High Science Inside the Belly of the Alps
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Think of the Swiss Alps and images of majestic glaciers, skilled skiers and pastoral valleys come to mind. But deep within the crystalline rock of the Aar Massif in central Switzerland Toni Baer is a modern day explorer chasing facts for the future. Almost half a kilometre underground in a mountain at an altitude of 1730 metres, he monitors computers, drills bore holes and contacts scientists scattered across the globe.
Mr. Baer is the local manager of the Grimsel Test Site, an underground rock laboratory that is looking at ways to safely dispose of radioactive waste produced by Switzerland's five nuclear power plants. They generate 40% of the country's electricity.
Part of the investigations at the Grimsel rock lab is finding ways to package these highly radioactive wastes deep underground, so that it is isolated and contained for generations to come.
Grimsel is run by NAGRA, a body founded by utilities and the Swiss Government for radioactive waste disposal. Switzerland is one of about ten countries running rock laboratories. They're seeking the best answers they can get about future possibilities. Could radioactive gas escape from the mountain caves or is there any route through which water and food could become contaminated?
Getting to Grimsel is not easy in winter. Mr. Baer must take a cable car up into the Juhlistock Alps. He then enters a tunnelled out cave and drives for about five minutes into the mountain itself before coming to a door. Behind the door the cave transforms. This middle–earth setting changes to become much like any other normal office (although possibly better equipped) with white walls and florescent lighting, toilets, kitchen and coffee machine. Beyond this floodlit reception, in cave laboratories, the experiments take place.
Simulating the Future
Real spent fuel is not used in the experiments at Grimsel. Its properties are simulated. For example, heaters are used to imitate the heat generated by the radioactive wastes, which could warm the rock to around 100 C – a temperature hot enough to boil water. The "mock" waste is put in steel containers designed to last for 10, 000 years, then placed in a deep tunnel making the mountainous rock itself a barrier against the release of radioactive materials. The tunnel is then backfilled with concrete or bentonite, which is a special clay used for sealing repositories.
Part of the investigative work at Grimsel is to analyse how water, as the transport vehicle for waste, moves and interacts with the bentonite, rock and concrete interfaces.
In November 2003, Mr. Baer showed IAEA sponsored scholars from Eastern Europe and Asia how to drill boreholes into the rock and investigate how air, water and gases move through the mountain of rock that surrounds the Grimsel Test tunnel. This is important because the main way radioactive particles could seep out of a repository into the human environment is if they are transported by water. Data from the Grimsel experiments is relayed via computer back to scientists in the Swiss office or to collaborating universities and countries. At present, Japan, Spain, Germany, Taiwan, China, the United States, Czech Republic, France and Sweden are also involved in experiments at Grimsel.
Learning to Find the Right Sites
This year marks Mr. Baer's twentieth year working the earth caverns. When he first started at Grimsel, it was thought that hard crystalline, granite rock (similar to that of the Juhlistock in which the Grimsel test site is excavated) would be the ideal barrier to enclose the waste. In unfractured rock, fluids typically travel only a few inches over hundreds, and even thousands, of years. But investigations showed because granites are hard and brittle, they can "crack" or fracture as a result of geologic movements. Geological repositories therefore need to be built in rock zones that are free of major fractures through which water can travel.
Further in situ research in Switzerland showed that the lowly permeable clay rock in Zurcher Weinland in the country's north might be suitable for a disposal site, says NAGRA Spokesperson, Mr. Heinz Sager. "The clay rock forms a tight sealing barrier that does not fracture and the area is tectonically stable," he said.
Around the world salt domes and volcanic tuff are among other formations being considered for repositories, says Mr. Malcolm Gray, an IAEA nuclear engineer overseeing the Centers of Excellence programme. "In general, it has been shown that by adapting the engineering approach to the different available geological formations, suitable underground waste disposal facilities can be designed," he said.
However, selecting a site does not just depend on geology and an appropriately engineered design. "Selecting a site is as much dependant on social factors as on technological choices," Mr. Gray said.
"Not in My Backyard"
While the experts generally agree that geological disposal will be safe, and countries such as the United States and Finland have decided to move forward with this option, in many countries, the public remains skeptical. A 2001 survey of Europeans about radioactive waste showed that just less than half of the 16,000 people interviewed did not think a safe method existed to dispose of this most hazardous radioactive waste.
As it has for other types of engineering projects, public opposition can and has slowed repository development in many countries. It is the reason why actual spent fuel is not used in the Grimsel experiments. Gaining public trust, acceptance and credibility when it comes to radioactive waste disposal still has a way to go.
"Those working in the nuclear industry must listen to the public's concerns, take them into account in their planning and present their case in a way that satisfies societal needs. Demonstrating that repositories can work – through rock laboratories such as Grimsel and others that are part of the IAEA network – can help to build public understanding that there is a safe solution to radioactive waste disposal," Mr. Gray said.
Scientists, engineers, policy and decision makers are beginning to recognize that transparency, communication and public involvement are critical for public acceptance and the political will needed to tackle radioactive waste disposal.
However, creating the conditions for public acceptance is not an easy task and the route to success is not clear. At an international conference on Issues and Trends in Radioactive Waste Management held by the Agency in December 2002, experts called for greater and better communication with stakeholders to build public acceptance. A December 2003 conference in Sweden at which IAEA Director General Mohamed ElBaradei spoke took a closer look at political and technical issues surrounding geological waste disposal.
In Switzerland, construction of a repository for spent fuel is not foreseen until well into this century. Right now, public attitudes support nuclear power, and Parliament has approved legislation permitting construction of new nuclear plants. Views on repositories there, however, are mixed. Swiss Ambassador Heinrich Reimann informed the IAEA General Conference in September 2003 that a referendum held in 2002 in a Swiss canton opposed exploratory tunnelling work as a first step toward a repository planned at Wellenberg for low and intermediate level radioactive wastes. The Government now is analysing documents on geological disposal of high–level waste and the construction, long–term safety and use of oplainus clay as a rock host for a repository.
Going Back to Nature
In an effort to sway a skeptical but curious public, Grimsel and other underground research labs have opened their doors to visitors. They offer underground tours of the rock labs to demonstrate how a repository can work.
Part of the problem says the head of NAGRA's Corporate Communications, Mr. Heinz Sager, is that nuclear waste is seen as somebody else's responsibility. "It's not like throwing out a drink container, where you see and touch the rubbish you throw away. Nuclear waste is invisible to people. They don't associate watching the TV or lighting a room with creating nuclear waste," he said.
Toni Baer does not need convincing. He has monitored underground experiments at Grimsel for two decades. He points to nature, as well as scientific testing, as a sign that geological repositories can work.
"Look at the crystals," Mr. Baer says. Near the Grimsel Test Site beautifully formed crystals stand perfectly preserved in a cave, kept intact for 15 million years and subjected to temperatures of 400 degrees. Nature's powers to preserve are also seen by the 30,000 year–old prehistoric cave paintings in Southern France. Or in Gabon, West Africa, when natural processes concentrated enough radioactive particles to cause an underground, non–explosive nuclear chain reaction. In two billion years the radioactive waste that was created has moved less than three metres.
"Look at Nature," Mr. Baer says. "Then you can understand it's possible."
Even as natural analogues show the possibilities, they raise technical and scientific considerations important to sound decisions about future waste repositories. The work being done in Switzerland and other countries is playing a key role toward the goal of safely isolating the world's radioactive waste. –– Kirstie Hansen, IAEA Division of Public Information