Dangerous jokulhlaups

For geologists and earth observers the volcanic eruption in Iceland is a thrilling happening. And so it is for dr. Andy Hooper and professor Ramon Hanssen of the Aerospace Engineering faculty’s remote sensing department. “It’s fascinating. What we’re witnessing here is the separation of America and Europe”,  says Hansen, whose scientific fascination is of course tempered by the genuine fear and concern among the people of Iceland.
Fascinating is not the word that first comes to the minds of the Icelanders. That word would be ‘jokulhlaup’, which is a flood caused by sub-glacial volcanic
eruptions. Owing to the magma, the water under the ice sheet melts and this can lead to huge amounts of water suddenly being released. In 1996 a similar eruption lead to such a flood, which washed away large parts of the road that encircles the island. For some people, what used to be a short ride from point A to B became a two-day journey, as they had to drive around the island in the opposite direction.

Hooper is keeping a sharp eye on the developments in Iceland. Since 2006 he has studied the deformations of this area – the Eyjafjallajökull region – that is now worrying the Icelanders. Up to 2008 he worked at the University of Iceland. Now he works on that same topic in prof. Hansen’s remote sensing group at TU Delft.

Hooper’s computer screen shows an image obtained by radar from satellites, in which blue, yellow, red and green dots indicate how strongly the area around the recently erupted Eyjafjallajökull volcano was uplifted over the past few months. In January and February the area rose in total by about three to four centimeters.

“You see, we did measure the seismic activity and deformations that lead to the eruption”,  Hooper explains, “but these kinds of activities also occurred a couple of times during the 1990s and did not lead to eruptions. I hesitate to use the word, but we failed to predict the eruption. We still need to better understand the magmatic plumbing in the underground.”
But Hooper and his colleagues might soon get a second chance.
Not far from Eyjafjallajökull is the Katla volcano. And this second volcano is what really worries the Icelanders. “The two volcanoes are geologically linked”,  Hooper says. “The eruption of one of them might trigger the other to erupt as well.” If the Katla erupts, it could have devastating consequences. The magma from Eyjafjallajökull surfaced at a spot that wasn’t covered with ice. The other volcano however is covered with a much bigger ice sheet, increasing the risk of a jokulhlaup flood.

The radar data with which Hooper created the colorful image showing the rise in the surface around Eyjafjallajökull in January and February were far from optimal. During the recent winter months most of the land was covered with layers of snow. Consequently, the radar waves could barely reach the ground, resulting in lots of background noise in the image. This week Hooper will receive the data from both volcanoes obtained by satellite the day before the eruption took place, and next week he will receive the data gathered a few days after the eruption. With these data sets he hopes to get a clearer picture of what is actually going on. There is less snow now, so this fact should benefit his research.

“But even with clear radar pictures, it’s a feat to understand the deformations”, Hooper warns. “In Iceland, many different things are happening. The tectonic plates are moving, there is volcanic activity, and there is postglacial rebound (the rise of the land in response to the retreat of ice caps). We have a couple of GPS stations just south of Katla that are moving southwards. And we cannot explain why.”
 

Naam: Karoly Nagy
Nationaliteit: Hongaar
Promotor: Professor Tim van der Hagen (Reactor Instituut Delft, Technische Natuurwetenschappen)
Onderwerp: Gesmolten-zoutreactoren
Tussenstand: Halverwege

“Het zou veel beter zijn als we in plaats van uranium, thorium als grondstof in kweekreactoren konden gebruiken. Er is op aarde namelijk vier keer zoveel thorium als uranium aanwezig. Ik probeer een zogenaamde gesmolten-zoutreactor te ontwerpen die thorium als grondstof kan gebruiken. Daarbij werk ik uitsluitend met computermodellen.
Waarom ik niet ook met een echte reactor experimenteer? Haha. Er bestaat nog helemaal geen gesmolten-zoutreactor. Waarschijnlijk komt de eerste pas in 2030 op de markt.
In de jaren zestig bouwden de Amerikanen overigens wel al een prototype van een reactor die lijkt op degene waar ik nu aan werk, het zogenaamde ‘Molten Salt Reactor Experiment’. Dit was de eerste reactor met gesmolten zout als koelmiddel, met daarin de splijtstof opgelost. Het was ook de eerste reactor die werkte op uranium-233, een kunstmatig uraniumisotoop die het goed doet als splijtstof voor reactoren. Uiteindelijk is het onderzoeksproject in 1970 afgesloten door hevige competitie uit de hoek van zogenoemde snelle kweekreactoren.
In de jaren vijftig hadden ze ook al het idee voor een gesmolten-zoutreactor opgevat. Ze wilden het aan boord hebben van bommenwerpers. Een vliegtuig met een kweekreactor hoeft bijna nooit bij te tanken, was het idee. Behalve kernenergie produceert een kweekreactor namelijk ook nieuw splijtmateriaal. Daardoor kan hij bijna permanent in de lucht hangen, klaar voor de aanval.
Maar ja, het project was natuurlijk gedoemd te mislukken. Want de reactor is veel te zwaar en je kunt hem niet plotseling veel harder laten draaien om extra gas te geven als je een luchtgevecht moet aangaan. De bommenwerpers zouden schietschijven geweest zijn.
Ik probeer een gesmolten-zoutreactor te ontwerpen die op thorium draait. De uitdaging is om de reactor zo te ontwerpen dat er altijd voldoende neutronen in de zoutvloeistof aanwezig zijn om de kettingreactie in stand te houden. Door bestraling met neutronen wordt thorium verrijkt tot het splijtbare uranium -233. De neutronen die vrijkomen als uranium -233 splijt, moeten voor een deel het resterende thorium omzetten tot nieuw uranium-233 en er voor een deel voor zorgen dat andere uraniumatomen splijten.
De zoutoplossing loopt in kanalen door grafietbuizen. Net als bij de reactor destijds in Amerika, gebruiken we grafiet om de neutronen af te remmen als ze te hard gaan. Als in de gesmolten-zoutreactor een lek ontstaat, dan dreigt er geen gevaar, omdat de brandstof en de koeling een en dezelfde vloeistof vormen. Als de koelvloeistof weglekt, is er dus ook geen brandstof meer en kan de reactor niet oververhit raken.
Als ik klaar ben met dit promotieonderzoek, ga ik waarschijnlijk terug naar Hongarije. Ik vind het hier in Nederland heel prettig, maar het is ook een prettig idee dat mijn contract op een gegeven moment afloopt en ik hier niet tot mijn pensioen zit. In Hongarije kun je spontaan met vrienden naar de kroeg. Hier halen mensen eerst hun agenda tevoorschijn om te kijken wanneer ze tijd hebben.”

For geologists and earth observers the volcanic eruption in Iceland is a thrilling happening. And so it is for dr. Andy Hooper and professor Ramon Hanssen of the Aerospace Engineering faculty’s remote sensing department. “It’s fascinating. What we’re witnessing here is the separation of America and Europe”,  says Hanssen, whose scientific fascination is of course tempered by the genuine fear and concern among the people of Iceland.
Fascinating is not the word that first comes to the minds of the Icelanders. That word would be ‘jokulhlaup’, which is a flood caused by sub-glacial volcanic
eruptions. Owing to the magma, the water under the ice sheet melts and this can lead to huge amounts of water suddenly being released. In 1996 a similar eruption lead to such a flood, which washed away large parts of the road that encircles the island. For some people, what used to be a short ride from point A to B became a two-day journey, as they had to drive around the island in the opposite direction.

Hooper is keeping a sharp eye on the developments in Iceland. Since 2006 he has studied the deformations of this area – the Eyjafjallajökull region – that is now worrying the Icelanders. Up to 2008 he worked at the University of Iceland. Now he works on that same topic in prof. Hanssen’s remote sensing group at TU Delft.

Hooper’s computer screen shows an image obtained by radar from satellites, in which blue, yellow, red and green dots indicate how strongly the area around the recently erupted Eyjafjallajökull volcano was uplifted over the past few months. In January and February the area rose in total by about three to four centimeters.

“You see, we did measure the seismic activity and deformations that lead to the eruption”,  Hooper explains, “but these kinds of activities also occurred a couple of times during the 1990s and did not lead to eruptions. I hesitate to use the word, but we failed to predict the eruption. We still need to better understand the magmatic plumbing in the underground.”
But Hooper and his colleagues might soon get a second chance.
Not far from Eyjafjallajökull is the Katla volcano. And this second volcano is what really worries the Icelanders. “The two volcanoes are geologically linked”,  Hooper says. “The eruption of one of them might trigger the other to erupt as well.” If the Katla erupts, it could have devastating consequences. The magma from Eyjafjallajökull surfaced at a spot that wasn’t covered with ice. The other volcano however is covered with a much bigger ice sheet, increasing the risk of a jokulhlaup flood.

The radar data with which Hooper created the colorful image showing the rise in the surface around Eyjafjallajökull in January and February were far from optimal. During the recent winter months most of the land was covered with layers of snow. Consequently, the radar waves could barely reach the ground, resulting in lots of background noise in the image. This week Hooper will receive the data from both volcanoes obtained by satellite the day before the eruption took place, and next week he will receive the data gathered a few days after the eruption. With these data sets he hopes to get a clearer picture of what is actually going on. There is less snow now, so this fact should benefit his research.

“But even with clear radar pictures, it’s a feat to understand the deformations”, Hooper warns. “In Iceland, many different things are happening. The tectonic plates are moving, there is volcanic activity, and there is postglacial rebound (the rise of the land in response to the retreat of ice caps). We have a couple of GPS stations just south of Katla that are moving southwards. And we cannot explain why.”