supplier of last resort for 19.75%-enriched uranium, in limited quantities, and only for the Tehran reactor. In return Iran agreed not to produce 19.75%-enriched uranium locally.
[58.] All uranium oxide enriched to between 5% and 20% will be fabricated into fuel plates
for the Tehran Research Reactor or transferred, based on a commercial transaction,
outside of Iran or diluted to an enrichment level of 3.67% or less. Scrap oxide and other
forms not in plates that cannot be fabricated into TRR fuel plates will be transferred,
based on a commercial transaction, outside of Iran or diluted to an enrichment level of
3.67% or less. In case of future supply of 19.75% enriched uranium oxide (U3O8) for
TRR fuel plates fabrication, all scrap oxide and other forms not in plates that cannot be
fabricated into TRR fuel plates, containing uranium enriched to between 5% and 20%,
will be transferred, based on a commercial transaction, outside of Iran or diluted to an
enrichment level of 3.67% or less within 6 months of its production. Scrap plates will be
transferred, based on a commercial transaction, outside Iran. The commercial
transactions should be structured to return an equivalent amount of natural uranium to
Iran. For 15 years, Iran will not build or operate facilities for converting fuel plates or
scrap back to UF6.
[...]
[60]. Iran will seek to enter into a commercial contract with entities outside Iran for the
purchase of fuel for the TRR and enriched uranium targets. The E3/EU+3 will facilitate,
as needed, the conclusion and implementation of this contract. In the case of lack of
conclusion of a contract with a fuel supplier, E3/EU+3 will supply a quantity of 19.75%
enriched uranium oxide (U3O8) and deliver to Iran, exclusively for the purpose of
fabrication in Iran of fuel for the TRR and enriched uranium targets for the lifetime of the
reactor. This 19.75% enriched uranium oxide (U3O8) will be supplied in increments no
greater than approximately 5 kg and each new increment will be provided only when the
previous increment of this material has been verified by the IAEA to have been mixed with aluminum to make fuel for the TRR or fabricated into enriched uranium targets. Iran
will notify the E3/EU+3 within 2 year before the contingency of TRR fuel will be
exhausted in order to have the uranium oxide available 6 months before the end of the 2
year period.
There are also some rather generic promises in the agreement that EU+3 will help Iran with other nuclear medicine projects (in annex III E), including the acquisition of a new cyclotron.
According to some commentators, the two issues are connected:
Upon reading the JCPA, it is surprising how much of the document deals with the matter of radioisotope production in one fashion or another. [...]
The JCPA explicitly seeks to shift radioisotope production from one mode—nuclear research reactors—to another—particle accelerators. The reason is simple: to reduce or eliminate Iran’s use of highly enriched uranium (HEU) targets and nuclear research reactors to produce radioisotopes. [...]
This is no small task: research reactors produce four-fifths of man-made radioisotopes worldwide. The remainder is produced by devices called particle accelerators—either circular ones called cyclotrons, or less commonly, straight or “linear” accelerators known as LINACS.
