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Nuclear waste tomb soon to reach final depth

Capsules of waste to wait at least ten years before being placed inside


Nuclear waste tomb soon to reach final depth
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At first it looks as if it were simply a more heavy-duty underground parking garage than usual. On the back seat of the four-wheel drive van, one can feel the steep descent and the endless rock. The lights illuminate the walls as the vehicle goes down.
      Hanging from the waist is a flashlight and an escape device which allows a few minutes of breathing. The trip to the depths takes several minutes. A safety container can be seen. It is there if anything goes wrong.
      A long straight road, then a turn to the right, straight again, then another turn. The Eurajoki Onkalo tunnel is a long, long spiral.
     
Then the lights on the walls of the tunnel run out, and ahead is just a dark rock face. Opening the door, one can notice the smell of explosive used for blasting the rock. On the roof of the tunnel a loud ventilation tube can be heard flapping. It makes the air surprisingly fresh, even though there has been a recent explosion. Around us is nothing but rock - 1.8 billion years old.
      If the Eiffel Tower were turned upside down, it’s tip would not reach this far. We are at a depth of 405 metres. It is four kilometres' drive back to the mouth of the tunnel.
      The tunnel is being excavated in three shifts, progressing five metres a day, with the help of a daily load of 650 kg. of explosive and an excavation drill.
     
This might be a good time to reflect on where we have come from and where we are going.
      Excavation of the Onkalo was launched by Posiva in 2004, and it is only now that the access tunnel is reaching the depths where comb-like final resting places for the capsuled nuclear waste will be dug.
      The burying of the waste there is to begin in the 2020s.
     
The process is set to continue for about 100 years. There should be enough space for a total of 2,800 capsules - the equivalent of the nuclear waste of seven reactors. This will require about 20 kilometres of new tunnel.
      And then - at a time when none of us will be around to see it - the installation is to be closed in 2120.
      The tunnels are to be filled with large boulders, compressed clay, crushed rock, and sealed off with a plug of steel-reinforced concrete.
     
According to Posiva, in 500 years’ time it will be possible to stand next to the capsule and get far less radiation than the dosage that comes from an ordinary CAT scan.
      The final absorption of the waste into nature is set to happen much later, in about 250,000 years.
      In that time, it is likely that at least one ice age will have taken place. The capsules are built to last at least 100,000 years.
     
But let’s return to the present. In the early part of the summer, three six-metre holes will be drilled in the Onkalo, which for now is simply a research space for the final disposal of nuclear waste.
      They will be used to measure the tensions in the rock, which grow the deeper the excavation goes. Posiva geologist Kimmo Kemppainen says that the holes will be used to measure how the rock behaves as the state of tension in the rock grows.
      Posiva will apply for a licence for the construction of an underground nuclear waste capsuling and disposal facility two years from now, and for a licence to use it in 2018.
      The existing nuclear waste will be allowed to sit in interim storage in Loviisa and Olkiluoto for another ten years at least.


Previously in HS International Edition:
  Government endorses two new nuclear reactors (22.4.2010)
  Nuclear plant application to come before Parliament this spring (1.3.2010)

Links:
  Posiva website

Helsingin Sanomat


  10.5.2010 - TODAY
 Nuclear waste tomb soon to reach final depth

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