Concentration of radioactive materials such as sewage sludge

Radioactive materials diffused following the accident at the Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Plant accident reach the sky of Yokohama City due to the airflow, flow into the sewer pipe due to rain, etc., and reach 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 pipe, radioactive material was also included in sewage sludge incineration ash.

September 9, 2011 Announced landfill site in landfill, Minamihonmoku

• Confirmation of safety of landfill waste incineration ash　→　Announcement of landfills after September 15

September 14, 2011 Frozen Landfill in landfill, Minamihonmoku

• Due to insufficient explanation to the parties concerned, the landfill was "freeze" until a sufficient explanation was given to all concerned parties.

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

In September 2013, we proposed a future response plan for sewage sludge incineration ash and explained to citizens and related parties.

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

July 2014 Started recycling as construction materials in addition to the improved Hijiwara fee, we started recycling resources as construction materials.
December 2014 Decided to reclaim ash from April 2014 onward to the land area of landfill, Minamihonmoku.

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

February to March 2015 A trial landfill was conducted at landfill Minamihonmoku waste, a mixture of ash from Resources and Waste Recycling Bureau and sewage sludge incineration ash.
July 2015 Started landfills in the same way as trial landfills.
September 2017 Landfill at Minamihonmoku Waste landfill was completed.
Present　　　　　Continue disposal by recycling resources as improved soil and construction materials.

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

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

※Measurement of iodine-131 was started as an index to confirm the effects of the nuclear accident.However, based on the fact that the half-life of iodine 131 has already passed for more than three years, September 1, 2014 From the day, two items of cesium-134 and cesium-137 are excluded from the measurement items.

• Past radioactive material concentration data (until the end of August 2014)　PDF（PDF：82KB）　excel (Excel: 145KB)
• Past radioactive material concentration data (September 2014 to mid-June 2002)　PDF（PDF：712KB）　excel (Excel: 57KB)
• Past radioactive material concentration data (from late June, 2020)　PDF（PDF：79KB）　excel (Excel: 132KB)

Sludge incineration ash is stored on the premises of northern and Nambu Sludge Treatment Plant.

1. The storage status of sewage sludge incineration ash is as follows:

Storage status of sewage sludge incineration ash (PDF: 399KB)

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

On the other hand, the concentration of radioactive materials in sewage sludge incineration ash has been reduced to about one-100th or less compared to the beginning of storage.

2. The spatial radiation dose rates at the site boundary are as follows.

※Measurement at a height of 1 meter above the ground

• Past spatial radiation dose rate data　PDF（PDF：43KB）　excel (Excel: 19KB)

1. Inflow sewage and discharge water

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

2. Concentration of radioactive substances in exhaust gas

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

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

• Safety evaluation report (PDF: 473KB) on disposal of sludge incineration ash containing radioactive materials (PDF: 473KB)
• Explanatory materials on the handling of sludge incineration ash containing radioactive materials　(Color version) (PDF: 6,692KB)　(Black and white version) （PDF：9,013KB）

※In “Fig. 3-4 Radiation Exposure around Body” on page 20 of this explanatory material has been updated. For details, please refer to the following URL.
http://jccu.coop/food-safety/qa/pdf/qa03_03_02.pdf (external site)

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