Safeguards by design at the Encapsulation Plant in Finland

W.S. Parka, J. Coynea, M. Ingegneria, L. Enkhjina, L.S. Chewa, R. Plentedaa, J. Sprinklea, Y. Yudina, C. Ciuculescua, K. Bairda, C. Koutsoyannopoulosb, M. Murtezib, P. Schwalbachb, S. Vaccarob, J. Pekkarinenb, M. Thomasb, A. Zeinb, M. Hämäläinenc, T. Honkamaac, E. Martikkac, M. Moringc, O. Okkoc

a Department of SafeguardsInternational Atomic Energy Agency

b European Commission, Luxembourg

c STUK Radiation and Nuclear Safety Authority, Finland

Abstract. Finland has launched a spent fuel disposal project to encapsulate its spent fuel assemblies and confine the disposal canisters in a deep geological repository. The construction of the underground premises started several years ago with the drilling, blasting and reinforcement of tunnels and shafts to ensure the safe deep underground construction and disposal techniques in the repository, while the design of the encapsulation plant (EP) enters the licensing phase preliminary to its construction. The spent fuel assemblies, which have been safeguarded for decades at the nuclear power plants, are going to be transported to the EP, loaded into copper canisters and stored in underground tunnels where they become inaccessible after backfilling. Safeguards measures are needed to ensure that final spent fuel verification is performed before its encapsulation and that no nuclear material is diverted during the process. This is an opportunity for the inspectorates to have the infrastructure necessary for the safeguards equipment incorporated in the design of the encapsulation plant before licensing for construction occurs.

The peculiarity of this project is that it is going to run for more than a century. Therefore, significant changes are to be expected in the technical capabilities available for implementing safeguards (e.g. verification techniques and instruments), as well as in the process itself, e.g. redesign for the encapsulation of future fuel types. For these reasons a high degree of flexibility is required in order to be able to shift to different solutions at a later stage while minimizing the interference with the licensing process and facility operations. This paper describes the process leading to the definition of the technical requirements by IAEA and Euratom to be incorporated in the facility’s design.

1. Introduction

Finland has launched a spent fuel disposal project to encapsulate its spent fuel assemblies and confine the disposal canisters in a deep geological repository. The construction of the underground premises started several years ago with the drilling, blasting and reinforcement of tunnels and shafts to ensure the safe deep underground construction and disposal techniques in the future repository [1]. The safety assessment based on this experience was a part of the 2012 application for a construction licence for the disposal facility (EPGR), which would consist of the encapsulation plant (EP) and the geological repository (GR). The spent fuel assemblies, which have been safeguarded for decades at the nuclear power plants, are going to be transported to the EP, loaded into copper disposal canisters and stored in underground tunnels where they become inaccessible after backfilling. The encapsulation plant will be constructed according to the specifications presented in the licence application.

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Therefore it is needed to include the requirements of the international safeguards that affect the room spaces, lighting, cabling, wall penetrations etc. in the construction licence conditions before the construction of the buildings begins (planned in 2015). In the geological repository, the infrastructure is constructed in the meanwhile (Fig. 1), but the emplacement of nuclear fuel is scheduled to begin in 2022. Therefore, the up-to-date C/S instruments can be installed in the EPGR at the time when operating licence is to be granted.

A continuous dialog, which is part of the safeguards-by-design (SBD) process [2], is essential during the construction of the EPGR facility. This paper describes the SbD process for the EP part of the disposal facility.

FIG. 1. – Current excavations / infrastructure at the Geological Repository

2. The safeguards concept

Safeguards measures are needed, in accordance to the safeguards agreement in force, to ensure that final spent fuel verification is performed before its encapsulation and that no nuclear material is diverted during the process. The nuclear material will not be accessible after its disposal in the GR, therefore specific safeguards measures will be needed for the underground part of the disposal facility. Continuity of knowledge must be ensured within the EP until the transfer of disposal canisters with nuclear material to the GR.

Safeguards for nuclear material are maintained after the repository has been back-filled and tight sealed, and for as long as the safeguards agreement remains in force. The safeguards

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applied should provide credible assurances of non–diversion of declared nuclear material and non-misuse of the geological repository and associated facilities, taking in to account the site-specific geological and environmental features.

The safeguards system for the EP should be based on: verification of design information during design, construction and operation; verification of receipts and flow of nuclear material; and maintenance of continuity of knowledge on the nuclear material content.

The safeguards systems must meet rigorous system specifications and standards in order to function for a very long period with minimum or no service and very high availability, perhaps in a rugged environment and in unattended mode. Safeguards requirements should be integrated into the EP design at an early stage in order to establish functional, non–intrusive and cost–effective safeguards measures. On the other hand, because of the projected operational time, it seems prudent to design a certain degree of flexibility into the system, allowing for changes which might be required if the operational scheme or other boundary conditions change.

Specific safeguards measures and activities, including their scope, frequency and intensity, to be applied at the EP would be part of a State-level safeguards approach and would be tailored for every State to address State-specific technical safeguards objectives in a most effective and efficient manner.

Working as partners, the IAEA and EC jointly apply safeguards at the EP and GR – although their roles and responsibilities do not always coincide – in order to effectively fulfil their mandates and draw independent safeguards conclusions. The respective safeguards approaches have not been finalized yet, but various technical safeguards measures have been identified with the aim to have the least possible impact on the process of spent nuclear fuel geological disposal. The specified technical measures are wide enough to cover the expected scope of the final safeguards approach, allowing for a degree of flexibility for possible future changes in the safeguards strategy.

The safeguards aspects of the Geological Fuel Disposal (GFD) process have been discussed over many years among the nuclear safeguards community. The generic guidelines for safeguarding geological repositories were proposed in 1997 based on work of the IAEA Working Group for the Development of Safeguards for the Final Disposal of Spent Fuel in Geological Repositories (SAGOR). The work of the SAGOR-I (1994-1998) and SAGOR-II (1998-2005) is continued since 2005 by the expert group on the Application of Safeguards to Repositories (ASTOR).

In order to assure the feasibility, the applicability and the acceptance of the proposed solutions, an informal forum for information exchange concerning GFD projects in Finland and Sweden was formed between 2007 and 2012, involving representatives from the IAEA, EC, Sweden and Finland.

In 2012, the 59th Lower Level Liaison Committee1 (LLLC) Meeting, which was held in Vienna on 26 September 2012, recommended that a Task Force be formed which would coordinate the activities of the EPGR Project and include representatives from the IAEA, EC,

1 The LLLC has its legal base in the Comprehensive Safeguards Agreement for the NNWS of the European Union, INFCIRC/193

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Sweden and Finland. This Task Force, named LLLC EPGR Liaison Group, would ensure good communication and collaboration between all parties involved, with regular reporting back to the LLLC.

The development of the safeguards approaches and techniques had started in parallel to the development of the final disposal concepts and technologies. Application of the safeguards-by-design principle allowed for bi-directional feedback between the designers and the operators of the GFD installations on one side and the safeguards inspectorates on the other.

One of the key points in the elaboration of the safeguards approach for final disposal of spent nuclear fuel (SF) was to define where in the process the final verification of SF would be made. Amongst the possible options, two have been considered: (1) the final verification of SF is carried out upon receipt at the EP; (2) the final verification of SF is carried out at the nuclear power plant (NPP) and/or the interim spent fuel storage, while keeping re-verification capabilities at the EP as a contingency measure. The second option was chosen to minimize strict time constraints on verification and approval actions in the case of the final verification at the EP.

The chosen verification option is based on existing equipment and procedures, leaving the possibility to move the verification to the EP at a later stage, when adequate in-air SF measurement devices will be available.

Compared to the scenario with final verification at the EP, the chosen option poses stricter continuity of knowledge (CoK) requirements. However, preserving the full capability at the EP for performing the final verification of the SF provides a high degree of flexibility. This would act as a back-up scenario in case of loss of CoK between the NPP, or the interim store, and the EP also reducing the NRT in-process requirements on the SF verification equipment.

The proposed equipment infrastructure is designed to ensure complete verification capability at the EP and to assure CoK inside the EP: from the arrival of the transport casks containing SF assemblies until their encapsulation into canisters and their transfer to the underground repository.

The high throughput of the EP and its operational timescale require efficient unattended material flow monitoring (with surveillance and radiation monitors), identity reading, fingerprinting and verification measurements' data transfer with strong Near Real Time (NRT) characteristics. Infrastructure requirements for the equipment described here are focussed on the possibility to upgrade and adapt the planned system components to future needs. The space reserved for the safeguards equipment assumes the possibility of adding in the future additional equipment, such as the unattended gamma emission tomography devices.

The flowcharts included in Fig. 2 and Fig. 3 present a foreseeable sequence of safeguards activities and the actors involved at different stages of the Finnish EPGR process; from interim stores, through transportation and encapsulation stages until the approval for disposal underground.

3. Safeguards equipment infrastructure requirements

The opportunity for the inspectorates to have the infrastructure needed for the safeguards equipment incorporated in the design of the encapsulation plant before licensing for construction was seized, with the full cooperation of Finland [3]. The peculiarity of this

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project is that it is going to run for several decades, therefore significant changes are to be expected in the technical capabilities available for implementing safeguards (e.g. verification techniques and instruments), as well as in the process itself, e.g. redesign for the encapsulation of future fuel types. For these reasons, a high degree of flexibility is required in order to be able to shift to different solutions at a later stage of the EPGR operational phase while minimizing the interference with the licensing process and facility operations.

The in-process nature of the safeguards measures call for conditional “green lights” to the operator in order to move nuclear material in different parts of plant. To achieve the Near Real Time data availability, high redundancy of the equipment and of the network infrastructure need to be included in the facility design, and as well the possibility to make servers available to the inspectorates to process locally the large amount of data in automatic mode. In addition, the safeguards system has to rely on the availability of Remote Data Transmission from the facilities in Finland to EC and IAEA.

A number of instruments ranging from surveillance cameras to radiation detectors and their optimum location have been identified to support the possible safeguards measures which may be implemented to maintain the CoK and eventually to allow a re-verification of the nuclear material if needed. The actual instruments to be used will be defined at a later stage, taking into account the safeguards approach and the latest technological developments.

4. Conclusions

The fact that Finland has planned the design and construction of the Encapsulation Plant well in advance has provided a unique opportunity for the inspectorates to cooperate between them and with the State to define safeguards measures that will allow meeting the respective goals and to incorporate all the technical requirements needed to support those measures into the plant design. This safeguards-by-design process will lead to an increased effectiveness of the measures, a limited intrusiveness of the safeguards activities in the operations and to a reduced cost for the inspectorates to install the necessary equipment and infrastructures at the encapsulation plant in Finland.

The biggest challenge in shaping the adequate safeguards concept is the reconciliation of the need to achieve the highest probability of detection of a possible diversion of nuclear material (effectiveness) with the capacity of the safeguards inspectorates to cope with the expected throughput in the process without significantly interfering with it (efficiency).

The safeguards measures that have been identified have led to the definition of technical requirements that are to be incorporated into the design of the facility, thus satisfying the requirements of the two international inspectorates. Given the long time until the start of operation, it is not possible to define which specific equipment will be used, but just the infrastructure. Nevertheless, the safeguards-by-design process is the basic prerequisite for a cost-effective implementation safeguards in the future facility.

REFERENCES

[1]Nuclear Waste Management at Olkiluoto and Loviisa Power Plants: Review of Current Status and Future Plans for 2013-2015. YJH-2012. Posiva Oy. May 2013.

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[2] INTERNATIONAL ATOMIC ENERGY AGENCY Nuclear Energy Series. No. NP-T-2.8. International Safeguards in Nuclear Facility Design and Construction. IAEA, Vienna, 2013.

[3] Implementing nuclear non-proliferation in Finland. Annual Report 2013. O. Okko (ed.). STUK-B 173/June 2014.

FIG. 2. – Schematic flow verification process at the EP

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FIG.3. Flowchart of the flow verification process at the EPGR

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