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Decommissioning Plan of Fukushima Daiichi Nuclear Power > Plan & Action > Major Initiatives for Water Management > Seawater Piping Trench

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Seawater Piping Trench

Since the accident, highly contaminated water has been accumulating inside the seawater piping trench; a underground tunnel originally designed to store pipes and cables, connected to the seaside of Unit 2 to Unit 4 turbine buildings. TEPCO has been trying to reduce the risks of soil/ocean contamination by removing this accumulated water and filling the inside of trench. Considering the conditions or the quality/quantity of water contained in the tunnels or vertical shafts of the trench, the contaminated water is carefully transferred to the turbine buildings. The inside of trench is also filled with materials selected considering the individual structure or length, combining several materials where needed.

Please refer to the following materials for more details since the structure of seawater piping trench differs among each unit.

  • Groundwater bypass
  • Landside Impermeable Wall
  • Subdrain
  • Groundwater drain
  • Sea-side impermeable wall

Progress of the Seawater Piping Trench Measures
(As of the end of December 2015)

Progress of Contaminated Water Removal: 100%

  Unit 2 Unit 3 Unit 4
Situation ・Tunnel completed to be filled on Dec. 18, 2014.
・Vertical shafts completed to be filled on Jul. 10, 2015 (until O.P. +4.0m*).
・Transfer of retained water completed on Jun. 30, 2015.
・Tunnel completed to be filled on Apr. 8, 2015.
・Vertical shafts completed to be filled on Aug. 27, 2015.
・Transfer of retained water competed on Jul. 30, 2015.
・Tunnel completed to be filled on Mar. 21, 2015.
・Vertical shafts (I to III) completed to be filled on Apr. 28, 2015.
・Transfer of retained water completed on Dec. 11, 2015.
・Tunnel above water discharge channels completed to be filled on Dec. 21, 2015.
Amount of retained water remained 0 m³ 0 m³ 0 m³
Amount being filled approx. 4,660 m³ approx. 5,980 m³ approx. 780 m³

*The filling was completed until O.P.+4.0m on July 10 and the entire filling was completed on July 28 except for the observation hole for Vertical Shaft C and the frozen drilling duct on the building side.

Photos

Fukushima Daiichi Nuclear Power Plant Filling Unit 2 Seawater pipe trench

July 30, 2015
Fukushima Daiichi Nuclear Power Plant Filling Unit 2 Seawater pipe trench

Unit 3 Trench-Filling operation

February 9, 2015
Unit 3 Trench-Filling operation

Operational Start to Fill in Unit 2 Seawater Piping Trench at Fukushima Daiichi Nuclear Power Station (Japanese only)

November 25, 2014
Operational Start to Fill in Unit 2 Seawater Piping Trench(Japanese only)

Archive

Gap-filling Starts: Progress of Water cutoff operation on the connection between the seawater piping trench and building of Unit 2 and 3 of Fukushima Daiichi Nuclear Power Station

October 16, 2014
Gap-filling Starts: Progress of Water cutoff operation on the connection between the seawater piping trench and Unit 2 and 3 buildings

海水配管トレンチ閉塞充填材の確認試験について

December 15, 2014
Confirmation Test of the Material to Fill in Seawater Piping Trench (Japanese only)

2、3号機海水配管トレンチ建屋接続部止水工事の進捗について

August 19, 2014
Construction Progress to Stop Water Movement between Unit 2 and 3 Seawater Piping Trenches and the Turbine Buildings (Japanese only)

2号機トレンチ凍結止水対策における氷の試験投入について

July 24, 2014
Operational Test to Insert Ice into Unit 2 Trench for Water Cutoff (Japanese only)

福島第一原子力発電所2,3号機海水配管トレンチ建屋接続部止水工事の進捗状況について

July 7, 2014
Construction Progress to Stop Water Movement between Unit 2 and 3 Seawater Piping Trenches and the Turbine Buildings (Japanese only)

福島第一原子力発電所 2号機海水配管トレンチ凍結止水工事凍結管挿入作業の状況

March 28, 2014
Construction to Inject Coolant Pipes to Freeze and Stop Water inside Unit 2 Seawater Piping Treanch (Japanese only)

福島第一原子力発電所2号機海水配管トレンチ内部カメラ観測状況

January 20, 2014
Camera Observation for the Inside of Unit 2 Seawater Piping Trench (Japanese only)

トレンチモックアップによる凍結止水試験

November 28, 2013
Mockup Test to Freeze and Cut off Water inside Trench (Japanese only)

Investigation of Unit 3, 4 Seaside Trench at Fukushima Daiichi Nuclear Power Station

August 13,2013
Investigation of Unit 3, 4 Seaside Trench

Videos

Approaches to Contaminated Water - Removing Contamination Sources - “Removal of Highly Contaminated Water Retained Inside the Trench”

2015.01.28
Approaches to Contaminated Water - Removing Contamination Sources - “Removal of Highly Contaminated Water Retained Inside the Trench”

Measures to stop water - Differences between freezing the trench water and the Ice Wall

2014.08.05
Measures to stop water - Differences between freezing the trench water and the "Ice Wall"

Measures for Contaminated Water in the Seaside Trenches of Turbine Buildings at Fukushima Daiichi

February 18, 2014
Measures for Contaminated Water in the Seaside Trenches of Turbine Buildings