- About 20 million consignments of all sizes containing radioactive materials are routinely transported worldwide annually on public roads, railways and ships.
- Radioactive materials are shipped in robust and secure containers.
- Some 300 sea voyages have been made carrying used nuclear fuel or separated high-level waste over a distance of more than 8 million kilometres. These cargoes are generally carried in purpose-built ships.
- Since 1971 there have been some 7000 shipments of used fuel (over 80,000 tonnes) over many million kilometres on land and sea.
- There have been accidents over the years, but never one in which a container with highly radioactive material has been breached, or has leaked.
- Though transport is a very minor cost in the nuclear fuel cycle, lack of harmonisation and over-regulation in authorisation create problems for transport between countries.
About 20 million consignments of radioactive material (which may be either a single package or a number of packages sent from one location to another at the same time) take place around the world each year. This adds up to over one billion safe consignments since 1961 when the IAEA safe transport regulations were issued. Radioactive material is not unique to the nuclear fuel cycle and only about 5% of the consignments are fuel cycle related. Radioactive materials are used extensively in medicine, agriculture, research, manufacturing, non-destructive testing and minerals' exploration.
International regulations for the transport of radioactive material have been published by the International Atomic Energy Agency (IAEA) since 1961. These regulations have been widely adopted into national regulations, as well as into modal regulations, such as the International Maritime Organisation’s (IMO) Dangerous Goods Code. Regulatory control of shipments of radioactive material is independent of the material's intended application. Because safety of any material being shipped depends primarily on the package, regulations set out several performance standards for packaging. They provide for five different categories of primary packages and set the criteria for their design according to both the activity and the physical form of the radioactive material.
Nuclear fuel cycle facilities are located in various parts of the world and materials of many kinds need to be transported between them. Many of these are similar to materials used in other industrial activities. However, the nuclear industry's fuel is mildly radioactive while some wastes are very much more so, and it is these 'nuclear materials' about which are the focus of concern. Transport is a very minor direct cost in the nuclear fuel cycle.
A Euratom Supply Agency study in 2015 identified lack of harmonisation and over-regulation in transport authorisation for radioactive materials, particularly between countries, as a significant risk from a security of supply perspective.
Nuclear materials have been transported since before the advent of nuclear power over 60 years ago. The procedures employed are designed to ensure the protection of the public and the environment both routinely and when transport accidents occur. For the generation of a given quantity of electricity, the amount of nuclear fuel required is very much smaller than the amount of any other fuels. Therefore, the conventional risks and environmental impacts associated with fuel transport are greatly reduced with nuclear power.
In the USA one percent of the 300 million packages of hazardous material shipped each year contain radioactive materials. Of this, about 250,000 contain radioactive wastes from US nuclear power plants, and 25 to 100 packages contain used fuel. Most of these are in robust 125-tonne Type B casks carried by rail, each containing 20 tonnes of used fuel.
Materials being transported
Transport is an integral part of the nuclear fuel cycle. There are some 440 nuclear power reactors in operation in 32 countries but uranium mining occurs in only about 20 countries, with most production being in countries without nuclear power. Furthermore, in the course of over 40 years of operation by the nuclear industry, a number of specialised facilities have been developed in various locations around the world to provide fuel cycle services. Hence there is a need to transport nuclear fuel cycle materials to and from these facilities. Indeed, most of the material used in nuclear fuel is transported several times during its its progress through the fuel cycle. Transport is frequently international, and often over large distances. Any substantial quantities of radioactive materials are generally transported by specialised transport companies.
The term 'transport' is used in this document only to refer to the movement of material between facilities, i.e. through areas outside such facilities. Most consignments of nuclear fuel material occur between different stages of the cycle, but occasionally material may be transported between similar facilities. When the stages are directly linked (such as mining and milling), the facilities for the different stages are usually on the same site, and no transport is then required.
With very few exceptions, nuclear fuel cycle materials are transported in solid form. The following table shows the principal nuclear material transport activities:
||Rare: usually on the same site
||Uranium oxide concentrate ('Yellowcake')
||Usually 200-litre drums in standard 6m transport container
||Natural uranium hexafluoride
|Special UF6 containers, type 48Y
||Special UF6 containers, type 30B
||Fresh (unused) fuel
||Used fuel storage
||After on-site storage, large Type B casks
|Used fuel storage
||Large Type B casks
|Used fuel storage
||Called reprocessed uranium (RepU)
||Vitrified (incorporated into glass)
||Sometimes on the same site
* Not yet taking place
Although some waste disposal facilities are located adjacent to the facilities that they serve, utilising one disposal site to manage the wastes from several facilities usually reduces environmental impacts. When this is the case, transport of the wastes from the facilities to the disposal site will be required.
Classification of radioactive wastes
There are several systems of nomenclature in use, but the following is generally accepted:
- Exempt waste – excluded from regulatory control because radiological hazards are negligible.
- Low-level waste (LLW) – contains enough radioactive material to require action for the protection of people, but not so much that it requires shielding in handling or storage.
- Intermediate-level waste (ILW) – requires shielding. If it has more than 4000 Bq/g of long-lived (over 30 year half-life) alpha emitters it is categorised as 'long-lived' and requires more sophisticated handling and disposal.
- High-level waste (HLW) – sufficiently radioactive to require both shielding and cooling,
generates >2 kW/m3 of heat and has a high level of long-lived alpha-emitting isotopes.
The principal assurance of safety in the transport of nuclear materials is the design of the packaging, which must allow for foreseeable accidents. The consignor bears primary responsibility for this. Many different nuclear materials are transported and the degree of potential hazard from these materials varies considerably. Different packaging standards have been developed by the IAEA according to the charactristics and potential hazard posed by the different types of nuclear material, regardless of the mode of transport.
Regulations setting out several performance standards for packaging provide for five different categories of primary packages, and set the criteria for their design according to both the activity and the physical form of the radioactive material. The categories are: Excepted, Industrial, Type A, Type B and Type C.
Ordinary industrial containers are used for low-activity material such as uranium oxide concentrate shipped from mines – U3O8. About 36 standard 200-litre drums fit into a standard 6-metre transport container. They are also used for low-level wastes within countries.
'Type A' packages are used for the transport of relatively small, but significant, quantities of radioactive material. They are designed to withstand accidents and are used for limited quantities of medium-activity materials such as medical or industrial radioisotopes as well as some nuclear fuel materials.
A particular ‘Type B’ package is used for shipping uranium hexafluoride (‘hex’), where the main accident hazard is chemical rather than radiological. Natural uranium is usually shipped to enrichment plants in type 48Y cylinders, 122 cm diameter and each holding about 12.5 tonnes of uranium hexafluoride. These cylinders are then used for long-term storage of DU as hexafluoride, typically at the enrichment site. Due to criticality concerns, enriched uranium is shipped to fuel fabricators in smaller type 30B cylinders 76 cm diameter and 2.1 m long, each holding 2.27 t UF6. These may be shipped with overpacks. Both kinds of hex cylinders must withstand a pressure test of at least 1.4 MPa, withstand a drop test and survive a fire of 800°C for 30minutes.
'Type B' packages used for high-level waste (HLW), used fuel, and MOX fuel are robust and very secure casks. They range from drum-size to truck-size and maintain shielding from gamma and neutron radiation, even under extreme accident conditions. Designs are certified by national authorities. There are over 150 kinds of Type B packages, and the larger ones cost some US$1.6 million each.
In France alone, there are some 750 shipments each year of Type B packages. This is in relation to 15 million shipments classified as 'dangerous goods', 300,000 of which are radioactive materials of some kind.
Smaller amounts of high-activity materials (including plutonium) transported by aircraft are be in 'Type C' packages, which give even greater protection in all respects than Type B packages in accident scenarios. They can survive being dropped from an aircraft at cruising altitude.
An example of a Type B shipping package is Holtec’s HI-STAR 80 cask (STAR = storage, transport and repository), a multi-layered steel cylinder which holds 12 PWR or 32 BWR high-burnup used fuel assemblies (above 45 GWd/t) which have had cooling times as short as 18 months. The HI-STAR 60 can transport 12 PWR used fuel assemblies, and two aluminium impact limiters. The HI-STAR 180 was the first one licensed to transport high-burnup fuel, and holds 32 or 37 PWR used fuel assemblies. The HI-STAR 190 cask has the world’s highest heat load capacity, at 38 kW, and is to be used domestically in Ukraine for PWR fuel. The HI-STAR 100 is based on a sealed multi-purpose canister containing the fuel which can be transferred to HI-STORM storage systems, exchanging one overpack for another.
In the UK 47- or 53-tonne rectangular Type B flasks have long been used to transport Magnox and AGR fuel, which is held in internal skips.
When radioactive materials, including nuclear materials, are transported, it is important to ensure that radiation exposure of both those involved in the transport of such materials and the general public along transport routes is limited. Packaging for radioactive materials includes, where appropriate, shielding to reduce potential radiation exposures. In the case of some materials, such as fresh uranium fuel assemblies, the radiation levels are negligible and no shielding is required. Other materials, such as used fuel and high-level waste, are highly radioactive and purpose-designed containers with integral shielding are used. To limit the risk in handling of highly radioactive materials, dual-purpose containers (casks), which are appropriate for both storage and transport of used nuclear fuel, are often used.
As with other hazardous materials being transported, packages of radioactive materials are labelled in accordance with the requirements of national and international regulations. These labels not only indicate that the material is radioactive, by including a radiation symbol, but also give an indication of the radiation field in the vicinity of the package.
Personnel directly involved in the transport of radioactive materials are trained to take appropriate precautions and to respond in case of an emergency.
Packages used for the transport of radioactive materials are designed to retain their integrity during the various conditions that may be encountered while they are being transported thus ensuring that an accident will not have any major consequences. Conditions which packages are tested to withstand include: fire, impact, wetting, pressure, heat and cold. Packages of radioactive material are checked prior to shipping and, when it is found to be necessary, cleaned to remove contamination.
Although not required by transport regulations, the nuclear industry chooses to undertake some shipments of nuclear material using dedicated, purpose-built transport vehicles or vessels.
Regulation of transporta
Since 1961 the International Atomic Energy Agency (IAEA) has published advisory regulations for the safe transport of radioactive material. These regulations have come to be recognised throughout the world as the uniform basis for both national and international transport safety requirements in this area. Requirements based on the IAEA regulations have been adopted in about 60 countries, as well as by the International Civil Aviation Organisation (ICAO), the International Maritime Organisation (IMO), and regional transport organisations.
The IAEA has regularly issued revisions to the transport regulations in order to keep them up to date. The latest set of Regulations for the Safe Transport of Radioactive Material is the 2012 edition.
The objective of the regulations is to protect people and the environment from the effects of radiation during the transport of radioactive material.
Protection is achieved by:
- Containment of radioactive contents.
- Control of external radiation levels.
- Prevention of criticality.
- Prevention of damage caused by heat.
The fundamental principle applied to the transport of radioactive material is that the protection comes from the design of the package, regardless of how the material is transported.
Challenges in Class 7 transport
Most transport of Class 7 materials is for radioisotopes for medical and industrial use (including some cobalt-60 sterilisation sources in 4-tonne type B packages). But all of it requires some training of people who handle the packages, hence there is cost and inconvenience to both shippers and others handling the packages, leading to occasional denial of shipment. Multiple layers of regulation with lack of international consistency provide disincentives to shippers. There are also problems with the competent authority on one country not being accepted in another. Occasionally there is de facto refusal to issue permits, and certain insurances for vessels carrying material with more than 1% fissile may need to be taken out by the consignor or consignee.
Most reports of denial of shipment relate to non-fissile materials, either type B packages (mainly cobalt-60) or tantalum-niobium concentrates. For uranium concentrates the main problem is limited ports which handle them, and few marine carriers which accept them.
Transport of uranium oxide from mines
Uranium oxide concentrate, sometimes called yellowcake, is transported from the mines to conversion plants in 200-litre drums packed into normal shipping containers. No radiation protection is required beyond having the steel drums clean and within the shipping container.
The importance of this is indicated by the fact that 80% of uranium is mined in five countries, only one of which (Canada) uses uranium for nuclear power.
In Australia, over more than three decades to 2014, 11,000 shipping containers with drums of U3O8 were moved from mines to ports with no incident affecting public health.
Transport of uranium hexafluoride
To and from enrichment plants, the uranium is in the form of uranium hexafluoride (UF6), which again is barely radioactive but has significant chemical toxicity. Natural uranium as hexafluoride is usually shipped to enrichment plants in type 48Y cylinders, each 122 cm diameter and holding about 12.5 tonnes of uranium hexafluoride (8.4 tU). These cylinders are then used for long-term storage of DU as hexafluoride, typically at the enrichment site. Enriched uranium is shipped to fuel fabricators in smaller type 30B cylinders, each 76 cm diameter and holding 2.27 t UF6(1.54 tU).
Transport of uranium fuel assemblies
Uranium fuel assemblies are manufactured at fuel fabrication plants. The fuel assemblies are made up of ceramic pellets formed from pressed uranium oxide that has been sintered at a high temperature (over 1400°C). The pellets are aligned within long, hollow, metal rods, which in turn are arranged in the fuel assemblies, ready for introduction into the reactor.
Different types of reactors require different types of fuel assembly, so when the fuel assemblies are transported from the fuel fabrication facility to the nuclear power reactor, the contents of the shipment will vary with the type of reactor receiving it.
In Western Europe, Asia and the US, the most common means of transporting uranium fuel assemblies is by truck. A typical truckload supplying a light water reactor contains 6 tonnes of fuel. In Russia and Eastern Europe rail transport is most often used. Intercontinental transports are mostly by sea, though occasionally transport is by air.
The annual operation of a 1000 MWe light water reactor requires an average fuel load of 27 tonnes of uranium dioxide, containing 24 tonnes of enriched uranium, which can be transported in 4 to 5 trucks.
The precision-made fuel assemblies are transported in packages specially constructed to protect them from damage during transport. Uranium fuel assemblies have a low radioactivity level and radiation shielding is not necessary.
Fuel assemblies contain fissile material and criticality is prevented by the design of the package, (including the arrangement of the fuel assemblies within it, and limitations on the amount of material contained within the package), and on the number of packages carried in one shipment.
Transport of LLW and ILW
Low-level and intermediate-level wastes (LLW and ILW) are generated throughout the nuclear fuel cycle and from the production of radioisotopes used in medicine, industry and other areas. The transport of these wastes is commonplace and they are safely transported to waste treatment facilities and storage sites.
Low-level radioactive wastes are a variety of materials that emit low levels of radiation, slightly above normal background levels. They often consist of solid materials, such as clothing, tools, or contaminated soil. Low-level waste is transported from its origin to waste treatment sites, or to an intermediate or final storage facility.
A variety of radionuclides give low-level waste its radioactive character. However, the radiation levels from these materials are very low and the packaging used for the transport of low-level waste does not require special shielding.
Low-level wastes are transported in drums, often after being compacted in order to reduce the total volume of waste. The drums commonly used contain up to 200 litres of material. Typically, 36 standard, 200 litre drums go into a 6-metre transport container. Low-level wastes are moved by road, rail, and internationally, by sea. However, most low-level waste is only transported within the country where it is produced.
The composition of intermediate-level wastes is broad, but they require shielding. Much ILW comes from nuclear power plants and reprocessing facilities.
Intermediate-level wastes are taken from their source to an interim storage site, a final storage site (as in Sweden), or a waste treatment facility. They are transported by road, rail and sea.
The radioactivity level of intermediate-level waste is higher than low-level wastes. The classification of radioactive wastes is decided for disposal purposes, not on transport grounds. The transport of intermediate-level wastes take into account any specific properties of the material, and requires shielding.
In the USA there had been 9000 road shipments of defence-related transuranic wastes for permanent disposal in the deep geological repository near Carlsbad, New Mexico, by October 2010, without any major accident or any release of radioactivity. Almost half the shipments were from the Idaho National Laboratory. The repository, known as the Waste Isolation Pilot Plant (WIPP), is about 700 m deep in a Permian salt formation.
Transport of used nuclear fuel
When used fuel is unloaded from a nuclear power reactor, it contains: 96% uranium, 1% plutonium and 3% of fission products (from the nuclear reaction) as well as a small amount of transuranics.
Used fuel will emit high levels of both radiation and heat and so is stored in water pools adjacent to the reactor to allow the initial heat and radiation levels to decrease. Typically, used fuel is stored on site for at least five months before it can be transported, although it may be stored there long-term.
From the reactor site, used fuel is transported by road, rail or sea to either an interim storage site or a reprocessing plant where it will be reprocessed.
Used fuel assemblies are shipped in Type B casks which are shielded with steel, or a combination of steel and lead, and can weigh up to 110 tonnes when empty. A typical transport cask holds up to 6 tonnes of used fuel.
Since 1971 there have been some 7000 shipments of used fuel (over 80 000 tonnes) over many million kilometres with no property damage or personal injury, no breach of containment, and very low dose rate to the personnel involved (e.g. 0.33 mSv/yr per operator at La Hague). This includes 40,000 tonnes of used fuel shipped to Areva's La Hague reprocessing plant, at least 30,000 tonnes of mostly UK used fuel shipped to UK's Sellafield reprocessing plant, 7040 t used fuel in over 160 shipments from Japan to Europe by sea (see below) and over 4500 tonnes of used fuel shipped around the Swedish coast. In the USA naval spent fuel is routinely shipped by rail to Idaho National Laboratory.
Some 300 sea voyages have been made carrying used nuclear fuel or separated high-level waste over a distance of more than 8 million kilometres. The major company involved has transported over 4000 casks, each of about 100 tonnes, carrying 8000 tonnes of used fuel or separated high-level wastes. A quarter of these have been through the Panama Canal.
In Sweden, more than 80 large transport casks are shipped annually to a central interim waste storage facility called CLAB. Each 80 tonne cask has steel walls 30 cm thick and holds 17 BWR or 7 PWR fuel assemblies. The used fuel is shipped to CLAB after it has been stored for about a year at the reactor, during which time heat and radioactivity diminish considerably. Some 6000 tonnes of used fuel had been shipped to CLAB by mid-2015, much of it around the coast by ship.
Shipments of used fuel from Japan to Europe for reprocessing used 94-tonne Type B casks, each holding a number of fuel assemblies (e.g. 12 PWR assemblies, total 6 tonnes, with each cask 6.1 metres long, 2.5 metres diameter, and with 25 cm thick forged steel walls). More than 160 of these shipments took place from1969 to the 1990s, involving more than 4000 casks, and moving several thousand tonnes of highly radioactive used fuel – 4200t to UK and 2940t to France.
Within Europe, used fuel in casks has often been carried on normal ferries, e.g. across the English Channel.
Canada’s Nuclear Waste Management Organization has published a paper showing spent nuclear fuel shipments worldwide:
- Canada: 5 per year by road.
- USA: 3000 up to 2013 by road, rail and ship.
- Sweden: 40 per year by ship.
- UK: 300 per year by rail.
- France: 250 per year by rail.
- Germany: 40 per year by rail.
- Japan: 200 to 2013 by ship.
Areva TN and EdF report 5000 rail and road shipments of used fuel from 1981 to 2015, with a current rate of more than 200 per year. More than 16,000 high burn-up fuel assemblies have been transported.
Transport of plutonium
Plutonium is separated during the reprocessing of used fuel. It is normally then made into mixed oxide (MOX) fuel.
Plutonium is transported, following reprocessing, as an oxide powder since this is its most stable form. It is insoluble in water and only harmful to humans if it enters the lungs.
Plutonium oxide is transported in several different types of sealed packages and each can contain several kilograms of material. Criticality is prevented by the design of the package, limitations on the amount of material contained within the package, and on the number of packages carried on a transport vessel. Special physical protection measures apply to plutonium consignments.
A typical transport consists of one truck carrying one protected shipping container. The container holds a number of packages with a total weight varying from 80 to 200 kg of plutonium oxide.
A sea shipment may consist of several containers, each of them holding between 80 to 200 kg of plutonium in sealed packages.
Transport of vitrified waste
The highly radioactive wastes (especially fission products) created in the nuclear reactor are segregated and recovered during the reprocessing operation. These wastes are incorporated in a glass matrix by a process known as 'vitrification', which stabilises the radioactive material.
The molten glass is then poured into a stainless steel canister where it cools and solidifies. A lid is welded into place to seal the canister. The canisters are then placed inside a Type B cask, similar to those used for the transport of used fuel.
The quantity per shipment depends upon the capacity of the transport cask. Typically a vitrified waste transport cask contains up to 28 canisters of glass.
Return nuclear waste shipments from Europe to Japan since 1995 are of vitrified high-level wastes in stainless steel canisters. Up to 28 canisters (total 14 tonnes) are packed in each 94-tonne steel transport cask, the same as used for irradiated fuel. Over 1995-2007 twelve shipments were made from France of vitrified HLW comprising 1310 canisters containing almost 700 tonnes of glass. Return shipments from the UK commenced in 2010, and there will be about 11 shipments over at least eight years to move about 900 canisters.
In 1993, the International Maritime Organisation (IMO) introduced the voluntary Code for the Safe Carriage of Irradiated Nuclear Fuel, Plutonium and High-Level Radioactive Wastes in Flasks on Board Ships (INF Code), complementing the IAEA Regulations. These complementary provisions mainly cover ship design, construction and equipment. The INF Code came into force in January 2001 and introduced advanced safety features for ships carrying used fuel, MOX or vitrified high-level waste.
There are at least five small purpose-built ships ranging from 1250 to 2200 tonnes (DWT), and four purpose-built ships almost of 3800 to 4900 tonnes (DWT), and able to carry class B casks and other materials. They conform to all relevant international safety standards, notably INF-3 (Irradiated Nuclear Fuel class 3) set by the IMO. This allows them to carry highly radioactive materials such as high-level wastes and used nuclear fuel, as well as mixed-oxide (MOX) fuel and plutonium.
The three largest ships belong to a British-based company Pacific Nuclear Transport Ltd (PNTL), a subsidiary of International Nuclear Services Ltd (INS)*. They all have double hulls with impact-resistant structures between the hulls, together with duplication and separation of all essential systems to provide high reliability and also survivability in the event of an accident. Twin engines operate independently. Each ship can carry up to 20 or 24 transport casks. The three PNTL vessels now in service, Pacific Heron, Pacific Egret and Pacific Grebe, were launched in Japan in 2008, 2010 and 2010 respectively. They are 4916 tonnes deadweight and 104 metres long.Pacific Grebe carries mainly wastes, the other two mainly MOX fuel. Earlier ships in the PNTL fleet mainly carried Japanese used fuel to Europe for reprocessing. The PNTL fleet has successfully completed more than 180 shipments with more than 2000 casks over some 40 years, covering about 10 million kilometres, without any incident resulting in release of radioactivity.
Sweden’s SKB has commissioned a slightly larger replacement for its 1982 Sigyn, the Sigrid, launched in Romania in 2012 and designed by Damen Shipyards in Netherlands. It is used for moving used fuel from reactors to the interim waste storage facility. Sigrid is equipped with a double hull, four engines and redundant systems for safety and security. It was commissioned in 2013 and carried its first shipment in January 2014. Sigrid is 99.5 metres long and 18.6 metres wide, 1600 deadweight tonnes (DWT) and capable of carrying twelve nuclear waste casks. (Sigyn was 1250 tonnes deadweight and carried ten casks. It awaits further assignment.)
Rosatomflot is operating the 1620 deadweight tonne (DWT) Rossita, built in Italy and completed in 2011. It is designed for transporting spent nuclear fuel and materials of decommissioned nuclear submarines from Russian Navy bases in North-West Russia. It will be used on the Northern Sea Route, between Gremikha, Andreyeva Bay, Saida Bay, Severodvinsk and other places hosting facilities which dismantle nuclear submarines. Spent fuel is to be delivered to Murmansk for rail shipment to Mayak. Rosatomflot has the Serebryanka (1625 DWT, 102 m long, built 1974) already in service. The Imandra (2186 DWT, 130 m long, built 1980) is described as a floating technical base but is reported to be already in service transporting used fuel and wastes from the Nerpa shipyard and Gremikha to Murmansk. (Andreyeva Bay is the primary spent nuclear fuel and radioactive waste storage facility for the Northern Fleet, some 60 km from the Norwegian border. It has about 21,000 spent nuclear fuel assemblies and about 12,000 m3 of solid and liquid radioactive wastes.)
Rossita is an ice-class vessel and is designed to operate in harsh conditions of the Arctic. The ship is 84 m long and 14 m wide, with two engines, and has two isolated cargo holds holding up to 720 tonnes in total. On board, the radiation monitoring is carried out by both an automated multi-channel system and a set of portable instrumentation. The EUR 70 million vessel was given to Russia as part of Italy’s commitment to the G-8 partnership program for cleaning up naval nuclear wastes, and is designed to cover all needs in spent nuclear fuel and radwaste shipments in northwest Russia throughout the entire period of cleaning up these territories
See also paper on Japanese waste and MOX shipments from Europe.
There has never been any accident in which a Type B transport cask containing radioactive materials has been breached or has leaked.
For the radioactive material in a large Type B package in sea transit to become exposed, the ship's hold (inside double hulls) would need to rupture, the 25 cm thick steel cask would need to rupture, and the stainless steel flask or the fuel rods would need to be broken open. Either borosilicate glass (for reprocessed wastes) or ceramic fuel material would then be exposed, but in either case these materials are very insoluble.
The transport ships are designed to withstand a side-on collision with a large oil tanker. If the ship did sink, the casks will remain sound for many years and would be relatively easy to recover since instrumentation including location beacons would activate and monitor the casks.
a. Any goods that pose a risk to people, property and the environment are classified as dangerous goods, which range from paints, solvents and pesticides up to explosives, flammables and fuming acids, and are assigned to different classes ranging from 1 to 9 under the UN Model Regulations:
- Class 1: Explosives
- Class 2: Gases
- Class 3: Flammable liquids
- Class 4: Other flammables
- Class 5: Oxidising agents
- Class 6: Toxic and infectious substances
- Class 7: Radioactive materials (regardless of degree of chemical or radiological hazard)
- Class 8: Corrosives
- Class 9: Miscellaneous: asbestos, lithium batteries, etc.
When transported these goods need to be packaged correctly as laid out in the various international and national regulations for each mode of transport, to ensure that they are carried safely to minimise the risk of an incident.
The US NRC defines, for transport purposes only, radioactive materials as those with specific activity greater than 74 Bq per gram. This definition does not specify a quantity, only a concentration. As an example, pure cobalt-60 has a specific activity of 37 TBq per gram, which is about 500 billion times greater than the definition. However, uranium-238 has a specific activity of only 11 kBq per gram, which is only 150 times greater than the definition.