FAES. STUDY ST. PETERSBURG MANAG. CENTER

In St-Petersburg and the Leningrad region a large number of scientific centers, nuclear power facilities (NPPs) and industrial companies of the North-West region of the Russian Federation complex are located, where liquid and solid radioactive waste (RW) are generated .

Waste from non-NPP plants and organizations of the region was in the time of the Project implementation sent to the LSC RADON for eventual processing and long term storage. Liquid waste was evaporated, the evaporator bottom was bituminized and product was stored in bulk in the LSC storage compartments. Solid radioactive waste of the North-West region was sent to the LSC for storage without reprocessing. Part of the solid waste was incinerated.

Radioactive waste, generated at Leningrad NPP, is stored (after eventual processing – e.g. bituminization of liquid operational waste) at the NPP. A part of solid radioactive waste was also transferred to LSC RADON for storage.

Leningrad special combinate (LSC) RADON, has received in the period of 1960-1990 more than 50 thousand m3 of radioactive waste from St-Petersburg and the entire Leningrad region for processing and long term storage. The average annual quantity of solid and solidified RW from the region companies was at the beginning of 90s higher than 3.5 thousands m3, and a significant increase of this quantity (more than twice) was expected in the coming years.

The RW reprocessing plants were obsolete and their capacity was insufficient. Existing RW storage facilities were practically filled up and in accordance with the existing nuclear, radiation and ecological safety requirements, they could not be further considered as final disposal facilities. Hydro geologic conditions of the RADON storage sites do not meet the requirements for a storage ground and they cannot provide for the function of the main protective barrier in RW disposal considering high level of the ground waters.

Considering the state and the further development in the North-West region, the problem of the development of the regional concept on radioactive waste management arose. The RWM center should meet the requirement of RW producing companies (exempt NPPs) and solve the general problem of conditioned RW safe disposal. The concept is based on the idea of the development of the regional North-West center for "institutional" RW management and disposal. Structurally, the regional center should consist of two complexes:

• Technological complex for RW collection, processing, control and temporary storage. This complex can be based at the site of existing RADON facility
• Regional site for reception and disposal or long-term storage of processed "institutional" waste (a new site in the region should be considered for this purpose)

Specific features of the "institutional" RW (mainly short-lived and low- and intermediate-level waste) makes it possible to resolve the problem of their isolation at the regional level by disposal in subsurface or underground structures in accordance with the requirements of the State RAW management concept being developed in Russia. The facility could serve also as a temporary storage facility for high-level and long-lived waste of the region.

To facilitate the solution of the above described problem and promote establishing of the regional organization (facility) for safe and sound management of the "institutional" RAW, the Project on "Feasibility Study for St. Petersburg Waste Management Centre" was awarded in December 1996 and completed in December 1997. This project provides a conceptual design for the most appropriate solution regarding type of the waste, costs, safety and technical feasibility.

The main objective of the Project was to provide the Leningrad (St. Petersburg) Specialized Centre RADON with a feasibility study for the construction of waste processing and storage facilities. The study had to contribute to improving the situation in waste management in line with the requirements of Minatom and Rosenergoatom, supported by the EC, in order to comply with present international safety standards.

Specific objectives of the project were:

• Undertake a review of the Leningrad Specialized Centre RADON and of other radioactive waste management installations of the North Western Region;
• Study for an updated centre for collection, treatment, conditioning and storage of radioactive waste arising in the North-Western region (both NPP and non-NPP waste);
• Conceptual design for a repository for the radioactive waste currently in storage at the RADON Centre and for the future arisings;
• Concept for a long-term monitoring system.

Following is only brief description of the project achievements and results. More details are available in the project documentation and the Project final report.

REVIEW OF THE LENINGRAD SPECIALIZED CENTRE RADON AND OF OTHER RADIOACTIVE WASTE MANAGEMENT INSTALLATIONS OF THE NORTH WESTERN REGION

Three sub-tasks were covered:

• Review of Russian RAW management legal basis – regulations

The Russian Federation appeared to have a good and applicable system in place to define, manage and regulate nuclear activities. In the RW area waste transport, storage and disposal is covered better than waste handling and processing. Russian system was found to be fully compliant with IAEA safety requirements.

• Collection of information on RAW inventory at RADON site

The data on RW inventory corresponds to the state in 1997 (when the Project was implemented). Following waste types are described in solid waste category: bulk non-processed institutional solid waste, disused sealed sources (alpha sources and high active irradiation gamma sources) and waste from territory remediation activities. The figures can be found in the Project documents.

Liquid RW from institutional applications represents the minor waste stream and after collection and control they are solidified at RADON facility by bituminization. In the future cementation into reinforced concrete high tight containers is also considered

• Evaluation of the status of RW management facilities at RADON site

Five waste streams are considered at RADON facility: disused sealed sources (either stored or cemented together with the primary containers), high activity solid waste (stored in shielded premises), non-combustible solid waste (stored as a bulk waste), combustible solid and liquid waste (after incineration, the ash is stored in the metallic containers) and liquid waste (after pre-concentration by evaporation bituminised and solidified product stored in bulk storage room).

Several improvements in existing system have been identified, besides others, better co-ordination of RW management activities between RADON and NPPs in the region, implementation of advanced sorting and characterization of the raw waste, further processing (conditioning) of the incinerator ash, putting the bituminized product to the metallic drums (to allow retrievability from storage facility).

For the future following technologies are recommended to be implemented: compaction, incineration (more advanced facility), decontamination of equipment, decontamination of soil, optionally also melting of metallic waste, cementation instead of bituminization of liquid waste, providing also for grouting of heterogeneous solid waste.

Existing disposal (actually storage) facilities cannot provide guarantee for 300 years of safe storage and they are not in conformance with present western European standards for the disposal of the radioactive waste. It is recommended to perform detailed survey of the stored waste and consider its retrieval, reprocessing and relocation to upgraded waste storage/disposal facility.

STUDY FOR AN UPDATED CENTRE FOR HANDLING, PROCESSING AND STORAGE/DISPOSAL OF THE RADIOACTIVE WASTE IN THE NORTH-WESTERN REGION

Five sub-tasks have been implemented:

• Type of repository

Two concepts (surface and sub-surface facilities) were compared on a technical and economical point of view. It has been demonstrated that safety and technical feasibility are guaranteed for both options and both options are consistent with the Russian legislative and regulatory framework.

At RADON’s request and according to the project terms of reference, the sub-surface concept was finally retained for this study. However, all parties involved in the project, agreed that there is a need to carry out a conceptual design for both alternatives, considering local site features, technical and economical conditions and requirements, which all can strongly affect the construction costs.

• Candidate site for repository

Present LSC RADON site is located approximately 16 km to the south-east of Sosnovy Bor and approximately 24 km south of the Gulf of Finland in the Leningrad region of Russia. The area of interest to this project is the region from the southern coast of the Gulf of Finland to approximately 80 km south of the coast (latitudes between 59.25 N and 60 N) and between longitudes of 28.5 and 30. This area is far greater than the scale of the potential repository, but is required to provide an adequate hydro geological model of the site.

The area is characterized by various geographical features. Therefore a preliminary hydro geological conceptual model (groundwater flows and velocities) was derived to describe the groundwater flow in the entire region. Based on this model was e.g. predicted that the time for groundwater to reach the Lomonosov stratum from the middle of the Blue Clay will be at least 500 years, what is more than required 300 years.

Based on the estimation hydro geological parameters, it is predicted that the Blue Clay stratum may be a potential site for the repository. However, large quantities of site characterisation work and numerical groundwater flow modelling would be required before any confidence could be placed in the present parameters.

• Design basis and safety targets

In the project documentation a conceptual design for sub-surface concept is provided only. The design basis was determined after consideration of several aspects, consistent with current IAEA, western European and Russian regulatory positions. The main of them are as follows:

RW related: waste type to be disposed, waste inventory, processed waste volume for disposal,
Site conditions: geological and hydro geological conditions at the proposed site, accessibility, transport, climate, population, erosion, potential future expansion of the site

Legislative and regulatory framework, including Waste Acceptance Criteria for storage and disposal of the waste

• Waste packaging and handling

The type, characteristics and selection of waste package is one of the most important parts of complex decision on waste storage/disposal. Based on deep analysis of waste management strategy the most appropriate waste containers for the incoming raw waste flows, as well as for the resulting processed waste flows have been proposed. Existing, proven and available types of containers of Russian as well as Western European design have been evaluated and the list of proposed containers is in the final project report.

Besides waste containers evaluation and selection, current and new (improved) waste packaging and transport systems in use at the RADON site have also been discussed.

Another considered issue was an overall strategy for recovery (retrieval) of the waste at the RADON site, its reprocessing and repackaging (if necessary). Newly proposed containers for the different kinds of waste should be then used for repackaging.

• Waste acceptance criteria

It was concluded that no approved Waste Acceptance Criteria (WAC) exist, however "informal" WAC and/or Waste Package Specifications are used in everyday practice. It was therefore strictly recommended that, in order for appropriate legislation to be put in place, and to meet current standards in use in Western Europe, the system of informal rules should be formalised into Waste Acceptance Criteria for storage and disposal of the waste at the RADON site.

This task was not a part of the project. WAC and the Waste Package Specification shall be developed separately, considering the design of the storage and/or disposal site.

CONCEPTUAL DESIGN FOR A REPOSITORY FOR THE RADIOACTIVE WASTE CURRENTLY IN STORAGE AT THE RADON CENTRE AND FOR THE FUTURE ARISINGS;

The conceptual design for the final disposal of low and intermediate-level nuclear waste for the needs of the Leningrad region (LSK RADON) can be considered as a main result of the Project. Two options have been considered and compared in the Project first phase, however, conceptual design has been performed only for sub-surface concept. The concept considers a separate repository for each waste type and class and the structure and technical barriers of the repositories have been chosen accordingly.

The structural solutions of the designed repositories are based on the technology of St Petersburg City metro. The layout of the repositories is based on stagewise building, transportation of the waste packages with lorries, remote controlled transportation of waste packages, proper compartmentation, radiation and industrial safety of the personnel, optimal location of the auxiliary processes, natural closing of the waste rooms, and safe isolation of the waste for a period of minimum 300 years.

The final disposal facilities comprise in their full extent 43 waste halls, one maintenance hail, two vertical shafts of the depth of some 100 metres and relevant transport tunnels. In addition, there will be two buildings on the surface. The full cubical content of the final disposal facility is 1,291,000 m3, the net volume is 887,000 m3. The total volume of the waste including packages is 340,000 m3. Clay + bentonite mixture is considered as backfilling material.
Costs estimation, schedule proposal and evaluation of the potential for future development of the repository are also included into the project report.

Preliminary safety assessment of selected variant has also been preformed.

CONCEPT FOR A LONG-TERM MONITORING SYSTEM.

As a part of conceptual design considerations also requirements to long term monitoring of repository impact to the environment were evaluated. In the case of reliable hydro geological data and proper model availability, no special ground water monitoring is necessary in the design phase and during repository active operation (before closure).

Since at this stage it is impossible to evaluate the requirements for institutional monitoring after closure of the repository, it is strongly recommended to make a specification and monitoring programme in the design phase. The type of monitoring system can only be decided at a later stage in the design, when more data is available.

The need for (very) long term monitoring (beyond 300 years) can also be decided only at a later stage, in close co-operation of the repository designer and the Regulatory Authorities.