Swipe Check: Collecting and Analysing Environmental Samples for Nuclear Verification

safeguards _ swipe sample at a nuclear facility

Inspectors taking a swipe sample at a nuclear facility. (Photo: IAEA Department of Safeguards)

The air is pressurized, carefully filtered and closely monitored. Scientists and technicians pass through air showers before entering. Welcome to the IAEA Environmental Sample Laboratory, or ‘clean laboratory’, in Seibersdorf, Austria, where 400 samples are analysed every year to verify that nuclear facilities have been used as declared.

The clean laboratory conditions are necessary so that the smallest traces of uranium and/or plutonium can be identified in the swipe samples taken by inspectors at research reactors, enrichment plants and other nuclear facilities for analysis. The machines used are so sensitive that they can pick out uranium and plutonium at weights below one trillionth of a gram in a sample.

“No matter how much you clean a kitchen, a speck of material dust always remains. This is also true in a nuclear facility. This enables environmental sample swipe analysis to detect what elements have been used,” said Stephan Vogt, Head of the Environmental Sample Laboratory.

While many safeguards verification methods aim to check and confirm the type and quantity of nuclear material declared by a State, environmental sampling is used to verify the absence of undeclared nuclear material.

How swipe sampling was born

In the 1990s, a nuclear facility in Iraq was bombed and there was no way for IAEA inspectors to collect conventional samples from the destroyed site. Instead, the inspectors innovated. They used cotton towels to ‘swipe’ items from the damaged facility to check whether there were any traces of the kind of elements used in the facility prior to its destruction. An entire spectrum of uranium — from depleted to highly enriched — was identified. The contaminated towels were able to reveal the history of the destroyed nuclear facility. The idea for swipe samples was born.

No matter how much you clean a kitchen, a speck of material dust always remains. This is also true in a nuclear facility. This enables environmental sample swipe analysis to detect what elements have been used.
Stephan Vogt, Head, IAEA Environmental Sample Laboratory
safeguards

Swipe samples being analysed at the IAEA Environmental Sample Laboratory in Seibersdorf (Photo: D. Calma/IAEA)

Environmental sampling is now part of the IAEA’s standard processes. The environmental sample kits for inspection purposes are all prepared in the laboratory’s ‘clean room.’ The sealed packaged swipes are only opened at the designated area of inspection. The package contains two pairs of latex gloves, 6 to 10 cotton swipes, as well as additional zip lock packets for the swiped samples. These are then placed in an outer sealed bag until they reach the IAEA. Surfaces at various locations at a nuclear or related facility are swiped a number of times. Back at the laboratory, these samples are subject to highly sophisticated analyses using advanced technology (see box below).

Samples are analysed at the IAEA laboratory as well as at the 18 accredited laboratories in eight IAEA Member States and the European Atomic Energy Community (Euratom). Labs in Australia, Brazil, France, Germany, Japan, Russia, the Republic of Korea, the United Kingdom and the United States are part of the IAEA’s network of affiliated laboratories.

To maintain the confidentiality of the process, all collected swipe samples are subjected to a rigorous labelling system that removes the identity of the country and the place of collection. Anonymized samples undergo an initial investigative screening for radioactive signatures and major elemental composition and are then sent to the designated laboratories in Member States, Vogt said. Among the samples the IAEA sends are also blind quality control samples so that measurements can be assessed against the standards set by the IAEA and a consistent high quality maintained.

Careful collection and thorough analysis of environmental samples is now an essential element of the IAEA’s safeguards work. “These activities enable the IAEA to verify that nuclear facilities have been used as declared and to build confidence in the peaceful uses of nuclear technology,” said Tero Varjoranta, Deputy Director General and Head of the Department of Safeguards.

Last update: 22 March 2016