Waste, dismantling: the tenable arguments of nuclear supporters COMMENTS

Tribune by Gérard Petit, Retired engineer from the energy sector

While nuclear has been invited to the forefront of the electoral campaign, let's come back to the downstream of the operation of reactors: the treatment of waste and the deconstruction of installations.

The apologue, says Emile Faguet, is: "the demonstration of a maxim by an example", and it is an apologue of Aesop that La Fontaine takes up again, in the fall of his famous fable "The Fox and le Bouc”: “In all things, the end must be considered”.

If we are to believe the critics of nuclear power, the proponents of the sector would therefore not have read Aesop, even less La Fontaine, not having considered the end of their machines, nor that of the waste they produced. products. But unlike the "goat friend", it would not be a question of levity, but of cynicism, in line with nuclearist ways of thinking: let's take advantage now, the generations that follow us will put up with the legacy, a situation presented, unsurprisingly, as an aporia by the opponents.

But what about these damning judgments, often delivered by militant mimicry, without trying to go back to the sources, or even worse, knowingly, twisting the arm of the realities?

Reprocessing, recycling

In addition to the fact that the production of really problematic waste is very low, the choice to reprocess the irradiated fuel, and therefore to separate the slag (fission products and minor actinides) from what is reusable (plutonium and depleted uranium), has made it possible to reduce the volumes to be treated and to specifically condition the said slag by vitrification...situation, which without being a definitive solution, constitutes a step towards it, and makes it possible to consider it, in complete safety, without the pressure of time, the protection conferred by the glass matrices being particularly durable.

This recycling policy, practiced for spent nuclear fuel, well before the said policy was established as a societal principle, allows the energy recovery of the products of the process, ie 96% of the materials initially present, a remarkable figure.

This is plutonium that can be reused in an FNR reactor (1) or in a PWR reactor (1), via MOX fuel (2) and URT reprocessed uranium (3) whose U 235 content is even higher than that of natural uranium, which makes it a material with potential.

By the way, it turns out that these practices, the prerogative of experts in the field, have nevertheless emerged on the stage of the campaign for the presidential election, with nuclear power occupying an unexpected place there.

In past years, part of the URT was sent to Russia to be enriched there to a level, again allowing its use in a reactor (by ultracentrifugation, a technique that France had not yet implemented, because its always relying on that of gaseous diffusion, which process, applied to the URT, did not lend itself well to the operation, among other things because of the presence of U236.

In accordance with international practices for this type of contract, Russia sent back the enriched uranium and kept the depleted uranium, potentially recoverable nuclear material, in particular in the RNR sector, therefore everything except nuclear waste.

Yannick Jadot, who opportunely transforms his campaign into an anti-nuclear platform, described the aforementioned scheme as a policy of exporting our waste to "less attentive" countries, proof if necessary that nuclear power is a dead end, in some way side we look at it.

Knowingly, we will appreciate the value of the argument, but his statement will probably remain in the minds, it is the goal.

The reprocessing of irradiated fuels is a process that France has developed for a long time and which it operates on a large scale, it is a specific know-how, the technology is complex but remarkably mastered and rich in a very significant return of he experience is an industrial link in its own right in our national nuclear power industry, and several countries (Germany, Japan, Belgium, etc.) have relied on France for the reprocessing of their irradiated fuel, in times when the horizon nuclear was more open for them.

Always topical, rather than taking back, as stipulated in the contracts, the plutonium resulting from the reprocessing of its fuels, Japan, which had not forgotten the turmoil caused by the repatriation of plutonium on its lands (the memorable episode of the ship Akatsuki Maru in 1992) preferred that it be integrated into MOX fuels, deliveries of which have just been completed, with the arrival of a third transport in the archipelago.

In earlier times, the Japanese acquired part of the “French-style” reprocessing process but failed to complete and industrialize it. The Chinese show interest, but the negotiations drag on. It must be said that the amounts involved are very significant.

In France, the plutonium extracted was originally intended for future FNR reactors, a sector that has since been put into political stalemate by the shutdown of Super-Phénix, a choice confirmed more recently by the abandonment of ASTRID (6).

But since the end of the 1980s, we have also known how to recover plutonium in PWR reactors, by using MOX fuels, which has so far saved more than 8,000 tonnes of natural uranium, in order of magnitude, a full year of operation of the EDF fleet.

In France, the fuel reloads of 22/32 reactors of the 900 MWe family contain MOX fuel elements. Around the world, about 44 reactors (i.e. roughly 10% of the fleet) have, or have used, this type of fuel.

Geological storage

In the national nuclear waste management strategy, it is planned that vitrified waste and other highly radioactive by-products from reprocessing (head and foot of duly compacted fuel assemblies), but also irradiated MOX assemblies (difficult to reprocess and less recoverable), be deposited definitively (subject to a guarantee of reversibility over 100 years) in a future geological repository, thus realizing the effective closure of the nuclear fuel cycle, to the chagrin of its opponents, headwind against what they qualify, although slightly moreover, of inconsistency.

This option, worked on in France for more than a third of a century, with regular parliamentary follow-up, has given rise to work which refers to the theoretical field (number of high-level theses) and experimental (with in particular the underground laboratory of Bure which tests in situ and life-size, the various technical aspects of the repository as envisaged).

Opponents, who can hardly dispute the seriousness and quality of the approach, even if the issue is difficult in itself, when it comes to very long-term projections, brandish the ethical dimension of the question, speaking of a poisoned legacy to future generations. , without having to consider that these same future generations would like the problem not to be theirs.

We must nevertheless consider that the proven resistance of the glasses (to leaching by the natural elements), relayed by the qualities of the layer of argillite chosen (located at a depth of 500m, stable since the Jurassic [> 150 million years] , free of faults and water circulation, located in a very low seismic zone), represent solid input data.

It is -in fine- to show that the obstacles opposed to the migration of radioelements, will delay their progression sufficiently so that, in the meantime, they have lost their harmfulness by radioactive decay, a simple but very demanding challenge, that we can nevertheless consider relevant, given the overall approach proposed.

Dismantling of facilities

On this specific subject, one can refer - with advantage - to the text that Dominique Grenèche and Michel Gay have just published on Counterpoints (4), one finds there the essential, strategies as orders of magnitude, a methodical demystification of the scarecrow so slightly opposed to the proponents of the nuclear industry.

In fact, a planned and anticipated stage of an industrial cycle, which should not be hampered by any technological limit, the required processes being already developed and financially accessible.

While there is no longer any safety issue and the only important questions relate to the radiation protection of the workers and the storage of the extracted components, the Brennilis site (5) is taken as an emblematic target in order, once again, show that all nuclear issues lead to dead ends.

It turns out that the mysteries of procedure which frame the dismantling, complicated at will, are as many blanks presented to the opponents who rush into it and excel there.

A caricatural illustration, it turns out to be much simpler to change the steam generators on an existing power plant, a site that is nevertheless substantial and complex, than to be able to dismantle and remove the equivalent exchangers (but much more modest) from the Brennilis reactor.

It is legally (and logically) incumbent on the operators of nuclear power plants to carry out the dismantling of the installations, after they have been definitively shut down, this same responsibility also falls on the operators of wind and solar farms, but they are discovering sometimes very large amounts to be provisioned.

As said, with regard to nuclear power, this dismantling has often been presented as difficult, expensive, even impossible, by some, but the reality is more prosaic.

The high degree of standardization of French reactors should greatly facilitate the industrialization of decommissioning processes and above all allow a strong valorization of experience feedback if we know how to sequence the different worksites correctly.

The difficulty will come rather from the outlets for the waste created, today notoriously undersized, especially if we persist in a "zoning" of the installations, generating large volumes of waste, declared radioactive only because they are located "in the wrong place ".

Furthermore, unlike the most common practices in Europe and elsewhere, there is no exemption threshold in France for truly radioactive waste, this provision prohibiting the reuse of materials (for example steel,) very weakly radioactive, a real waste.

Finally, in terms of dismantling, we have control of the schedule, which is an essential asset. There is no need to rush, because we thus benefit from the natural decrease in radioactivity, but when the time comes, we will then have to create and maintain a pace in the worksites to allow the real industrialization of the processes and the valuation of the corresponding investments.

Financing is already provisioned and protected (dedicated assets), with specific taxes being levied on electricity bills. Among other control bodies, “La Cour des Comptes” monitors these aspects in particular and regularly assesses them.

In this respect, it is clear that the extension of the lifespan of the installations mechanically increases the provisions, another benefit, little valued this one.

Argument deconstruction

So, even after a quick overview of these questions, can we still say that the downstream operation of reactors is an unthought?

The fact remains, however, that it is strategic for the detractors of nuclear energy to discredit the sector by directing public opinion towards a field that is presented to it as mined, intractable waste, impossible deconstruction.

These dimensions being eminently technical, it is not easy to argue in defense by presenting obvious data; on the other hand, creating doubt remains trivial and these subjects lend themselves perfectly to it.

Once again, for those who seek to discredit nuclear power definitively, to show that under the significant advantages, which can be less and less eluded, it is essential to show that there is a thick dark stratum (waste, deconstruction, etc.). ) by giving the discourse an ethical dimension, for lack of being able to technically counter-argue in a credible manner, on the scale of the risks actually incurred.

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(1) RNR: fast neutron reactors, PWR: pressurized water reactor.

(2) MOX (Mix oxide) nuclear fuel composed of plutonium oxide and uranium oxide

(3) URT (reprocessed uranium) uranium recovered in the process of reprocessing irradiated fuels, its content of fissile isotopes (by thermal neutrons), of the order of %, is higher than that of natural uranium, where the strategies of valorization by re-enrichment (we then speak of URE)

In addition to U 235, the URT contains a small proportion of U 236, which indicates passage through the reactor.

(4) https://www.contrepoints.org/2021/11/26/414822-demantelement-dune-centrale-nucleaire-facile-et-pas-cher

(5) Brennilis plant, known as Monts d'Arée, known as EL4, reactor operating on natural uranium, moderated with heavy water, cooled with carbon dioxide, with a power of 70 MWe, commissioned in 1967 , shut down in 1985…Mid-2021, EDF presented a new scenario and a new schedule for final completion of dismantling in 2040!!

(6) ASTRID: 4th generation prototype reactor, intermediate power fast reactor, sodium cooled, project abandoned in 2019.

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