Radioactive material is highly toxic to unimaginable timescales.

But in Finland, they’d proposed with the world's first permanent nuclear-waste

repository -- "Onkalo" -- a huge system of underground tunnels, being hewn out of solid rock and THAT must last at least

100,000 years.

GREATEST QUESTION OF OUR AGE:

WHAT TO DO WITH NUCLEAR WASTE?

INTO INFINITYONKALO SPENT NUCLEAR FUEL REPOSITORYFINLAND

…….on track to be the first “official” repository in the world to quarantine high-level nuclear waste for a long

time……

INTRODUCTION

• It is currently under construction at the Olkiluoto Nuclear Power Plant in the municipality of Eurajoki, on the west coast of Finland, by the company Posiva.

• The estimated cost of this project is about €818 million, which includes construction, encapsulation, and operating costs.

• The Onkalo repository is expected to be large enough to accept canisters of spent fuel for around one hundred years, i.e. until around 2120.

• Onkalo is being designed to last 100,000 years.

• Deep geological repository for the final disposal of spent nuclear fuel, the first such repository in the world

• Onkalo will be ready to take waste in 2020, and then will be finally sealed in 2120, after which it will not be opened for 100,000 years. 

• Why 100,000 years???• Because, by 100,000 years the

spent nuclear waste will loose its harmful radioactivity.

HISTORY • After the Finnish Nuclear Energy Act was amended in 1994 to specify that all nuclear waste produced in Finland must be disposed of in Finland, Olkiluoto was selected in 2000 as the site for a (very) long-term underground storage facility for Finland's spent nuclear fuel.

• The facility, named "Onkalo" (meaning "cave" or "cavity") is being built in the granite bedrock at the Olkiluoto site, about five km from the power plants.

• The municipality of Eurajoki issued a building permit for the facility in August 2003 and excavation began in 2004.

The Surrounding Bedrock

• The main rock type in Olkiluoto bedrock is gneiss.

• The bedrock in the area is approximately 1,800 to 1,900 million years old.

• There are various types of structures in the rock, some of them water conductive. 

Spent nuclear fuel will be disposed of in a

depth of about 400-450 meters inside Olkiluoto

bedrock. Deep inside the bedrock, the

prevailing conditions are stable and

predictable.

Continue…

• Olkiluoto bedrock has been studied ever since the 1980s.

• There have been a number of studies, some of which are still underway, using such methods as aboveground drilling and investigation trenches, as well as constructing the underground rock characterisation facility, ONKALO.

An approximately 2 billion year old gneiss sample from the Onkalo deep geologic repository

Site Investigation

• Site investigations related to final disposal of spent nuclear fuel have been carried out in Olkiluoto ever since the 1980s.

• One of the major site investigation methods is to drill deep drillholes and to use them in various groundwater investigations.

• Other important methods are excavating investigation trenches and conducting variable geophysical examinations.

Drilling • The bedrock in Olkiluoto is investigated by drilling holes of up to one kilometre deep, from ground surface.  By 2014, a total of about 60 holes have been drilled.

• Drilling produces a drill core sample of some five centimetres in diameter.

• It is carefully studied to establish the degree of fracturing and types of rock present in the bedrock.

• The in-hole measurements and samples taken from the drill hole allow studying of the flow and qualities of groundwater.

• Geophysical measurements and imaging also take place in the holes.

Drill core samples reveal the structures and rock

types of the bedrock

Geophysical investigations

• Geophysics can be used to examine rock structures which are hidden to naked eye.

• Geophysics makes use of the physical properties of the Earth, such as

– magnetism– electrical conductivity– density– elasticity– radioactivity.

Geophysical investigations in the summer of 2013 in

ONKALO.

Seismic investigatio

ns

• Downhole logging methods  applied in deep drill holes.

– These include imaging surveys (acoustic and optical), and methods describing directly physical properties of rock mass, like magnetization, density, conductivity, and velocity.

• Acoustic logging is carried out in all deep drill holes and pilot holes of ONKALO. They reveal the elastic properties of rock in immediate vicinity of measurement holes.

Seismic measurements have

been carried out in Olkiluoto in

conjunction with site investigations since the beginning of the

1990s.

Research Conducted in

ONKALO

• Helps to ensure the suitability of the Olkiluoto bedrock for the final disposal.

• Helps to identify the areas where the construction of the final disposal tunnels is the most cost-effective.

• Geological mapping is the method for collecting information related to the tunnel walls.

• Information about the rock to be excavated is obtained by drilling probe and pilot holes.

• From the tunnel, it is also possible to perform exploratory drillings and to study the groundwater flowing into the tunnel.

Geological Mapping of

ONKALO

• The geological mapping of ONKALO is divided into two parts: 

– mapping performed in the constructed tunnel immediately after excavation

– a more precise systematic mapping.• The first phase mapping

proceeds simultaneously with excavation work so that the mapped area is located at 10 to 15 metres from the rear end of the tunnel.

• Geologists determine the main rock type in the area and collect versatile information on the fracturing and quality of the rock.

Probe and Pilot Holes

• From the rear end of the ONKALO tunnel, a number of pilot holes have been drilled at pre-determined locations. These pilot holes will remain within the tunnel profile. 

• The purpose of these pilot holes is 

– to verify the rock quality at the location the tunnel

– to locate any water-conducting fracture zones

– other rock characteristics that may be significant for the construction.

Electrical charged

potential measurements

• The electrical charged potential method, a well established method in ore exploration, has proven to be an excellent tool for verifying the geological connections in Olkiluoto.

• The method involves measuring the flow of electricity through the rock. An electrical connection is often an indication of a hydraulic connection, and this knowledge is useful in predicting groundwater movements.

Ground water

studies in Onkalo

• The volume of water leaking into tunnel is measured and characteristics of groundwater are studied.

• Measurement of volume of leaked water is recorded by measuring weirs installed in tunnel.

• A visual leak water analysis is performed for ONKALO roof and walls twice a year to find leak spots and detect possible changes.

• Composition of groundwater is also examined by groundwater stations and monitoring holes.

CONSTRUCTION PHASES

• The facility is being constructed by and will be operated by Posiva, a company owned by the two existing producers of nuclear power in Finland; Fortum and TVO.

• ONKALO consists of one access tunnel and three shafts: a personnel shaft and two ventilation shafts. The slope of the tunnel is 1:10. It is 5.5 m wide and 6.3 m high.

CONTINUE…

• The facility's constructions plans are divided into four phases:

– Phase 1 (2004–09) focused on excavation of the large access tunnel to the facility, spiralling downward to a depth of 420 metres (1,380 ft).

– Phase 2 (2009–11) continued the excavation to a final depth of 520 metres (1,710 ft). The characteristics of the bedrock were studied in order to adapt the layout of the repository.

– Phase 3, the construction of the repository, is expected to begin around 2015.

– Phase 4, the encapsulation and burial of areas filled with spent fuel, is projected to begin around 2020

CONTINUE…• Once in operation, the disposal process would involve

putting twelve fuel assemblies into a boron steel canister and enclosing it into a copper capsule. Each capsule would then be placed in its own hole in the repository and packed with bentonite clay.

The ONKALO area in August 2004. The first blast of the construction had been implemented a few months before...

...and this is how the area looked in summer

2014, ten years later.

Construction method

• The access tunnel is excavated by drilling and blasting:

– at the beginning of excavation, a number of holes are drilled and then filled with explosives.

• Once the rock material has been blasted, the rock waste is moved away. The rock walls are then washed and any broken stones are dropped down.

• The rock is sealed, where necessary, by grouting before and after excavation.

• Cemented anchor bolts made of ribbed steel bars as well as shotcrete are used to strengthen the rock.

The method used for excavating ONKALO is drilling and blasting. The shafts are constructed by raise boring.

Shafts Constructed by Raise

Boring

• There will be three shafts in ONKALO: a personnel shaft, a supply air shaft and an exhaust air shaft.

• The diameter of the passenger shaft is 4.5 m and the diameters of the supply air shaft and exhaust air shaft are 3.5 m.

• The shafts are constructed with the raise boring method.

• The reamer bit moves upward at about half a meter per hour.

• Approximately 100 m of shaft is drilled at one time.

Threat to ONKALO

Project

• Constant water leakage into the tunnel from the surrounding bed rock is of high concern.

• The droplets are leaking into the tunnel from tiny fractures in the rock, smaller than a millimeter, at a rate of about 20 liters per minute. In tunnel terms, that’s slow, and that’s good news. 

• At each new depth, geologists extract slim rock cores in search of telltale ”structures”—the fractures and crevices that determine how water moves in rock.

• So far, Onkalo appears to have uncharacteristically few structures, which explains why the tunnel is only damp and muddy rather than flooded with a torrent of water escaping from its high-pressure home in the rock.

The Criticism

• Research argues that corrosion in pure copper advances at about one micrometre a year, whereas KBS-3 depends on a rate that’s a thousand times slower. 

• STUK (Finnish nuclear safety office) has asked Posiva for further explanation, and independent research conducted in Finland has supported the results of Szakálos's group.

• Posiva dismissed it all in public. Later studies by SKB determined corrosion process does not exist & initial experiments were not correctly executed and/or wrong conclusions were drawn.

• 2012: A research group at Royal Institute of Technology (Stockholm, Sweden) published research suggesting that copper capsules of KBS-3 are not as corrosion-proof as Posiva claims.

• Research group led by Peter Szakálos found that copper capsules would last only about 1,000 years, instead of 100,000 years claimed by companies.

Into Eternity is a feature documentary

film directed by Danish director Michael

Madsen, released in 2010. It follows the construction of

the Onkalo waste repository at the Olkiluoto Nuclear Power

Plant on the island of Olkiluoto, Finland. Director

questions Onkalo's intended eternal existence, addressing

an audience in the remote future.

Into Eternity raises the question of the authorities'

responsibility of ensuring compliance with relatively

new safety criteria legislation and the principles at the core

of nuclear waste management