W. Pfeifer
Forschungszentrum Karlsruhe GmbH
Technisch/administrative Leitung Stillegung
Hermann-von-Helmholtz-Platz 1
76344 Eggenstein-Leopoldshafen

In the financial responsibility of the Karlsruhe Research Center, 5 reactors and 1 reprocessing plant are being decommissioned with these activities reaching a total volume of 1.93 billion Euro.

Three reactor projects have already been completed: The FR 2 research reactor is in the state of safe enclosure, the reactors KKN and HDR have been dismantled completely and the premises have been recultivated (green field).

The state of the other projects and the experience gained so far with regard to the technology and the licensing procedure shall be described in the following sections. The decommissioning progress is decisively determined by the direct disposal of the radioactive wastes. The FZK facilities and processing units available for this purpose shall be presented. Furthermore, the consequences of establishing specific organizational units as well as of a consistent project management shall be outlined.

The Forschungszentrum Karlsruhe (Karlsruhe Research Center, FZK) was founded in 1956 for research and development in the field of the peaceful use of nuclear energy. In 1961, the first research reactor built in Germany (FR 2) was taken into operation as a neutron source for materials research. In a number of scientific institutes on the premises of the FZK, the fundamentals were established for the development of

The activities particularly focused on the development of the breeder and reprocessing technology. Under the safety and radiation protection program, accident scenarios were investigated both experimentally and by means of model calculations and radiation protection systems were developed and tested.

Many experiments were performed in test facilities with irradiated and unirradiated nuclear fuel.

Other FZK activities concentrated on the building of prototype nuclear facilities on the basis of the results obtained in laboratories and pilot plants as well as on demonstrating that these facilities could be operated economically at a given safety standard.

In 1982, the proportion of nuclear projects in the entire budget of the Research Center amounted to about 75%, today it is below 15%. As a consequence, nearly all nuclear laboratories and prototype facilities were shut down in the past 10 years.

Current activities of the Karlsruhe Research Center, on the premises of which about 4000 scientists, engineers and technical staff are employed, focus on environmental research, nuclear fusion and new technologies such as microengineering and nanostructure technology as well as medical technology. Remaining activities in the nuclear field include safety research for new light water reactors and safety research in connection with the repository storage of nuclear wastes.

The state of decommissioning of the nuclear prototype plants shall be outlined below. Furthermore, aspects of the performance of decommissioning, licensing procedure, waste treatment and project execution shall be explained.

On behalf of the federal government, six larger prototype facilities were built by the Karlsruhe Nuclear Research Center. The plants were mainly operated by operation companies that had been established by industry with a view to make use of the findings obtained in the industrial facilities to be built later.

The current state of the decommissioning activities of the individual plants is as follows:

The first German research reactor, FR 2, with a thermal power of 44 MW, which is located on the premises of the Research Center, was shut down in 1981. This heavy water reactor had been taken into operation in 1961. At that moment, no experience was available as far as the technical execution of dismantling and the respective licensing procedure were concerned. The objective was not to completely dismantle the plant, but to provide for its safe enclosure /1/.

The following activities were performed until 1997:

Today, the rooms around the biological shield of the reactor are used for an exhibition on the FZK contributions to the development of nuclear technology.

The envisaged safe enclosure time is 30 years.

The HDR was taken into operation in October 1969. The HDR was a boiling water reactor with a thermal power of 100 MW. Because of a fuel element failure it was finally shut down in April 1971. Following extensive decontamination and reconstruction work, the HDR was used as a test bed for reactor safety experiments from 1974 until the end of 1991. The spectrum of experiments ranged from the simulation of airplane crashes to earthquake experiments, material parameter studies, blow down tests and hydrogen deflagration and burning experiments.

After 1991, all components of the reactor including the reactor pressure vessel were dismantled directly, the buildings were removed and in 1998 the premises were recultivated completely (green field). As the activation of the reactor pressure vessel was very low, remote-controlled technology was not required for dismantling /2/.

The KKN pressure-tube reactor was cooled and moderated with D₂O. It was erected in Niederaichbach (Bavaria) between 1966 and 1972 and then operated until 1974. It had an electric power of 100 MW. The initial decommissioning objective was to establish safe enclosure. Later it was decided to aim at obtaining a "green field" which was achieved in 1995 /3/.

This was the first time of the decommissioning of a reactor pressure vessel in the Federal Republic of Germany using remote-controlled technology. The parts were packed into transport containers and transferred to the Decontamination Department of the Karlsruhe Research Center for further treatment. The reactor internals, the pressure vessel and the biological shield were dismantled and cut into pieces by means of a grinding disc and a ring saw.

The MZFR on the premises of the Karlsruhe Research Center is a pressurized water reactor with an electric power of 60 MW, which was cooled and moderated with heavy water.

At the moment (status: end of 1998), all plant components located around the reactor pressure vessel have been dismantled and disposed of. Currently, the transfer of the remote-controlled technology into the reactor is being prepared. The reactor internals and the moderator tank will be dismantled under water using the plasma cutting technique /4/.

The objective of a "green field" is planned to be reached in 2003.

The KNK II on the premises of the Karlsruhe Research Center is a test reactor with an electric power of 20 MW. From 1971 to 1974, the plant was operated with a thermal core as KNK I. After 1977, fast core were used for fast breeder operation as KNK II.

The fuel elements, which had been highly enriched with U-235 and Pu, as well as the primary and the secondary sodium have been disposed of.

The machine hall and the secondary systems have been dismantled. At the moment, accesses for the dismantling of the primary systems are being built. Remote-controlled dismantling of the reactor tank will be started in 2001 /5/. The complete removal and the green field are expected to be reached in 2003.

The WAK has been shut down since July 1991. From 1971 to the end of 1990, about 208 t of nuclear fuel from experimental and nuclear power reactors were reprocessed.

In the main processing building, the fuel element storage pool and the auxiliary systems as well as the units of the head-end cell have been dismantled. The installations of the extraction cycles and accessory equipment are being dismantled in a remote-controlled manner /6/.

80 m³ of high-level radioactive waste concentrate (HAWC) are stored in tanks in a separate building (LAVA). A plant for HAWC solidification is being built and will be taken into operation in 2003. The major component of this facility will be a ceramic melting furnace developed by the Institute for Nuclear Waste Management (INE) /7/. The WAK decommissioning project shall be completed by the year 2009 with a green field.

According to the experience gained from the dismantling of the HDR and the KKN, the KNK may well be used as an example of the procedure as it is applied today.

The time from the beginning of decommissioning until the completion of the project with a "green field" is about 12 years, including the following major steps:

According to the Atomic Law, the decommissioning and dismantling of a nuclear facility require a license. The requirements to be complied with by decommissioning and dismantling are specified with the rules and regulations valid for the erection and operation of these facilities applied mutatis mutandis. In the seventies, uncertainty prevailed as to whether the licensing procedure of a decommissioning project had to include a public hearing in analogy to the licensing procedure required for the erection of a plant.

The decision in case of the decommissioning of the FZK reactor in Niederaichbach was made in favor of a complete licensing procedure including a public hearing. Meanwhile, the licensing procedure in the federal states of Bavaria and Baden-Württemberg is as follows:

As a prerequisite, a complete technical and operational documentation must be available at the beginning of decommissioning. Furthermore, this documentation must be adapted continuously to the respective state of the plant.

Practice shows that the evaluation and the receipt of the license can no longer be considered a time-determining step during decommissioning.

The progress of decommissioning is completely dependent on the speedy disposal of the radioactive wastes. In the case of the FZK, the radioactive wastes are being disposed of by the Central Decontamination Department (HDB). The facilities required for the processing paths shown in Fig. 2 are available at the HDB. The vitrification facility for the solidification of the high-active waste concentrate stored at the reprocessing plant (WAK) is being erected on the WAK premises.

Most of the processing facilities available at the HDB /8/ are equipped with barriers and safety systems for the treatment of alpha-containing wastes. Following the dismantling of laboratories and pilot plants of the fuel cycle, the alpha-containing radioactive wastes presently treated are generated by the current dismantling of the reprocessing plant (WAK).

The minimization of the conditioned radioactive wastes to be stored is of crucial importance. Moreover, release measurements in the controlled areas and the treatment of materials for unlimited reuse are in the center of attention.

Fig. 2. Radioactive Waste Processing Paths

According to the experience gained during the Niederaichbach decommissioning project, the following waste fractions are produced when dismantling a reactor:

Conditioning of non-heat generating wastes takes place in accordance with the preliminary repository storage conditions. The packages to be subjected to repository storage are mainly standard containers of about 7.2 m³ volume. In the FZK storage buildings 15,000 containers can be subjected to intermediate storage until a transfer to a repository will be possible.

With the adoption of a new research program by the FZK in 1994, a decommissioning division with an own budget was established in addition to the research division. A mutual financial compensation of the budgets of these divisions is not possible.

The nuclear facilities are provided with an autonomous operating organization which is responsible for decommissioning under the Atomic Law. In the decommissioning division, a small staff agrees on

The operating companies or FZK facilities are largely independent as far as the implementation is concerned. This became possible only after the transparency of the licensing procedure had been achieved as described under the section of "Licensing Procedure" above.

Decommissioning work including radiation protection at the respective working places is usually accomplished by external companies. Depending on the availability of own staff, more or less comprehensive packages of services are rendered. In case of remote-controlled dismantling of the MZFR reactor pressure vessel, a contract of the following scope was placed at a fixed price:

• detailing and procurement of the equipment
• installation of the auxiliary equipment in the reactor building
• performance of the work including radiation monitoring

The licensing documents were drafted by FZK in cooperation with engineering offices. These documents then served as a basis for the awarding of contracts.

The costs of the decommissioning projects are obvious from Fig. 3. As far as the reactors KKN, FR 2 and HDR are concerned, the operating costs are low as compared to the decommissioning costs. This must be attributed to the fact that these reactors were decommissioned before 1980 and that the experienced personnel is now employed again for the new projects.

Fig. 3. Project Costs of the Decommissioning Division

The experience gathered from the WAK, MZFR and KNK demonstrates that a socially acceptable reduction of personnel can only be achieved very slowly. The decommissioning costs decrease with the increasing technical experience of the contracted firms.

The high costs required for the decommissioning of the WAK in comparison with those of the reactors are explained by the fact that the handling of alpha-contaminated plant components requires an increased expenditure as regards barrier systems and waste treatment. Experience from the decommissioning of a comparable plant in Germany is lacking.

Technical controlling of the work packages is accomplished by means of a project management system /9/ which is coupled with the SAP accounting system of the individual contracts. The following elements are of crucial importance:

With three reactor decommissioning projects completed, sufficient experience is available for the complete dismantling of the two remaining reactors within the given cost frame until the year 2003. The remote-controlled dismantling technology employed is largely independent of the thermal power and may therefore also be applied to the decommissioning of power reactors. During the previous work, accidents or large operation failures that might have questioned the entire decommissioning concept did not occur. Radiation exposure of the staff was far below the estimated dose levels.

The deadlines fixed within the framework of the decommissioning activities performed with regard to the Karlsruhe reprocessing plant are determined decisively by the solidification of the liquid high-level waste (HAWC). Construction of the vitrification facility has started already. It will be commissioned in 2003.

By means of strict project management, cost transparency was achieved. The dismantling steps are carried out in a speedy and flexible manner. The granting of licenses is time-determining in individual cases only. The delegation of responsibility to the executing project management level and the facilities themselves proved successful.

 REFERENCES