THE WORLD NUCLEAR TRANSPORT INSTITUTE (WNTI) is a non-governmental organisation that is dedicated to promoting the safe and secure transportation of nuclear and radioactive material. It has 46 members globally, which range from major utilities, fuel producers and fabricators to transport companies, package producers and the producers and suppliers of large radiation sources. Through five WNTI Working Groups, members work together to promote a sound international framework for international consensus, co-operation and understanding. WNTI represents its members within United Nations agencies such as the International Atomic Energy Agency and the International Maritime Organisation.

WNTI has produced standards, good practice guides, information papers and fact sheets, encompassing a wide range of topics concerning the transport of nuclear and radioactive material. These publications are freely available on the WNTI website. It is the belief of WNTI that making this information available can assist all stakeholders in understanding and complying with regulations and that this benefits the whole industry.

An example of a recent collaboration success was solving a specific problem with the packaging of uranium hexafluoride (UF6). In collaboration with the Oak Ridge National Laboratory (ORNL), a WNTI standard for the unique identification of UF6 cylinders was developed. 

ORNL is celebrating its 75th anniversary and is the largest US Department of Energy science and energy laboratory. Its strengths include neutron scattering, high-performance computing, advanced materials and nuclear science and technology for national security. Its mission is to deliver scientific discovery and technical breakthroughs, by creating and deploying multidisciplinary and multi-institutional teams to conduct basic and applied research on compelling problems in energy and nuclear security.

Some recent achievements include: applying physics and nuclear engineering expertise to the discovery of element 117m (named tennessine), restoring the US ability to produce plutonium-238 for deep space missions, producing the largest solid 3D printed item; and revealing a new molecular state of water using neutron scattering and computational modelling.

UF6 is shipped and stored in standard cylinders to conversion, enrichment, fuel fabrication, and de-conversion facilities. These facilities report their inventory and transfers of UF6 to national authorities and, when required, to international agencies such as International Atomic Energy Agency (IAEA) and European Atomic Energy Community (Euratom).

Cylinders used for commercial transport are fabricated from carbon steel in accordance with standards established by the International Organization for Standardization (ISO) and the American National Standard Institute (ANSI) to withstand the service conditions in the industry. These standards provide criteria for packaging used for transporting UF6 and define the requirements for in-service inspections, cleanliness and maintenance for packaging in service. All cylinders are periodically inspected and tested throughout their service life, which typically extends beyond 40 years.

International standards require cylinders to display a metal nameplate with information such as owner, serial number and certifications, but the information can often be difficult to read and there is no industry standard for the format of the assigned serial number.

The nameplates of cylinders that have been fabricated in accordance with the standards are stamped with the official code U symbol and are registered with a national board. The nameplates also contain additional identification information provided by the purchaser (eg, owner and serial number), the national board and associated with the certification testing performed by the cylinder fabricator. This information is stamped or engraved on a nameplate that is welded to the valve end of the cylinder.

While a cylinder is on an operating site, it is usually placed in a storage area. These storage areas can be inside a building or outside and open to the weather. Cylinders can be stacked two or three high, and close together. The nameplates at the ends of the cylinders can be difficult to access, and it can be especially difficult to read the serial numbers. A cylinder containing depleted materials may be placed in long-term storage and remain unmoved for more than 40 years.

Because the cylinder identification can be difficult to read, even from short distances away, many companies add an identifier for their own use. The supplemental cylinder identifiers are applied with a variety of techniques, including marking, stencilling, adhesive labels, paint markings and stickers. These identifiers may use the serial number stamped on the nameplate or a different number created by the cylinder owner. Some of these identifiers can read by automated methods (eg bar code, RFID) and some are not permanently attached.

The wide variety of identification formats and supplemental labels used across industry has limited the ability of the international inspectorates to automate their verification activities. During on-site inspections, the inspectors have to quickly locate and identify all the cylinders provided on the physical inventory listing and in the inventory change reports. Verification activities remain a manual process that is labour intensive and time consuming. The challenges in reading the cylinder identification can lead to reading and transcription errors that require additional time to resolve.

Industry has also identified additional operational benefits of applying a standard, machine-readable global identifier to each cylinder.

In May 2014, a WNTI and ORNL working group was set up to identify an industry-wide identification format to uniquely identify cylinders, and to investigate methods for making the global identifier machine-readable and independently verifiable.

The need was to correctly identify cylinders as they are stored on site, moved and processed on site, and transported between facilities. While the existing UF6 cylinder numbering system has proven to be adequate for the logistical operations within the supply chain of UF6, a global identifier can offer benefits:

  • All enterprise management systems within the supply chain using the same UF6 cylinder identifier;
  • All transport documentation within the supply chain sign the same UF6 cylinder identifier;
  • There is improved communication within the supply chain between consignor, consignee, transport agent, carriers, port authorities, customs, etc;
  • Improved tracking of UF6 cylinders within the supply chain; and
  • More efficient operation.

The capability to correctly identify cylinders during their processing and storage at fuel cycle facilities is extremely important for:

  • Providing traceability for filling customer orders;
  • Managing cylinder inventories and cylinder transactions, such as sales or loans of cylinders to another operator or customer;
  • Supporting databases that contain cylinder information, to ensure that only compliant cylinders are placed in use;
  • Facilitating compliance with national nuclear material control and international nuclear material safeguards requirements.

It was agreed that the global identifier should meet the following requirements:

  • A number/lettering scheme that is not duplicated across industry;
  • An identification number that is large enough to be visually read from a reasonable distance, such as from 3 metres away;
  • Machine-readable;
  • The capability to withstand all the environment conditions associated with cylinder transport and processing;
  • Ability to endure for the entire cylinder service life; and
  • Reasonable application and maintenance costs.

After consultation with the IAEA it was determined that the welding of the global identifier to the cylinder would also enable international inspectorates to verify the cylinder’s authenticity.

Cylinder owners will be responsible for assigning and managing the 10-character identification numbers assigned to the cylinders.

Each cylinder owner will select a 3-letter prefix for its use. To prevent owners using the same prefix, they will be reserved at WNTI. Cylinder owners that do not wish to have their own 3-letter prefix can be assigned a WNTI prefix.

For new cylinders, the organisation purchasing the cylinder will be responsible for assigning the global identification, and having it attached to the cylinder. For newly fabricated cylinders the global identifier should also be used as the serial number on the nameplate so that these numbers agree.

Initially there will be discrepancies between the identification numbers on the global identifiers and the serial numbers engraved on existing nameplates, but this will fall over time, as existing cylinders reach the end of their service life.

WNTI has published a standard detailing the UF6 cylinder identification, which has generally been well received by the industry.

Industry has indicated that for new cylinders the barcode system described in the standard will be added to the nameplate of the cylinder.

For the existing fleet, industry is awaiting additional test data on the performance of the additional identifier being developed by ORNL. This information will be added to the development plans to retrofit existing cylinders with the barcode, ‘unique identifier’.  

Author information: Marc-Andre Charette, Director of Transportation, Security and Regulatory Relations at Cameco Corporation and Chair of WNTI’s Uranium Concentrates Industry Working Group; Michael Whitaker, Manager, International Safeguards, Nuclear Security and Isotope Technology Division at Oak Ridge National Laboratory; Captain Simon Chaplin, Specialist Advisor, World Nuclear Transport Institute