L. Nachmilner, of the Waste Technology Section in the Division of
Nuclear Fuel Cycle and Waste Technology in the Department of Nuclear
Energy at the International Atomic Energy Agency (IAEA) in Vienna, tells
E. Odjargal about the latest in the safe disposal of nuclear waste
Disposal of radioactive waste has been practised from the middle of the
last century: the collected experience has resulted in developing
several disposal concepts for all waste categories and their
construction. The only exemption is disposal of high level waste
(including spent nuclear fuel), which is not operational yet. However,
viability of disposal of this waste type has been demonstrated in the
number of underground research laboratories.
The current status of disposal technologies is indicated with respect to
recent IAEA waste classification system. Very short lived waste is
stored for decay and then cleared for disposal as non-radioactive waste.
Very low level waste can be directed into surface trenches with limited
engineered barrier system. Such facilities have been built in Sweden
(at each nuclear power plant), France and Spain (see Fig. 1). In other
countries this waste is disposed of together with low level waste.
Low level waste is typically put in near surface engineered facilities
(France, Spain, Czech Republic, Slovakia – see Fig. 2), but in arid
areas (South Africa, USA, Iran – see Fig. 3) it is disposed of in open
trenches with limited or no isolation layers (but capping of trenches
prevents water ingress into the disposal spaces). Some countries have
built subsurface engineered facilities (Sweden, Finland, Norway, Czech
Republic, Hungary, Korea – see Fig 4), others are developing a deep
geological facility (Germany, Switzerland, Canada – see Fig. 5) for this
waste category.
There is only one operational disposal facility for intermediate level
waste in the world: WIPP (USA) accepts waste contaminated by long lived
nuclides from defence programmes (see Fig. 6); Japan has initiated
construction of such a repository.
High level waste (and spent nuclear fuel) must be disposed of in a deep
geologic formation. Intensive research performed in underground
laboratories (see Fig.7) has demonstrated viability of this approach for
salt (Germany, USA), granite (Switzerland, Canada, Sweden, Japan),
plastic clay (Belgium), and claystone (Switzerland, France) host rocks.
The first repositories are anticipated to become operational in early
twenties (Sweden, Finland, France), some other countries have initiated
relevant siting and investigation programmes (Germany, Switzerland,
Czech Republic, Slovakia, Hungary, Russia).
The selection of the type and number of disposal facilities depends on
many aspects: national waste and spent fuel management policy and
strategy, waste inventories, plans for nuclear energy exploitation,
extent of the national nuclear programme. But in principle, larger
programmes prefer separate facilities for particular waste categories;
small programmes need just two of them for low level waste and
intermediate/high level waste, or may even consider co-disposal of all
waste categories in a single deep geological facility.