Recent announcements by Russia that it will decommission the Leningrad nuclear plant’s No 1 reactor have opened a broader discussion of how Moscow will handle closing similar reactors whose designs defy conventional dismantlement.

Shortly before Christmas, officials with Rosatom, Russia’s state nuclear corporation, revealed they were beginning decommissioning work on the reactor, the plant’s first, which came online in 1974. The reactor is one of four at the plant, and one of 11 nationwide that was built on the RBMK 1000 design. Four others were built in Ukraine at the Chernobyl nuclear power plant – one of which exploded in 1986 – and two similar RBMK-1500 reactors were constructed at the Ignalina nuclear plant in Lithuania,

While each of these RBMKs underwent comprehensive upgrades in the years following the Chernobyl catastrophe, no amount of remodeling was able to finesse the reactors’ most deviling flaw as far as safe decommissioning and dismantlement are concerned – their graphite stacks.

A graphite stack is essentially bulky cylinder about 7 meters high and 11 meters across made of graphite bricks and weighing about 2000 tons. Fuel is fed into the reactor via channels cut in the masonry, and the graphite acts as the moderator.

The concept originated in the late 1940s, when the Soviet Union and the United States began to build reactors to produce weapons plutonium – a time when considerations about how to dismantle them were not a priority. While most reactors in commercial operation around the globe are of the boiling water type, the Soviet Union’s first steps in civilian nuclear power were based on the unwieldy graphite moderated design.

Inside one of the Leningrad Nuclear Power Plant's RBMK reactors. Credit: Rosenergoatom

Now, all 11 of Russia’s RBMK reactors are reaching retirement age. But as Rosatom’s plans for dismantling the Leningrad nuclear plant’s No 1 reactor come into focus, it’s clear that the question of how to safely dismantle RBMK reactors remains largely unanswered.

According to Vladimir Pereguda, the Leningrad plant’s director, the No 1 reactor will be treated essentially as an operating reactor, both financially and technically, for the foreseeable future – a phase called “operation without generation.”

This amounts to removing the reactor’s fuel while continuing to cool it for as long as five years before it can be safely stored, and decontaminating what remains of the reactor’s structure aside from its graphite stack. After that, it’s essentially a process of waiting until nuclear science catches up in order to deal with the graphite stack.

It’s a costly process. Without the profits from the sale of electricity generated by Leningrad’s No 1 reactor, the Russian business newswire RBK daily calculated that Russia will lose $203 million over the duration of the reactor’s decommissioning.

When that decommissioning will be completed, however, remains foggy. Experts who spoke with RBK estimated that the reactor might not be fully decommissioned for another 50 years because the technology for dealing with the irradiated graphite stacks simply doesn’t exist.

This presents a problem for Rosatom, Russia’s nuclear corporation. The remaining three RBMK 1000 reactors at the Leningrad plant are scheduled to stop service between 2020 and 2025. Those closures will be followed by the four RBMK 1000 reactors at the Kursk Nuclear Power Plant, and another three at the Smolensk Nuclear Power plant sometime within the next 10 years. That leaves a lot of irradiated graphite hardware on Rosatom’s hands.

This is where things start getting more expensive. Russia, like most other countries operating nuclear reactors, funds decommissioning and dismantlement on the back of electricity tariffs charged by its nuclear power plants. These funds are collected by Rosenergoatom, Russia’s nuclear power utility.

But where other countries have been collecting these tariffs for more than fifty year, it was only in 1995, after the fall of the Soviet Union, that the Russian nuclear industry began earmarking a portion of electricity revenues toward the work of eventual decommissioning.

According to RBK, the total funding that has been set aside for decommissioning all four of the Leningrad nuclear plant’s RMBK reactors is about $820 million – a sum that’s meant to be doled out over the course of 35 years.

The problem, however, is that Rosenergoatom’s total decommissioning reserve amounts to only a little more than $148 million as of 2017, according to RBK – obviously well short of what’s needed to decommission even the Leningrad plant’s No 1 reactor.

For contrast, the European Commission has set aside € 3 billion to decommission the mere two RBMK 1500 units in Lithuania. In order for Russia’s nuclear industry to spend that much on its own decommissioning projects, it would either have to raise what it deducts from energy tariffs for decommissioning, or ask the state to underwrite shortfalls of millions, possibly billions, of dollars to make up the shortfall.

At the same time, there is little to suggest any breakthroughs in removing and storing the reactors ’ graphite stacks. At Lithuania’s Ignalina – as well as at other graphite moderated weapons reactors both in Russia and the United States – decommissioning has involved simply mothballing the graphite stacks and waiting until better times, when more is known about how to safely deal with them.

That’s not to say that breakthroughs won’t come. The International Atomic Energy Agency is currently underwriting research at Rosatom’s closed nuclear city in Seversk, near Tomsk, to deal with exactly this issue. It will be interesting to watch what materializes – most especially for the good of those who have to live among these reactors’ remains.