General objectives

Ø  Assessing the technology for filling the gaps between packages, in final repositories for low and medium active waste, applied in similar facilities, and selecting an appropriate filling technology, to implement at the Băiţa, Bihor disposal facility;

Ø  Development of the closure plan at NRRW Băiţa, Bihor, in terms of nuclear safety;

Ø  Finishing NRRW Băiţa, Bihor Closure Plan in safety conditions;

Ø  Proposal of a closure system at NRRW Băiţa, Bihor;

Ø  Closing System performance assessment, proposed at NRRW Băiţa, Bihor.

Estimated General Results

Based on the analysis of the operation of similar deposits, alternative technologies for filling the gaps between containers will be identified. At the same time will be demonstrated the properties of the Romanian bentonite currently used at Băiţa - Bihor to retain radionuclides.

It will be search the optimization of the systems of engineering barriers both in terms of the storage process, as well as of the completion of the sealing function. It will be considered  the improvement to the system, optimizing the conditioning matrix, through addition of absorbent additives and possibly replacing the material used for the formwork to stabilize the bentonite. At the same time, studies on different mixtures for filling the gaps between packages (to replace the current variant – bentonite in powder form), as well as the behaviour of bentonite geo-composites in the warehouse environment, will allow the choice of an optimal alternative for the modernization of engineering barriers.

Based on the obtained data, an analysis of the innovative technologies will be conducted ensuring the feasibility of proposed technologies. It is awaiting the ranking of the proposed technologies to be dependent of factor series which may impose an adequate approach of the selection process.

Estimated results in Stage I

            This stage of the work will deal with an assessment regarding the experience and current practices used for storing low and intermediate level waste in the European Union. It will highlight the operation and management of these deposits as well as the approach used in estimating the evolution in time of the disposal system barriers. The work also aims at monitoring the filling of the gaps between disposal packages and analyzing the performance assessment of the disposal system components, emphasizing the role of the buffer material in contact with the storage package metal.

The report will be structured so as to perform:

Ø  An overview of the main technical requirements for disposal of radioactive waste;

Ø  An overview of the different types of deposits in operation;

Ø  Detailed descriptions of deposits similar to the Baita Bihor repository;

Ø  Detailed descriptions of deposits that represent "best practices" in the EU.

Based on the data obtained, the buffer materials and techniques for filling gaps between packages will be identified, so that this barrier is improved compared to the current one, both with respect to waste containment and radiation protection of the operators.

Waste isolation level within the deposit, as compared to the environment, depends on the performance of the waste-deposit system as a whole, taking into account the waste package, buffer materials, engineering works in the deposit and the geology of the site. The components of the system should be selected and/or designed so as to be considered an overall system to keep the isolating functions at a predetermined level required for radiological safety of the population and the environment in the present and in the future.

Another important objective of the project is to model the release of radionuclides from disposal galleries for safety assessment. Within this assessment it is necessary to consider the best expected option for achieving the engineering barriers. At this stage there are to be created the prerequisites for detailed assessment of storage system components.

Estimated results in Stage II

In order to achieve the main objective of this stage, it is necessary to conduct an analysis of the technologies for closure of similar radioactive waste deposits.

In the case of DNDR, an important objective of the project is to model the release of radionuclides from the radioactive waste disposal galleries. Compared to waste disposal near the soil surface, where the radionuclide release models are virtually standardized, radionuclide release at Baita Bihor repository involves major difficulties due to the different sizes of the galleries, asymmetrical arrangement in relation to the main gallery and diversity of waste deposited. In addition, some galleries are closed without filling material, and a closed gallery is partially filled with bentonite. Developing a real model for the source term at Baita Bihor repository is actually impossible. However, it should be noted that the simulated release of radionuclides from the repository is performed in the context of the Safety Scenario, whose aim is to provide a justifiable estimate of the exposure of an individual belonging the critical group. In this context, the release of radionuclides from the repository is handled by developing a simplified conceptual model, which provides a conservative estimate of the radionuclides release rate from the storage unit.

For an accurate assessment on closing DNDR, the following issues will be analyzed: the practices used for similar deposits (geological formations), experiments conducted to analyze the effectiveness of the closure, in-situ and laboratory proposal experiments and the long term behaviour of closing and sealing materials. The major objective is to evaluate the current practice for filling the access and ventilation galleries with materials which comply with the safety requirements, finding effective solutions for isolation or delay of radionuclide migration by creating an additional global "confinement" of conditioned radioactive waste disposed at DNDR Baita, Bihor.

In this context, at this stage, the testing program for feasible buffer materials will be finalized, proposing a closing system for DNDR, based on preliminary experiments.

A reference Safety Scenario will also be estimated, taking into account the parameters of the improved buffer.

 Estimated results - stage III

At this stage, the project aims at completing the DNDR Baita Bihor closure plan. The Project Coordinator, CITON, will develop the conceptual closure technology for DNDR Baita Bihor, based on the experimental results obtained from the consortium partner P1, IFIN HH, and the risk assessment methodology performed by the consortium partner P2, UTCB.

Activities related to the repository closure must be developed so as to meet environmental regulations prevailing in the Member States of the IAEA.

Closure techniques and procedures are specific to the site and repository. In case of DNDR Baita Bihor, mainly, the procedure consists in placing the waste packages in deposit galleries set up in abandoned ore extraction galleries, and then filling the voids between these packages.

At this stage, it also aims at confirming the critical components of the storage system or radioactive waste immobilization matrix and buffer material in direct contact with the metal barrel containing the radioactive waste matrix.

It also aims at identifying all the components of the closure system and the possibilities to increase the performance of each component.

For the repository closure, the following factors will be considered:

- Waste forms and waste acceptance criteria;

- Limiting the voids in packages;

- Placing packages;

- Placing buffer materials for filling the voids between packages;

- Closing filled galleries;

- Technical means for closing and sealing the repository.

DNDR Baita Bihor closure will be based on the experience of mine closure in Romania, but considering the design criteria and requirements of a repository for radioctive low and intermediate level short-lived waste, according to national and international norms.

Estimated results in Stage IV

Establishing the final closing at DNDR Baita, Bihor, the only radioactive waste repository in Romania, is a task of great responsibility because of the implications of national and international nuclear safety.

The development and optimization of a radioactive waste repository and the design of an engineer barrier system require a continuous process of interactions between detailed research and process modeling studies, performance and safety assessment studies, and actual design of engineering components of the repository, also taking into account the economic and social factors.

This process involves a simultaneous transfer of stringent system requirements and detailed characterization of processes and materials, as well as the performance assessments, coupled with the periodic safety assessment, which must integrate various types of new information or, in our case, experimental results conducted to confirm the performance of the barriers.

In compliance with the work plan updated, the objectives of stage IV of the SARAWAD Baita, Bihor project are:

- Improving the option for closing DNDR Baita, Bihor, based on the experimental work carried out;

- Conducting laboratory experiments with representative key radionuclides Co-60 and Cs-137;

- Studying the evolution engineering barriers made based on experimental data.

In this phase are to propose closure system DNDR Baita, Bihor, safe nuclear improved based on experimental data and evaluated (see Figure 1).

Figure 1 Activities in stage IV

For the storage of radioactive waste, several options have been developed, with the following purposes:

   a) to confine waste;

  b) to isolate waste from the accessible biosphere and to substantially reduce the probability and the possible consequences of unwanted human intrusion to the deposited waste;

  c) to inhibit, reduce and permanently delay the migration of radionuclides to the accessible biosphere;

  d) to ensure that radionuclides may reach the accessible biosphere, due to any migration of the storage facility are such that, radiological consequences are acceptably low throughout the life of the repository.

The balance between the importance of each of the purposes mentioned varies depending on the characteristics of the waste and the type of storage facility.

In the case of DNDR Baita, Bihor, a phased approach of the activities will allow:

- Accumulating scientific and technical data required for safety assessments;

- Assessing the evolution of the storage facility;

- Improving the engineering components of the storage facility;

- Conducting iterative studies for safety assessments, with progressive improvement of the data;

- Technical revisions and regulations;

- Public consultation and implementation of political decisions.

This stage will continue research under the Experimental Program to demonstrate the performances of alternative buffer filling materials, of which the best option will be selected in the last phase of the project.

During this phase, there shall be carried out research in two directions:

- Research to determine the optimum technical solution for the buffer filling materials in contact with barrels filled with radioactive waste;

- Performance evaluations to confirm the technical solution for closing DNDR Baita, Bihor, proposed under this phase of the project.

It is expected to get relevant data leading to the selection of the best option for buffer filler as well as the possibility of confirming the current version of radioactive waste conditioning matrix.

Figure 1 Activities in stage IV

For the storage of radioactive waste, several options have been developed, with the following purposes:

   a) to confine waste;

  b) to isolate waste from the accessible biosphere and to substantially reduce the probability and the possible consequences of unwanted human intrusion to the deposited waste;

  c) to inhibit, reduce and permanently delay the migration of radionuclides to the accessible biosphere;

  d) to ensure that radionuclides may reach the accessible biosphere, due to any migration of the storage facility are such that, radiological consequences are acceptably low throughout the life of the repository.

The balance between the importance of each of the purposes mentioned varies depending on the characteristics of the waste and the type of storage facility.

In the case of DNDR Baita, Bihor, a phased approach of the activities will allow:

- Accumulating scientific and technical data required for safety assessments;

- Assessing the evolution of the storage facility;

- Improving the engineering components of the storage facility;

- Conducting iterative studies for safety assessments, with progressive improvement of the data;

- Technical revisions and regulations;

- Public consultation and implementation of political decisions.

This stage will continue research under the Experimental Program to demonstrate the performances of alternative buffer filling materials, of which the best option will be selected in the last phase of the project.

During this phase, there shall be carried out research in two directions:

- Research to determine the optimum technical solution for the buffer filling materials in contact with barrels filled with radioactive waste;

- Performance evaluations to confirm the technical solution for closing DNDR Baita, Bihor, proposed under this phase of the project.

It is expected to get relevant data leading to the selection of the best option for buffer filler as well as the possibility of confirming the current version of radioactive waste conditioning matrix.

Estimated results in Stage V

In this stage of project finishing will be confirmed the applied technical solutions until present at DNDR Baita-Bihor, where will be made operational improvements, recommended in all stages of this project.

The report will be structured as following:

-          Durability assessment of engineering barriers, inclusive those for closing, proposed in optimal variant.

-          Engineering barriers systems components, including those for closing from point of view of radionuclide migration delay. 

            It will be taken in account the IAEA recommendations, which will constitute the basic elements of the project.

It will revealed the major barriers which assure the safety of DNDR Baita-Bihor, as following:

-          The waste package which contain the waste matrix (primary barrier);

-          Host rock natural barrier, which is the most important at this deposit.

It will be presented the DNDR evolution, in accordance with base scenario concerning post-closing safety assessment and following to be made assessments of closing system durability:

-The air shaft and access tunnels;

-The closing and sealing plug;

-The cover;

-The deposit warning markers.

It will assessed the long term of this barriers, taking in account the experimental data obtained by first partner (IFIN-HH) and international experience from research field of radioactive waste disposal components obtained in the frame of Coordinated Research Projects of IAEA.

It will be assessed the barrier system efficiency from point of view of structural stability and safety function accomplishment – retention and radionuclide migration delay which are disposed on the established period, after the radioactive dangerous effects are not significant.

Also, on the base of documentary studies will be assessed optimized matrix for radioactive waste conditioning and too, different backfilling materials for making a concrete assessment.

On the experimentally assessment making in laboratory will be made the behavior mode of:

a)      Conditioning matrix;

b)      Buffer filling materials;

c)      Closing system.