Issue Paper 4 - Management, storage, disposal of nuclear and radioactive waste
Submission from the World Nuclear Association to the South Australian Nuclear Fuel Cycle Royal Commission
Full submission available as a pdf
The World Nuclear Association welcomed the opportunity to answer the Commission’s questions regarding the management, storage and disposal of radioactive wastes in South Australia. There is considerable international experience in handling radioactive material and wastes, which it may be noted are neither particularly hazardous nor hard to manage relative to some other toxic industrial wastes.
The storage and handling of civil nuclear wastes has been safely undertaken for more than 50 years.
The aim in radioactive waste management is to protect people and the environment utilising three general principles – concentration and containment, dilution and dispersal, delay and decay. The first two principles are also used in the management of other, non-radioactive, wastes. The third principle works by storing the waste long enough until radioactive decay renders the waste no longer radiologically hazardous.
Unlike some other toxic wastes, such as heavy metals, the principal hazard associated with nuclear waste – radioactivity – diminishes with time.
The pillar of any national waste management plan is the responsible implementation of an institutional framework. Authoritative international organisations provide advice on institutional frameworks for the management of nuclear wastes. These include the International Atomic Energy Agency (IAEA), the Nuclear Energy Agency (NEA) of the Organisation for Economic Co-operation and Development (OECD), the European Commission (EC) and the International Commission on Radiological Protection (ICRP). International agreements in the form of conventions under the auspices of the IAEA have also been established, such as the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management.
Nuclear waste can be separated broadly into three categories, requiring different treatment and disposal.
Low-level wastes comprise about 90% of the volume of civil radioactive wastes but only about 1% of the radioactivity. They are often incinerated in a closed environment to reduce volume before disposal. In many countries, low-level waste disposal facilities are established and operating without contention.
Intermediate-level wastes require some shielding and comprise sludges, resins and reactor components. They make up about 7% of the volume and 4% of the radioactivity of all civil radioactive wastes. Before disposal, it is common practise to incorporate intermediate-level waste into concrete or bitumen. Repositories are operating in Sweden, Finland, Spain, South Korea and the USA.
High-level wastes comprise about 3% of the volume and 95% of the radioactivity of all civil radioactive wastes. They may consist of separated fission products and actinides from used fuel, or the used fuel itself where national policies preclude reprocessing. National policies typically require high-level waste to be stored for about 50 years so that its radioactivity has decayed by two or three orders of magnitude before it is ready for disposal. A typical composition for used fuel is shown in Figure 1. It should immediately be apparent that the vast majority (~95%) of material is in fact unused uranium and plutonium which can be recycled if desired.
Upon being unloaded from a reactor, used fuel is initially stored under water in pools inside the reactor building, and it may then be transferred to central pool storage on site or to an offsite storage facility. Fuel pools are 7-12 metres deep to allow ample water coverage of the fuel assemblies, and to act as a shield and coolant for the fuel. The pools are robust, constructed from reinforced concrete with steel liners and are often designed to hold all of the used fuel for the operational life of the reactor. Of the world's 230,000 tonnes of used fuel, most is currently held in storage pools.
After about five years cooling under water, used fuel may optionally be transferred to dry storage. Most dry storage capacity is at reactor sites, but centralised facilities are being built in Ukraine and are proposed in the USA. Dry storage for used fuel can exist in the form of sealed steel casks, concrete cylinders, or vaults with air circulation inside concrete shielding. There is a variety of possible dry storage arrangements, either above ground or largely buried.
There is international consensus that deep geological disposal is the solution for high-level radioactive wastes.
While no facilities for civil high-level wastes are yet operating in the world, there is no reason to doubt that South Australia could safely dispose of high-level wastes in either small or large quantities. As indicated in Figure 2, the radioactivity of waste continues to fall with time, although the rate depends upon the composition of the waste.
The overwhelming lesson from attempts to construct waste facilities and repositories around the world is that public support and resolute political will are the critical elements of success.
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