Radioactive material concentration in sewage sludge

The radioactive material diffused following the accident at the Tokyo Electric Power Company, Incorporated Fukushima Daiichi Nuclear Power Station reaches Yokohama City due to atmospheric flow, flows into sewer pipes due to rain, etc., and reaches the Water Reclamation Center. Sewage is treated at the Water Reclamation Center and the Sludge Recycling Center, and eventually becomes sewage sludge incineration ash. As mentioned above, radioactive materials flowed into the sewer pipes, so sewage sludge incineration ash also contained radioactive materials.

September 9, 2011 Announced landfill at Minamihonmoku landfill

• Safety confirmation of landfill of sewage sludge incineration ash　→　Landfill announced on or after September 15

September 14, 2011 Freeze landfill at Minamihonmoku landfill

• Since the explanation was insufficient to the people concerned, the landfill was "freeze" until sufficient explanation was given.

• We explained to citizens and related parties using materials that explained the contents of the "Safety Evaluation Study Report on Landfill of Sewage Sludge Incinerated Ash at Management Type Disposal Site" in an easy-to-understand manner. .

We proposed future correspondence plan of sewage sludge incineration ash in September, 2013 and explained to citizen, related people. .

• About past process of sewage sludge incineration ash and future correspondence (plan) (PDF: 1,327KB)

July 2014 In addition to the improvement to date as a Hijiwara fee, recycling as a construction material began.
Dec. 2014 Dec. 2014 The Company decided to reclaim incinerated ash from April 2014 onwards in the land area of Minamihonmoku landfill.

• About landfill disposal of sewage incineration ash (PDF: 353KB)

From February to March 2015, a mixed ash mixture of Resources and Waste Recycling Bureau's main ash and sewage sludge incineration ash was carried out at the Minamihonmoku Waste landfill.
July 2015 Landfill commenced in the same way as reclamation.
September 2017 Completed landfill at the Minamihonmoku Waste landfill.
Current　　　　　Continued disposal through improved soil and resources as construction materials.

Radioactive material concentrations in dewatered sludge, sludge incineration ash, and improved soil are as follows.

※Non-detection indicates that the value is below the lower limit of quantification.

※We started measuring iodine-131 as an index to confirm the effects of the nuclear accident, but based on the fact that the half-life of iodine-131 has already passed three years or more, September 2014 From 1st, there are two items, cesium-134 and cesium-137, excluding the measurement items.

• Past Radioactive Material Concentration Data (~ End of August 2014)　PDF（PDF：82KB）　excel (Excel: 145KB)
• Past Radioactive Material Concentration Data (September 2014 to mid-June 2014)　PDF（PDF：712KB）　excel (Excel: 57KB)
• Past Radioactive Material Concentration Data (from late June 2020)　PDF（PDF：526KB）　excel (Excel: 133KB)

Sludge incinerated ash is stored in the northern and Nambu Sludge Treatment Plant sites.

1. The current and past storage status of sewage sludge incineration ash is as follows.

Storage status of sewage sludge incineration ash (PDF: 259KB)

The storage status of sewage sludge incineration ash was nearly 38,000 tons in the south and Hokubu Sludge Treatment Plant at its peak, but the disposal has gradually decreased. However, the situation has to be placed in the hall, which affects the operation of the facility.

On the other hand, the concentration of radioactive materials incinerated ash in sewage sludge has been reduced to less than one-tenth of the level compared to the beginning of storage.

2. The spatial radiation dose rate at the site boundary is as follows.

※Measurement at a point 1 meter high from the ground

• Past space radiation dose rate data　PDF（PDF：179KB）　excel (Excel: 19KB)

1. Inflow sewage and discharge water

• Radioactive material concentration data of inflow sewage and discharge water (PDF: 34KB)

2. Radioactive substance concentration in exhaust gas

• Radioactive material concentration data in exhaust gas (PDF: 38KB)

3. Radioactive material concentration data of Minamihonmoku landfill mixed ash PDF (PDF: 63KB) excel (Excel: 50KB)　
   (The landfill disposal ended in September 2017)

• Safety evaluation study book (PDF: 473KB) about disposal of sludge incineration ash including radioactive material
• Explanatory materials on the handling of sludge incineration ash, etc. containing radioactive materials　(Color version) (PDF: 6,692KB)　(black and white version) （PDF：9,013KB）

※"Figure 3-4 Radiation Exposure around People" on page 20 of this explanatory document has been updated with the data from the source. For more information, please refer to the following URL.
http://jccu.coop/food-safety/qa/pdf/qa03_03_02.pdf (external site)

• Answer to frequently asked questions (updated in March 2016) (PDF: 326KB)