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Small Progress of Landside Impermeable Wall freezing

The purpose of the Landside Impermeable Wall construction lies not in freezing soil to form an underground wall but in keeping groundwater from flowing into the reactor/turbine buildings and preventing new contaminated water being generated.

By closing less than 95 percent of the mountain side of the Landside Impermeable Wall in Phase 2 of the first stage, it is expected that the amount of groundwater flowing into the areas around the reactor/turbine buildings will be reduced. This will help keep groundwater from being contaminated during the first stage.

Throughout the first stage, how freezing of the Landside Impermeable Wall has progressed will be checked by monitoring the difference in groundwater levels inside and outside of the wall and the amount of groundwater pumped up by the subdrain and groundwater drain systems and the wellpoint system.

Groundwater levels and hydraulic heads (in the medium-grained sandstone layer 1 on the seaside)

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Groundwater levels and hydraulic heads (in the medium-grained sandstone layer 2 on the landside)

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Groundwater levels and hydraulic heads (in the alternating strata layer and the fine-and rough-grained sandstone layer 1 on the seaside

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Groundwater levels and hydraulic heads (in the alternating strata layer and the fine-and rough-grained sandstone layer 2 on the landside)

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Location map of groundwater level observation wells (as of June 2016)

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Progress of supplementary work

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Progress of supplementary work (1BLK)

Over-time changes of the soil temperatures in the north side area of Unit 1 where the supplementary work is in progress The soil temperatures temporarily increased because of water which was used to bore through the ground during the supplementary work, but it has gradually decreased. Since the soil temperature around the thermometer pipe of 120-1S has not dropped sufficiently, however, the second round of injection is currently under way. TEPCO Holdings will continue to monitor the temperature changes.

Progress of supplementary work (9BLK)

As seen in the soil temperatures in the 1BLK area, that in the 9BLK area temporarily increased because of water which was used to bore through the ground during the supplementary work. The soil temperature around the thermometerpipe of 30-9S0 has dropped to around 0 degrees Celsius, and TEPCO Holdings will continuously monitor it. In the area around the thermometer pipe of 70-9S, the second round of injection is progressing.

Progress of supplementary work (12BLK)

Over-time changes of the soil temperatures in the east side area of Unit 2 (12BLK) where the supplementary work is in progress The soil temperatures have gradually decreased. Monitoring of the temperatures will continue.

Progress of supplementary work (13BLK)

Over-time changes of the soil temperatures in the east side area of Unit 2 (13BLK) where the supplementary work is in progress Since the soil temperature around the thermometer pipe of 30-13S has slowly decreased, the second round of injection is planned. Although the decrease of the soil temperatures around the thermometer pipes of 50-13S and 90-13S have been gradual but steady, monitoring of the temperatures is still under way.

Purpose of supplementary work

To help further freeze soil in places where the soil temperatures have slowly dropped due to fast flowing groundwater, the speed at which the groundwater runs has to be reduced by making the permeability of the soil as low as that of soil in the vicinity of the places.

The purpose of the supplementary work lines not in constructing different walls from the landside impermeable wall but in changing locally highly permeable soil areas into areas with low permeabilities observed in the soil of the surrounding area.

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Source: Tepco

Click to access handouts_160728_02-e.pdf

 

 

August 3, 2016 - Posted by | Fukushima 2016 | ,

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