Chornobyl Center for Nuclear Safety, Radioactive Waste and Radioecology
At the Vienna Chernobyl Conference in April 1996 Germany and France declared to support the international cooperation in view of a solution of the Chernobyl related issues.
In 1998 the multinational Sarcophagus Project was launched in the frame of this initiative.
The aim of the project was the collection, analysis, selection and verification of all safety relevant data concerning building constructions, systems and equipment, radiological situation, nuclear fuel, radioactive waste and environmental impact in a comprehensive data base.
ArcView® GIS, ArcView® Spatial AnalystT and ArcView® 3D AnalystT serve as a navigation system to retrieve the information from the data base using different cross sections of the Sarcophagus.
After the declaration of Germany and France at the Vienna Chernobyl Conference in April 1996 to support the international cooperation of institutions of the Ukraine, Belarus and Russia in view of a solution of the Chernobyl related issues, three projects were identified, i.e. the safety state of the Chernobyl Sarcophagus, the radioecological consequences due to the radioactive contaminated areas and the health consequences to the liquidators and the population in Ukraine, Belarus and Russia after the Chernobyl accident. The projects have been funded by the governments and by the electricity utilities of Germany and France, respectively. In this paper the Sarcophagus project will be presented.
Sixteen years after the accident of unit 4 of the Chernobyl NPP the Sarcophagus still remains one of the most dangerous nuclear facilities in the world. The ruin of the destroyed unit 4 and its surrounding Sarcophagus together are termed object Shelter.
The Sarcophagus was erected in a relatively short time period of several months on the basements of old structures of unknown stability of the former unit 4. Inside the Shelter remained about 96 % of the irradiated nuclear fuel inventory of the reactor of unit 4 before the accident, i.e. 180 t of Uranium of total radioactivity 7 x 1017 Bq. The radioactive releases to the industrial site of 500 m radius around the Chernobyl NPP during the first ten days after the accident were estimated to amount 0,5 - 1,0 % of the fuel inventory.
The spent fuel inside the Shelter and the radioactive contamination at the industrial site have an essential impact on all human activities concerned with investigation work, maintenance and stabilization measures which are presently under progress e.g. in the framework of the Shelter Implementation Plan because of the radiation exposure.
For planning of any actions towards a stabilization of the unstable building constructions of the Shelter and of measures to retain the radioactive materials inside the Sarcophagus a unified and comprehensive data base of all safety relevant technical data describing the present safety state of the Shelter is required.
Hence, the main aim of the Shelter project was the collection, analysis and selection as well as verification of all existing safety relevant data of the Shelter and the creation of an appropriate data base.
2. PROJECT ORGANISATION
The project management is being carried out by GRS and IRSN on behalf of the German and French governments and utilities, respectively. The local project coordination in Ukraine is carried out by the Chornobyl Centre which will also be the beneficiary of the work. The work is being performed by local contractors in Ukraine and Russia. The progress of work is being frequently estimated and ruled by the project review group from the above mentioned organizations together with the contractors.
During a preparation phase after the declaration of the initiative in 1996 the main tasks of the project were identified and the terms of references including detailed technical specifications of the work were elaborated. These main tasks are Building Constructions, Systems and Equipment, Radiological Situation, Fuel Containing Materials and Radioactive Waste and Environmental Impact. In May 1998 the first sub-projects with the local contractors were launched.
The project duration was three years, the total budget amounts to 2 Million Euro. The technical organization of the project is the following. For each technical task, in a first step, the main sources of information, i.e. technical documents, publications etc., were identified and described in a bibliography. In the next steps the technical quantities of interest were extracted from theses documents and input into the data base. The input of data is being performed by the contractors using especially designed interfaces, which address the kind and the total amount of data for the given task. The development of interfaces, the structure and the configuration of the data base as well as the data integration are subject to a separate contract. This work is being performed by ECOMM, which is the main Esri distributor for Ukraine.
Besides internal quality control of the technical data, performed by each of the contractors, additionally an independent expert team of Atomaudit (AA), Kiev, Ukraine, was involved in external quality control of the work. The configuration of the data base and data integration was also subject to independent control by a GRS supervisor.
3. CONTENTS OF WORK
3.1 Building Constructions
The contents of this work is the description of the building constructions before and after the accident. To the parameters considered in this task belong the geometrical dimensions of the rooms, of the walls and of special objects, their properties, e.g. quality of concrete and other building materials, load bearing capacity, order of destruction of walls and other construction elements, newly filled concrete and accessibility of rooms, etc. These data serve as a basis for new projects to reinforce the Sarcophagus. This work is being carried out by the State Research Institute of Building Constructions (NIISK), Kiev, Ukraine. For a total number of 956 rooms technical information is available now in the data base. Accordingly the reactor building, deaerator building, auxiliary building and the machinery hall are described.
3.2 Systems and Equipment
This work contains the description of all systems and equipment installed in the Shelter before and after the accident, i.e. electricity supply systems, water supply and drains, ventilation system, measuring and monitoring systems, etc. This work is being carried out by NIISK in cooperation with the Chernobyl Nuclear Power Plant, Object "Shelter" (CNPPOS), Chernobyl, Ukraine. The data base contains information on more than 1600 units of systems and equipment.
3.3 Radiological Situation
The scope of this work is the description of the radiological situation inside the Shelter, i.e. the dose rates of the radiation fields and the radioactive contamination in the rooms of the Shelter. In order to estimate the radiation exposure in advance, when planning work to be carried out by the personnel, these data are of special interest. This work is being carried out by the Russian Research Center "Kurchatov Institute" (RRCKI), Moscow, Russia, in cooperation with the CNPPOS. Today the data base contains radiological information of almost all rooms.
3.4 Fuel Containing Materials and Radioactive Waste
The contents of this work is the description of the remaining fuel containing materials (FCM) inside the Shelter, i.e. fragments of spent fuel elements, molten fuel lava, radioactive dust and Uranium and Plutonium solutes in the water in the lower rooms, the nuclide compositions, the physical and chemical properties etc. These data are very important because of their direct relevance for risk estimates. On the basis of these data for example, GRS investigated together with RRCKI the potential. Radiological consequences of a roof collapse of the Sarcophagus followed by a release of radioactive dust /1/, /2/ as well as the criticality behaviour of the fuel lava under the destroyed reactor vessel /3/, /4/. The data base contains information of about 97 locations FCM. Among them are:
fuel lava assemblies - 46 locations,
fragments of an active zone - 11 assemblies,
fuel dust - 3 concentrations,
solutions of salts of Uranium and Plutonium in water - 37 concentrations.
This work is being carried out by the RRCKI.
3.5 Environmental Impact
This work deals with the description of the influence of the accident to the Shelter site, i.e. the radiation situation above the ground, the contamination and the behaviour of the groundwater, the airborne effluents from the Sarcophagus and the radioactive air contamination at the Shelter site. These data are also of special interest e.g. for planning preparation work near the Shelter for stabilization measures etc. This work is being carried out by the Interdisciplinary Scientific and Technical Centre "Shelter" (ISTC), Chernobyl City, Ukraine.
3.6 Data Base Configuration and Data Integration
The scope of this work is the development of the data base structure, including the bibliography and the contributions of the different technical tasks, described above, as well as the development of a proper technique to retrieve the required information by key words as well as by the help of the optical navigation system ArcView GIS. This work is being carried out by JV "ECOMM" Co., official distributor of Esri, Kiev, Ukraine.
4. STRUCTURE AND FEATURES OF THE DATA BASE
The data are is organized and structured according to the main
topics of contents described above in a data base under Microsoft Access. The
technical topics are subdivided into objects, e.g. rooms, construction elements,
systems, equipment elements, measuring devices, fuel assemblies and fuel debris,
pieces of fuel lave, etc., which are generally connected with the corresponding
3D coordinates (axis, row and height level). The 3D coordinates of the Shelter
are prolonged towards the industrial site allowing the description of the environmental
impact to the Shelter site in a uniform coordinate system.
The states of the objects are described by a text abstract and by the technical parameters with regard to the terms of references of the contracts. Auxiliary data, e.g. graphs, construction drawings, photos, original and animation videos, are also linked with the technical data to facilitate a better understanding.
The main technical quantities contained in the data base are always linked with the corresponding main sources of information described in the bibliography. A hint to the responsible contractor validating the technical data is also always given.
All data are presented bilingual in English and in Russian using a switch button.
All information available in the database can generally be retrieved by an optical navigation system based on ArcView GIS 3.2. For each height level of the Shelter a 2D cross section containing the main objects, e.g. walls, doors, rooms, stairs, main constructions elements, newly filled concrete, fuel containing materials, main systems and equipment, etc. was elaborated.
Analogously, for the Shelter site a 2D cross sections containing data about the elevation levels of the territory, the radiation fields at height levels from 1 m up to 70 m above ground as well as about the groundwater table and the radioactive contamination of the groundwater was designed.
From the ArcView platform via the information button a direct entry to the access data base is released and all primary technical and auxiliary data can be found. Using the animation button additional information from original and animation video films can be started.
Selected images can be viewed by means of the 3D analyst. This is of special interest for the whole Shelter and the industrial site as well as for different objects belonging to more than one height level. For such kind of objects also a direct access from the 3D images to the database was realized.
5. RESULTS AND APPLICATION
The bibliography compartment of the data base contains different data, describing the main sources of information, from which the technical data are extracted. It contains also links to the compartments, where the technical data are stored as well as the key words for retrieval. Fig. 1 shows a plot of the interface for input of the main sources of information.
Figure 1: Interface for main sources of information (Bibliography)
5.2 Object Shelter and Industrial Site
Using the 3D analyst the whole object Shelter can be shown under different angles. Fig. 2 shows the ruin of the former reactor building of unit 4 of the Chernobyl NPP and the newly built Sarcophagus in front from the west, adjacent to the south are the de-aeration building and the machinery (turbine) hall at the industrial site.
Figure 2: General view of the object Shelter and the industrial site from the west
Impact of the Sarcophagus to the Shelter Site
Fig. 3 shows a 2D plot of the total elevation level of the Shelter site above Baltic Sea level in m. Furthermore the positions of observations wells for investigation of the groundwater and the aspiration units for air contamination sampling are depicted. Fig. 4 shows Shelter site from the north-west with height profile of the territory and the groundwater table. Fig. 5 shows the groundwater contamination with the radionuclide Sr 90, the contamination for Cs 137 is very similar.
Figure 3: 2D plot of the total elevation level of the Shelter site above Baltic Sea level in m
The scope of the Sarcophagus project of the French-German Initiative does in general not include processing of primary data and production of secondary data for special practical applications by means of models etc. However, some simple applications based on a straight algorithm, i. e. prognosis of dose rate in the future based on the radioactive decay of Cs 137 etc., have been foreseen. Other applications available are facilitated by the spatial analyst. One example is the calculation of the dose uptake of personnel due to radiation exposure when walking over contaminated areas at the Shelter site or in rooms inside the Sarcophagus in high radiation fields. Indicating a walk route and a constant moving velocity of the personnel, the spatial analyst calculates the accumulated dose along the pathway.
Figure 4: Shelter site from the north-west with height profile of the territory and the groundwater table
Figure 5: Groundwater concentration of the radionuclide Sr 90 in Bq/l
5.4 Cross Sections of the Shelter
In the cross sections of the different height levels of the former reactor building the main objects described in the data base are indicated. Fig. 6 is examples for a general view of 2D plots of the Shelter cross sections. This figure shows the cross section of the Shelter at level 9.00 m.
Figure 6: Cross section of the Shelter at height level 9.00 m
5.5 Building Constructions
The data base will be useful for different applications, e.g. for performing stabilization measures of building constructions in the framework of the Shelter Implementation Plan (SIP). For such practical purposes and different other applications a processing of the primary data contained in the data base is of interest.
Using the building construction data a modeling of planned necessary actions towards stabilization of the object Shelter could be performed. In this context, Fig. 7 shows the current condition of building constructions which demand stabilization actions (left), and also shows an example of modeling stabilization actions of this construction unit (right).
Figures 7: Photo indicating selected building constructions to be stabilized (left)
Modeling of stabilization measure of the selected building constructions (right)
5.6 Radiation Situation
In this section an example of the radiation fields at height level 0.00 m and an application with the spatial analyst are demonstrated.
Fig. 8 shows a 3D plot of the dose rate in the central room at height level 0.00 m.
Figure 8: 3D plot of the dose rate in the central room at height level 0.00 m in mR/h
5.7 Fuel Containing Materials
Fig. 9 shows the photo of a heap of FCM at level 0.00 m (top picture). Using the ArcView GIS navigator and pushing the animation button animation video films illustrating the selected fuel assembly will be available. The picture below left of Fig. 9 shows an animation video of the fuel lava assembly, indicated at the 2D cross section by the red spot (below right).
Figure 9: Photo of fuel lava heap at Level 0.00 m (top)
Animation video illustrating the fuel lava heap (below left) and 2D plot of Level 0.00 m (below right)
The Sarcophagus Project is a multinational project with contributions from Germany, France, Russia and Ukraine. Referring to the contracts almost 50 experts are contributing to the Chernobyl Sarcophagus data base. The authors deeply appreciate the collaboration with all organizations involved, especially with the managers and main experts of the contractors, namely:
Y. I. Nemchinov and A. K. Khavkin (NIISK)
V. N. Senatorov and V. I. Kupny (CNPPOS)
A. A. Borovoy and S. A. Gavrilov (RRCKI)
S. A. Bogatov and A. A. Kluchnikov (ISTC)
A. B. Mazur, V. E. Kozlitin, D. S. Datsko and O.O. Ischuk (ECOMM)
N. A. Steinberg and I. Semenova (AA)
R. Roloff (GRS)
/1/ G. Pretzsch
"Radiological Consequences of the Hypothetical Accident
"Roof Breakdown" of the Chernobyl Sarcophagus",
Proc. IAEA/EC/WHO Int. Conf. "One Decade after Chernobyl",
Vienna, Austria, April 8-12, 1996,
IAEA-CN-63/415, IAEA-TECDOC-964, pp.591-597, Sept. 1997
/2/ G. Pretzsch, F. Lange, S. Bogatov and A. A. Borovoy
"Radioactive Dust inside the Chernobyl Sarcophagus",
Proc. of Spectrum'98, International Conference on Decommissioning
and Decontamination and on Nuclear and Hazardous Waste Management,
Sept 13-18, 1998, Denver, Colorado, U.S.A., Vol. 1, pp. 221-226
/3/ B. Gmal, G. Pretzsch, E. Moser and U. Quade
"Investigation of the Criticality Behaviour of the Fuel Containing
Lava Masses inside the Chernobyl Shelter",
Proc. ICNC '99, Sixth International Conference on Nuclear Criticality Safety,
Sept 20-24, 1999, Versailles, France
/4/ G. Pretzsch
"The Chernobyl Sarcophagus Data Base of the German-French Initiative
for Robotics Applications",
ANS 9th International Topical Meeting on Robotics and Remote Systems,
March 04-08, 2001, Seattle, Washington, U.S.A.
Dr. Gunter G. Pretzsch
Gesellschaft fur Anlagen- und Reaktorsicherheit (GRS) mbH,
TEL: 0049 30 885 89 145
FAX: 0049 30 885 89 111
Mrs. Véronique Lhomme
Institut de Radioprotection et de Sûreté Nucléaire (IRSN)
B.P.17 - 92265 Fontenay-Aux-Roses Cedex,
TEL: 0033 1 4654 7308
FAX: 0033 1 4654 7088
Mr. Alexander N. Seleznev
Chornobyl Centre for Nuclear Safety, Radioactive Waste and Radioecology
17, Kharkov Chaussee
TEL: 0038 044 558 7471
FAX: 0038 044 559 9806
Mr. Eugene S. Seredynin
JV "ECOMM" Co.
18/7 Kutuzov str.
TEL: 0038 044 294 4218
FAX: 0038 044 294 8202