Summary of the review result of the project for the managed recycling at the Prime Minister’s Office

Date: July 29, 2025

1. Background

• On July 16, 2025, the applicant requested a review of this project.
• This project involves the managed recycling of removed soil（approximately 2 m³）in the front courtyard of the Prime Minister’s Office.

2. Summary of the review result

• The contents of the plan for this project is recognized to be in compliance with the ministerial ordinance to provide for criteria and appropriate in accordance with the precautions set out in the guidelines.
• The construction work at the site was also deemed to have been carried out appropriately in accordance with the above plan.

Main review matters	Review result
Radioactivity concentrations in the removed soil used	Removed soil with a radioactivity concentration of 8,000 Bq/kg or less is used to ensure that the additional dose for the workers and the general public is kept at 1 mSv/year or less.
Measures to prevent the scattering and runoff of removed soil	In addition to placing soil at least 20 cm thick to cover the removed soil, other measures are taken to prevent scattering and runoff during construction, such as using protective sheets as needed.
Radiation dose monitoring	The monitoring methods and frequency, etc., before construction（0.07-0.10 μSv/h）, during construction（maximum 0.40 μSv/h）, after construction（0.12 μSv/h）and during maintenance comply with the ministerial ordinance to provide for criteria and guidelines.
Responses in the event of abnormal occurrence, emergency repairs, etc.	In the event that damage is caused to the construction site where removed soil is used due to a natural disaster or other reasons, response measures（emergency repairs and permanent repairs）are in accordance with the guidelines.

Location map and cross section view of the construction site

Post-construction monitoring