Danger: radioactive waste – a message in a bottle to last… a million years

Photo Marie-Claude Dupuis / Chief Executive Officer for Andra (French National Radioactive Waste Management Agency) / June 23rd, 2011

All nuclear countries are faced with the thorny question of how to handle waste. France has made the decision to bury the most radioactive waste 500 meters underground in a 150 million year old layer of clay 130 meters thick, at Bure in the heart of the Lorraine countryside. According to the timeline, a law will be passed in 2016 to authorize construction. Marie-Claude Dupuis, CEO of Andra (French National Radioactive Waste Management Agency) and Chairperson of the Radioactive Waste Management Committee of the OECD discusses the project.

ParisTech Review – Whether France scales back its nuclear program or not, the issue of waste will remain a major preoccupation for years to come. Other countries are facing similar questions. Could you explain the nature of the waste?

Marie-Claude Dupuis - France has long chosen to conduct a reprocessing program which is by no means the case in all of the countries concerned. Our French nuclear reactors are responsible annually for 9000 cubic meters of low and intermediate level waste (LILW and known in France as FMA-VC), 750 cubic meters of intermediate level waste long-lived (ILW and known in France as MAVL), and 150 cubic meters of high level waste (HLW and known in France as HA).

Nuclear waste is a broad term for a wide range of materials but when the word is used by the media, it tends to imply waste produced through spent fuel reprocessing which in fact accounts for only 2% of the total, albeit the most radioactive portion. At present the waste is held at one of two surface storage facilities in La Hague (Manche) and Marcoule (Gard).

The European atomic energy agency Euratom has issued directives stating that certain metals recovered during plant decommissioning can be reused in the event their radioactivity is so low as to pose no danger but French national policy forbids this practice and has set up a specific program for handling all waste from these activities. In fact, Andra maintains two surface repositories in the Aube region of France. One handles low and intermediate level waste (CSFMA) while the other takes care of very low level waste (CSTFA).

Long term, the goal is to bury the most radioactive waste deep underground. Why hasn’t this already been done?

The decision to stock waste underground will require a huge expenditure of political will, due to the national scope of the proposals. No concrete steps can be taken without extremely advanced investigations and far-reaching discussions with the various stakeholders.

In the future, will all waste be placed underground?

It depends on the level of ‘activity’ and the length of time it will remain radioactive which can be anything from a couple of days for hospital waste, to millions of years for uranium or iodine. For short-lived radioactive waste (indicating a half-life of less than 30 years) surface storage is an adequate solution. Sites would be monitored for 300 years to ensure that radioactivity had sufficiently dissipated so as to pose no threat to public health. For long-lived waste such as that produced through reprocessing, we need to demonstrate it will be secure for millions of years. The OECD, by way of its Nuclear Energy Agency (NEA), and the IAEA, have recommended that these types of waste be buried in geologically stable parts of the earth’s core in chambers at least 500 meters deep.

Why a million years?

A million years should not be viewed as a definitive statement by the French Nuclear Safety Agency (NSA) on what is acceptable because, really, the timeline could extend much further, but it is reasonable given what we know about the lifespan of the radioactive elements covered by the recommendation. We also know that a million years is the time it takes to reduce the levels of radio toxicity found in spent fuel to levels that correspond to those found naturally in uranium deposits.

How far has research into the matter of underground storage progressed?

When dealing with storage of radioactive waste, water is the principal enemy as it can serve as an artery for the transfer of radioactive elements—the canisters to which the material is confined degrade over time—back to the surface, the biosphere, and eventually humans. It’s why we are studying the sedimentary rock left by clay deposits as the best solution for storage, it is highly impermeable.

Do you honestly envisage surveillance of the selected site for a period as long as a million years? Is this really practical?

To ensure the long-term security of the canisters, we are focusing on the three barriers we have at our disposal. The first is a French invented process of vitrification which involves blending fission products with glass to create an inert matrix which is then poured into stainless steel casks and eventually encased in steel. Second, are the barriers that will seal the chambers where the steal-encased canisters will be stored. The final barrier is the geological host material and the relative importance of this third part of the safety equation depends largely on the location of the chosen site. At the US site in New Mexico for example waste is entombed in salt, a highly impermeable substance, making the construction of the canisters less critical.

Along with the United States the other two dominant models of storage are found in Sweden and France. Sweden’s bedrock contains granite, whose geological properties make it highly susceptible to fracture and water infiltration. Out of necessity Sweden has had to put more effort into copper-based canister construction and sealing technology capable of lasting a virtual eternity. They are also making use of a type of clay called Bentonite which has rather unique expansion qualities allowing the canisters to be encased in a naturally impermeable shell. French soil also contains granite but we have settled on an alternative solution. Research led to the designation of a 150 million year old layer of Callovo-Oxfordian argillaceous rock, 130 meters thick and buried 500 meters beneath the rolling countryside above. In 2009, a site with a surface footprint of 30 square kilometers was chosen and swiftly approved by the government in 2010. Near the tiny village of Bure, in the Lorraine region of north-east France, a subterranean laboratory is already in place. The geological properties of the site offer not only excellent impermeability but are uniquely suited to prevent the transmission of the most toxic radioactive elements. The designated capacity has been set at a level high enough to serve waste disposal needs at their current level for the next 50 years.

Can you confirm that, in the event a canister cracks, the geological makeup of the site will eliminate the risk of radioactivity rising to the surface?

There is really no danger of a canister cracking but it will progressively disintegrate and we have developed modeling technology to calculate the behavior of the rock and the canister over a million years. The vitrification process as well as the stainless steel cask will ensure that the contents are safely sealed off for at least several tens of thousands of years at which point the canister will begin to deteriorate and at this point the earth surrounding the chamber will begin to take over. We have already tested the hypothesis at the laboratory in Bure. We make use of radioactive tracers of either iodine or tritium to observe the rate at which they propagate through the rock, using both convection (radioisotopes carried by water) and diffusion (radioisotopes that penetrate the rock). The results confirm that the rock keeps the radioactivity isolated long enough to dissipate safely. From this we can demonstrate that over the course of a million years, the impact of radioactivity on the surface will stay below levels that already occur naturally and we can back it up with concrete proof.

How can you reconcile the timescales envisioned through the policy of underground storage with the fleeting nature of political and social directives?

The issue of radioactive waste appeared before the French National Assembly in 1991 and again in 2006. In 1991, Andra was transformed into a wholly public institution with no ties to production interests. In the same year a date was set for the next review, to take place in 15 years, and three primary directives were fixed: Andra was to take charge of the dossier for construction of a geological repository and the French Atomic Energy Commission (CEA) would be charged with surface policy as well as the process of partitioning/transmutation of long-life radioactive elements (actinides) into something safer. The CEA concluded that it was impossible to guarantee surface repository safety beyond a few hundred years. Canisters would need to be reconditioned and structures would need to be maintained due to deterioration of the former and crumbling concrete in the latter. Partitioning/transmutation was identified as a promising way to reduce the amount of radioactive material but would never replace long-term storage as a solution.

The government brought the issue of nuclear waste up for public debate in 2005-2006, the first time this had happened on an issue of such critical national importance. The result was a government decision to make geological storage the pillar of future policy, and the solution for handling waste from all current and planned reactors, by 2025. One of the main conditions that will have to be met is the cooling of canisters to below 90 °C before they are lowered underground, no mean feat considering this could take several decades. Testing at the laboratory in Bure has shown that anything above this temperature could create unpredictable effects and would not be safe. High level waste will have to be stored in micro-tunnels no more than one meter in diameter while canisters containing intermediate level waste, already cold, could be stored in larger cavities of up to eight meters in diameter. Lawmakers in the National Assembly also stipulated that the storage be reversible in the event that future generations have the desire to change the policy at a later date.

How do you define “reversible”?

Reversibility is both a technical as well as political notion. The idea has gained traction with the Social and Human Sciences (SHS) community because, quite aside from the fact that reversibility is a noble goal in itself, the notion also implies that any truly innovative industrial policy involves a degree of risk and the possibility for error. Additionally, any successful project requires full community backing and, of course, there is the economic dimension. The two regions chosen to host the laboratory benefit from €30 million annually from a diverse group including producers, the French power utility EDF, the nuclear builder Areva, and the CEA (French Center for atomic Energy). The “deal” is between the nuclear sector and the locale that agrees to accept the waste generated by activity which benefits the whole country. The objective is to provide support for economic development in these areas and to create employment.

It would seem that, in practice, reversibility has yet to prove its worth.

No, we anticipate that a law will be signed, probably in 2016, to establish the modalities of reversibility. I’ve made the debate international in my capacities as Chairperson of the Radioactive Waste Management Committee of the OECD. Promotion of one level of reversibility, the idea that canisters once sealed can still be retrieved, is creating the political will to expand the reach of reversibility to other levels. The difficulty lies in reconciling the desire to leave open the option for recovery with the need to keep the site hermetically sealed so that the rock can fulfill its role as an impermeable sheath. All the chambers and shafts will be sealed with stoppers, and they must be full proof, otherwise our objective of preventing the escape of radioactive elements through these paths will come to naught. The cavities containing intermediate level waste could be left open for up to 100 years through a ventilation system and could be closed at any time. For the cavities containing high-level waste, however, this is not really feasible. The canisters need to fuse with the host geological resource, in order to prevent degradation of the rock through contact with oxygen in order to maintain long term safety, making a ventilation system impossible.

Will safety be compromised by reversibility?

Not in the least. What is essential is that we do not to become a prisoner to a single policy and this depends directly on the choices we make: Is safety active or passive ? To what degree? If storage chambers are left open the human element becomes essential to verify ventilation systems, maintain surveillance, and monitor the condition of the rock to ensure there is no degradation. In the opposite scenario, if the chambers are hermetically sealed, we could almost forget about them completely which is the last thing we want to happen. The degree of reversibility is the capital question and different options are available: the sealing in of the HA containing cavity; closing off a whole group of cavities; access chambers; the shafts, etc. There are many different degrees of retrievability.

Who will be responsible for making decisions to shift from one degree to another at the facility?

Parliament will make a decision in 2016 on where the responsibility lies for choosing to close the first cavity, followed by the first chamber, and then the shafts. Will it be Andra? The ASN (french Autorité de Sûreté Nucléaire)? The government ? Parliament ? What communication protocols will have to followed ? The 2006 law has already laid down the goal of reversibility for a period of at least 100 years. That being said, even at the end of this period, as long as we have adequate records, we can always retrieve the canisters if the need should arise.

Leaving open the option to retrieve canisters comes with a price tag. How high is it?

There will always be options and advances in robotics will go some way toward meeting the challenge. Costs will rise if there is a desire to return to a previous level of security however and, of course, the retrieval scenario assumes the discovery of a more effective way to handle nuclear waste. The more secure the storage, the more expensive the corresponding cost of retrieval. The choice to excavate or not will ultimately be based on the prevailing political wisdom. Future generations will have the ability to remake the measures we have already put into place if they find it justified from a financial and technical perspective.

Is there any international consensus on how to handle nuclear waste?

Across the entire international community, the urgency of the problem has been widely acknowledged and where differences exist, they are based largely on timetables and methods. Europe is the recognizable leader. Making up the trio at the head of the pack are Sweden and Finland (granite), and France (argillaceous rock). The Americans bury their military waste in New Mexico but civil sector policy has reached an impasse. Previous to the election of President Obama the United States led the world with its Yucca Mountain, Nevada facility. While on the campaign trail the President promised the state’s residents that if he was elected operations would be halted. He kept his word.

How is it possible to convince the residents of the site chosen as a repository that it will be safe for a million years? It seems somewhat farfetched.

Building public confidence rests on a convincing demonstration of the scientific and technological evidence underpinning decision making. In Sweden this was straightforward as the sites chosen were already intimately linked to the nuclear economy. In France the process could be somewhat trickier as the designated site is deeply rural which is why so much rests on inspiring confidence in our technology. Our policy is total transparency, our facilities are open to the public as well as anti-nuclear NGOs, and we are painstaking in our explication of technical constraints as well as the political process. The Chairman of Andra, François-Michel Gonnot, is an elected representative in the National Assembly. To strengthen our initiative we have also placed special emphasis on how we will monitor the repository and we are developing, along with our partners, an innovative system of sensors. These sensors will have to operate 500 meters underground, need a reliable source of power to remain failsafe, and must not deteriorate. Moreover, they must resist radioactivity. Right now the best scientific minds in France are working on a solution. For the surface we have created a permanent observatory capable of monitoring the flora and fauna, earth, water, and air over a radius of 500 square kilometers for the next 300 years.

How is it possible to keep record over a period of 10,000 centuries? What about the danger posed by random exploration such as prospecting for shale gas (found in similar rock formations 1500 meters underground)?

For surface repositories, the requirement is 300 years. We have settled on a record keeping system that makes use of permanent paper made from 100% pure materials. The paper contains no mechanical wood pulp, recycled paper, composite materials or pulp mixtures. We are betting on the fact that our institutions will still exist in 300 years. We will store records in town halls, churches, and other buildings that represent social and political cohesion.

And beyond 300 years?

Research is only just beginning. We are in the process of testing engraving on sapphire disks as a possible solution. We are working with linguists on the best way to word the documents. We have drawn from the talent available in numerous SHS laboratories for an interdisciplinary approach that includes economics, sociology, history, and geography to draw a path to the future. History has demonstrated that we preserve what is beautiful which is why the supporting structure for the whole project must also be beautiful. A work of art, perhaps.

You are assuming the existence of organized society on what is now French territory in 300 years, in 3000 years, in 300,000 years. That’s a gamble.

Society will certainly have changed. We have opened a discussion with health and safety professionals. Can we predict the evolution of radiation safety standards over a million years? No, the only assumption we can make is that they will remain the same. What we can reasonably predict are the outlines of geological evolution and climate change. Andra has a wealth of geologists. We have for example drawn up a scenario that includes a possible ice age. For scientists, a timeframe of a million years is not mission impossible. We welcome the contributions of various anti-nuclear organizations to keep the discussion relevant. As long as people are talking, the memory will remain.

The cost of storage has provoked heated exchanges between Andra and the producers who must finance the project. How do you negotiate costs?

The modalities for cost were fixed by the 2006 law. Our principal objective right now is to obtain permission to initiate construction in 2017. We will always search to achieve the maximum economic efficiency and the fact that it will be 70 years before a number of initiatives kick in means we have adequate time to find solutions that satisfy both parties. The most expensive element of the plan is digging the actual chambers. The more compact the waste, the less actual digging will have to be accomplished. The state mandated timeline for cost evaluation has been set at 100 years and this is to include all expenses associated with the dismantling of surface installations as well as any taxes or other associated charges. The long-term financial planning at EDF, Areva, and the CEA must include these expenses as well as the resources necessary to ensure the required manpower. With so much on the line the producers have been somewhat heavy handed in their demands to have more control over the direction of the project but the fight we have on our hands is a noble one whose outcome will ultimately be decided by the state.

(*) Andra has 500 employees and an annual budget of €170 million of which €100 million is devoted to R&D for deep geological storage.

——–
Note from the editors : AREVA, quoted in this article, is a patron of ParisTech Review

More on paristech review

By the author

  • Danger: radioactive waste – a message in a bottle to last… a million yearson June 23rd, 2011

www.paristechreview.com

This content is licensed under a Creative Commons Attribution 3.0 License
You are free to share, copy, distribute and transmit this content

Logo creative commons

5 quai Voltaire 75007 Paris, France - Email : contact@paristechreview.com / Landline : +33 1 44 50 32 89