Japan Considers Fukushima Cleanup Soil for Yokohama's 2027 Green Expo

Fukushima's Cleanup Legacy Could Become an Expo Garden

Japan is considering using soil removed during cleanup after the Fukushima No. 1 nuclear disaster in flower beds and landscaping at the International Horticultural Expo 2027 in Yokohama. The proposal would bring a small part of a stockpile of approximately 14 million cubic meters to an international event expected to attract more than 10 million visitors.

As of April 24, 2026, the government is examining the plan for the exhibition, which is scheduled to begin in March 2027. Officials call the material "reconstruction and revitalisation soil" and intend to select soil with low radioactivity that meets government safety criteria.

The proposal connects two very different settings: interim storage facilities around the damaged nuclear plant in Fukushima Prefecture and an exhibition devoted to gardens, sustainability and urban greening. Participants from 61 countries and international organizations are expected at the Yokohama event, giving Japan a large international audience for its efforts to demonstrate the soil's reuse.

Government and ruling party sources describe two aims. The soil would have a practical use in the expo's landscaping, while its presence would help build public understanding and acceptance of similar applications elsewhere in Japan. The government hopes that visitors seeing flowers growing in the material will become more comfortable with its use in public projects.

Why Japan Has 14 Million Cubic Meters to Manage

The soil comes from decontamination work carried out after the disaster of March 11, 2011. A magnitude 9.0 earthquake and the tsunami that followed triggered reactor meltdowns at the Fukushima No. 1 plant, operated by Tokyo Electric Power Company Holdings. Radioactive material spread across the surrounding countryside.

Cleanup crews removed topsoil, vegetation and other material from large areas to reduce radiation levels and help residents return to communities that had been evacuated. The work moved contaminated material away from places where people lived, leaving the government with a vast quantity to store, process and eventually relocate.

Approximately 14 million cubic meters of soil is now held at interim storage facilities around the plant in Okuma and Futaba, two towns in Fukushima Prefecture. Bagged material and large storage sites remain among the most visible consequences of the accident, more than fourteen years later. Much of the material has been stored for over a decade.

Japanese law requires final disposal outside Fukushima Prefecture by March 2045. That deadline makes the issue larger than finding a use for a few flower beds. Japan must develop a workable approach for a huge stockpile, including material with higher radioactivity that needs more restricted handling.

What the Radiation Measurements Mean

The Environment Ministry says approximately three quarters of the stored soil has radioactivity of 8,000 becquerels per kilogram or less. That figure is central to government planning because it separates soil considered suitable for wider reuse from material requiring tighter controls or disposal in specialized facilities.

A becquerel measures radioactive activity: one becquerel means one radioactive decay per second. The figure per kilogram describes how much activity occurs in a given weight of material. It gives officials a way to compare soil samples and decide which material meets the criteria for a proposed use.

Officials calculate that even people working close to the selected soil would receive an annual radiation dose of 1 millisievert or less. A millisievert measures the biological effect of radiation on the body, taking account of different kinds of radiation and their effects on human tissue.

The International Commission on Radiological Protection recommends that public exposure from artificial sources should not exceed 1 millisievert a year, excluding natural background radiation. Natural background radiation averages between 2 and 3 millisieverts a year globally in most regions. The becquerel measurement describes activity in the soil; the millisievert calculation describes the resulting exposure to a person.

The government presents these measurements as placing the proposed reuse within internationally recognized safety parameters. Public confidence remains a separate challenge after the 2011 disaster. Explaining the figures in understandable terms is part of the effort to persuade communities that selected material can be used safely.

A Large Stockpile, Very Limited Reuse

Japan has so far used only 68 cubic meters of the soil across ten locations nationwide. The applications include the front garden of the Prime Minister's Office and ministry buildings in Tokyo's Kasumigaseki government district. Those projects give officials and visitors opportunities to see the material in ordinary landscaped settings.

The scale is tiny compared with the approximately 14 million cubic meters in storage. Using those figures, the 68 cubic meters represents about 0.00049 percent of the stockpile. The comparison shows how little material the demonstration projects have absorbed, even while they serve a public communication purpose.

The government has struggled to turn years of storage and processing into concrete plans for reuse on a large scale or permanent disposal. The Yokohama proposal would extend the demonstrations to a much more prominent setting, with visitors arriving from Japan and abroad.

The quantity to be used at the 2027 expo has not been specified, and the proposal remains under consideration. Its immediate importance lies in the visibility of the project and the government's attempt to build acceptance for future uses, alongside the practical task of managing the stockpile.

What Visitors Will See in Yokohama

The International Horticultural Expo 2027, also known as Green x Expo, will occupy approximately 100 hectares of a former United States military facility across Yokohama's Seya and Asahi wards. Organizers plan to fill the venue with 10 million flowering and non-flowering plants.

The exhibition's theme is "Scenery of the Future for Happiness." Its gardens and displays are intended to show how nature can be integrated into densely populated cities, with sustainable urban greening and ecological coexistence at the center of the event.

The four connected subthemes align with the United Nations Sustainable Development Goals. They address the design of resilient cities, relationships within communities, new agricultural industries and cooperation across borders:

• Co-adaptation focuses on green infrastructure that helps urban environments remain sustainable and withstand climate pressures.
• Coexistence promotes community bonds through horticulture and the sharing of agricultural activities.
• Co-creation encourages new industries combining agriculture, technology and life sciences.
• Co-operation promotes global exchange, multicultural coexistence and environmental harmony.

The proposed Fukushima soil would become part of that setting through flower beds and landscaping. The government sees a connection between the exhibition's environmental themes and the effort to find useful applications for material collected during recovery from the nuclear accident.

Why Yokohama Adds Historical Meaning

Yokohama has served as a gateway for Japan's exchanges with the world since its port opened internationally in 1859. Horticulture was part of that history: Western plant varieties entered Japan through the city, while Japanese plants reached markets abroad.

The 2027 exhibition draws on that role by bringing countries and international organizations together around plants and landscapes. Using Fukushima cleanup soil there would place a difficult part of Japan's recent history within a venue associated with exchange and the movement of plants across borders.

The site itself is also undergoing a conversion. A former military facility will become a large garden venue, reflecting the exhibition's themes of renewal and changing uses for urban land. The proposed soil reuse would give the same setting another example of material being put to a new purpose.

For the government, Yokohama offers a way to present Fukushima's reconstruction to a broad audience. The expo's size, international participation and focus on sustainability make it a prominent setting for a policy that has remained politically sensitive since the earthquake, tsunami and nuclear accident.

Smaller Displays Have Already Tested the Approach

The 2025 Osaka-Kansai Expo provided a recent example of the government's demonstration strategy. Planters using decontaminated soil from Fukushima contained twelve varieties of plants, including akebi. The displays put the material into a familiar setting where visitors could see it supporting plant growth.

Japan's approach relies on a series of visible applications intended to build confidence in uses that officials consider low risk. The government wants these practical examples to accompany radiation measurements and scientific explanations, making the policy easier for the public to understand.

A member of the ruling Liberal Democratic Party described the importance of using the soil at the forthcoming horticultural exhibition, calling attention to its status as a national project:

The use of reconstruction and revitalisation soil at the horticultural expo, which is a national project, is highly significant.

The representative's comment reflects the political weight attached to the venue. A national exhibition with international attention would give the reuse policy a much wider audience than the small displays in government gardens.

The government also intends to expand promotional efforts to regional offices nationwide. More demonstration sites would bring the material into landscaping and public works settings beyond the capital, extending the effort to make its use familiar before larger decisions on reuse and disposal.

Safety Oversight Will Be Part of the Debate

Japan's nuclear sector faces rigorous monitoring in the years since the Fukushima disaster. The Nuclear Regulation Authority continues to oversee atomic energy matters, including recent probes into data fraud involving major utility companies and reactor safety assessments.

Those investigations reflect the importance authorities attach to reliable safety documentation and verification. The Environment Ministry's measurements and assessments of the soil will be central to the government's explanation of the reuse proposal, especially at a venue expecting more than 10 million visitors.

The International Association of Horticultural Producers, which oversees global exposition standards, inspected the Yokohama site in March 2026. The inspection took place as preparations entered their final phase before the opening in 2027.

International oversight is expected to provide another layer of verification around the exhibition's requirements, including the materials used in its gardens. The proposed soil application will face scrutiny from domestic and international observers concerned with construction, landscaping and visitor safety.

The government therefore has to address both the technical criteria and the public's confidence in how those criteria are checked. The exhibition provides a prominent demonstration setting, while the wider disposal program requires decisions that reach far beyond the venue.

The Deadline Extends Well Beyond the Expo

The government plans to begin selecting and surveying candidate sites for final disposal around 2030. That work would address all the decontaminated soil, including portions with relatively higher radioactivity, and leave about fifteen years before the March 2045 legal deadline.

Japan's task combines engineering, transport and storage decisions with the need to find communities willing to receive material connected to a nuclear disaster. Previous efforts to establish nuclear waste disposal sites have frequently stalled because of local opposition, complicating cleanup planning across the country.

The sequence of events shows how the proposed expo demonstration fits into a much longer process:

• March 11, 2011: The earthquake and tsunami triggered meltdowns at Fukushima No. 1, followed by extensive decontamination work.
• 2025: The Osaka-Kansai Expo displayed planters using Fukushima soil with twelve varieties of plants.
• March 2026: The International Association of Horticultural Producers inspected the Yokohama exhibition site.
• March 2027: The International Horticultural Expo is scheduled to begin in Yokohama.
• Around 2030: The government plans to start selecting and surveying candidate sites for final disposal.
• March 2045: Final disposal outside Fukushima Prefecture must be completed under Japanese law.

The Yokohama proposal has two connected purposes: putting a small quantity of soil to immediate use and preparing the public for much larger decisions in the 2030s. Japan hopes that flowers growing in selected material at an international exhibition will help build trust before communities are asked to consider permanent disposal facilities.

Key Points

• As of April 24, 2026, Japan is considering Fukushima cleanup soil for flower beds and landscaping at Yokohama's 2027 horticultural expo.
• Approximately 14 million cubic meters is stored in Okuma and Futaba, while only 68 cubic meters has been used at ten locations nationwide.
• The Environment Ministry says about three quarters of the soil measures 8,000 becquerels per kilogram or less; officials calculate annual exposure of 1 millisievert or less for people working close to selected material.
• The expo will cover approximately 100 hectares, feature 10 million plants and include participants from 61 countries and international organizations.
• Candidate site selection and surveys for final disposal are planned to begin around 2030.
• Japanese law requires final disposal outside Fukushima Prefecture by March 2045.