There are two main sets of laboratories: one for testing declared nuclear materials and another to process "environmental" samples designed to pick up clues to possible undeclared nuclear activity.

It's in these labs that the IAEA's scientists carry out their painstaking work of analysing the samples collected by their inspectors in the field.

But the site houses the International Atomic Energy Agency's laboratories, which are key to verifying Iran's compliance with the Joint Comprehensive Plan of Action (JCPOA), signed in 2015 between Iran and world powers.

One place that could feel the ramifications of Trump's decision is an unassuming lab complex near the Austrian town of Seibersdorf -- at first sight a world away from geopolitical manoeuvering over Tehran's nuclear programme.

As US President Donald Trump reimposes sweeping sanctions on Iran on Monday, all eyes are again on the precarious future of a landmark international deal meant to curb Tehran's nuclear programme.

For the former, samples are taken from containers of nuclear material up to hundreds of kilograms in weight.

"By the time we go to the measurement lab, they'll be measuring millionths of a gram," explains Steve Balsley, head of the Nuclear Materials Laboratory.

The nuclear materials lab deals with around 500 samples a year but has the capacity to handle much more than that at busier periods.

The second main type of testing is "environmental" sampling, which consists of intricate analysis of "swipes" resembling small square cloths.

s Nuclear Materials Lab, carry out the painstaking work of analysing the samples collected by field inspectors (photo by: ALEX HALADA/AFP)

This gives clues as to the kinds of nuclear activities that have been carried out at a given location.

The analysis can for example tease out traces of different sorts of uranium detected at a site, to see if isotop

es are present which suggest enrichment activity over and above what a country has declared.

Such work could be key to verifying a deal like the JCPOA, where limits on enrichment activity are central to ensuring the absence of a military nuclear programme.

However, to avoid bias, samples are given random numbers so that scientists don't know where they come from.

Painstaking process

For both kinds of analysis, spikes in workload can occur when inspectors gain access to a facility and need to establish a "baseline" of information about activity at that site.

Such intensive work would probably be necessary if the IAEA were to play a role in verifying any future deal on North Korea's nuclear programme, as so much time has elapsed since its inspectors were expelled from the country in 2009.

The machines used for the most detailed work cost several million euros (photo by: ALEX HALADA/AFP)

Depending on how much detail is needed in the result, a single "swipe" can take weeks to analyse and cost several thousand euros in labour and chemicals.

The machines used for the most detailed work -- able for example to analyse a particle of plutonium 50 times smaller than the diameter of a human hair -- cost several million euros.

Moreover, there is only a limited pool of staff worldwide who would have the required knowledge to operate them, meaning vacancies are not always easy to fill.

Stephan Vogt, head of the Environmental Sample Laboratory, says that given the scientists work from such tiny amounts of source material, "we spend about 60-70 percent of our time not doing anything else than engaging in quality assurance and quality control, just to make sure the numbers we produce are defendable."

The IAEA can also call on a network of partners in several other countries to which it can send samples for analysis (photo by: ALEX HALADA/AFP)

But he is confident that the painstaking processes will always pick up nuclear activity.

"Any nuclear process you pursue will leave traces in the enviro

nment of the materials that you have handled inside the facility," he says.

The environmental sampling lab frequently runs at capacity but the IAEA can also call on a network of partners in several other countries to which it can send samples for analysis.

But no matter how impressive the facilities and manpower that the IAEA has as its disposal, when it comes to the survival of an agreement like the JCPOA, the technical results will ultimately matter less than the politics.