STATUS OF PLANNING AND LICENSING OF
THE GERMAN HLLW VITRIFICATION PLANT
J. Fleisch, W. Grünewald, W. Lumpp
K.G. Roth, W. Tobie
Forschungszentrum Karlsruhe GmbH (FZK)
Hermann-von-Helmholtz-Platz 1
D-76344 Eggenstein-Leopoldshafen
ABSTRACT
The former German pilot reprocessing plant WAK (Wiederaufarbeitungsanlage Karlsruhe) is subject of decommissioning since 1991. Completion to the green field is foreseen until the year 2009. A main subproject of the decommissioning activities concerns the conditioning of the high level liquid waste (HLLW) currently stored on site.
The HLLW will be vitrified in a new vitrification facility designated VEK. The plant is designed with particular reference to the limited waste volume to be vitrified and to the subsequent immediate decommissioning. The technology used is based on a liquid-fed ceramic waste glass melter. The features and the general layout of this plant are presented.
Planning and licensing activities are running since 1996. According to the German Atomic Law, and based on an extensive Safety Analysis File, erection and operational licenses have been applied for in December 1996. A conceptional expertise finished in late 1997 indicates that there is no technical deficit within the facility concept. A public hearing is envisaged for mid of 1998. The progress achieved for planning and licensing as well as the results of an environmental impact analysis are presented.
INTRODUCTION
As a consequence of the abandoning of the Wackersdorf Reprocessing Plant Project in 1989 the Karlsruhe Reprocessing Plant WAK, designed as a pilot plant for the development of future commercial reprocessing, was shut down in late 1990. After approximately 20 years of operation and 208 metric tons of oxide fuel with a burn-up up to 40 GWd/MTU were processed. Under contract between the German government, The Forschungszentrum Karlsruhe (FZK), the Wiederaufarbeitungsanlage Karlsruhe GmbH (WAK) and the Deutsche Gesellschaft für Wiederaufarbeitung von Kernbrennstoffen (DWK) the complete decommissioning of the WAK plant is foreseen until the year 2009.
Decommissioning and dismantling of the WAK plant includes vitrification of the 70 m3 of high level liquid waste (HLW) currently stored in two tanks at the site and containing 8.9E17 Bq of b /g radioactivity in total. The initial efforts for vitrification of this waste were directed to make use of the existing PAMELA vitrification plant at Mol/Belgium, which had been actively operated during 1985-91 at the former EUROCHEMIC site, now BELGOPROCESS (BP) site.
Vitrification of the HLLW in PAMELA involved the transport of the liquid high level waste from WAK to the plant in Belgium including erection of a filling station at WAK and a receiving station at BP. Although the techniques for performing these presteps prior to vitrification were considered well available and safe, this efforts were given up two years ago and replaced by an on site solution. It involves the design and erection of a site-adjusted new vitrification facility with the aim to start up hot operation in the year 2003.
By on-site vitrification of the HLLW in a new facility foreseeable cost related risks can be avoided, which could arise from transportation to Belgium. The expenditure caused by filling and transporting about 30 flasks over a distance of about 300 miles can be avoided and hence also the difficulties encountered by restricted acceptance in politics and by the public. Compared to the complex procedure of border crossing transports, the licensing procedure can be implemented purpose oriented. The facility can be built on an already secured site.
The on site project has been established since September 1996. Licensing of the plant is under the responsibility of the Ministry for Economic of the Federal State of Baden-Württemberg. The license for the waste form qualification for final disposal will be issued by the Federal Office for Radiation Protection (Bundesamt für Strahlenschutz, BfS).
PROCESS DESCRIPTION
The on site vitrification plant VEK (Verglasungseinrichtung Karlsruhe) is based on the liquid-fed ceramic melter process as it is used at various sites (PAMELA in Belgium, Savannah River and West-Valley in US, Tokai Mura in Japan). A simplified flowsheet of the VEK process is shown in Fig. 1. The nitric acid HLLW is batchwise transferred from the storage area into a receiving tank of the VEK via a short pipe bridge. After transfer to a feeding vessel in the vitrification cell, the HLW is continuously fed into the ceramic lined melter. Borosilicate glass frit is directly added to the melter through a separate line via an airlock system. On top of the molten glass pool a cool process zone ("cold cap") is formed, where subsequently evaporation of the liquid waste, decomposition of the nitrates and melting of the frit with the waste residue takes place. The glass melt is periodically poured into stainless steel canisters through a medium-frequency heated bottom drain freeze valve of the melter. The glass pool is Joule-heated by passing electric current between power electrodes placed on opposite melter walls and fabricated of INCONEL 690. The melter has a pool surface of 0.4 m2 and is designed for a glass melting rate of minimum about 5 kg/h. A waste glass loading with waste oxides of nominally 16 wt.% is envisaged /1/.
Fig. 1. Simplified flowsheet of the VEK vitrificatin process.
The off-gas is cleaned in an off-gas system consisting of a wet part and a dry section. The first component is a dust removal wet scrubber, followed by a condenser, a jet scrubber, and a NOx-column. Whereas the dust scrubber solution is directly recycled into the process, the condensate and the other secondary liquid waste are concentrated by evaporation and then recycled. The dry section of the off-gas system consists of redundant sets of glass fiber filter, Iodine filter, two HEPA filters and off-gas blower.
The glass canisters are welded after cooling, decontaminated in a nitric-acid pool by ultra sonic cleaning, and checked before loaded into transport and storage casks of the CASTOR type for interim storage.
STATUS OF PLANNING
Conceptional Design
The conceptional design has been completed in late 1997. The VEK process building has been placed close to the HLLW storage area in order to use the existing pipe bridge for transfer of the HLLW from the storage area to the new building. The location of the process building and the existing buildings is shown in Fig. 2.
Fig. 2. Location of the VEK process building at the WAK site.
According to the basic concept of the arrangement, the major hot cells, including the receiving cell, the vitrification cell with the melter, the canister handling cell, and the subsequent loading area of glass canisters into CASTOR casks are placed in a line. A longitudinal cross section of the process building is shown in Fig. 3.
Fig. 3. Longitudinal cut view of the VEK process building.
The receiving cell comprises two receiver tanks of app. 2 m3 volume each and the evaporator systems where the secondary wastes from the scrubbers and the vessel off-gas system are concentrated and recycled into the process. The adjacent vitrification cell contains, besides the melter, the feeding vessel and the two first off-gas cleaning systems, the dust scrubber, and the condenser. The off-gas is cleaned and reduced in volume there leaves the vitrification cell and passes the off-gas cell 1 accommodating the jet scrubber and NOx absorbers. In off-gas cell 2 the dry filter section for finalizing purification has been installed.
Filled canisters are transferred by a transport vehicle and a crane from the vitrification cell; into the canisters handling cell, where the cooling station, the welding station, and the decontamination equipment (ultrasonic bath) with check of the surface contamination are foreseen. A buffer storage with a capacity of 36 positions decouples the continuous vitrification process from the subsequent periodical transport to an external interim store in suitable transport flasks, e.q. the CASTOR HAW 20/28.
Because of the short service life of the facility, replaceability of the process components is limited to the necessary extent. All components outside the vitrification cell are permanently installed. Within the vitrification cell the melter and the dust scrubber can be completely replaced by remote handling. In case of a melter failing precociously a storage place has been provided between the vitrification cell and the canister handling cell. The melter will be dismantled in the vitrification cell at the end of the operational time.
Detailed Design and Safety
Detailed engineering and licensing procedures for construction and operation are in an advanced stage. The VEK facility is designed in a way that even under extreme accident conditions nontolerable higher radiation exposure to the operational staff and the environment can be excluded. The main characteristic production data of the VEK plant are given in TABLE I .
Table I . VEK Production Data
Starting from the VEK minimum throughput of 8 l HLW per hour a net service life (24-h-operation) of 14 months is calculated which is needed to vitrify the total HLW inventory. Considering real availability, a total service life of eighteen months is assumed.
A detailed accident analysis has been carried out, considering external and internal events e.q. aircraft and earthquake impacts, criticality, explosion, loss of power supply, fire, strong chemical reactions. Thus the building is equipped with an outer wall thickness of 1.80 m resistant against aircraft crashes, preventing any wall penetration with the consequence of a severe activity release. The mechanical and process components are designed in a way that earthquake accelerations up to 2 m/s2 (horizontal) do not have any influence on the global stability and integrity. A HLW leakage of 1.6 m3 into the receiving cell and a sudden break of the melter off-gas jumper have been identified as radiological representative accidents, resulting in emission rates of 4 x 108 Bq and 1.8 x 108 Bq, respectively. The effective dose rate to the public has been calculated under very conservative conditions to be in the range of 0,2 mSv, which is by a factor of more than 102 below the relevant acceptable limits according to the German Law.
The call for bid documents are being prepared and as far as site preparation and civil work concerned already sent off.
LICENSING
The application of FZK/WAK for licensing was submitted to the Ministry of Economic of the Federal State of Baden-Württemberg in late 1996. The application included the Safety Analysis File, a Security File and an Environmental Impact Analysis. The various involved authorities and institutions (mainly independent experts) are indicated in Fig. 4.
Fig. 4. Institutions and organizations involved in the licensing procedure of the VEK plant and of the Waste form qualification.
For licensing, the Ministry of Economic of the state of Baden-Württemberg in turn cooperates closely with the Ministry of Environment and Traffic as well as with the Ministry of Interior of the state. Some other licensing authorities and state institutions are also involved in the licensing procedure. Examinations of experts based on the FZK/WAK application documents, are prepared by the independent technical control organisation TÜV (Technischer Überwachungsverein Energie- und Systemtechnik GmbH Baden-Württemberg) and by others. The result of expert examinations are reported to the state licensing authorities.
The intention of the basic licensing procedure is to get the license stepwise for both the erection of the plant and for its operation. The partial licenses, which have been applied for within this procedure are listed in Table I I :
Table II. Structure of Licensing Procedure
In order to prove that the properties of the glass product will be determined with sufficient accuracy and reliability, a process qualification procedure will be carried out. These properties are based on the preliminary relevant parameters for final HLW disposal in Germany. The aim of the process qualification is to make sure that on one hand the process itself is suitable to produce a waste package within well defined limits and on the other hand to prove that the product really meets the required properties thus allowing to access the acceptance for a given repository /2/.
The waste form qualification includes the definition of the values for several quality parameters of the glass product, and their range of tolerable variations. The license has been applied for in late 1996 by submitting a waste form qualification report. It contains the relevant data of the glass product in respect to the process technique and the intermediate and final disposal, respectively. The process qualification file is currently being reviewed by the Federal Office for Radiation Protection (BfS), supported by its Quality Control Group (PKS).
After decontamination of the process area and removal of all usable nuclear material, WAK has a totally dry process area since 1993. In 1998 the dissolver will be removed, one year later the extraction batteries. Then WAK will have lost totally its reprocessing capability and may be released from IAEA safeguards. With respect to the dismantling status of WAK the IAEA may accept the "measured discard" category for the HLLW and terminate safeguards on this material. Consequently safeguards measures are not foreseen for the VEK plant /3/.
PROJECT EXECUTION
Key milestones are the public hearing in May 1998 and the 1st Construction License in the second half of 1998. The total civil work and equipment installation is scheduled for the period between 1999 and the year 2002. Hot vitrification operation is foressen from mid 2003 until 2005. Actually the detailed engineering work is running with the objective to place the first orders for civil work and component manufacturing mid 1998.
REFERENCES