July 2nd 2014 the US MV Cape Ray ship was deployed to destroy a stockpile of chemical weapons as a part of an international effort to neutralise the threat of weapons of mass destruction. Chemical weapons would be disposed at sea with guarantee that it would not damage the marine ecology. Chemical weapons significantly differ from conventional waste from ships thus warrants a more sophisticated approach and action; something that not many maritime operators are prepared for.
Assume that your company got hold of hazardous waste, possibly even radioactive and thus has a chance to cause massive damage to your reputation, the environment and other maritime operators in close proximity to you; what to do with this dangerous load and how to avoid all the potential damage. We recommend taking a cargo survey first in order to get another perspective from experts who know more about hazardous cargo and will give recommendations based on what they may have experienced.
Radioactive waste comes in different categories:
- Exempt waste; excluded from regulatory control due to negligible radioactive hazard.
- Low-level waste ;( LLW) contains enough radioactive material warranting a response but not handling or storage.
- Intermediate-level waste; (ILW) requires shielding, may contain 4000Bq/g and have Half-life of over 30 years and alpha emitters.
- High-level waste; (HLW) requires shielding and cooling and generates >2kW/m3 of heat and long Half-life periods and alpha-emitting isotopes.
As nuclear waste comes in different categories it requires different handling from transport to disposal as consequences will vary. Twenty million consignments of varied sizes get routinely transported on sea, roads and rails while 430 nuclear power reactors operate in 32 countries and transport is often at a long distance. Transporting of nuclear waste starts from containers as this decision provides assurance for safe freight so it is worth discussing package types and purposes. Firstly, selection and design of a container is the responsibility of the consignor which leaves him with the prediction of potential hazards and accidents. LLW waste such as Uranium Oxide (U3O8) concentrate shipped from mines are transported with standard industrial/Type A containers and are capable of withstanding minor accidents. Medical or industrial radioisotopes can be transported in such containers.
HLW waste such as used fuel rods and MOX fuel are to be transported by Type B containers which shield from gamma and neutron radiation under extreme conditions; Type B packages have 150 variants and can cost a maximum of 1.6 million US Dollars per piece. In France, for example there are 750 yearly shipments of Type B packages in relation to 15 million shipments classified as “Dangerous Goods” out of which there are 300,000 radioactive materials. An example of a Type B shipping package is the Holtec HI-STAR 80 (Storage, Transport and Repository) consists of numerous steel layers covering a cylinder structure holding 12PWR or 32BWR high burn-up used fuel assemblies and two aluminum impact limiters. The HI-STAR 190 container holds the highest heat load capacity worldwide with 38kW.
Uranium oxide concentrate which is transported from mines to conversion plants does not require radiation protection aside from clean steel drums within the container. However, upon transportation to and from enrichment plants the uranium is in the form of uranium hexafluoride (UF6) which is not radioactive but highly toxic.
Fuel assemblies, which are manufactured at fabrication plants, are made up of ceramic pellets which are formed from pressed uranium oxide sintered over 1400 degrees; pellets are aligned within long hollow metal rods. Western Europe, Asia and the US transport uranium fuel assemblies commonly by truck/on the road with a typical load that supplies a light water reactor with 6 tonnes.
LLW and ILW waste generates from the nuclear fuel cycle and from production of medical and industrial radioisotopes. LW wastes are composed of materials emitting low-level radiation which consist of solids, (cloth, contaminated soil, tools) where radioactive properties are given by radionuclides but regardless its level is low and does not require special shielding. LLW is transported in 200 liter drums which are compacted to reduce total volume of waste and are transported in a 6 meter container and is commonly transported by road locally in the country where it is produced and internationally by sea.
ILW is composed of a varied chemical composition but it requires shielding and comes from nuclear power plants and reprocessing facilities. Classification of radioactivity of ILW is decided for disposal purposes only; however transport mode is takes into account properties of the ILW material.
Used Nuclear Fuel
Upon unloading from a reactor the waste contains 96% uranium, 1% plutonium and 3% fission products along with transuranics. It will emit high levels of radiation and heat which means it is stored in water pools adjacent to the reactor, stored for 5 months; decreasing heat and radiation levels in advance. Later, waste is shipped in Type B containers lined with steel and lead; holding 6 tonnes of used fuel. 7000 shipments, (over 80,000 tonnes) were made since 1971.
It is separated during reprocess of used fuel and converted to mixed oxide/MOX fuel; plutonium is then transported as an oxide powder, the most stable form; insoluble in water and harmful only upon inhalation. A typical shipment will consist of several containers holding 80-200kg of plutonium in sealed packages.
Highly radioactive and mostly a product of nuclear fission and coming from the reactor itself; stabilised by a glass matrix; later transported in a Type B container, containing 28 canisters in a typical situation.
Overall, different categories of hazardous waste warrant different methods of shipping and handling to avoid accidents. Disposal is done in large quantities and on a global scale where most of it comes from industry; however modern days are now seeing disposal of weapons-grade waste which differs significantly and thus warrants further development in technology of waste disposal.