Finland’s only research reactor, FiR 1, a 250kW Triga Mk II open-tank reactor, was operated from March 1962 until it closed permanently in June 2015. The reactor is now in extended shutdown, in which the technical maintenance and security surveillance of the reactor and the premises continue at the same level as during normal use. Preparations for immediate decommissioning have been started.

The supplier, General Atomics, designed the Triga reactors (from Training Research Isotopes General Atomics) for use in university environments. FiR 1 was originally in the possession of Helsinki University of Technology (which became the Aalto University in 2010), but it was transferred to VTT Technical Research Centre of Finland following a government decision in 1971.

Early history

The FiR 1 reactor was purchased through an agreement between the International Atomic Energy Agency (IAEA) and the government of Finland, following a request by Finland for assistance in establishing a research reactor project. The contract between General Atomics and the government of Finland was signed on 30 May 1960 and the fuel for the reactor was purchased through four Supply Agreements between the IAEA, the Finnish and US governments. The first agreement entered into force on 30 December 1960 and the fourth on 27 November 1969. The last fuel delivery arrived at the reactor in January 1971. All fuel is 20% enriched uranium. The FiR 1 reactor project at the IAEA was the first one concluded in this trilateral form and was the prototype for other research reactor projects.

FiR 1 was started up ceremonially at the Otaniemi campus in Espoo on 31 August 1962. First criticality had been achieved on 27 March 1962. The ceremony culminated in a power pulse launched by Urho Kekkonen, the long-standing president of Finland.

For FiR 1 the 1960s was a decade of training and basic research in reactor physics and formed the basis for all upcoming operations. The facility was a training hub for personnel from the two Finnish nuclear power companies IVO (later Fortum) and TVO, which started up Loviisa 1&2 and Olkiluoto 1&2, respectively, between 1977 and 1980.

The most remarkable project at FiR during the early years was a power upgrade from 100kW to 250kW in 1967. The motivation for the project was not to increase the thermal power but the neutron flux, to carry out irradiations in a shorter time, and a flux level of 10^13 1/cm2s was achieved. Before the power upgrade a power range up to 1MW was considered, but model calculations, supported by indirect measurements, showed that the durability of aluminium-clad fuel elements had a significantly lower limit for safe operation. Power levels up to 318kW were tested in February 1966 and a new nominal power of 250kW was confirmed safe [1].

Neutron activation analysis was developed in the 1970s by installing sample changers and automatic gamma spectrometers with analysis software for instrumental multi-element analysis [2]. For uranium ore prospecting a rapid pneumatic transfer irradiation system with delayed neutron counting was developed [3]. The activity evolved into a cost-effective service for companies carrying out ore exploration in Finland and Sweden, and in particular for the broad geochemical survey carried out by GTK (Geological Survey of Finland). The number of samples analysed annually approached 50,000 and the technology was also exported to some other countries. Analysis at FiR 1 also included some lunar samples from Apollo 12 [4].

In the 1970s, the first version of a reverse time-of-flight diffactrometer (Actacus) was developed and in the 1980s a novel system, based on a Fourier chopper and dedicated electronics, was constructed in collaboration with the Nuclear Physics Institute at Leningrad. One of these devices is still in use at JINR in Dubna, Russia [5].

In 1981, to extend operation for another 10 to 20 years, a renewal of the reactor control instrumentation was carried out in cooperation with the Central Research Institute for Physics (KFKI) at the Hungarian Academy of Sciences. KFKI delivered the nuclear part of the instrumentation and Finnish company Valmet Oy delivered the conventional instrumentation, including the automatic power control system and the control console [6].

Development of BNCT

A major upgrade took place at FiR in the 1990s, when radiotherapy equipment was installed [7]. The goal was to achieve an intensive and clean epithermal neutron beam for Boron Neutron Capture Therapy (BNCT).

Capacity factor of FiR 1 over its lifetime

Due to the low power level of the reactor, the treatment aperture had to be positioned as close to the core as possible to obtain sufficient beam intensity for practical treatments. This was achieved by removing the thermal column and part of the concrete shielding of the reactor to release space for the treatment station, see Figure 1. Core loading was modified to maximise the flux towards the aperture. Because the aperture was close to the core it required the development of a moderator material that could sufficiently reduce the dose from direct gamma radiation and fast neutrons. After materials screening it was decided that aluminium and fluorine would form an effective epithermal moderator. The development yielded the Fluental™ moderator, consisting of 69% aluminium fluoride, 30% metallic aluminium and 1% lithium fluoride to absorb thermal neutrons. The constituents were combined into a metal-ceramic product (density 3g/cm3) by hot isostatic pressing. VTT has delivered this patented BNCT material to the UK, Taiwan and three BNCT projects in the USA.

In clinical trials patients showed improved tumour control and survival, especially those with head and neck tumours [8]. BNCT treatments at FiR 1 conducted in collaboration with Boneca Ltd and Helsinki University Central Hospital were included in the national healthcare service system. Unfortunately this radiotherapy service ended in the bankruptcy of Boneca Ltd, which organised the treatments, in January 2012. In total over 300 patient irradiations were given at FiR 1.

As a result of the BNCT project, FiR 1 became an important research and education unit for medical physics. Since the early 1990s several graduate and postgraduate students from the medical physics programme of the University of Helsinki have worked at the FiR 1 BNCT facility and were credited with up to one year of the required hands-on experience for the hospital physicist exam. Research projects included dosimetry, radiation transport modelling, treatment planning, prompt-gamma imaging and other medical physics aspects of BNCT.

Coming to the end of an era

The main use of the reactor after 2012 was radioisotope production for tracer studies in industry (Br-82, Na-24 and La-140). The isotopes are used to calibrate liquid or gas flow meters and analyse disturbances in chemical or other processes. The total yearly production was 3-4TBq. Earlier Sm-153 was also produced for bone cancer treatment and Dy-165 for treatment of arthritis. The spin-off company established at the reactor in 1999, MAP Medical Technologies, has been successful but relies now on other sources for its radioisotopes – the accelerator at the Jyväskylä University in central Finland and traditional international radioisotope producers.
Neutrons from FiR 1 were also used to test scientific equipment. Among the equipment irradiated was neutron-tolerant microelectromechanical magnetometers for the Iter fusion reactor, and new radiation detection and imaging devices.

Activation analysis was used for nuclear power plant accident studies and development of nanoparticles for radiotherapy.
Aalto University used the reactor to run two courses a year for technical physics and energy technology students. One-day intensive courses with hands-on exercises, or demonstrations and excursions in connection with longer lecture courses, were also organised for students of Lappeenranta University of Technology and nuclear power company personnel. Over 300 Swedish nuclear professionals trained at FiR 1 in 2007-2014. In the future this kind of training will be organised at other European sites, for example in France or the Czech Republic.

The capacity factor of FiR 1 over its whole lifespan is shown in Figure 2. During the latter years the annual operating costs of FiR 1 were in the range of €500,000 ($570,000).

Preparing for decommissioning

FiR 1 will be the first nuclear facility to be decommissioned in Finland. Although the fuel, dismantling waste and activity inventories are smaller than a power reactor’s, similar licensing procedures apply. This implies such a high workload that VTT will not attempt to tackle the complete project alone. Instead it hopes to engage partners or subcontractors.

Ideally FiR 1 decommissioning will become a pioneering project for domestic nuclear power utilities that will face decommissioning issues in the coming decades. Several similar reactors have been decommissioned, for instance in Denmark and Germany, and experience from those projects will be drawn on.

The Finnish licensees are obliged to maintain their nuclear waste management plans over the whole operating lifetime of their reactors. Each licensee is obliged to contribute to the fund for nuclear waste management that is managed by the Ministry of Employment and the Economy. The fund reimburses costs gradually to the licensees as they complete their decommissioning duties.

Significant refinement of the nuclear waste management plans is required when proceeding towards decommissioning. This planning was developed in the Environmental Impact Assessment (EIA) for FiR 1 decommissioning carried out by VTT in 2013-15 (reports in Finnish and Swedish available). The Ministry of Employment and the Economy gave its final statement on the EIA report in February 2015. A few stakeholders provided the Ministry with their remarks on the report, which will be accounted for in the detailed decommissioning planning.

The project is proceeding on three fronts: (i) spent fuel management; (ii) procurement of dismantling and dismantling planning; (iii) preparations for interim storage for the dismantling waste (both low- and intermediate level).

In parallel, VTT is preparing the application for an operating licence amendment, which it aims to submit to the State Council by the end of 2016. This procedure is necessary because the concept of a "decommissioning licence" does not exist in Finnish legislation. The current operating licence for FiR 1 was extended in 2011 until the end of 2023.

Spent fuel management

There are about 100 spent fuel elements at FiR 1 (about 15kg uranium of which 3kg is U-235); this corresponds to about 1/100,000th of the spent fuel produced by a typical nuclear power reactor during its lifetime. The amount of activated construction materials is also only a minor fraction of of the amount that would be produced by a nuclear plant.

The fuel is subject to the return programme of US Department of Energy (DOE), which runs until May 2019. The primary scenario for disposal of the nuclear fuel is to send it back to its country of origin, specifically to Idaho National Laboratory, where batches of nuclear fuel from Triga research reactors have previously been returned from various countries. Presently the programme is, however, halted as Idaho is blocking all nuclear waste transports to Idaho National Laboratory (INL) due to breaches of the Idaho Settlement Agreement.

VTT considers US return as the primary option for spent fuel and is preparing the licensing and contracts required for fuel return and transport while it waits for the issue to be resolved. The secondary option would be final disposal in Finland. However this would require re-licensing of the encapsulation and spent fuel disposal facilities to be constructed in Olkiluoto on the Western coast of Finland.

Dismantling waste

Dismantling of the reactor can commence once the spent nuclear fuel has been removed from the reactor core. The dismantling will yield a small volume and inventory of low- and intermediate-level waste – some tens of cubic metres.

Final disposal of the dismantling waste is intended to be in the waste repositories of the Olkiluoto or Loviisa nuclear power plants. An interim storage period of about 20 years is foreseen and VTT is investigating alternative locations for storage.

Computational estimates for the activation of reactor structures have been calculated [9] using modelled neutron flux distributions and the operating history of the reactor. Beside the concrete, aluminium and steel structures, the active inventory of the BNCT station with the Fluental™ moderator is significant. During operation, lithium has produced about 40TBq tritium, which is thought to remain in the structure and could potentially constitute up to 97% of the total activity inventory of the dismantling waste. The tritium activity and its distribution will be measured before the waste management method is proposed.

Finnish nuclear plants do not produce irradiated graphite nor contain significant amounts of aluminium. Therefore the chemistry andlong-term safety of these materials were taken as the subject of a literature survey. A further survey covered international practices related to the final disposal plans for treatment of graphite and aluminium, and experimental methods to measure organic and inorganic carbon-14 release from graphite have been surveyed [10].

Conclusion

FiR 1 served as a centre for training and research for over 50 years, educating an early generation of nuclear energy professionals who were needed to start up four power reactors in 1977-1980. These four units are still operating with very high capacity factors. Yet, while construction of new nuclear plants continues in Finland, the era of the Finnish research reactor has come to its end.

 

About the authors

Markus I. Airila, Iiro Auterinen, Petri Kotiluoto, Timo Vanttola and Olli Vilkamo, VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, 02044 VTT, Finland

 

References

[1] P. Hiismäki, "To be or not to be", the story of FiR1 in the nineties, 15th European TRIGA Conference, VTT Symposia 197 133-138, 1999. (ISBN: 951-38-5273-3; ISSN: 0357-9387).

[2] M. Lipponen, R.J. Rosenberg, 1988. Quality control in routine instrumental epithermal neutron activation analysis of geological samples. J. Res. Nat. Bur. Stand. Vol. 93, 3, 224 – 228, 1988.

[3] R.J.Rosenberg, V. Pitkanen and A. Sorsa, An automatic uranium analyser based on delayed neutron counting. J. Radioanal. Chem. Vol. 37, No. 1, 169-179, 1977.

[4] R.J. Rosenberg, Instrumental activation analysis of 11 lanthanide elements in Apollo 12 Lunar Samples. Radiochem. Radioanal. Letters, Vol. 6, 45, 1971.

[5] A.M. Balagurov, I.A. Bobrikov, G.D. Bokuchava, V.V. Zhuravlev, V.G. Simkin, Correlation Fourier Diffractometry: 20 Years of Experience at the IBR-2 Reactor, Phys. Part. Nuc., 2015, Vol. 46, No. 3, pp. 249-276.

[6] B. Bärs, L. Kåll, Instrumentation renewal at the FIR 1 research reactor in Finland, 7th European conference of TRIGA reactor users. 1982. http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/40/026/40026071.pdf

[7] I. Auterinen, S. Salmenhaara, Current utilization and long term strategy of the Finnish TRIGA research reactor FiR 1, Proceedings of the 4th World TRIGA Users Conference, Lyon (France); 7-10 Sep 2008, INIS-FR–08-1293, 2008b. http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/40/007/40007431.pdf

[8] L. Kankaanranta et al., Boron neutron capture therapy in the treatment of locally recurred head-and-neck cancer: Final analysis of a phase I/II trial, Int. J. Radiation Oncology Biol. Phys., Vol. 82 e67-e75, 2012.

[9] P. Kotiluoto and A. Räty, FiR 1 activity inventories for decommissioning planning, report VTT-R-02457-15, VTT Technical Research Centre of Finland, 2015.

[10] T. Carlsson, P. Kotiluoto, O. Vilkamo, T. Kekki, I. Auterinen and K. Rasilainen, Chemical aspects on the final disposal of irradiated graphite and aluminium. A literature survey, VTT Technology 156, VTT Technical Research Centre of Finland, 2014.