GRR-1: Greece’s research reactor at Demokritos

What GRR-1 is, and what it is not

GRR-1 is located at the National Centre for Scientific Research "Demokritos" (NCSR "Demokritos"). Its nominal power is 5 MW thermal1.

The comparison that matters is one of orders of magnitude. A nuclear power plant runs at a far higher thermal power. GRR-1 is not a smaller version of the same thing; it is a different class of facility.

Its purpose is different too. A research reactor does not generate electricity. It produces neutrons, which are used for materials analysis, radioisotope production, sample irradiation and training. The heat is a by-product to be removed, not the output.

That distinction is why the statement "Greece has a nuclear reactor" is both true and misleading, depending on what the listener takes it to mean.

Its current status: licensed extended shutdown

The reactor is out of service. Its status is not informal idleness, though. It is a licensed state of extended shutdown, under a licence the Greek Atomic Energy Commission (EEAE) granted in 20142 and renewed in 20192, valid until October 20242 according to the latest published national report.2 We found no later public record of its renewal.

Extended shutdown sits between operation and decommissioning. The reactor is neither running nor being dismantled, and the licence sets out what the holder must do in the meantime.

The difference matters. A facility in licensed shutdown stays inside the regulatory framework: the licence holder keeps its obligations and supervision continues. According to the same report, the EEAE set the inspection frequency for a reactor in this state at 1 per year2. Our explainer on the EEAE covers the regulator itself.

This regime is what separates a facility that has been stood down in an orderly way from one that has simply been closed.

Where the fuel went

This is the part missing from most public accounts, and the one that matters most for safety: the fuel is no longer in the country.

The fuel left in separate phases, matching the two types the reactor used over its life. The used high-enriched uranium (HEU) fuel elements were returned to the country of origin, the United States, in 20052, under the terms of the fuel purchase agreement between the US Department of Energy and the Greek government. The used low-enriched uranium (LEU) elements were returned to the United States in several shipments, completed in 20192.

The fresh fuel, meaning elements that had never been used, was exported for use in another country in 20231.

In practice, the most active material on the site has gone, and with it the part of the facility that weighed most on safety. What remains as a radiological matter comes from materials activated during operation and from residues of earlier activities. That is real work to manage, but it is a problem orders of magnitude smaller than the fuel.

Could it run again?

Not by decision alone. The EEAE’s national report under the Convention on Nuclear Safety is explicit: if the licence holder decided to resume the refurbishment project and operate the reactor again, a licensing process comparable to that for building a new reactor would follow, with an assessment of every aspect of nuclear safety and approval of the refurbishment work. 2

Loading fuel into the core would also be allowed only after the refurbishment or reconstruction work had been licensed and the commissioning programme approved.

Then there is the practical side. With the fuel gone, a restart would need a new supply, with everything that implies for contracts, safeguards and transport.

Taken together, a restart would not be a maintenance job. It would in effect be a new project.

What comes next: decommissioning

The direction recorded in the official documents is decommissioning. NCSR "Demokritos" appears in the national programme in two roles: as operator of the interim storage of radioactive waste, and as a producer of waste from the decommissioning of GRR-1. The same institution therefore holds both the facility to be dismantled and the store where its waste would first go.

The IAEA peer review mission on radioactive waste, spent fuel, decommissioning and remediation (ARTEMIS) that visited Greece made a recommendation on this point: complete the decommissioning plan and the safety assessment that supports it. 1 A recommendation in such a report is not an accusation. It is how the improvement mechanism works, and publishing it is part of the system.

There is also a structural issue that concerns the whole country. Greece has no final disposal facility for radioactive waste, and central interim storage is at Demokritos. Decommissioning produces waste, and that waste needs somewhere to go.

This ties GRR-1 to the wider question. A country that ever seriously considered nuclear power generation would need a credible plan for disposal from the start, and today Greece has no final disposal route even at the scale of a research reactor.

Why its history matters for any future programme

First, it shows that Greece has institutional memory. There is a regulator that licenses and inspects a nuclear facility, there is experience in managing fuel and waste, and the country takes part in international frameworks that are subject to review. It is not starting from a blank sheet.

Second, it gives a sense of scale. Managing a 5 MW thermal1 reactor that is not operating already involves a regulator, international missions and a national programme. Comparing that with what a power plant would require shows the size of the gap better than any argument. Our analysis of whether Greece can support a nuclear programme looks at that gap in more detail.

Third, a point of method. The story of GRR-1 circulates with wrong figures and wrong dates, because it is copied second-hand. Every number in this article comes from the EEAE’s national report or from the ARTEMIS mission report, and carries its citation. For a wider picture of where things stand, see where Greece stands.

The editor works as an engineer in the nuclear sector. Views here are his own and do not represent any employer. The platform receives no funding from anyone. Not yet independently reviewed by a second engineer. Read in Greek.