Hvordan efterlader du en advarsel, der varer lige så længe som atomaffald?

I januar 1997 besætningen på et fiskefartøj i Østersøen fandt noget usædvanligt i deres net:en fedtet gulbrun klump af lerlignende materiale. De trak den ud, anbragte den på dækket og vendte tilbage til at behandle deres fangst. Den næste dag, besætningen blev syg med alvorlige hudforbrændinger. Fire blev indlagt. Den fedtede klump var et stof kaldet yperit, bedre kendt som svovlsennep eller sennepsgas, størknet af temperaturen på havbunden.

Ved slutningen af ​​Anden Verdenskrig, USA, britisk, Franske og sovjetiske myndigheder stod over for et stort problem - hvordan man kunne slippe af med omkring 300, 000 tons kemisk ammunition genvundet fra det besatte Tyskland. Tit, de valgte det, der syntes at være det sikreste, billigste og nemmeste metode:at dumpe tingene ud på havet.

Det skønnes, at mindst 40, 000 tons kemisk ammunition blev deponeret i Østersøen, ikke det hele i udpegede dumpningsområder. Nogle af disse steder er markeret på forsendelseskort, men omfattende registreringer af præcis, hvad der blev dumpet, og hvor der ikke findes. Dette øger sandsynligheden for trawlerbesætninger, og andre, kommer i kontakt med dette farlige affald.

Problemet forsvinder ikke, især med øget brug af havbunden til økonomiske formål, inklusive rørledninger, havkabler og havvindmølleparker.

Historien om de uheldige fiskere illustrerer to punkter. Først, det er svært at forudsige, hvordan fremtidige generationer vil opføre sig, hvad de vil værdsætte, og hvor de vil hen. Sekund, skabe, At vedligeholde og overføre registre over, hvor affald er dumpet, vil være afgørende for at hjælpe fremtidige generationer med at beskytte sig selv mod de beslutninger, vi træffer i dag. Beslutninger, der omfatter, hvordan man bortskaffer noget af nutidens mest farlige materialer:højaktivt radioaktivt affald fra atomkraftværker.

Den røde metallift tager syv rystende minutter at køre næsten 500 meter ned. Ned, ned gennem cremet kalksten for at nå et 160 millioner år gammelt lag ler. Her, dybt under de søvnige marker og stille skove langs grænsen mellem Meuse og Haute-Marne departementerne i det nordøstlige Frankrig, det franske nationale agentur for håndtering af radioaktivt affald (Andra) har bygget sit underjordiske forskningslaboratorium.

Laboratoriets tunneler er stærkt oplyste, men for det meste øde, luften tør og støvet og fyldt med brummen fra et ventilationsaggregat. Blå og grå metalkasser rummer en række igangværende eksperimenter – måling, for eksempel, korrosionshastigheden af ​​stål, holdbarheden af ​​beton i kontakt med leret. Ved at bruge disse oplysninger, Andra ønsker at bygge et enormt netværk af tunneler her.

Det planlægger at kalde dette sted Cigéo, og fylde det med farligt radioaktivt affald. Den er designet til at kunne rumme 80, 000 kubikmeter affald.

Vi udsættes for stråling hver dag. Public Health England anslår, at i et typisk år kan nogen i Storbritannien modtage en gennemsnitlig dosis på 2,7 millisievert (mSv) fra naturlige og kunstige strålekilder. En transatlantisk flyvning, for eksempel, udsætter dig for 0,08 mSv; en dental røntgen til 0,005 mSv; 100 gram paranødder til 0,01 mSv.

Radioaktivt affald på højt niveau er anderledes. Det er, primært, brugt brændsel fra atomreaktorer eller restprodukter fra oparbejdning af dette brændsel. Dette affald er så potent, at det skal isoleres fra mennesker, indtil dets niveauer af stråling, som falder over tid, ikke længere er farlige. Tidsplanen Andra ser på er op til en million år. (For at sætte dette ind i en slags sammenhæng, det er kun 4, For 500 år siden blev Stonehenge bygget. Omkring 40, 000 år siden, moderne mennesker ankom til Nordeuropa. For en million år siden, kontinentet var midt i en istid. Mammutter strejfede rundt i det frosne landskab.)

Nogle videnskabsmænd kalder dette langlivede affald "atomkraftens akilleshæl, "og det er et problem for os alle - uanset vores holdning til atomkraft. Selv hvis alle verdens atomkraftværker skulle ophøre med at fungere i morgen, vi ville stadig have mere end 240, 000 tons farligt radioaktivt materiale at håndtere.

I øjeblikket, atomaffald opbevares over jorden eller nær overfladen, men inden for branchen anses dette ikke for at være en acceptabel langsigtet løsning. Denne form for opbevaring kræver aktiv overvågning. Ud over regelmæssig renovering skal den beskyttes mod alle former for farer, inklusive jordskælv, brande, oversvømmelser og bevidste angreb fra terrorister eller fjendens magter.

Dette lægger ikke kun en uretfærdig økonomisk byrde på vores efterkommere, som måske ikke længere bruger atomkraft, men forudsætter også, at der i fremtiden altid vil være folk med viden og vilje til at overvåge affaldet. På en million-års tidsskala kan dette ikke garanteres.

Så, efter at have overvejet en række muligheder, regeringer og atomindustrien er kommet til den opfattelse, at dybt, geologiske depoter er den bedste langsigtede tilgang. At bygge en af ​​disse er en enorm opgave, der kommer med mange komplekse sikkerhedsproblemer.

Finland er allerede begyndt at bygge et geologisk depot (kaldet Onkalo), og Sverige har påbegyndt licensprocessen for sit websted. Andra forventer at ansøge om sin byggetilladelse inden for de næste to år.

Hvis Cigéo går i drift, vil den rumme både højaktivt affald og det, der er kendt som mellemaktivt langlivet affald - såsom reaktorkomponenter. Når depotet har nået kapacitet, om måske 150 år, adgangstunnelerne vil blive genfyldt og forseglet. Hvis alt går efter planen, ingen vil nogensinde komme ind i depotet igen.

Stå foran en uskærmet strålingskilde, og du vil ikke se eller mærke noget. Imidlertid, noget af den stråling vil passere ind i din krop. Atomaffald er farligt, fordi det udsender ioniserende stråling i form af alfa- og beta-partikler og gammastråler. Mens alfapartikler er for svage til at trænge ind i huden, beta-partikler kan forårsage forbrændinger. Hvis det indtages, begge kan beskadige indre væv og organer.

Det er gammastråler, imidlertid, der har den største gennemtrængningsområde, og derfor potentialet til at forårsage den mest udbredte skade på dine cellers DNA. Denne skade kan føre til en øget risiko for kræft senere i livet, og det er i vid udstrækning ansvarlig for det sæt af symptomer kendt som strålingssyge.

Nogle eksperter vurderer, at en dosis på over 1 sievert er nok til at forårsage strålingssygdom. Symptomerne omfatter kvalme, opkastning, blærer og sår; disse kan begynde inden for få minutter efter eksponering eller blive forsinket i dagevis. Genopretning er mulig, men jo højere stråledosis, jo mindre sandsynligt er det. Typisk, døden kommer fra infektioner og indre blødninger forårsaget af ødelæggelsen af ​​knoglemarven.

For affald begravet dybt under jorden, den største trussel mod folkesundheden kommer fra vandforurening. Hvis radioaktivt materiale fra affaldet skulle blandes med strømmende vand, det ville være i stand til at bevæge sig relativt hurtigt gennem grundfjeldet og ned i jorden og store vandområder såsom søer og floder, endelig ind i fødekæden via planter, fisk og andre dyr.

For at forhindre dette, et underjordisk depot som Cigéo vil være meget omhyggeligt med at afskærme det affald, det opbevarer. Inden for dens vægge vil der være metal- eller betonbeholdere til at blokere strålingen, og flydende affald kan blandes i en smeltet glaspasta, der vil hærde omkring det for at stoppe lækage.

Ud over disse barrierer, planlæggerne vælger deres websteder omhyggeligt, så de kan udnytte egenskaberne af den omgivende sten. Hos Cigéo, pressemedarbejder Mathieu Saint-Louis fortæller mig, leret er stabilt og har meget lav permeabilitet, making it hard for any radioactive material reach the surface. After around 100, 000 years a few very mobile substances with a long half-life, such as iodine-129, might manage to migrate upwards in extremely small quantities, but at that point, Saint-Louis says, the "potential impact on humans and the environment is much lower than that of radioactivity that is naturally present in the environment."

Deep geological repositories are designed as passive systems, meaning that once Cigéo is closed, no further maintenance or monitoring is required. Much more difficult to plan for is the risk of human intrusion, whether inadvertent or deliberate.

In 1980, the US Department of Energy created the Human Interference Task Force to investigate the problem of human intrusion into waste repositories. What was the best way to prevent people many thousands of years in the future from entering a repository and either coming into direct contact with the waste or damaging the repository, leading to environmental contamination?

Over the next 15 years a wide variety of experts were involved in this and subsequent projects, including materials scientists, anthropologists, architects, archaeologists, philosophers and semioticians—social scientists who study signs, symbols and their use or interpretation.

Science fiction author Stanislaw Lem suggested growing plants with warning messages about the repository encoded in their DNA. Biologist Françoise Bastide and semiotician Paolo Fabbri developed what they called the "ray cat solution"—cats genetically altered to glow when in the presence of radiation.

Quite apart from the technological challenges and ethical issues these solutions present, both have one major drawback:to be successful they rely on external, uncontrollable factors. How could the knowledge required to interpret these things be guaranteed to last?

Semiotician Thomas Sebeok recommended the creation of a so-called Atomic Priesthood. Members of the priesthood would preserve information about the waste repositories and hand it on to newly initiated members, ensuring a transfer of knowledge through the generations.

Considered one way, this is not too different from our current system of atomic science, where a senior scientist passes on their knowledge to a Ph.D. candidate. But still, putting such knowledge, and therefore power, into the hands of one small, elite group of people is a high-risk strategy easily open to abuse.

Perhaps a better way to warn our descendants about the waste is to talk to them directly, in the form of a message.

At Andra's headquarters outside of Paris, Jean-Noël Dumont, head of Andra's memory program, shows me a box. Inside, fixed in plastic cases, are two transparent discs, each around 20 centimeters in diameter. "These are the sapphire discs, " he says. The brainchild of Dumont's predecessor, Patrick Charton, each disc is made of transparent industrial sapphire, inside which information is engraved using platinum.

Costing around 25, 000 euros per disc, the sapphire (chosen for its durability and resistance to weathering and scratching) could last for nearly 2 million years—though one disc already has a crack in it, the result of a clumsy visitor on one of Andra's open days.

In the very long term, selvom, these plans also have a major drawback:how can we know that anyone living one million years in the future will understand any of the languages spoken today?

Think of the differences between modern and Old English. Who of us can understand "Ðunor cymð of hætan &of wætan"? That—meaning "Thunder comes from heat and from moisture"—is a mere thousand years old.

Languages also have a habit of disappearing. Around 4, 000 years ago in the Indus Valley in what is now Pakistan and north-west India, for eksempel, people were writing in a script that remains completely indecipherable to modern researchers. In one million years it is unlikely that any language spoken today will still exist.

In the early 1990s, architectural theorist Michael Brill sought a way to side-step the issue of language. He imagined deterrent landscapes, "non-natural, ominous, and repulsive, " constructed of giant, menacing earthworks in the shape of jagged lightning bolts or other shapes that "suggest danger to the body... wounding forms, like thorns and spikes."

Anyone venturing further into the complex would then discover a series of standing stones with warning information about the radioactive waste written in seven different languages—but even if these proved unreadable, the landscape itself should act as a warning. To help convey a sense of danger there would be carvings of human faces expressing horror and terror. One idea was to base them on Edvard Munch's The Scream.

The drawback is that such a landscape—a strange, disturbing wonder—would probably attract rather than repel visitors. "We are adventurers. We are drawn to conquer forbidding environments, " says Florian Blanquer, a semiotician hired by Andra. "Think about Antarctica, Mount Everest."

Or think about the 20th-century European archaeologists, people not noticeably hesitant when it came to opening up the tombs of Egyptian kings, despite the warnings and curses inscribed on their walls.

As Dumont sees it, a memory program is necessary for three main reasons. Først, to avoid the risk of human intrusion by informing future generations about the existence and contents of Cigéo.

Sekund, to give future generations as much information as possible to allow them to make their own decisions about the waste. They might, for eksempel, want to retrieve the waste because new uses or solutions have arisen. Gerry Thomas, chair in molecular pathology at Imperial College London, believes that much of the waste destined for repositories may one day provide an important new non-carbon fuel source.

Third, cultural heritage:a properly documented geological repository would provide a wealth of information for a future archaeologist. "I have no knowledge of other places or systems where you have at the same time objects from the past and very large, concrete descriptions of how these products were manufactured, where they come from, how we considered them and so on, " says Dumont.

One way that memory is transmitted is orally, from generation to generation. To study this, Dumont asked researchers to consider historical examples of oral transmission, using as a case study the 17th-century Canal du Midi between the Mediterranean and Atlantic Ocean. Her, for 300 years, the same families have worked on maintaining the canal, passing down know-how from father to son.

Dumont also talks about the need to ensure that as many people as possible hear about Cigéo. As part of this strategy, Andra has held a series of annual competitions asking artists to suggest ways to mark the site. For eksempel, Les Nouveaux Voisins, winners of the 2016 prize, imagined constructing 80 concrete pillars, 30 metres high, each with an oak tree planted at the top. As the years passed, the pillars would slowly sink and the oak trees replace them, leaving tangible traces both above and below the repository.

Leaving Andra's visitors' center, I drive through a landscape patchworked with colors, from the russet of the woods to the bright limey green of a wheat field, towards Bure, a tiny village of around 90 inhabitants. The population is aging.

"Young people can't stay here if they want to study and find jobs, " Benoît Jaquet tells me. A village that once supported around ten farmers is now home to only two or three. Although not a resident of Bure, Jaquet is the general secretary of CLIS, an organization of local elected officials, representatives from trade unions and professional bodies, and environmental associations. Its purpose is to provide the local community with information about Cigéo, host public meetings, and monitor the work of Andra by, for eksempel, commissioning independent experts to review the agency's work.

If the repository is built, Jaquet says, French law requires that CLIS be transformed into a local commission that will last as long as the repository. "So it's also a way to pass the baton, " he says. "If there is a local commission there is a memory—not Andra's memory but an external memory."

På samme tid, Andra has set up three regional memory groups, each composed of around 20 interested locals. They meet every six months and make their own suggestions for passing on the memory of the repository. Ideas so far include collecting and preserving oral witness accounts and developing an annual remembrance ceremony to take place on the site, organized by and for the local people. A nuclear beating the bounds, a radioactive summer solstice, an atomic maypole.

This last idea resonates with the work of Claudio Pescatore and Claire Mays, former employees of the Nuclear Energy Agency, a Paris-based body that supports intergovernmental cooperation on nuclear issues. They wrote in a research paper:"Do not hide these facilities; do not keep them apart, but make them A PART of the community… something that belongs to the local, social fabric." They went on to suggest that a monument celebrating the repository could be created, and argued that if it had "a distinctiveness and aesthetic quality, would this not be one reason for communities to proudly own the site and maintain it?"

Could the repository, I ask Jaquet, one day become a tourist destination? On the contrary, han siger, some members of the CLIS say that "every person living here will quit the district because of the risk, because of the image of the repository as a rubbish bin. Of course some also think the repository will create employment and that this will become a new Silicon Valley. Maybe the reality will be somewhere between the two—but a tourist attraction? I'm not sure about that."

Across the road from CLIS and the town hall is a large, ramshackle stone house decorated with a banner. It translates:"Free zone of Bure:house of resistance against nuclear waste." Since 2004, this has been home to a rotating group of international anti-nuclear, anti-repository protesters. By continually campaigning against Cigéo—and, formentlig, by passing their beliefs on to future generations—the protesters would necessarily keep the memory of the repository alive and in the public eye, the ramshackle stone house becoming its own sort of monument for Cigéo.

"So in fact the pro-repository groups need the anti-repository groups to stay alive in order to provide a good memory, " says Florian Blanquer. "Fortunately, we are in France—in France there are always opponents to something!"

Rely only on the transmission of knowledge between generations and you can never guarantee an unbroken line of succession. Rely only on direct communication and you risk leaving behind a message that, even if it survives physically, eventually no one will be able to understand. So Andra asked Blanquer to research how to convey a message without written language.

Many visual signs are, like languages, kulturelt specifik. Desuden, we know that the meanings of signs are not always stable over time.

Stadig, Blanquer thought that there was one universal sign:an image of a human figure. "And every human being… apprehends its body through space the same way as well. There is an up and down, a left and right, a front and back, " he wrote in a conference paper. Pictographs (pictorial symbols for a word or phrase) based on an anthropomorphic figure in movement are likely to be recognized universally, he decided.

Now he had the beginnings of an idea, but it wasn't enough. You might draw a cartoon strip showing a person approaching a piece of radioactive waste, touching it and falling down. But how can you guarantee that the panels will be read in the correct order? Or that touching the waste will be interpreted as a negative action? And how can a pictograph relying on the visual representation of tangible objects convey a message about radioactivity—something that can be neither seen nor touched?

In response to these problems, Blanquer has designed what he calls a "praxeological device." Independent of any verbal language, it works by teaching the person encountering it a brand-new communication system created specially for this purpose.

Blanquer envisages a series of passages built underground, perhaps in the access tunnels of the repository. On the wall of the first passage is a rectangular pictograph showing a person walking along the passage and a line of footprints indicating the direction of movement.

At the end of the corridor is a hole and a ladder and three more pictographs. A circular pictograph shows a person holding on to the ladder; a triangular pictograph shows a person not holding on and consequently falling off. And so it continues.

In this way you begin to establish patterns:you learn first that the figure drawn on the walls relates to a person's actions here, and second that you should copy the actions in the circles and avoid the actions in the triangles. "What is really interesting is the idea of people learning by themselves, " Dumont says. "Learning is important in the long term when you cannot just rely on transmission from generation to generation."

There has been one more radical proposal about how to deal with the threat of human intrusion—hide the repository completely from future generations.

Some argue that because the repositories are passive systems, most likely buried far underground in areas with no deep natural resources, the question of memory preservation is moot.

I øjeblikket, no one can conceive of a reason why anyone in the future might want to dig down 490 meters to reach the clay formation that Cigéo is planned for. This reduces the chances of inadvertent intrusion. And after around, sige, 100, 000 år, almost all surface traces and any complex above-ground markers will have vanished. The only things left behind will be some slight indentations, perhaps a gentle protuberance or two. Things that to the untrained eye may appear to be only the natural shape of the land. Eventually it will be as though no one was ever there, as though there is nothing for anyone to remember.

But Blanquer warns that forgetting is not so easy:"You cannot say to yourself, "I will forget about that." It's like trying not to think about pink elephants. If you want to forget about it then first you have to get rid of any information about it. That would mean shutting down the web and destroying a lot of computers, a lot of newspapers, a lot of books."

In his opinion it is no longer possible that Cigéo could become, as Danish film maker Michael Madsen has said about the Finnish repository, "the place you must always remember to forget."

Last summer I set out with some friends to walk part of the Ridgeway, an ancient long-distance route through the Chiltern Hills and North Wessex Downs in the south of England. On Whiteleaf Hill, the chalky white path passes near the remains of a Neolithic barrow, omkring 5, 000 år gammel. You can tell immediately that it's not natural, the way the earth has been lumped up on the hillside, but today there is little to see except a low grassy mound with a view over the fields and woods of Buckinghamshire and the small town of Princes Risborough.

We don't know who built the burial chamber or the name of the person interred there, what language they spoke and what they believed the world would be like in 5, 000 år. Staring at the barrow, it was not continuity with the past I felt, but distance.

In the 1930s an archaeologist called Lindsay Scott broke open the Whiteleaf Hill barrow and discovered the remains of a human skeleton, around 60 pieces of pottery, flint shards and animal bones. And just as we enter burial chambers in search of answers, so archaeologists of the future may one day find themselves penetrating the concrete passageways and tunnels of the place we call Cigéo.

Peering into the darkness they will ask themselves, who built this place and why? Why did they come here, digging down so far below the surface of the land? What were they running from, or trying to hide?

In the light they carry, the archaeologists will see markings on the passage walls. Moving closer, they make out a series of footprints stretching away in front of them, down the passageway. In the looming darkness, it becomes clear—someone has left them a message.

This article first appeared on Mosaic and is republished here under a Creative Commons licence.