Nuclear Stores
Before becoming suitable for nuclear energy, producers extract uranium from the ground and process it into uranium ore concentrate (UOC). UOC must then be transported to a facility to be converted to uranium dioxide (UO2) or hexafluoride (UF6). The transportation process is extensive, presenting a host of formidable yet manageable security risks.
The most common compound of UOC is triuranium octoxide (U3O8), often called yellowcake, though some processes produce other compounds such as ammonium diuranate (ADU), uranium tetrafluoride (UF4), uranyl peroxide (UO4) or uranium trioxide (UO3). U3O8 contains 85 per cent uranium by weight. The U3O8 content of UOC can vary from around 76 per cent to more than 99 per cent.

There are four primary techniques for uranium recovery: open pit mining, underground mining, in situ leaching and heap leaching. Open pit mining is used to recover uranium located near the earth’s surface. Explosives are used to break up the rock, which is loaded on to large dump trucks and then to crushers and separators to prepare the ore for leaching. Uranium mines such as the Ranger mine in Australia, the Rössing mine in Namibia and the Arlit mine in Niger are open pit. When uranium is located at depths that make the open pit method uneconomical, extraction is done by digging a shaft underground into the uranium deposit. Horizontal tunnels are then excavated to access the ore, which is broken up by explosives or boring machines. Mechanical conveyors then hoist the broken rock to the surface. Russia’s Priargunsky mine and Canada’s MacArthur River and Cigar Lake mines are underground. At Cigar Lake, where concentration levels are higher than average, the rock is crushed to a finer consistency and mixed with water to produce a slurry that is pumped to the surface and transferred to a mill for further processing. Given its high concentrations, Canada is the only producer that has to ‘water down’ its rock.

Heap leaching uses a series of chemical reactions that absorbs specific minerals and then re-separates them after extraction. After the ore has been removed and crushed, it is placed into heaps on a protective liner which is sprayed with a leaching solution (alkali solution or sulphuric acid) to separate the uranium from the ore. The Caetité uranium mine in Brazil is open-pit and uses the heap leaching technique as does AREVA’s Somair mine in Niger.

In situ leaching (ISL), also known as in situ recovery (ISR), is similar except that the ore is not mined; instead the leaching solution is pumped through a network of piping into the deposit, dissolves the uranium and pulls a pregnant solution up to the surface. As such, ISL extracts uranium without excavating it. Mines in Kazakhstan and United States are predominantly ISL.

The uranium is then precipitated and finally filtered, dried and packaged as UOC into 200 litre drums (400kg/881lbs) or four-ton hoppers ready for transport by land and/or sea to a conversion facility. During conversion, the high purity required for nuclear fuel is achieved by dissolving UOC in nitric acid, and then filtering and treating the solution with chemical solvents. The resulting uranyl nitrate is more than 99.95 per cent pure. It is reconverted into uranium oxide, which in turn is converted into highly volatile UF6 which is the feedstock for centrifuges in the enrichment process. In the case of heavy water reactors, which are fueled with natural uranium, enrichment is not required; instead UO2 is produced from the uranyl nitrate and shipped directly to a fuel fabrication plant.

Most of the output from approximately 50 operating uranium mines worldwide is delivered to only a handful of conversion facilities – in Canada, China, France, India, Russia, and the United States. Until its closure in August 2014, UOC was also converted at the Springfields conversion plant in the United Kingdom.

Of these countries, Canada is the only one that does not possess nuclear weapons. China, France, Russia, the United Kingdom and the United States are legally recognized nuclear-weapon states under the Nuclear Non-Proliferation Treaty (NPT) while India – not a party to the NPT – became the sixth major destination for UOC after its re-entry in 2008 to the global civilian market.

The majority of the world’s uranium therefore passes through one of these countries before it is further processed as fuel for a nuclear reactor. For example, a drum of yellowcake leaving a mill in Australia can travel 5,000 km (approx. 3,106 mi) to China, 15,000 km (approx. 9,320 mi) to Europe or upwards of 20,000 km (approx. 12,427 mi) to conversion facilities in Illinois, United States or Ontario, Canada.

The transport of shipping containers of UOC from mine site to conversion facility creates a potential security vulnerability, given the significant distances travelled, the number of transfers of authority that a shipping container goes through, often across several borders, requiring multiple approvals in multiple jurisdictions. Such vulnerabilities are addressed by the IAEA through its safety and security standards and through industry best practice.

Physical protection practices can be quite rigorous – as mine owners in conjunction with transporters and in some instances governments put in place specific measures to manage and mitigate risk. Precautions often include designated routes requiring designated rest stops, requirements for additional drivers, and GPS tracking on trucks to monitor location and driving behavior. The fitting of container bolt seals to shipping containers or dry van trailers assists in detecting any tampering with cargo containers during intermediate or long-term storage, a technique used for many high value cargoes.

A container carries around 20-35 drums, or approximately 8-14 tonnes of UOC, containing 7-12 tonnes of uranium. Ten metric tonnes of uranium is defined as a “significant quantity,” i.e. the quantity for which the possibility of manufacturing a nuclear explosive device cannot be excluded. The “significant quantity” is a basic parameter used in IAEA safeguards.

Diversion or theft of a single cargo container of UOC is a valid concern from an international safeguards perspective. The IAEA has determined that the timeline for detection of diversion of a significant quantity of uranium is one year. However, industry and regulators have expressed that being able to detect the unauthorized removal of a single drum over a one-month period is a prudent goal.

As of mid-2017, no accident beyond level 1 on the International Nuclear Event Scale (INES) has ever been reported for nuclear material transportation. UOC transportation follows international rules related to nuclear material transportation with respect to both containment and control. These measures should be continuously evaluated against threats to ensure a graded approach when suppliers are experiencing heightened security environments and the risk of sabotage and unauthorized acquisition requires increased protection, inspection and enforcement.

At conversion facilities, uranium ore concentrate is processed to create uranium hexafluoride (UF6), which is the feed for enrichment, or uranium dioxide (UO2) which is the feed for natural uranium fuel fabrication (e.g. for heavy water reactors). UO2 can be produced from UF6, but it can also be produced from UNH (uranium nitrate hexahydrate), in which case a conversion plant does not need to produce UF6.

Conversion facilities face a number of economic and efficiency challenges. Currently, countries are aiming or attempting to optimize conversion rates and cut costs as existing conversion facilities are aging and the uranium market is struggling with oversupply, low demand and a low spot price.

Along with the conversion facilities in Canada, China, France, Russia, and the United States, there is a handful of smaller conversion facilities located in Argentina, Brazil, India, Iran, Romania and South Korea. Of these countries, Romania and South Korea produce only UO2 for heavy water reactor fuel fabrication, and Brazil is running a pilot facility for its nuclear propulsion program at the Aramar Experimental Center.

Israel, North Korea and Pakistan have conversion plants as part of their military programs, as does India. The five-recognized nuclear-weapon states under the NPT (China, France, Russia, United Kingdom and United States) are currently not enriching or converting uranium for weapons but some may be doing so for powering naval reactors. There is no information publicly available to confirm this.

Secure transport of “yellowcake” is just one area of concern as uranium flows around the globe. Another is the path from “ore to bomb.”