Deep geological disposal of nuclear waste in the Swedish crystalline bedrock

Full text


Deep geological disposal

of nuclear waste in

the Swedish crystalline


Claes Thegerström and Saida Laârouchi Engström, Stockhom/Sweden

Address of the Authors: Claes Thegerström and Saida Laârouchi Engström Swedish Nuclear Fuel and Waste Management Company P.O.Box 250 101 24 Stockholm/Sweden Revised version of a paper presented at the VGB Congress 2012, Mannheim, 10 to 12 October 2012.

The Swedish solution –

Regulations and history

The 1. Swedish reactor, Oskarshamn 1, was taken into commercial operation in 1972. The following year, the nuclear power utili-ties set up SKB (Swedish Nuclear Fuel and

Waste Management Co). The initiative came

from the Government, which wanted to have a single organisation to deal with nu-clear fuel. The company’s primary mission was at that time to coordinate the supply of nuclear fuel.

Until then little attention had been paid to issues related to spent fuel and nuclear waste management. The general view was that spent fuel should be reprocessed and

fuel from the first reactor was contracted

for reprocessing at Windscale (Sellafield). According to that contract, the reprocessing wastes would be stored at Windscale, only the fissile elements (Pu and U) would be taken back for reuse in the reactors. Opera-tional low- and medium level wastes from

the reactors were collected and solidified at

the plants but no long-term planning had been made concerning their storage and disposal.

In 1976, Sweden got a new Government after an election campaign in which nuclear power was a major issue. Now a radical change took place in how nuclear waste management was viewed. The new Govern-ment’s policy statement declared that “the

nuclear power utilities shall demonstrate an absolutely safe method for disposal of the spent fuel.”

Six months later the Stipulations Act was passed. It stated that the reactors under construction may only be started if certain stipulations are met. The law offered 2 al-ternatives for the spent nuclear fuel:

reproc-essing and final disposal of the high-level waste or final disposal of the nuclear fuel

without reprocessing.

The nuclear power utilities in Sweden now bore the responsibility for disposal of the waste from their electricity generation plants. Many reactors were in the process of being built or designed, and a solution had to be found – otherwise they might not be taken into operation.

Two agreements were signed in 1977 and 1978 with a French company for re-processing of spent nuclear fuel from Swed-ish reactors. The agreement was submitted in support of an application for operating li-cences for 4 new reactors.

The KBS project was commenced when the Stipulations Act came into force. (KBS stands for Kärnbränslesäkerhet = nuclear fuel safety). The goal of the project was to establish a method for disposal of nuclear waste. For several years, the project worked

with vitrified waste from reprocessing. In

the third project report, published in 1983, a method for “direct disposal” was present-ed. This means that the fuel is not

reproc-essed prior to final disposal. The report rec

-ommended a final repository in the Swed -ish crystalline bedrock, with barriers of nat-ural materials. This is the method we are still working on. It is called the KBS-3 meth-od and constitutes the basis for the

applica-tion to build a final repository for the spent

nuclear fuel which is to be submitted soon. In 1984 the Government decided that the KBS-3 method “in its entirety has been found essentially acceptable with regard to safety and radiation protection.” (Govern-ment decision of June 28, 1984.) This

means that the Government accepted direct disposal as a feasible method and acknowl-edged that the geological conditions neces-sary for such disposal exist in Sweden.

The new Nuclear Activities Act of 1984 gave the reactor owners full technical and

financial responsibility for the waste. They

gave in turn SKB the responsibility for all nuclear waste management. This meant that reprocessing was no longer required to be allowed to operate the reactors. From 1985, when an interim storage for spent fu-el was taken into operation, there was a consensus based on political as well as in-dustrial arguments to abandon the reproc-essing strategy.

Since the early 1980s, everyone who us-es electricity generated from nuclear power

also bears financial responsibility for man -agement and disposal of the waste. This fee is still being charged today. For every kilo-watt-hour of electricity generated from nu-clear power, about 1 öre (a 10th of a Euro

cent) goes to the Nuclear Waste Fund. With that money research, development of tech-nology, facilities, and all other investments related to nuclear waste management in

Sweden are financed.

A process for regular reporting and re-view of results and plans was also set up.

This contributed significantly to the devel -opment of a high scientific quality of the work and an open and transparent review mechanism. The regular review of the SKB R&D-programmes every 3 years has had a

significant influence on the programme in

several aspects. To mention one example, the plan for step-wise implementation of a deep repository was introduced by SKB in the 1992 RD&D-programme following com-ments and suggestions by KASAM, the

Swed-ish National Council for Nuclear Waste, on

the 1989 R&D-programme. Other examples are the systematic evaluation of alternative strategies and methods for spent fuel

man-agement and final disposal reported in year

2000 following requests from safety author-ities as well as municipalauthor-ities involved in the siting feasibility studies.

The Swedish system takes shape

SKB has planned a system that can handle all

kinds of radioactive waste that arises in a nu-clear power plant. The waste is divided into different categories depending on its radio-toxicity. The largest portion in terms of vol-ume, approximately 90 % of the waste, aris-es during the operation of a nuclear power plant. It is called operational waste.

The final repository for the operational

waste – SFR – (Slutförvaret för kortlivat ra-dioaktivt avfall) is built at the Forsmark nuclear power plant, and was taken into operation in 1988 (Figure 1 and 2). The waste has to be isolated here for about 500


Fig. 1. Air photo of the SFR (Final Repository for Operational Waste, Slutförvaret för kortlivat radioaktivt avfall) at the Forsmark site. (Photo: SKB)

Fig. 3. Transport of spent nuclear fuel from m/s Sigyn to Clab. (Photo: SKB) Fig. 2. Transport down into the SFR. (Photo: SKB)

years. After that its radioactivity is compa-rable to that which occurs naturally in the surrounding bedrock. Two tunnels, each a kilometre in length, lead down to the re-pository, which is located about 50 metres beneath the sea bed. There are 4 rock vaults and one silo. Radioactive waste aris-ing from medical care, industry, and re-search is also disposed of here.

The spent nuclear fuel will be kept in an interim storage for around 30 years prior to

final disposal. This is done in the Central In -terim Storage Facility for spent nuclear fuel – Clab outside Oskarshamn. All handling of the fuel in Clab takes place under water. The water acts as a radiation shield while also cooling the fuel. The decay heat gener-ated by the spent fuel is one reason for

stor-ing waste in interim-storages prior to final

disposal. If the radioactivity in the fuel is al-lowed to decay, it will emit less heat in the deep repository, which is an advantage.

The existing Swedish system also in-cludes a specially built ship for

transporta-tion of radioactive waste. Since the Swedish nuclear power plants are situated on the coast, the radioactive waste is transported by SKB’s ship m/s Sigyn (Figure 3). Trans-portation safety is primarily guaranteed by the transport casks and containers which are designed to suit the type of waste to be shipped and to withstand extreme stresses. In the event of an accident they will retain their radiation-shielding properties.

The establishing of these facilities has been an important step in the national pro-gramme for management of the radioactive waste. The programme provides however for management and disposal of all nuclear waste. The most important programme facil-ities that are still under development and re-main to be built are the encapsulation plant

and the final repository for spent fuel. They

are the core facilities of the KBS-3 system. In addition we need to build a canister factory, which is not, however, a nuclear facility.

The KBS-3 system and

technical development

The Swedish method for disposing of radi-ocative waste, the KBS-3 method, entails encapsulating the spent nuclear fuel in copper canisters, which are embedded in bentonite clay at a depth of about 500 me-tres in the Swedish crystalline bedrock. The principle is based on the use of multiple protective barriers to isolate the fuel. The barriers prevent the radio nuclides from be-ing transported to the ground surface and into the ecosystem via the groundwater.

The first barrier is a copper canister with an insert of cast iron. The fuel assem-blies are entirely encapsulated. In the ear-ly stages of the programme they were assumed to be encapsulated without fuel boxes and boron glass rods, which were dis-posed of separately. Nowadays, the fuel as-semblies are assumed to be disposed of complete (including fuel boxes).


Fig. 4. Parts from a copper canister proposed for the disposal of radioactive waste. (Photo: SKB)

Fig. 5. Air photo of Äspö Hard Rock Laboratory. (Photo: SKB)

Cast iron protects the canister against external pressure. The copper protects against corrosion in the oxygen-free envi-ronment that prevails in a deep repository. As long as a canister is intact, no radio nu-clides will escape.

The second barrier is a layer of bentonite clay. The clay is a buffer that protects the canister against movements in the rock and holds it in place. The bentonite absorbs wa-ter while swelling. Due to this property, the water is bound in the clay and kept virtually

immobile. The clay also acts as a filter. If a

canister should be breached, most of the ra-dio nuclides will remain in the canister. Most of the radio nuclides that do escape will be retained in the bentonite.

The third barrier is the crystalline bed-rock, which retards the transport of radio nuclides up to the ground surface. The pri-mary purpose of the rock is to give the can-ister a stable and protective environment.

The fuel itself can also be regarded as a barrier. It is ceramic in form and thereby highly insoluble in water. As a result, the ra-dio nuclides are held in place for a long time. The work on research, development and demonstration of deep geological disposal of spent fuel has been an intensive one last-ing for more than 25 years. Although the

KBS-3 concept all over the time has been

the basis for the work there has over the pe-riod also been a consolidation and broaden-ing of the knowledge on conceivable ways of storing spent fuel in the Swedish bed-rock. The KBS-3 method has continuously

been modified and refined.

Much of the technological development is performed in the Äspö Hard Rock

Labora-tory and in the Canister LaboraLabora-tory, both

lo-cated in Oskarshamn.

Full-scale deposition tests are undertaken in the Äspö Hard Rock Laboratory at a depth of 340 to 460 metres in the bedrock. This is where the dress rehearsal prior to

construc-tion of the final repository is taking place.

The scene is the 3.6 kilometre long and 460 metre deep tunnel that comprises SKB’s un-derground research laboratory. (Figure 5)

Here, in the nearly 2 billion year old crystalline bedrock, we are demonstrating how we plan to build the deep repository. Here we are also conducting various

exper-iments to find out more about the method

that will be used to isolate nuclear waste from man and the environment.

There is no spent nuclear fuel down here. Otherwise it is very similar to the fu-ture final repository. Most things are in place: the canisters, the machines, the

tun-nels, and the boreholes where the canisters will be emplaced.

The development and testing of sealing methods for the canisters takes place in the canister laboratory. The plan is that the cop-per canisters for the fuel will be fabricated in a separate canister factory. The fuel will be taken from Clab to the encapsulation plant, where it will be dried and placed in the canister. Then a lid will be welded onto the canister and the canister will be inspect-ed to make sure it is leak tight.

The technology for encapsulation and in-spection is being developed and tested in the

Canister Laboratory. Here the technology for

welding the lid onto the copper canister is

being refined, and here the welded joints are

checked to make sure they are really leak proof. The welded joints are examined by means of radiographic, ultrasonic, and ed-dy-current inspection. In the laboratory we also test equipment for the encapsulation plant. This facility will be built at roughly

the same time as the final repository.

Alternative methods

Another important research area has been to follow and study various alternatives to the main line (deep disposal according to the KBS-3 method). A large number of al-ternative methods have been described and analysed in depth. The results of this analysis provide strong support for the choice of the KBS-3 method.

The siting process

Area survey studies

Faced with the choice of locations for type area studies reconnaissance and surveys of nearly 1,000 sites scattered across the


country were performed. On the basis of mainly geological, but also non-geological siting factors (including land ownership) were 8 sites chosen as suitable for drilling studies in the years 1976 to 1983.

The intention was not to find a location

for a repository, but obtaining data from large depth in different areas spread throughout the country. These data were necessary to have to get a picture of how the material qualities and conditions, such as hydraulic conductivity and groundwater redox status, vary. On the basis of some ar-ea survey type studies SKB concluded that

it is possible to find many places in Sweden,

where the geological conditions are suita-ble for the construction of a repository. This meant that other important factors, such as societal factors, could be taken into consid-eration in the choice of site.

Feasability studies

Since 1992 a stepwise process has been

un-der way, aiming at finding a site for the final


By means of regional studies, we ex-plored the general siting prospects in dif-ferent parts of the country. These studies

show that good prospects exist for finding suitable sites for a final repository at many

places in the Swedish crystalline bedrock. However, geological conditions

disquali-fied the Caledonide mountains in the north

and parts of Skåne and Gotland in the south. For nearly 20 years ago the siting process for the final repository for spent nuclear fuel started. This was based on our view that a successful work requires that

the safety of the site finally selected is met

and that the municipality supporting the repository.

The feasibility studies were conducted during the period 1993 to 2000 evaluated the siting prospects in a total of 8 munici-palities: Storuman, Malå, Östhammar,

Nyköping, Oskarshamn, Tierp, Älvkarleby,

and Hultsfred. The purpose was to judge, on the basis of existing material, whether pros-pects existed for further siting studies for a

final repository. The judgements were based

on 4 factors: safety,


land and environment,

how society can be affected by a



In 2000, we presented the “Integrated ac-count of site selection and programme prior to the site investigation phase”. Three areas were prioritised for site investigations:


in the municipality of Östham-mar,

an area in the northern part of the


nicipality of Tierp, and

the Simpevarp area in the municipality

of Oskarshamn.

The municipal councils in Östhammar and

Oskarshamn consented to further

investiga-tions, while Tierp refused additional tests.


In 2002, SKB initiated site investigations

for siting of a final repository on 2 sites: the

Simpevarp and Laxemar areas (Oskarshamn

municipality) and the Forsmark area

(Öst-hammar municipality). The site

investiga-tions covered studies of rock characteris-tics, including measurements from the sur-face, and in 1,000 meter deep boreholes. In addition, SKB made an inventory of natural and cultural values, and investigated how a repository might affect society. The investi-gations were concluded in 2008.

After that we analysed the results of the site investigations, especially assessments of the long-term safety for a KBS-3 reposi-tory at Forsmark and Laxemar. The analysis revealed a clear advantage for Forsmark concerning long-term safety, so the choice became obvious

In June 2009 SKB selected Forsmark as site for the final repository for Sweden’s spent nuclear fuel. The Forsmark site offers rock at the repository level which is dry and has few fractures. These properties are of a

major significance for long-term safety. In

addition, a repository in Forsmark would require less space compared to a repository in Laxemar. This is an advantage, as less rock needs to be excavated and less

materi-al will be needed for backfilling. The facili -ties on the surface will be constructed in the existing industrial area, which reduces the environmental impact and provides ac-cess to the infrastructure of the area.

Consultation and communication

The consultation process

Our goal is to obtain permits to site and build an encapsulation plant and a deep repository for spent nuclear fuel. Basically, 3 different

permits/licences are required for both the fi -nal repository and the encapsulation plant (see below). We submitted applications for

the encapsulation plant in 2006 and we filed the applications for the final repository and

the complete system in March 2011. The licensing process begins with a con-sultation process the main purpose of which is to optimise the prospects of obtaining a good environmental impact statement (EIS). The consultation starts with an early consul-tation with the county administrative board and private individuals who are likely to be particularly affected. A much wider circle is later invited to the consultation: other gov-ernment agencies, municipalities, members of the public, and non-governmental organi-sations who may be concerned. SKB is thus

responsible by law to interact with the local population, the elected decision-makers in the municipality, the local and national NGOs, and the authorities involved on the local, regional, and national level.

An EIS should be capable of being read and reviewed by a number of different target groups, each with different interests and backgrounds. This means that we have taken up a very wide range of questions for investi-gation, and also topics such as various kinds of impacts on the community, health impacts and other sorts of non-technical aspects.

There has been constant feedback be-tween ongoing investigations, surveys, de-sign work, and consultations. As the siting investigations and design process progress and different surveys are carried out, the de-sign of the facilities and their adaptation to their surroundings and impact on the

envi-ronment is refined and improved. Results of

investigations and surveys together with pro-posals for facility design have been present-ed at the consultation meetings, and the par-ticipants have been given an opportunity to offer their viewpoints on SKB’s proposals.

During the consultation, SKB solicits viewpoints regarding the scope of the envi-ronmental impact statement. When the site investigations are concluded and the neces-sary investigations have been completed, an EIS will be compiled for the site selected.

External communication

The communication activities described so far have made up the formal part of SKB’s external communication. SKB will, howev-er, also face a number of new communica-tion challenges in addicommunica-tion to the work with the formal consultations.

SKB has now been working in the site

in-vestigation regions for more than 10 years. We feel that the residents generally have trust in our work. SKB has occasionally commissioned opinion polls on people’s at-titudes towards a deep repository. One of the clearest tendencies is that people with the most knowledge about SKB and the fi -nal disposal method are the ones who are the most positive. This is particularly clear in the municipalities where we have per-formed feasibility studies and site investiga-tions, and where the issue has been dis-cussed for a long time. Around 4 out of 5 of the people in Oskarshamn and Östhammar

are in favour of building a final repository if

a suitable site will be found in their munici-pality. This is a confidence in our project that must be maintained.

SKB’s record of communication related

activities includes a wide variety of experi-ences, and we have learned from all of them. Over time have we identified a number of basic conditions, which are fun-damental for a stable and successful siting process. We will now meet new types of


Fig. 6. Storage pool for spent nuclear fuel in the Clab. (Photo: SKB)

communication challenges, but the key components of the stakeholder communica-tion process are the same:

The siting process shall be transparent and based on voluntary participation. It is easy to be suspicious of people who are not

open about their plans, and it is very diffi -cult to regain trust once it is lost. The munic-ipalities must have the ultimate conclusion about our continued work within their boundaries.

It is important to maintain a constant di-alogue and to express it in comprehensible

terms. It is not sufficient to simply supply a constant flow of information along a

one-way channel.

A clear division of responsibilities be-tween stakeholders is a key question. The implementing party can not pretend to be a neutral player, and it is therefore important that another player adopts this role.

Give the process the time that is needed – try to avoid being in too much of a hurry.

It takes time to build confidence, and one

single attempt to speed up the process might ruin much more than you gain. Other opinions, anxieties and fears must be re-spected.

A step-wise and adaptive approach to the implementation of the disposal system. Allow scope for possible changes or im-provements to the project. You cannot be expected to know everything from the start, and constructive criticism should be wel-comed.

Despite all non-technical aspects of com-munication, the continued good perform-ance of operating facilities and of R&D work to guarantee top-quality technical systems are a must. You must always be able to clearly demonstrate that the nuclear waste will be handled with care and skill.

Submitting the applications

The site selection is a milestone for the Swedish nuclear waste programme. In March 2011, when admitting the

applica-tions for permits to build the final reposi -tory for spent nuclear fuel in Forsmark and the encapsulation plant in Oskarshamn, an-other milestone was reached.

Apart from the future repository, the ap-plication according to the Nuclear Activities Act also includes the existing interim storage facility in Oskarshamn, Clab. We have al-ready applied for an encapsulation plant ad-jacent to Clab (Figure 6). Then, the applica-tion according the Environmental Code

in-cludes the whole system, which is the final

repository, Clab and the encapsulation plant. The applications according to the Nucle-ar Activities Act and to the Environmental Code are formally the bases for 2 separate legal examinations, and we therefore had to draw up 2 different documents. The con-tent of the documents are to a great excon-tent

the same, but there are also important dif-ferences since there are a number of issues that are considered only according to one of the regulations.

The Environmental Court will prepare the case and review it according to the Envi-ronmental Code. After some preparatory procedures they will hold a main hearing. Then they will give a statement to the Swed-ish Government which will request state-ments from the municipalities of

Östham-mar and Oskarshamn. The municipalities

will accept or reject and have a right of veto. The Government will then make a decision

on whether the final disposal system is per -missible or not. If the application is accept-ed, the Environmental Court will hold a new hearing. Thereafter, the Court will grant permits and stipulate conditions pursuant to the Environmental Code.

SSM, the Swedish Radiation Safety Au-thority (Strålsäkerhetsmyndigheten), will

prepare the case in accordance to the Nu-clear Activities Act and put forward a state-ment to the Governstate-ment. If the Governstate-ment grants the permit, the authority will subse-quently stipulate conditions pursuant to the Nuclear Activities Act as well as to the Radi-ation Protection Act.

The factual review started at the end of May 2011. In conjunction with this, the ap-plication documentation was also sent out to experts in a broad national referral, both by SSM and by the Land and Environmental

Court. Environmental organizations,

con-cerned municipalities and county adminis-trative boards, universities and colleges, other authorities and more were allowed to give their opinions.

At SSM, the work on the application is also divided up between its own personnel and hired external experts. The authorities can request supplementary information and

clarification from SKB during the course of

the entire process. SKB will also be able to respond to the statements of opinion that come in.

The government also requested that an independent international review of the ap-plications should be made. This was carried out by the OECD’s Nuclear Energy Agency

(NEA) between May 2011 and June 2012.

The team of experts reviewed SKB’s descrip-tion of long-term radiadescrip-tion safety as well as

the selection of site and method. In their fi -nal statement you can read “From an inter-national perspective, SKB‘s post-closure ra-diological safety analysis report, SR-Site, is

sufficient and credible for the licensing de -cision at hand. SKB‘s spent fuel disposal programme is a mature programme - at the same time innovative and implementing

best practice – capable in principle to fulfil

the industrial and safety-related require-ments that will be relevant for the next li-censing steps.”

Concluding remarks

The selection of the site and the licence ap-plication is the result of over 30 years of technical research and development and close to 20 years of siting work. During the siting process we have conducted surveys throughout Sweden, feasibility studies in 8 municipalities and site investigations at

Forsmark and Laxemar. We are now ready

to change the emphasis of our work to-wards more of industrial accomplishment. At the same time we will, however, carry on and follow up our programme for com-munication and stakeholder involvement which we consider to have been a corner stone behind a successful development and siting work. 





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