Small device, big effect

One of the main tools that IAEA inspectors use to detect the diversion and misuse of nuclear material and technology comes in the form of a device no larger than a coin. This small but mighty instrument is called a passive seal. With it, an IAEA safeguards inspector can close a container, a hatch to a room or a nuclear material cask, and return years later to verify whether it was opened. In 2021, the IAEA verified over 17 000 passive seals applied to nuclear material, facility critical equipment or IAEA monitoring and other equipment at nuclear facilities.

“Seals are a simple and effective means to meet an important verification need. Used around the world, metal seals are an important part of an inspector’s toolkit when verifying that nuclear material and facilities remain in peaceful use,” said Joel Hoyt, seals modernization project lead and Senior Project Engineer at the IAEA.

A passive seal ensures continuity of knowledge regarding nuclear material. If the seal has not been tampered with, the inspector knows that the integrity of the equipment or material it encloses is still intact. A passive seal is also used to ensure the integrity of the IAEA’s on-site verification tools and equipment, such as surveillance cameras.

The traditional passive seal, used since the 1960s, is a copper and brass device called the E-CAP metal seal (CAPS). CAPS is a general purpose, non-reusable passive loop seal. To close the seal, a double copper cap is snapped onto the base. Both the cap and its base have unique markings on the inside surface to ensure the authenticity of the seal. The metal base and its cap serve as the point of closure with a multistranded wire threaded between them. This wire encircles the item to be sealed. After an inspector confirms that the wire and the sealed enclosure have not been tampered with, they cut the wire and bring the seal, base and wire to the IAEA’s Headquarters for verification.

To identify the next generation passive seal, the IAEA considered advancements in materials, modern technologies and machining techniques to design and address the requirements of an effective seal. The prototypes of the new seal were subject to field conditions and extreme situations to confirm if the design could meet all requirements. The result was the adoption of the field verifiable passive seal (FVPS), which is made from aluminium and polycarbonate and requires no tools to apply, no maintenance while deployed, and no batteries or electronics to power. 

Both the CAPS seals and the new FVPS have unique pattern designs etched onto their surfaces to ensure that they cannot be replicated or replaced, as well as other tamper-indicating design features. However, one of the main advantages of the new seals is that they can be verified in the field.

The device used to verify seals employs customized software and a specialized lens and light attachment housed in a bespoke case. When an inspector attaches a new seal, they use the dedicated software to input information about where the seal is installed and take three reference photos. These pictures and the related facility information are relayed back to the IAEA’s Headquarters, simplifying the inspection reporting process. When an inspector returns to the facility at a later date, the verification device is used by the inspector to take photos for comparison with the reference photos. This allows the inspector to confirm the integrity of the seal and whether it was subject to tampering.

“Having an in-field verification technique for the seal means we have faster verification results, and we can reduce the administrative burden,” said Nicolette Seyffert, the new seal implementation project team member and Information Security Officer at the IAEA. “By having an in-field customized reader, it is immediately obvious if a seal was tampered with and removes the need to bring the seal back to the IAEA’s Headquarters in Vienna.”

The IAEA has produced the new FVPS for pilot use, with a planned expansion of deployment starting in 2023. Eventually, the new FVPS will replace all of the traditional CAPS seals.