Design of spent fuel interim storage of Hanhikivi-1 newbuild NPP

Fortum was contracted for designing a spent fuel interim storage for Hanhikivi-1 Nuclear Power Plant by Fennovoima. In June 2015, Fennovoima applied for Construction License for the spent fuel storage as well as for the Hanhikivi-1 Nuclear Power Plant. In the first phase, Fortum supported Fennovoima in decision-making by compiling conceptual design of different site-specific storage concepts and based on the concepts, comprehensive technical and economic feasibility studies of the options were performed. In the second phase, Fortum successfully implemented the basic design of the wet pool storage and compiled the documents needed for construction license application.

A 3D model of Hanhikivi 1 spent fuel interim storage

Case description

The spent fuel interim storage design project for Hanhikivi-1 nuclear power plant was divided into two distinctly different phases: in the first phase, Fennovoima was supported in decision-making regarding optimal storage type, and in the second phase, the chosen storage concept was designed.

The first phase started in 2016. Based on framework and initial data given by Fennovoima, fuel cycle analysis was performed. This led to definition of the needed storage space and cooling capacity for both storage alternatives. And this, combined with analysis of safety requirements, enabled Fortum to build a preliminary system design and ultimately a preliminary 3D model for both the wet and the dry storage alternatives. Cost estimates were made for both storage methods, and the safety and feasibility of the concepts were also evaluated.

Based on the report, the wet pool storage was presented to Fennovoima as the final proposal. In autumn 2016, according to Fortum's proposal, Fennovoima ended up choosing the wet pool storage. Some of the significant selection criteria were related to consistency with the Finnish disposal process, compliance with the safety requirements and beneficial investment parameters.

The second phase was started after Fennovoima made its decision for a wet storage. The design of the wet storage was refined from conceptual design of the first phase.


The design included, among other things:

  • Conceptual design (structural design, I&C, electrical) / basic design (process systems, building services, lay-out) of a wet pool storage
  • Safety engineering documents with ADLAS®-method
  • PSAR documents
  • Topical reports, including safety analyses.

Unique opportinity for learning

Decision in Principle was applied for both NPP and spent fuel storage at the same time and the facilities share some of the auxiliary systems. In addition, STUK needed to have a holistic view on nuclear safety in Hanhikivi, so it was necessary to design the spent fuel storage in parallel with the power plant itself. The construction permit material, including PSAR of spent fuel storage, was submitted to Radiation and Nuclear Safety Authority (STUK, Säteilyturvakeskus) for review.

After STUK’s first comments were received, the PSAR was updated. Safety regulations (YVL guides) were also renewed during the process, and these changes were taken into account systematically. Also Human Factors Engineering (HFE) program was added to design process and Operational Experience Review was performed in spent fuel storages of Loviisa and Olkiluoto.

The final updated construction permit material was sent to STUK in autumn 2021.

While spent fuel storage designing is compulsory for all nuclear power plants in Finland, the project as a whole was unique and had some unforeseen challenges. Requirement management played a major role, as the safety requirements (YVL guides) were updated by STUK in the middle of the project. Despite the hurdles, the requirements management succeeded, Fortum experts could adapt to changing requirements quickly and the project was finished on time and within planned budget.

The intergenerational learning process was emphasised during the project. At the beginning of the project, there were still retiring senior experts available, whose learnings and responsibilities were successfully transferred to other experts. It was also significant achievement to systematically collect practical user experiences from fuel storage facilities in Loviisa and Olkiluoto, and use these experiences as valuable design input. Also methods to implement Human Factors Engineering (HFE) aspects to the design were systematically developed.

The project was large in scope, and during the project we enhanced our competence by multi-disciplinary transfer of knowledge between generations of Fortum´s engineers, according to project manager Jukka Hautojärvi.

Fortum as an experienced contractor

As a trustworthy, experienced, and large organization, Fortum could support Fennovoima in many different phases of initial planning of a newbuild nuclear power plant. Prior knowledge of Finnish official requirements proved essential since the regulations are strict and can prove difficult to fulfill. As the owner of Loviisa Nuclear power plant, Fortum has prior experience of dealing with nuclear waste and preparing interim storage planning and implementation. Being a large company with extensive knowledge on nuclear projects, Fortum could quickly form an efficient team of professionals to support Fennovoima with spent fuel storage design alongside many other projects.

The project was Fortum’s first in which Human Factors Engineering (HFE) project philosophy was utilized. In practice, HFE accounts for wider range of risks than conventional project planning by considering human errors as expected and natural occurrences which can be mitigated similarly to any other sources of risks. HFE was used in all of the phases of planning with excellent results which further increased the reliability of the results.


Antti Ketolainen

Decommissioning and Waste
Tel: +358 40 751 8956
Antti [dot] V [dot] Ketolainen [at] fortum [dot] com

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