Cleaning up the past:lessons from Eastern Europe1 February 1998
The ICEM* meetings, organised by ASME at venues outside the US, provide a global forum for discussing the problems of and sharing the lessons learnt from cleaning up environmental black spots, such as Chernobyl and the waste piles in the eastern part of Germany left over from uranium mining which the Wismut Corp is now cleaning up. There are many other smaller cases of contamination, also legacies of the old Soviet bloc, which are now being dealt with. The meeting also provides an opportunity to introduce some sensitive issues, such as the desirability of setting up regional repositories.
This sixth ICEM conference was originally planned for Beijing and significant support came from the Chinese Nuclear Society. However, the location was later changed to Singapore. Perhaps it was this change of venue and/or the reported haze in the atmosphere from the forest fires raging in the region, but whatever the reasons, the attendance was less than expected. Chinese participation, of particular interest for the exhibitors, was not notable.
However, the conference participants were treated to an interesting collection of over 200 technical papers during the 31/2 day meeting. For this occasion, participants received paper copies of the proceedings, instead of the compact discs that have become more or less the rule at many large international meetings. This was specially appreciated by the delegates.
REMEDIATION OF WISMUT SITES
One of the largest and most significant on-going remediation projects is the rehabilitation of the large uranium mining and processing complex, called Wismut, in the provinces of Saxony and Thuringia in the eastern part of Germany. Starting as a wholly Soviet-owned company in 1946, the Wismut Corporation (the German word “wismut,” for the metal bismuth, was the code name for the project) was converted into a joint Soviet-German stock company in 1954. By the end of the 1960s, the company employed almost 100000 people. Uranium ore was mined both from open pits and in underground mines, the deepest going to a depth of 1800 m. When production was terminated at the end of 1990 after about 45 years of operation, a total of about 220 000 t of uranium had been produced. This puts the Wismut Corp as the third largest producer of uranium in the world over the past 50 years, after the US and Canada.
After more than four decades of intensive uranium production, the environmental effects in an area of about 200 km by about 50 km along the Czech-German border, are clearly visible. The intensive mining in this densely populated area has left behind it a large number of shafts, waste rock piles, tailings ponds and an open pit mine.
The affected area is about 37 km2 and has been placed under the responsibility of the remediation programme managed by the reorganised company Wismut GmbH. The programme is organised in several hundred decommissioning and remediation projects.
The largest potential health hazards to the public and the risks to the environment are presented by the uranium mill tailings, which are deposited in ponds up to 70 m deep near the milling operations. The ponds near the Seelingstädt and Crossen mills contain about 160 million m3 of extremely fine-grained, water-saturated tailings, with about 1.5 x 1015 Bq of Ra-226. In-situ stabilisation is planned by step-wise drying and solidifying the upper part of the tailings and covering the surface with clay and soil.
Another major problem is the contaminated ground water at the mining sites. During the operating years, the mines were drained by pumping. After shutdown in 1990, the shafts have been filled by ground water. The problems here are contamination from the uranium bearing rock as well as sulphuric acid generation due to oxidation of back-filling material. So water treatment plants have had to be built at a number of sites. More are under construction.
The Wismut decommissioning and remediation programme is federally financed and has a budget of $7 billion for completing the project over a period of 15-20 years. $2.8 billion has been spent to date. The clean-up effort executed up to now has already begun to produce economic, ecological and social changes in a area that had depended solely on uranium production. The photographs show the site of the Schlema/Aue uranium mine before and after remediation.
REMEDIATION IN SLOVENIA
Remediation on a totally different scale, but interesting in its own way, took place in an old military barracks near the village of Zavartec in Slovenia. The radioactivity involved was tiny compared to the Wismut project – 370 MBq released from a radium ampule that had been opened by mistake in a laboratory in Ljubljana in 1961. The waste resulting from the decontamination of the rooms in which the activity had been spread, consisting of medical equipment, furniture, books, wall and floor coverings etc, had been secretly transported to and stored in this barrack. The local public were not informed. After a break-in, the entrance to the barrack was walled up.
The crucial problems in this case were the strongly negative public attitude towards nuclear issues and a deeply rooted distrust of all state institutions. The mushrooming of public speculation and pressure led to the Slovenian government decision in 1992 to instruct RAO, the national agency for radwaste management, to clean up the facility. The remediation was to be performed in two phases. In a first phase, the sealed barrack would be opened, the waste would be radiologically characterised and, if found necessary, repacked for intermediate/final storage. The second phase would involve a decision as to whether the repacked waste would remain on site or be relocated at the central storage for waste producers such as medicine, industry and research. Slovenia has no final repository for low and intermediate level waste.
An effective public relations and information programme was a central feature of this project. Transparency of all decisions and actions was the main imperative of the programme. In response to local demands and as compensation for the illegal radioactive waste storage over 35 years, the state agreed to financially support the construction of a water supply system for the village. Remediation activities took 10 days after the opening of the facility. The media and public were invited to watch, in spite of the reduction this caused in project efficiency. The reporting was mainly objective, the sensational content reducing each day.
The waste was measured and repacked into 200 litre drums, with 320 litre overpacks, resulting in 77 overpacks and 20 drums. At present the repacked waste is stored in the decontaminated, plastic lined barrack. Discussions are going on regarding the future storage site for the repacked waste: to remain where it is or to be relocated at the central storage. Again, it looks as if economic compensation will be an important factor in the decision making process.
SURF AT CHERNOBYL
An on-site waste management centre (CPPRO) is being planned as part of the remediation of the Chernobyl exclusion zone. A central feature of this centre is a melting plant for radioactively contaminated material in the area: SURF (Smelter for the Ukrainian Radwaste Facility). The metal scrap in the 30 km exclusion area, mainly consisting of spare parts for the power plant and naval equipment at the Chernobyl shipyard, amounts to more than 100 000 t and has a radioactivity content of about 400 Bq/g for beta/gamma nuclides, dominated by Cs-137 and Sr-90. This makes it very suitable for decontamination by melting, where the volatile nuclides, like Cs-137, can be trapped in the dust filters and the heavy nuclides can be slagged out. The secondary waste will be only a few percent of the original mass and is disposed of as radioactive waste.
The melting technology is based on the experiences at the German company Siempelkamp’s CARLA plant at Krefeld, where 10 000 t of contaminated scrap from nuclear facilities had been melted for recycling within the nuclear industry. The recycled material has gone into the production of transport casks for waste or fine granules for heavy concrete used as shielding. At Chernobyl this concrete could go into the refurbishment work on the Sarcophagus.
The melting plant will have a capacity of 10 000 t/y, with both inductive and electric arc furnaces, a blasting shop for pre-treatment, a segmenting shop, with ventilation and filtration to nuclear facility standards. Its proposed location, as shown in the diagram, is close to the cooling ponds in the power plant area. The melting plant will be part of the CPPRO facilities, using a common infrastructure and utilities. The plant is planned for handling material with up to 1000 Bq/g or 1000 Bq/cm2 radioactivity. At present, the expected release limits for material from the plant are 74 Bq/g (beta/gamma) and 7.4 Bq/g (alpha). It is probable, however, that in actual practice, levels closer to the European values of 1 Bq/g (beta/gamma) will be used.
The project has been an excellent example of international co-operation in waste management. The licensing of the plant is following German procedures and regulations, suitably modified to harmonise with Ukrainian regulations and local conditions. The Ukrainian authorities, the German local licensing authorities and Siempelkamp AG have co-operated in this work. The planning study as a whole has been sponsored by the European Commission.
An interesting topic which comes up from time to time was cautiously mentioned in the keynote lecture: international regional repositories. A recent German study had shown that the largest part of the costs for siting, constructing and operating an underground repository for waste could be classified as fixed costs, not relating quantitatively to the amount of waste disposed. So jointly owned and operated international repositories would be economically advantageous, especially for producers of small quantities of waste.