Friday, October 29, 2010

Radioactive Waste Management

  • Nuclear power is the only large-scale energy-producing technology which takes full responsibility for all its wastes and fully costs this into the product.
  • The amount of radioactive wastes is very small relative to wastes produced by fossil fuel electricity generation.
  • Used nuclear fuel may be treated as a resource or simply as a waste.
  • Safe methods for the final disposal of high-level radioactive waste are technically proven; the international consensus is that this should be deep geological disposal.
All parts of the nuclear fuel cycle produce some radioactive waste (radwaste) and the cost of managing and disposing of this is part of the electricity cost, i.e. it is internalised and paid for by the electricity consumers.

At each stage of the fuel cycle there are proven technologies to dispose of the radioactive wastes safely. For low- and intermediate-level wastes these are mostly being implemented. For high-level wastes some countries await the accumulation of enough of it to warrant building geological repositories; others, such as the USA, have encountered political delays.

The radioactivity of all nuclear waste decays with time. Each radionuclidea contained in the waste has a half-life – the time taken for half of its atoms to decay and thus for it to lose half of its radioactivity. Radionuclides with long half-lives tend to be alpha and beta emitters – making their handling easier – while those with short half-lives tend to emit the more penetrating gamma rays. Eventually all radioactive wastes decay into non-radioactive elements. The more radioactive an isotope is, the faster it decays.

The main objective in managing and disposing of radioactive (or other) waste is to protect people and the environment. This means isolating or diluting the waste so that the rate or concentration of any radionuclides returned to the biosphere is harmless. To achieve this, practically all wastes are contained and managed – some clearly need deep and permanent burial. From nuclear power generation, none is allowed to cause harmful pollution.

All toxic wastes need to be dealt with safely, not just radioactive wastes. In countries with nuclear power, radioactive wastes comprise less than 1% of total industrial toxic wastes (the balance of which remains hazardous indefinitely).

Types of radioactive wastes

Exempt waste & very low level waste

Exempt waste and very low level waste (VLLW) contains radioactive materials at a level which is not considered harmful to people or the surrounding environment. It consists mainly of demolished material (such as concrete, plaster, bricks, metal, valves, piping etc) produced during rehabilitation or dismantling operations on nuclear industrial sites. Other industries, such as food processing, chemical, steel etc also produce VLLW as a result of the concentration of natural radioactivity present in certain minerals used in their manufacturing processes (see also information page on Naturally-Occurring Radioactive Materials). The waste is therefore disposed of with domestic refuse, although countries such as France are currently developing facilities to store VLLW in specifically designed VLLW disposal facilities.

Low-level waste

Low-level waste (LLW) is generated from hospitals and industry, as well as the nuclear fuel cycle. It comprises paper, rags, tools, clothing, filters etc, which contain small amounts of mostly short-lived radioactivity. It does not require shielding during handling and transport and is suitable for shallow land burial. To reduce its volume, it is often compacted or incinerated before disposal. It comprises some 90% of the volume but only 1% of the radioactivity of all radioactive waste.

Intermediate-level waste

Intermediate-level waste (ILW) contains higher amounts of radioactivity and some requires shielding. It typically comprises resins, chemical sludges and metal fuel cladding, as well as contaminated materials from reactor decommissioning. Smaller items and any non-solids may be solidified in concrete or bitumen for disposal. It makes up some 7% of the volume and has 4% of the radioactivity of all radwaste.

High-level waste

High-level waste (HLW) arises from the 'burning' of uranium fuel in a nuclear reactor. HLW contains the fission products and transuranic elements generated in the reactor core. It is highly radioactive and hot, so requires cooling and shielding. It can be considered as the 'ash' from 'burning' uranium. HLW accounts for over 95% of the total radioactivity produced in the process of electricity generation. There are two distinct kinds of HLW:
Used fuel itself.
Separated waste from reprocessing the used fuel. 

HLW has both long-lived and short-lived components, depending on the length of time it will take for the radioactivity of particular radionuclides to decrease to levels that are considered no longer hazardous for people and the surrounding environment. If generally short-lived fission products can be separated from long-lived actinides, this distinction becomes important in management and disposal of HLW.

Waste management for used fuel and HLW from nuclear power reactors
CountryPolicyFacilities and progress towards final repositories
  • Central waste storage at Dessel
  • Underground laboratory established 1984 at Mol
  • Construction of repository to begin about 2035
CanadaDirect disposal
  • Nuclear Waste Management Organisation set up 2002
  • Deep geological repository confirmed as policy, retrievable
  • Repository site search from 2009, planned for use 2025
  • Central used fuel storage at LanZhou
  • Repository site selection to be completed by 2020
  • Underground research laboratory from 2020, disposal from 2050
FinlandDirect disposal
  • Program start 1983, two used fuel storages in operation
  • Posiva Oy set up 1995 to implement deep geological disposal
  • Underground research laboratory Onkalo under construction
  • Repository planned from this, near Olkiluoto, open in 2020
  • Underground rock laboratories in clay and granite
  • Parliamentary confirmation in 2006 of deep geological disposal, containers to be retrievable and policy "reversible"
  • Bure clay deposit is likely repository site to be licensed 2015, operating 2025
but moving to direct disposal
  • Repository planning started 1973
  • Used fuel storage at Ahaus and Gorleben salt dome
  • Geological repository may be operational at Gorleben after 2025
  • Research on deep geological disposal for HLW
  • Underground laboratory at Mizunami in granite since 1996
  • High-level waste storage facility at Rokkasho since 1995
  • High-level waste storage approved for Mutsu from 2010
  • NUMO set up 2000, site selection for deep geological repository under way to 2025, operation from 2035, retrievable
  • Underground laboratory in granite or gneiss in Krasnoyarsk region from 2015, may evolve into repository
  • Sites for final repository under investigation on Kola peninsula
  • Various interim storage facilities in operation
South KoreaDirect disposal
  • Waste program confirmed 1998
  • Central interim storage planned from 2016
SpainDirect disposal
  • ENRESA established 1984, its plan accepted 1999
  • Central interim storage probably at Trillo from 2010
  • Research on deep geological disposal, decision after 2010
SwedenDirect disposal
  • Central used fuel storage facility – CLAB – in operation since 1985
  • Underground research laboratory at Aspo for HLW repository
  • Osthammar site selected for repository (volunteered location)
  • Central interim storage for HLW at Zwilag since 2001
  • Central low & ILW storages operating since 1993
  • Underground research laboratory for high-level waste repository at Grimsel since 1983
  • Deep repository by 2020, containers to be retrievable
United KingdomReprocessing
  • Low-level waste repository in operation since 1959
  • HLW from reprocessing is vitrified and stored at Sellafield
  • Repository location to be on basis of community agreement
  • New NDA subsidiary to progress geological disposal
USADirect disposal
but reconsidering
  • DoE responsible for used fuel from 1998, $32 billion waste fund
  • Considerable research and development on repository in welded tuffs at Yucca Mountain, Nevada
  • 2002 decision that geological repository be at Yucca Mountain was countered politically in 2009

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