June 27, 2025 • 9 mins
Iran’s highly enriched uranium was last seen by UN nuclear monitors a few days before the start of Israel’s bombing campaign on June 13. Its whereabouts are unknown for now, a major cause of concern for experts at the International Atomic Energy Agency. How dangerous is this uranium, and how does nuclear diplomacy proceed from here? Our reporter Jonathan Tirone joins host Stephen Carroll to discuss.
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Speaker 1 (00:02):
Bloomberg Audio Studios, Podcasts, radio news.
Speaker 2 (00:08):
I'm Stephen Carroll and this is Here's Why, where we
take one new story and explain it in just a
few minutes with our experts here at Bloomberg.
Speaker 3 (00:20):
Our objective was the destruction of arrange nuclear and richimid
capacity and a stop to the nuclear thread poised by
the world's number one stage sponsor of terror. Tonight, I
can report to the world that the strikes were a
spectacular military success.
Speaker 2 (00:39):
It was an unprecedented series of strikes against Iran's nuclear ambitions.
The United States targeted facilities at four dou Natanz and
Isfahan in a thirty seven hour operation that included one
hundred and twenty five aircraft, submarine launched Tomahawk missiles, and
fourteen thousand kilogram bombs. While the effectiveness of those strikes
(01:00):
as still being assessed, they've compounded another problem. The UN's
nuclear inspectors don't know where Iran's highly enriched uranium is now.
Speaker 4 (01:09):
I'm not so sure. At a time of war, all
nuclear sites are closed, so our inspectors who are still
i must say still in Iran, although they are in
a protected place. As you can imagine, no inspection, normal
activity can take place.
Speaker 2 (01:28):
That's the head of the International Atomic Energy Agency, Raphael
Mariano Grossi. So here's why Iran's unaccounted for uranium worries experts.
Jonathan Trone, who covers nuclear diplomacy for Bloomberg, joins me.
Now for more, Jonathan, First of all, how much uranium
(01:49):
does Iran have and how dangerous is it?
Speaker 1 (01:53):
Uran has various stockpiles. The most concerning is the four
hundred and nine kilograms of highly enriched uranium. That material
is equivalent to the amount needed to make about ten
nuclear weapons if it was further enriched to ninety percent.
That material was last seen a few days before Israel's
bombing commenced on June thirteenth. It was stored in underground
(02:15):
tunnels at Isfahan complex. However, Rafael Mariano Grussi, the IEA
Director General, told us on June eighteenth that his inspectors
had lost track of that material. They were no longer
to verify its location. The concerns compounded because even before
the bombing began, Iranian diplomats had told the IAEA that
if Israel and he did attack, they would move that
(02:36):
material to an undeclared location. So at this point we
don't have any visibility on the inventory of nuclear material
that was existing at the site before. But we're looking
at about ten days now of that material being out
of contact with international verification measures.
Speaker 2 (02:54):
Why is it that we don't know more about where
it is?
Speaker 1 (02:58):
Well before the bombing began, International Aconomic Energy Agency monitors
were in Iran every day. The IAEA has two hundred
and seventy four monitors that are going in and out
of Iran constantly, So all of that material was under
what's called safeguards. They're under seal of the IAEA. The
International community and inspectors were going in and out of
(03:19):
those facilities inspecting an average at one point four a
day last year once the bombing began, for obvious reasons,
because you know, the IAEA is not going to be
entering onto a site under active attack. You know, once
the attacks began, you eliminated the ability to verify the
location of that material. Compounding that problem is that Iran
(03:39):
had informed the IAEA that if Israel did begin to attack,
it would remove that material to an undisclosed location, and
as of yesterday, the Iranians still had not told the
IAEA where they had put it, and you know, just
to go a step further, Iranians are also making a
move to restrict IAEA movements and country going forward. They're
(04:02):
talking about leaving the Nuclear Non Proliferation Treaty, which is
the bedrock legal arrangement that imposes IAEA inspections in Iran.
If Iran bars IAEA or leaves the treaty, then we
face the potential of losing sight of that four hundred
kilograms of highly iriched material that could be quickly turned
(04:23):
into bomb material for a long time, and that questions
the metrics of success for the attacks. So while there's
no doubt that there was a grave damage dealt to
the above ground facilities, perhaps some of the underground in
Richmond's facilities, the attacks did not take account of the
existing inventory of Iran's nuclear material.
Speaker 2 (04:44):
I want to come back to the framework in a
moment that underpins all of this that you mentioned, But
how far could this uranium have been moved? In theory?
How easily transport able is this.
Speaker 1 (04:55):
There's a vast body of scientific literature about the amount
of material that be packed to into a canister when
it's at that enrichment level because there are safety concerns
about criticality incidents. Basically, that material is limited to a
canister about the side of a scuba tank that can
carry about twenty five kilograms of this highly enriched uranium.
(05:15):
That means, for all practical purposes, an individual or a
small vehicle, could you know, carry that out and spirit
it away to an undisclosed location. The handling requirements of
enriched uranium are not that complicated. It's only after the
fuel has been irradiated instead of a reactor or in
a bomb, that you know you're facing a real radiological risk.
(05:38):
So this is not a complicated task to bring those
canisters out and put them into a place that has
not been declared.
Speaker 2 (05:47):
Let's return to the monitoring that was possible before this
war erupted. How effective was that system thought to have
been beforehand.
Speaker 1 (05:58):
There's a very dispute about the declared nuclear material in Iran.
The IAEA has been keeping track to gram levels of
this vast volume of enriched material that Iran has and
less I forget it's not just the four hundred nine
kilograms of highly enriched uranium. They also have thousands of
kilograms of lower enriched uranium, So that was never the dispute.
(06:20):
What was the dispute, and the reason that Iran on
June twelfth was found in non compliance of its safeguards
agreements was because the agency had detected trace elements of
uranium at several locations that had not been declared. Now,
these trace isotopes that were detected were decades of years old,
I mean they go back to the early two thousands,
(06:43):
so this was not a smoking gun, so to speak.
But the standards of verification are so high at the IAEA,
not just in Iran but in every country that any
anomaly prompts an investigation, and the Iranians were not cooperating
in this investigation. The Iranians considered that their cooperation leading
(07:04):
into the twenty fifteen nuclear agreement that the US left
in twenty eighteen had sufficed that it was under no
obligation to continue cooperating in these old investigations, and they
were basically stonewalling the IAEA, which then resulted earlier this
month in this finding give non compliance. But in terms
of the actual enriched uranium, we've always had a good
(07:26):
bead on what that inventory actually looks like.
Speaker 2 (07:29):
Okay, well, then I suppose what does the future of
the Nuclear Non Proliferation Treaty, the structure that underpins all
of this inspection system, What does the future of that
framework look like?
Speaker 1 (07:39):
Now, well, that's the good question. And frankly, IAEID Director
General Raphael Mariano Grossi has been warning about this four
months because it's been a slow motion train wreck in
the eyes of people who are paying close attention to this.
The Iranians have been warning, you know, for at least
the last year that if this escalates diplomatically, never mind militarily,
(08:00):
they were prepared to trigger their so called Article ten
rights under the NPT that would give the IAEA three
month notice that they were going to be withdrawing from
that treaty. If they withdraw, that essentially ends IAEA inspections,
and that is a massively escalatory move in light of
the conflict we've just witnessed. And let's not forget I mean,
(08:23):
even in the best case scenario where Iran remains within
the treaty and inspections continue, it is going to take
years for the IAEA to re establish a material accountancy baseline.
There's so much localized chemical and radiological hazards it's going
to take a while for them even to get back
on site doing investigations, doing inspections, and once they're in there,
(08:47):
they're going to have to basically start from point zero
and rebuilding their data on Iran stockpile. This has caused
a massively complex challenge to the non proliferation regime.
Speaker 2 (08:59):
Okay and run our nuclear diplomacy reporter. Thank you. For
more explanations like this from our team of three thousand
journalists and analysts around the world, go to Bloomberg dot
com slash explainers. I'm Stephen Carroll. This is Here's why.
I'll be back next week with more. Thanks for listening.
Bloomberg Audio Studios, Podcasts, radio news.
Speaker 2 (00:08):
I'm Stephen Carroll and this is Here's Why, where we
take one new story and explain it in just a
few minutes with our experts here at Bloomberg.
Speaker 3 (00:20):
Our objective was the destruction of arrange nuclear and richimid
capacity and a stop to the nuclear thread poised by
the world's number one stage sponsor of terror. Tonight, I
can report to the world that the strikes were a
spectacular military success.
Speaker 2 (00:39):
It was an unprecedented series of strikes against Iran's nuclear ambitions.
The United States targeted facilities at four dou Natanz and
Isfahan in a thirty seven hour operation that included one
hundred and twenty five aircraft, submarine launched Tomahawk missiles, and
fourteen thousand kilogram bombs. While the effectiveness of those strikes
(01:00):
as still being assessed, they've compounded another problem. The UN's
nuclear inspectors don't know where Iran's highly enriched uranium is now.
Speaker 4 (01:09):
I'm not so sure. At a time of war, all
nuclear sites are closed, so our inspectors who are still
i must say still in Iran, although they are in
a protected place. As you can imagine, no inspection, normal
activity can take place.
Speaker 2 (01:28):
That's the head of the International Atomic Energy Agency, Raphael
Mariano Grossi. So here's why Iran's unaccounted for uranium worries experts.
Jonathan Trone, who covers nuclear diplomacy for Bloomberg, joins me.
Now for more, Jonathan, First of all, how much uranium
(01:49):
does Iran have and how dangerous is it?
Speaker 1 (01:53):
Uran has various stockpiles. The most concerning is the four
hundred and nine kilograms of highly enriched uranium. That material
is equivalent to the amount needed to make about ten
nuclear weapons if it was further enriched to ninety percent.
That material was last seen a few days before Israel's
bombing commenced on June thirteenth. It was stored in underground
(02:15):
tunnels at Isfahan complex. However, Rafael Mariano Grussi, the IEA
Director General, told us on June eighteenth that his inspectors
had lost track of that material. They were no longer
to verify its location. The concerns compounded because even before
the bombing began, Iranian diplomats had told the IAEA that
if Israel and he did attack, they would move that
(02:36):
material to an undeclared location. So at this point we
don't have any visibility on the inventory of nuclear material
that was existing at the site before. But we're looking
at about ten days now of that material being out
of contact with international verification measures.
Speaker 2 (02:54):
Why is it that we don't know more about where
it is?
Speaker 1 (02:58):
Well before the bombing began, International Aconomic Energy Agency monitors
were in Iran every day. The IAEA has two hundred
and seventy four monitors that are going in and out
of Iran constantly, So all of that material was under
what's called safeguards. They're under seal of the IAEA. The
International community and inspectors were going in and out of
(03:19):
those facilities inspecting an average at one point four a
day last year once the bombing began, for obvious reasons,
because you know, the IAEA is not going to be
entering onto a site under active attack. You know, once
the attacks began, you eliminated the ability to verify the
location of that material. Compounding that problem is that Iran
(03:39):
had informed the IAEA that if Israel did begin to attack,
it would remove that material to an undisclosed location, and
as of yesterday, the Iranians still had not told the
IAEA where they had put it, and you know, just
to go a step further, Iranians are also making a
move to restrict IAEA movements and country going forward. They're
(04:02):
talking about leaving the Nuclear Non Proliferation Treaty, which is
the bedrock legal arrangement that imposes IAEA inspections in Iran.
If Iran bars IAEA or leaves the treaty, then we
face the potential of losing sight of that four hundred
kilograms of highly iriched material that could be quickly turned
(04:23):
into bomb material for a long time, and that questions
the metrics of success for the attacks. So while there's
no doubt that there was a grave damage dealt to
the above ground facilities, perhaps some of the underground in
Richmond's facilities, the attacks did not take account of the
existing inventory of Iran's nuclear material.
Speaker 2 (04:44):
I want to come back to the framework in a
moment that underpins all of this that you mentioned, But
how far could this uranium have been moved? In theory?
How easily transport able is this.
Speaker 1 (04:55):
There's a vast body of scientific literature about the amount
of material that be packed to into a canister when
it's at that enrichment level because there are safety concerns
about criticality incidents. Basically, that material is limited to a
canister about the side of a scuba tank that can
carry about twenty five kilograms of this highly enriched uranium.
(05:15):
That means, for all practical purposes, an individual or a
small vehicle, could you know, carry that out and spirit
it away to an undisclosed location. The handling requirements of
enriched uranium are not that complicated. It's only after the
fuel has been irradiated instead of a reactor or in
a bomb, that you know you're facing a real radiological risk.
(05:38):
So this is not a complicated task to bring those
canisters out and put them into a place that has
not been declared.
Speaker 2 (05:47):
Let's return to the monitoring that was possible before this
war erupted. How effective was that system thought to have
been beforehand.
Speaker 1 (05:58):
There's a very dispute about the declared nuclear material in Iran.
The IAEA has been keeping track to gram levels of
this vast volume of enriched material that Iran has and
less I forget it's not just the four hundred nine
kilograms of highly enriched uranium. They also have thousands of
kilograms of lower enriched uranium, So that was never the dispute.
(06:20):
What was the dispute, and the reason that Iran on
June twelfth was found in non compliance of its safeguards
agreements was because the agency had detected trace elements of
uranium at several locations that had not been declared. Now,
these trace isotopes that were detected were decades of years old,
I mean they go back to the early two thousands,
(06:43):
so this was not a smoking gun, so to speak.
But the standards of verification are so high at the IAEA,
not just in Iran but in every country that any
anomaly prompts an investigation, and the Iranians were not cooperating
in this investigation. The Iranians considered that their cooperation leading
(07:04):
into the twenty fifteen nuclear agreement that the US left
in twenty eighteen had sufficed that it was under no
obligation to continue cooperating in these old investigations, and they
were basically stonewalling the IAEA, which then resulted earlier this
month in this finding give non compliance. But in terms
of the actual enriched uranium, we've always had a good
(07:26):
bead on what that inventory actually looks like.
Speaker 2 (07:29):
Okay, well, then I suppose what does the future of
the Nuclear Non Proliferation Treaty, the structure that underpins all
of this inspection system, What does the future of that
framework look like?
Speaker 1 (07:39):
Now, well, that's the good question. And frankly, IAEID Director
General Raphael Mariano Grossi has been warning about this four
months because it's been a slow motion train wreck in
the eyes of people who are paying close attention to this.
The Iranians have been warning, you know, for at least
the last year that if this escalates diplomatically, never mind militarily,
(08:00):
they were prepared to trigger their so called Article ten
rights under the NPT that would give the IAEA three
month notice that they were going to be withdrawing from
that treaty. If they withdraw, that essentially ends IAEA inspections,
and that is a massively escalatory move in light of
the conflict we've just witnessed. And let's not forget I mean,
(08:23):
even in the best case scenario where Iran remains within
the treaty and inspections continue, it is going to take
years for the IAEA to re establish a material accountancy baseline.
There's so much localized chemical and radiological hazards it's going
to take a while for them even to get back
on site doing investigations, doing inspections, and once they're in there,
(08:47):
they're going to have to basically start from point zero
and rebuilding their data on Iran stockpile. This has caused
a massively complex challenge to the non proliferation regime.
Speaker 2 (08:59):
Okay and run our nuclear diplomacy reporter. Thank you. For
more explanations like this from our team of three thousand
journalists and analysts around the world, go to Bloomberg dot
com slash explainers. I'm Stephen Carroll. This is Here's why.
I'll be back next week with more. Thanks for listening.
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