WIPPing up enthusiasm at WM ‘98

In May, the US Department of Energy’s Waste Isolation Pilot Plant (WIPP) was certified by the Environmental Protection Agency as able to operate safely. Despite recent hitches (see this month’s news) this was an indication that the licensing of a deep disposal facility for long-lived nuclear waste, with a system of passive barriers, is an achievable goal.

Approval for WIPP was what the participants of the recent Waste Management symposium – WM ‘98 – were waiting for at their meeting in early March. This year, the WM symposium, always one of the biggest nuclear conferences, attracted a record number of attendees (over 2000) and exhibitors (over 150). The US Department of Energy (DOE) is a prominent participant and supporter.

Topics range from international waste management policies, high and low level waste management, transportation and packaging to environmental restoration and public communication.

Besides the status reports on WIPP, other interesting presentations covered the waste progress being made in Germany and France.

THE WIPP FACILITY

Transuranic (TRU) waste generated by the US defence industry has hitherto been temporarily stored at 23 DOE sites. To receive this waste, the DOE constructed the WIPP repository, which has undergone many years of scientific analysis and political debate.

The movement of the TRU and its disposal at WIPP represents a first step in the environmental remediation of the many sites where it is currently stored. It also represents the first practical demonstration of long lived radioactive waste in an underground repository in the United States.

The repository is located in a thick bedded salt formation at a depth of 650 m below the surface. WIPP is thus likely to be the first facility in the world licensed for the deep geological disposal of long-lived nuclear waste. The salt bed at the disposal site is about 225-250 million years old and has been characterised by the US National Academy of Sciences as being “stable”. The transport of the waste from the current locations to WIPP and at the WIPP site itself has been the subject of rigorous analysis and public debate. The Academy report states that the site has one of the safest transportation systems in the US, and possibly, the world. The transport route has been tested in dry runs, where more than 10000 emergency response workers have been trained to deal with almost every imaginable scenario of mishaps that could take place on the route.

WIPP is administered by the Carlsbad Area office of the DOE and operated by the Westinghouse Waste Isolation Division. The licence application to the Environmental Protection Agency (EPA), by the WIPP developer, was supported by an international, independent appraisal of the long term performance analysis, which was performed jointly by the IAEA and the OECD Nuclear Energy Agency.

LILW DISPOSAL IN FRANCE

Turning to France, the operation of 55 nuclear power reactors for electricity generation and facilities for fuel reprocessing gives rise to large quantities of low and intermediate level radioactive waste (LILW). The responsibility for the management of this waste lies with the National Radio-active Waste Management Agency (ANDRA) which is specifically responsible for:

• The establishment of radioactive waste acceptance criteria for disposal.

• Siting and implementation of new repositories.

• Operation of repositories.

• Research on repositories for long-lived and high level waste.

• Inventory of radioactive material at all sites on French territory.

ANDRA is totally financed by the waste generators.

According to French regulations for the disposal of LILW, the disposal system must protect the general public and the environment. It must also be possible to reuse the site after a monitoring period of 300 years after closure. This restricts the disposed wastes primarily to beta/gamma emitters with half-lives of less than 30 years and

to very low amounts of long-lived alpha emitters.

The amounts of LILW generated by the three main producers are:

• EDF 7000 m3/year

• Cogema 8000 m3/year

• CEA 3000 m3/year

Waste reduction remains a priority for the French industry. Between 1988 and 1997, the volume has been reduced from 32 000 m3 to about 17 000 m3. Currently, the radwaste treatment centre, CENTRACO, is being commissioned for operation later this year. The centre will have both a solid and liquid waste incinerator as well as a melter for contaminated scrap. The total LILW volume is expected to reduce, when CENTRACO becomes operational, to an estimated 12 000 m3 in the year 2000.

The first low level waste repository in France was the La Manche Surface Radwaste Disposal Facility. The early units, when building started in 1969, were simple trenches (as was the practice in other countries) where very low level waste was packed in steel drums and more active waste was conditioned (grouted) in concrete containers or steel drums. ANDRA took over the facility in 1979. Disposal techniques had already been improved and ANDRA developed these further into two types of structures:

• Monoliths with reinforced concrete walls, top and bottom slabs, generally below ground level, for intermediate level waste or low level waste without self-sufficient containment of nuclides.

• Tumuli, generally built above ground on top of monoliths, for very low level waste or low level waste with adequate containment.

All structures are drained, with the runoff (from the top) and the leachate (through the structures) kept separate. The leachate is collected in tanks for monitoring.

The La Manche facility was closed in 1994 by capping with a layer of earth several metres thick. At closure, it held 525000 m3 of waste of about 40 000 TBq (about two-thirds is Co 60 and Cs 137).

The annual leachate reduced from 20 000 – 40 000 m3 to less than 1 000 m3 after capping.

The second repository for LILW is the Centre de l’Aube, about 200 km east of Paris. It was built between 1987 and 1991 after extensive public hearings and was taken into operation in 1992. About 76 000 m3 of waste had been deposited by the end of 1997. The total capacity, when fully built, will be 1 000 000 m3.

Waste containers are stacked in concrete vaults to be covered after filling by means of a concrete slab. During operation, the vaults are protected from rain by movable lids. Water is collected and monitored to detect infiltration into the disposal units. All handling of the waste containers is by remotely operated cranes.

MANAGING RADWASTE IN GERMANY

Moving to Germany there are 19 nuclear power plants with a power capacity of 22 GW operating today. To date, nuclear power and other radioactive waste producers have given rise to 63 000 m3 of conditioned waste and 31 000 m3 of unconditioned waste. In addition, the accumulated spent fuel has a heavy metal content of 6700 t. By the year 2080, it is estimated that there will be some 395 000 m3 LILW and about 24 000 t of heavy metal in the HLW.

An early decision was taken to dispose of all radioactive waste in deep geological repositories. The Federal government acquired the Asse salt mine in 1965 to establish the first European underground research laboratory. For more than 30 years, an R & D programme has been proceeding, now being brought to an end with a heater test, involving six spent fuel cask mockups with a total output of 36 KW.

Radioactive waste management is regulated federally by the Atomic Energy Act and related ordinances. Treatment and repository facilities are licensed by the local state. The construction and operation of repositories is the exclusive responsibility of the privately owned DBE company, under contract to the Federal government. The controversial status of nuclear power has led to long delays in licensing of facilities, due to repeated public hearings, court decisions, etc. However, considerable progress can be reported in the construction and operation of waste repositories. Three sites are being utilised and/or being developed:

Morsleben

Morsleben in the former GDR shutdown its potassium and rock salt mine. Work started in 1970 to convert it to a repository for LILW. After extensive investigations, waste disposal started in 1978, in rock cavities below the 500 m level. After the reunification of Germany, the safety was re-evaluated and confirmed by a Federal government study in 1991.

Today Morsleben is the only operational deep geological repository. LLW is packed in drums, stacked in chambers, where the voids are filled with fly ash. Higher level activity waste is delivered in shielding overpacks, stored in closed chambers, with fly ash backfilling. The waste changes ownership upon delivery, for a fee that covers all costs. By the end of 1997 Morsleben contained 32 000 m3 of LILW and 6600 sealed radiation sources.

The operational licence for Morsleben was originally valid until 30 June 2000, but has since been extended by five years. However, the quantity and activity of waste permitted to be disposed remains the same. The total amount of waste is expected to be 55000 m3 with about 1016 Bq of beta /gamma nuclides and 1013 Bq alpha emitters.

Gorleben

The salt dome at Gorleben was selected by the government of the state of Lower Saxony in 1979 as a possible site for a repository for radioactive waste. After surface exploration confirmed the suitability of the site for this purpose, underground work started in 1982. Two shafts of diameter 7.5 m have been sunk as part of an exploratory mine. Four deep boreholes to about 2000 m depth gave preliminary information regarding the stratigraphy of the dome. Drifts and boreholes will be started soon to explore the prospective waste disposal areas.

In addition, seismic profiles, geoelectric, geomagnetic and gravimetric surveys will be made to complement the direct geological mapping.

Konrad

The former iron ore mine of Konrad in Lower Saxony, which was shut down in 1976, has been investigated as a possible site for a repository. The mine is very dry and is isolated from the ground water by clayish rock.

The licence application describes a layout with six emplacement fields at depths of 800 m, 850 m, 1100 m and 1300 m. A total capacity of 650 000 m3 is envisaged, with beta-gamma activity of up to 5 x 1018 Bq and alpha activity of 1.5 x 1017 Bq. The licence is expected to be granted soon.