25 years on – WM99 looks to the past and the future

The Waste Management (WM) Symposium, held annually at Tucson, Arizona, celebrated its 25th anniversary this year with over two thousand delegates from 30 countries. As was befitting this mature age, the event was marked by its low key, business as usual style, with delegates being treated to over 600 technical papers. A third of the participants were from abroad. As usual, there was a well arranged commercial technical exhibition, with over 150 exhibitors.

THE KEYNOTE

The keynote speaker at the opening session, Neville Chamberlain, Deputy Chairman, British Nuclear Fuels plc (BNFL), made a broad overview on the management of radioactive waste and its emergence over the years as a major issue in discussions on nuclear power. All industries give rise to waste, but nuclear waste has been seen to be uniquely dangerous to the public.

Perhaps the industry has been guilty of being too complacent. Twenty-five years ago, much of the UK low level waste was discharged into the sea with minimum treatment. Difficult to treat solid wastes were stored, mostly unconditioned, in silos and tanks, where they would be difficult to retrieve. Highly active liquid wastes were concentrated and stored in tanks. Obsolete plants and wastes were locked up, with no plans for their future decommissioning. This label of complacency could also be applied to the regulators, who did not require more.

Exciting developments have taken place during the last 25 years in radioactive waste management. Chamberlain pointed to a few of these, particularly those which his company, BNFL, had been associated with:

• Its prominent participation in the clean-up of historical residues and obsolete plants in the United States.

• The reduction of low level liquid discharge to the sea at Sellafield to a concentration which is virtually at safe drinking water levels.

• The treatment of UF6 tails in a plasma medium, separating out the uranium in an easily managed metal form and allowing the recycling of fluorine (this process is still under development).

Chamberlain went on to discuss the opposition to the reprocessing of fuel. The policy of direct disposal instead of reprocessing had been adopted because of the desire to reduce the risks of proliferation. The speaker considered that reprocessing would reduce these risks as the plutonium would be under safe supervised storage and reserved for positive end use. The chemistry of reprocessing spent fuel is relatively simple and could be carried out by many countries. And there is a lot of spent fuel around. Even if no new nuclear plants are built, there would be about 340 000 t world wide by 2010. Chamberlain advocated the construction of interim waste storage, where spent fuel can be monitored and is retrievable, while awaiting a final decision.

The keynote speaker concluded on an optimistic note regarding the future of nuclear power. The world wide recognition of the non-reversible dangers of global warming as a result of CO2 emissions from fossil fuel as well as the technological developments in radioactive waste management have contributed to dispersing some of the dark clouds that have gathered over the nuclear industry during the last twenty-five years.

INTERNATIONAL ISSUES

Most of the papers at WM Symposia tend to be “narrow and deep” on specialist radioactive waste management subjects. However, there are exceptions, with some presentations on themes with a broader significance, including attempts to find international solutions to solve “national” problems, which in reality can affect the whole world.

Swords into ploughshares

One of the most challenging tasks facing the nuclear industry today is the safe management of the weapons grade fissile material that will arise from the effectuation of the disarmament treaties being negotiated today by the United States and Russia. Several international studies have indicated that conversion of weapons grade plutonium to MOX fuel would be a safe, efficient, non- proliferating and economic method of dealing with this problem.

Since 1992, separate bilateral studies (Russia/France and Russia/Germany) had affirmed the feasibility of recycling weapons grade plutonium by the production of MOX for Russian VVER 1000 and fast reactors (eg the BN 600). In 1996, the three countries decided to combine their efforts. Cogema and Siemens, supported by MINATOM, launched the DEMOX project aiming to design, construct and start-up a MOX demonstration plant in Russia.1

All three parties bring considerable experience into the co-operation. Cogema’s Advanced MIMAS (A-MIMAS) process has been developed for 30 years together with Belgonucleaire. Over 1000 MOX fuel assemblies of MIMAS and A-MIMAS fabrication have been loaded into 30 European reactors. Cogema has also the experience of utilising 135 t heavy metal for making fast reactor fuel. Siemens has produced 160 t of LWR MOX fuel and 8 t of fast reactor fuel at its first production plant at Hanau. A newer plant, almost completed in 1995, was not taken into operation due to political reasons. Russia has accumulated very diversified experience in both fabrication and irradiation of mostly fast reactor fuel in experimental or prototype programmes.

The DEMOX demonstration plant will be built in Russia. It will use PuO2 produced by an upstream Russian plant and UO2 to make MOX fuel to be loaded into four operating VVER 1000 reactors and fast reactor fuel for a BN 600 reactor. It will process 2 t Pu per year to start with. The exact site has not been chosen. The A-MIMAS process will be used and equipment from the new (but unused) Hanau plant will be utilised as much as possible, with some small modifications. During 1999, the basic design phase will be carried out, including the production of a consolidated cost estimate. In parallel, discussions will be taken up on financing the project. It is hoped that the plant will be in operation in the early 2000s.

Another international concept aired at WM 99 was the possibility of a Japanese-Russian agreement to establish a MOX fabrication plant as well as on international spent fuel storage facility in far east Russia.2 This would be a follow-up of the DEMOX demonstration plant described above and envisages:

• MOX fuel production from excess weapons plutonium for utilities in Japan,

• Spent fuel storage for utilities in Japan, South Korea and Taiwan, where storage space is running out.

The concept is illustrated in in the first figure.

An interesting aspect of this concept is that the financing of the disposition of Russian excess weapons plutonium would be using the funds for nuclear fuel cycle management (spent fuel storage and fresh fuel) in Japan. Needless to say, there are substantial political difficulties with such an approach, the main one being of course: will this not make Russia into “the world’s nuclear dumping grounds”?

Both the above concepts include reprocessing of fissile material from weapons or fuel. There are other proposals for international storage of spent fuel. One such, being discussed between the United States and MINATOM, envisages a “Non-proliferation Trust” to set up a commercial spent fuel storage facility in Russia.3 The “profits” from this operation will be used by the Trust for non-proliferation and clean-up purposes, not for building new reprocessing plants. Another proposal, based on siting such storage facilities primarily for geological reasons was outlined by Pangea.

The Pangea concept

At a special session at WM’99, the concept of a multinational disposal facility was presented and discussed. The facility was proposed to be sited primarily for its geological suitability, without regard to political or national boundaries.4,5 The driving forces for such a development are easy to perceive. Over the last few decades, national and international programmes have invested immense efforts in developing the deep geological concept. Over the years, the importance of engineered barriers – such as the long lived copper canisters in Sweden or the high integrity overpacks in the United States – has grown in relation to depending on the inherent retentive properties of the geological media. This has been partly because of the increasing awareness of the difficulties of characterising complex geological systems with sufficient accuracy to convince the public of the long term reliability of repository performance.

The Pangea international repository concept has been developed by a broadly based team experienced in the design, construction and operation of repositories as well as in geological investigations, including the Swiss waste agency, Nagra, Golder Associates/EHL and BNFL (see NEI, July 1997, p30-32).

The approach was to first list key technical siting factors based on a review of the problems that have arisen in the various national programmes, then to identify favourable characteristics for these factors and put together a “signature” of an ideal site, with the “high isolation” properties required for a high level waste repository. This signature of seven safety-connected technical factors, along with socio-political and technical feasibility factors were used in a screening procedure, starting with a global review, successively moving to smaller regions. The global survey for large, flat, historically arid areas with stable and simple geological formations pointed to the Pangea continental mass that started to disintegrate about 80 million years ago. As seen in the world map, the largest stretch of such geologically stable land is in the desert basins of Western and Southern Australia. This area has also the socio-political stability and the technical capability for the siting of an international repository.

The publication of the proposal has however provoked very strong reactions from a spokeswoman for the Australian Industry, Science and Resources Minister, Nick Minchin, who said that the government’s position was clearly against such a scheme. However, two prominent Australian scientists have said that the Pangea proposal could provide the only solution to the international problem. The campaign for the advocacy for Australia to consider the plan includes a top adviser to President Bill Clinton, Robert Gallucci, who says that Australia’s geography and political stability make it one of the few places on the globe for such a sensitive gatekeeping job.