EURAJOKI, Finland -- The world’s first permanent nuclear waste repository is under construction on the small and tranquil island of Olkiluoto here.

This storage facility, named Onkalo, which means cave or cavity, is being built in the granite bedrock deep underground about five kilometers from the two nuclear power plants at Olkiluoto just off the southwest coast of Finland.

It is designed to keep high-level radioactive waste, the most worrisome by-product of nuclear power generation, secure for at least 100,000 years. High-level nuclear waste, which consists of spent fuel and some of the fuel’s decay products, can emit dangerous radiation for tens of thousands of years.

To date, high-level waste has mostly been stored in water-filled pools at the atomic power plants where it was produced or in temporary offsite dry storage facilities. But these are impermanent and insecure solutions. Many experts say the only fundamentally viable solution may be facilities like Onkalo.

At the Onkalo underground bunker, the waste will be secured through a system of multiple barriers, based on a method of nuclear waste burial developed in Sweden.

Once the facility begins operations (possibly in 2023), the final disposal process will first involve putting 12 spent fuel assemblies into a steel canister to be enclosed into a corrosion-resistant copper capsule. Each capsule will then be placed in its own hole in the repository and packed with bentonite clay. The bedrock will be the final barrier at a depth of 520 meters in a geologically stable zone.

The Onkalo repository is designed to be large enough to accept canisters of spent fuel for about 100 years until around 2120, when it will be backfilled and decommissioned.

It took 17 years for Finland to select Olkiluoto in 2001 as the site of the geological repository for the final disposal of spent nuclear fuel. A construction license was issued by the government in November 2015, based on a decade of tests on the specific characteristics of the bedrock.

Behind the successful process of selecting and building the final disposal site is an effort to win trust from nearby residents by pushing for the work in a transparent and well-organized manner.

“They (Finnish officials) have been frank with and open to the public all the time,” said Kimmo Lehto, sales manager at a subsidiary of Posiva Oy, the company constructing the site.

“They are telling what they are doing and discussing it with people,” he said, adding the Finnish people have trust in their government.

His view seems shared by most residents in Eurajoki.

Mika Rapala, a 52-year-old woman who teaches at an elementary school in this municipality with a population of about 6,000, said she supports the construction of the nuclear waste storage facility at a place near where she lives, expressing confidence in its safety.

“There have been many hearings and all information regarding safety is open to us,” she said.

The Finish government interviews residents in Eurajoki every year to find out and settle whatever concerns may remain among them, according to Lehto, the official at Posiva Solutions Oy.

Finland’s pioneering work in the area of final disposal may imply many useful suggestions for South Korea, which has recently drawn up a long-term road map for building its own facility for the permanent storage of high-level nuclear waste.

A plan approved by the Cabinet in July calls for selecting a site within 12 years and completing the construction of the final disposal facility by 2053.

Experts note this time schedule should not be delayed, given the temporary storage facilities at the country’s 24 nuclear reactors will begin being filled up from 2019.

But it will certainly be tough to go ahead with the plan as scheduled, as local governments hosting nuclear power plants are complaining that the road map has been worked out without full consultation with them.

“We should make many technical achievements in the road toward building the permanent nuclear waste repository. But the most important and thorniest part of the work may be how to secure consent from people in possible candidate sites,” said Lim Hyoung-jin, an official at the Ministry of Trade, Industry and Energy, who is tasked with putting the road map into practice.

Vehement protests led the government in 2004 to decide to push for the construction of disposal facilities for high-level and less dangerous nuclear waste separately. A permanent storage facility for intermediate- and low-level radioactive material was built in the southeastern city of Gyeongju last year.

The importance of winning public support through long-term, transparent policies was echoed by Mariano Molina, head of international relations department at Enresa, a Spanish company set up in 1984 to handle the disposal of nuclear waste and decommission aged nuclear power plants.

In 2011, Spain selected Villar de Canas as the site for the interim storage facility for high-level nuclear waste, which is planned to begin operation in 2050. But the country has yet to undertake work to build a final repository.

Molina conceded that policy transparency and public confidence in the government remain low in Spain, which he said partly explains why Spain lags behind Finland and other countries in the field of nuclear waste disposal.

Aside from Finland, Sweden and France have selected sites for the permanent disposal of spent nuclear fuel. Several other countries, including Germany, Canada, the UK and Switzerland, are in the process of choosing final disposal sites.

By Kim Kyung-ho (khkim@heraldcorp.com) / Korea Herald correspondent