TKS Nuclear Waste Management of the Olkiluoto and Loviisa Power Plants: Programme for Research, Development and Technical Design for

Transcription

1 TKS-2003 Nuclear Waste Management of the Olkiluoto and Loviisa Power Plants: Programme for Research, Development and Technical Design for Posiva Oy December 2003 POSIVA OY FIN OLKILUOTO, FINLAND Tel Fax

2 TKS-2003 Nuclear Waste Management of the Olkiluoto and Loviisa Power Plants: Programme for Research, Development and Technical Design for Posiva Oy December 2003 Base maps: National Land Survey, permission 41/MYY/03

3 ABSTRACT This report is the first in a new series of reports that will be produced every three years and will describe the progress made by Posiva and the two power companies, Teollisuuden Voima Oy (TVO) and Fortum Power and Heat Oy, in research, development and technical design activities (RTD) related to the management of radioactive waste, and the proposed programme of work, which will focus on the period of the subsequent three years. The report covers both Posiva s RTD programme for spent fuel and the RTD programmes for low and intermediate level nuclear wastes (I/LLW) that are being carried out by the power companies themselves. Chapter 1 introduces the system under which nuclear wastes are managed in Finland and presents the disposal concepts for I/LLW and spent fuel. This is followed by Chapter 2, which presents a review of the past RTD activities related to the spent fuel disposal. The chapter starts with a discussion of the RTD needs and priorities for the programme for spent fuel disposal, and which sets out the background to the programme, with specific reference to the recommendations from STUK, the Finnish Radiation and Nuclear Safety Authority. The framework for the RTD programme is outlined and the safety concept for a KBS-3 type repository, the type that is proposed for development at Olkiluoto, is explained in terms of the primary roles and the different components of the disposal system. This, in turn, leads onto the design requirements for the repository. The rest of Chapter 2 is devoted to the current state of the RTD programme for spent fuel disposal Finland, and covers the developments that have taken place since the RTD programme that was presented in POSIVA Extensive information is provided that describes the progress that has been made in the past few years with regard to the ONKALO (the underground rock characterisation facility that is to be constructed at Olkiluoto), the design and technical developments associated with the repository, and its components and subcomponents, the understanding of the site, in terms of its geology, hydrogeology, hydrogeochemistry, rock mechanics and biosphere, and the development of the safety case. This description includes summaries of work that are presented in more detail elsewhere, such as in the Baseline Report, that discusses the baseline conditions at Olkiluoto before the construction of the ONKALO, but also presents in one place the developments that have occurred in, for example, canister development, which are otherwise spread over many Posiva Working Reports. The developments that have taken place in the safety case are discussed in terms of Posiva s long-term aim which, in the period since TILA-99, has been to develop an understanding that will enable it to adapt the details of its disposal concept to the conditions at Olkiluoto and to develop analysis tools for the PSAR (Preliminary Safety Assessment Report), which will support the application for a construction licence for the disposal facility. In Chapter 3 the future RTD programme is presented in relation to Posiva s overall goal for this programme over the next three years, which is to make a smooth and timely progress towards the maturity needed for submitting the application for the construction licence for the disposal facility in 2012 assuming that the suitability of the Olkiluoto site for the repository can be confirmed. The discussion of the future RTD programme is presented in a similar manner to that of the current state of the programme, in that it covers the design and construction of the ONKALO, developments in design and technology, future developments in the safety case, increasing site knowledge and understanding, and increasing the understanding of both the repository near- and far-fields.

4 Much of the description of the future site investigation and monitoring programme is, as would be expected, related to the development of the ONKALO, and there is extensive discussion regarding the site modelling that is to take place. A description is presented of an alternative disposal concept, KBS-3H, which Posiva is investigating jointly with SKB. In fact, in many areas of development, particularly in design and technical development, but also in the development of the safety case, in biosphere modelling and in increasing understanding of the near- and far-fields, there can be seen to be extensive co-operation between Posiva and SKB. Posiva s involvement in international collaborative projects, particularly in relation to near-field and far-field processes, is also described. Chapter 4 of the report presents the RTD programmes for nuclear wastes from the Olkiluoto and Loviisa power plants and Chapter 5 discusses the division of responsibilities between Posiva and the two power companies and other matters, such as QA.

5 TKS-2003; OLKILUODON JA LOVIISAN LAITOSTEN YDINJÄTEHUOLTO: TUTKIMUS-, KEHITYS- JA TEKNISEN SUUNNITTELUTYÖN OHJELMA VUOSILLE TIIVISTELMÄ Käsillä oleva raportti sisältää katsauksen Posiva Oy:n sekä sen omistajayhtiöiden, Teollisuuden Voima Oy:n ja Fortum Power and Heat Oyj:n viime vuosina tekemään ydinjätehuollon TKStyöhön sekä suunnitelman seuraavien vuosien toiminnalle keskittyen ajanjaksoon Tarkoitus on, että vastaavansisältöinen ohjelma toimitetaan vastedes säännöllisesti kolmen vuoden välein. Raportti käsittää sekä Posivan ohjelman käytetyn polttoaineen loppusijoituksen TKS-työlle että vähä- ja keskiaktiivisiin ydinjätteisiin ja käytöstäpoistoon liittyvän TKS-ohjelman, josta molemmat voimayhtiöt huolehtivat itse. Luvussa 1 kuvataan lyhyesti Suomen ydinvoimaloiden ydinjätehuollon periaatteet ja esitetään eri ydinjätteiden loppusijoitusratkaisut. Luku 2 sisältää laajahkon katsauksen käytetyn polttoaineen loppusijoituksen viimeaikaiseen TKS-työhön. Luvun aluksi selostetaan ne lähtökohdat ja periaatteet, joihin nykyisen vaiheen TKS-työn sisältö ja painotukset perustuvat. Tässä yhteydessä esitellään Posivan nykyinen turvallisuuskonsepti KBS-3 tyyppiselle loppusijoitusratkaisulle ja konseptin yhteys loppusijoitusjärjestelmälle asetettavien vaatimusten hallintaan. Ohjelman taustaksi esitetään myös yhteenveto siitä palautteesta, jota Posiva on eri yhteyksissä saanut Säteilyturvakeskukselta ja heidän kansainvälisiltä asiantuntijaryhmiltään. Luvun 2 pääosa sisältää kuvauksen viime vuosina tehdystä käytetyn polttoaineen loppusijoituksen TKS-työstä jäsenneltynä samaan tapaan kuin voimassa olevassa pitkän aikavälin TKSohjelmassa (POSIVA ). Luvussa käsitellään maanalaisen tutkimustilan, ONKALOn, suunnittelun lähtökohtia ja suunnitelmien nykytilaa, loppusijoituslaitoksen ja loppusijoitusjärjestelmän kehitys- ja suunnittelutyötä, loppusijoitustilojen kallioympäristön geologisten, hydrogeologisten, pohjavesikemian ja kalliomekaniikan ominaisuuksien sekä biosfääriolosuhteiden selvittämistä samoin kuin turvallisuuden arviointiin tähtäävää tutkimusta. Kuvaus muodostaa yhteenvedon TKS-työstä, joka on tarkemmin dokumentoitu pääosin POSIVAraportteina ja Posivan työraportteina. Luku 3 sisältää ohjelman käytetyn polttoaineen loppusijoituksen seuraavien vuosien TKStyölle. Tavoitteena on edetä tasaisesti ja oikea-aikaisesti kohti pitkän ajan TKS-ohjelman tavoitetta, valmiutta jättää lupahakemus käytetyn polttoaineen loppusijoituslaitoksen rakentamista varten vuoden 2012 loppuun mennessä edellyttäen, että tehtävät tutkimukset varmistavat Olkiluodon soveltuvuuden loppusijoituspaikaksi. Teksti on jäsennelty samaan tapaan kuin kertomusosa, joskin tässä osassa on pyritty ongelmakeskeisempään esitystapaan. Erityisesti paikkatutkimusohjelmasta suuri osa liittyy ONKALOn toteutukseen, ja erityisesti tässä yhteydessä on korostettu tutkimuksiin liittyvää mallinnusta ja tulkintaa. Merkittävä osa tulevien vuosien TKS-työstä liittyy KBS-3H- ratkaisun kehittämiseen (loppusijoitussäiliöiden vaakasuuntainen sijoittaminen tunneleihin), jota Posiva tekee yhteistyössä Ruotsin SKB:n kanssa. Erityisesti kapselointi- ja loppusijoitustekniikan TKS-työssä SKB-yhteistyö

6 on muutoinkin laajaa. Posiva on laajasti mukana myös monissa muissa loppusijoitukseen liittyvissä yhteistyöhankkeissa, erityisesti EU:n puiteohjelmissa. Luvussa 4 käsitellään verrattain lyhyesti vähä- ja keskiaktiivisten jätteiden huoltoon ja voimaloiden käytöstäpoistoon liittyvää TKS-työtä. Viimeisessä luvussa 5 esitetään muutamia täydentäviä huomautuksia mm. ydinjätehuoltoon liittyvistä vastuista ja vastuunjaosta.

7 1 Contents Abstract Tiivistelmä Contents Introduction Nuclear waste management in Finland Disposal concepts Current stage of development Purpose and contents of the present report Current status of RTD for spent fuel disposal RTD needs and priorities Background to the Posiva RTD programme Framework for RTD programme planning and concept development The safety concept Strengths and protection against weak points Design requirements The ONKALO Introduction Design requirements Decision on type of access Selecting the location Layout at the main drawings stage The Underground Characterisation and Research Programme (UCRP) Disturbance caused by construction and operation of the ONKALO Design and technical development Description of the facility The encapsulation plant Canister development Canister design Canister manufacture Development of the copper shell manufacture Development of copper lid manufacture Development of the canister insert manufacture Sealing of the copper canister Canister quality assurance Inspection of canister welds Inspection of the canister Development of repository technology Preliminary design, stage Development of disposal techniques Operational safety Transportation of spent fuel Development of the alternative disposal concept KBS-3H Background Feasibility study Basic design Site understanding General understanding of the bedrock... 70

8 Baseline conditions at Olkiluoto Site investigations The bedrock model Modelling of structures Hydrogeology and hydrology Surface hydrology Hydraulic head Hydraulic conductivity Hydrogeochemistry Geogases and microbes present at Olkiluoto External factors affecting hydrogeological and geochemical evolution Rock Mechanics Rock Mass Classification Engineering rock mass classification Anisotropy of the rock mass Mechanical properties Thermal properties In situ stress Measurement of block-scale stability Understanding and characterisation of the biosphere and overburden Physical and chemical main characteristics of the site Overburden Flora and fauna Radioactivity in the environment Summary of the site characterisation programme Evaluation of site suitability Confidence in site assessments Safety case Background Focus and scope of Posiva The evolution of near-field conditions external to the canister THM processes Chemical evolution and interactions Repository-generated gas Colloids Microbiological processes Effects of freezing and thawing The characteristics and evolution of the canister Initial defects in the copper shell Copper corrosion processes Evolution subsequent to breaching of the copper shell Radionuclide release Retention and transport processes Solubility limitation Sorption and geochemical immobilisation Groundwater flow and advective transport Gas-mediated transport Colloid-facilitated transport Microbially-facilitated transport Model and code development and testing

9 Biosphere studies and safety and performance indicators Regulatory background Evolution of biosphere conditions at Olkiluoto Biosphere model development and testing Impact on non-human biota Additional safety and performance indicators Summary of studies supporting the safety case Future RTD for spent fuel disposal General framework Structure of the programme description Planned facilities The design and construction of the ONKALO Engineering Design Construction Coordination of Engineering, Investigations and Construction (CEIC) Monitoring the effects of ONKALO construction Design and technical development Design principles Design strategy Encapsulation technology Preliminary design: Encapsulation plant Canister development Repository technology Preliminary design, stage Development of disposal techniques Development and testing of the construction methods Buffer development Backfill development Rock mechanics analysis for repository technology Closure of the repository and sealing of the disposal site Engineered and stray materials in the repository Retrievability and long-term monitoring Development of alternative disposal concept KBS-3H Transportation of spent fuel Safeguards Developing the safety case Planning for the PSAR Elements of the safety case Initial state and pre-closure evolution of the disposal system Post-emplacement evolution of the disposal system Release and transport of radionuclides Development of assessment cases Understanding of release and transport Model development Uncertainties related to modelling Modelling exercises Increasing site knowledge and understanding General requirements of the site characterisation programme Introduction Objectives and purpose

10 Characterisation and research Integration Olkiluoto Site Characterisation Programme Site Descriptive Modelling Site characterisation activities Surface investigations Underground investigations Investigations for the monitoring programme Investigations for the extension of the potential repository area Overburden Environmental studies Site modelling Bedrock model Rock mechanics model Hydrogeological model Hydrogeochemical model Model integration Evolution of the site and the disposal system Assessment of site suitability Establishing a method for evaluating the site suitability During construction of the access tunnel to the ONKALO When considering the rock mass encompassing the ONKALO When considering the anticipated repository volume Increasing understanding of the repository near-field General requirements and international collaboration The evolution of conditions external to the canister THM processes Chemical evolution and interactions Repository-generated gas Colloids Characteristics and evolution of the canister Initial defects in the copper shell Copper corrosion processes Evolution subsequent to breaching of the copper shell Radionuclide release Evaluation of radionuclide retention and transport in the near-field Improving understanding of far-field processes Retention and transport in the bedrock The biosphere Evolution of biosphere conditions at Olkiluoto Radionuclide transport and distribution Evaluation of dose Impact on non-human biota RTD for other nuclear wastes Wastes from the Olkiluoto nuclear power plant General Research and development Progress in waste management Operating waste management Decommissioning

11 Programme Operating waste management Decommissioning Wastes from the Loviisa nuclear power plant Introduction Spent fuel management in Management of operating waste in Solidification plant Second stage of the VLJ Repository Treatment of dry operating waste Technical studies on concrete Decommissioning investigations in Plants to be made independent during the decommissioning Updating the scope of dismantlement of the contaminated material Activity and scope of dismantlement of the biological shield, and updating of its dismantling plan Updating of the activity inventory Asbestos study Constructions and sealing of the repository A proposed standardised list for costing purposes in the decommissioning created by the OECD/NEA Ensuring readiness for carrying out the safety analysis and decommissioning studies Preliminary plans in Management of spent nuclear fuel Management of operating waste Decommissioning investigations Supplementary remarks References

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13 7 1 Introduction 1.1 Nuclear waste management in Finland According to the Nuclear Energy Act, all nuclear waste generated in Finland must be handled, stored and permanently disposed of in Finland. The two nuclear power companies, Teollisuuden Voima Oy (TVO) and Fortum Power and Heat Oy, are responsible for the safe management of the waste and for all associated expenses and have established a joint company, Posiva Oy, to implement the disposal programme for spent fuel, whilst other nuclear wastes are handled and disposed of by the power companies themselves. The principles of the policy on nuclear waste management were originally defined in a Government decision in Following the revision of the nuclear energy legislation in 1987, it is the Ministry of Trade and Industry (KTM) which defines the principles and time schedules for nuclear waste management, and the Ministry has subsequently redefined the overall policy in its decisions of 19 March 1991, 26 September 1995 and 23 October Most of the policy principles are similar to the 1983 decision and provide a basis for both the practical implementation of nuclear waste management and for the research and development related to the eventual development of a repository for spent fuel. The construction and operation licences for nuclear facilities can be granted by the Government but, before actual licensing can take place, a policy decision called the Decision-in-Principle (DiP) needs to be approved by the Parliament. The Radiation and Nuclear Safety Authority, STUK, is responsible for the control and supervision of activities involving radiation; and in this role they are advised by the Nuclear Safety Board and its committee for nuclear waste. Nuclear waste is defined in the Nuclear Energy Act as radioactive waste in the form of spent fuel or in some other form, which is generated in connection with or as a result of the use of nuclear energy. Spent fuel management is based on the once-through cycle and, hence, aims at its direct disposal without reprocessing. The solid and liquid wastes arising from the controlled area of a nuclear power plant (NPP), which contain mainly short-lived beta and gamma emitters, are grouped into the following two activity categories: Low level waste (LLW) contains so little radioactivity that it can be treated at the NPP without any special radiation protection arrangements. The activity concentration in waste is, as a rule, not more than 1 MBq/kg, Intermediate level waste (ILW) contains radioactivity to the extent requiring effective radiation protection arrangements in its treatment. The activity concentration in the waste is, as a rule, from 1 MBq/kg to 10 GBq/kg. The regulations allow conditional (case-by-case) or unconditional removal of control (clearance) provided that certain criteria are met. Mass and surface specific limits for unconditional removal of control are given in the regulations. The limits can be applied for limited waste quantities not exceeding 100 tonnes/year for one NPP or other nuclear installation.

14 8 In addition to spent fuel and wastes from the NPP operations, the decommissioning of the facilities gives rise to nuclear waste and the NPP operators have to maintain technical plans for decommissioning and disposal of the waste arising. 1.2 Disposal concepts The low and intermediate level wastes from NPP operations are disposed of in the bedrock at the power plant sites. TVO s Olkiluoto repository consists of two silos at a depth of 60 to 95 m, one for bituminised ILW and the other for solid LLW (Figure 1-1). The silo for bituminised waste is lined with a thick layer of concrete. The Loviisa repository is located at a depth of approximately 110 m and consists of two tunnels for solid LLW and a cavern for immobilised ILW (Figure 1-2). This cavern has been excavated but, to date, no ILW has been emplaced. The plans for the disposal of spent fuel are based on the KBS-3 concept, which was originally developed by the Swedish SKB. In this concept, spent fuel elements are encapsulated in metal canisters and emplaced at a depth of several hundreds of metres (Figure 1-3). A bentonite clay buffer is installed between the rock and the canisters and, after emplacement of spent fuel canisters is complete, all access routes from the surface to the disposal tunnels are backfilled and sealed, following which the repository needs no further control or maintenance. Control building Transport tunnel Shaft LLW Silo Excavation tunnel ILW Silo Figure 1-1. The Olkiluoto VLJ Repository for low- and intermediate-level wastes from reactor operation.

15 9 Figure 1-2. The Loviisa Repository for low- and intermediate-level wastes from reactor operation. Figure 1-3. The KBS-3 concept for the disposal of spent fuel.

16 Current stage of development The current stage of development of the Finnish nuclear waste management programme can be summarised as follows: For the disposal of low- and intermediate-level waste (L/ILW), repositories are in operation both at Olkiluoto and Loviisa (in Loviisa no ILW has as yet been emplaced). For spent fuel, a DiP regarding disposal was approved by the Parliament in According to this decision, a spent fuel repository can be developed on the basis of a KBS-3 type concept and sited at Olkiluoto in the municipality of Eurajoki. The spent fuel elements will be stored at interim storage sites at Olkiluoto and Loviisa until the repository is available for use. At present, Posiva is preparing for the start of construction of an underground rock characterisation facility at Olkiluoto (the ONKALO). The plan is that, on the basis of underground investigations and other RTD (Research, Technical Design and Development) work, Posiva will submit an application for a construction licence for the disposal facility in the early 2010s, with the aim of starting disposal operations in The KTM has given its decision on the targets to be met in preparation for geological disposal (decision 9/815/2003). According to this decision, Posiva should be prepared to present the studies and plans necessary for a construction licence by the end of In addition to this target, the Ministry also requires that, in 2009, Posiva should deliver a report that indicates the level of maturity of the material that is necessary for this licence. 1.4 Purpose and contents of the present report The Nuclear Energy Act requires that the nuclear power companies submit each year a programme to the KTM which gives a detailed account of the planned nuclear waste management activities over the next calendar year and an outline of the activities for the next five years. In addition, every year the power companies have to prepare a report of the activities carried out during the previous year. These reports have been published both in Finnish and English, whereas the programmes have been produced only in Finnish. A specific reporting schedule for the spent fuel disposal programme was first provided in the 1983 decision by the Government and later slightly modified in the KTM decisions of 1991 and According to these decisions, progress reports had to be submitted to the KTM at specified times before final site selection took place. After the siting decision and the DiP, activities entered a new phase, and Posiva prepared a programme for these activities covering the RTD work that was foreseen over the period leading up to the submission of the construction licence application (Posiva 2000). The programme defined the main objectives that needed to be achieved before the application could be submitted and explained how Posiva intended to proceed towards them. One of the main activities in the spent fuel disposal programme will be the construction of the ONKALO and specific planning documents have been prepared and published on the ONKALO during The documentation includes the underground characterisation and research programme (UCRP), which explains the main goals, activities and expected results

17 11 of the underground rock characterisation work during the period preceding the submission of the construction licence application. The present report provides the RTD programme related to the management of nuclear waste from the Finnish nuclear power companies, and aims to place RTD planning in a logical framework 1. The focus is on the activities that are planned for the next three years, but a review of the current status of the programme is also provided, in order to place the future programme in its appropriate context. For spent fuel disposal, in particular, the idea is to provide a description of how the future RTD programme is staged, so as to enable a smooth progress towards the goals stated in the framework programme in Presenting the programme in this manner should enable external review and discussion of the objectives, the achievements and the future emphases of the programme to take place. In this way, dialogue should be promoted between the various stakeholders on issues related to the process of disposal system development. The intention is to produce a similar report every three years, the next one in The main contents are as follows. Chapters 2 and 3 are devoted to the programme for spent fuel disposal. Chapter 2 deals with the progress since the time of the DiP and the current status of work, and Chapter 3 describes the future programme. Chapter 4 describes the planned activities related to other nuclear wastes from the Olkiluoto and Loviisa nuclear power plants. Some supplementary remarks follow in Chapter 5. 1 The title of this report,tks-2003, stands for the Finnish words meaning Research (tutkimus), Development (kehitys) and Technical Design (suunnittelu); i.e. it has a similar meaning to RTD.

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19 13 2 Current status of RTD for spent fuel disposal 2.1 RTD needs and priorities Background to the Posiva RTD programme The RTD programme for spent fuel disposal was presented in Posiva (2000) and covers the period before the submission of an application for a construction licence. It therefore has the overall goal of establishing the necessary knowledge base and programme maturity needed in order to submit a successful application for a construction licence for a disposal facility assuming that the suitability of the Olkiluoto site for the repository can be confirmed including the production of the PSAR (Preliminary Safety Assessment Report). An important part of the programme is the planning, technical design and construction of the ONKALO, and the investigations that are to be carried out in it. The programme was also formulated to address the comments and recommendations received from the Finnish Nuclear and Radiation Safety Authority (STUK) and their review group on the application for the DiP in 1999 (STUK 2000). Three areas of development were considered of particular importance: the development of the avoidance strategies (how suitable rock volumes for repository tunnels and deposition holes can be identified and unsuitable rock can be avoided), the current stress situation in Olkiluoto, and the safety strategy (how RTD activities should be prioritised to address the most important areas regarding long-term safety). STUK and their international expert team reviewed the programme (STUK s letter Y811/35 to KTM, 26 September, 2001). Most reviewers found the overall programme well thought out and well structured. The division into different stages was found to be logical, even if there were some overlaps and imbalance between individual chapters. The reviewers also identified several RTD needs and made other general comments. These are briefly outlined below: There is a need for a logical framework for RTD planning. The guiding principles for developing the needs of the RTD programme should be stated, as well as the means applied for identifying and prioritising these needs. Adequate time is needed to collate and assess data, integrate it into a performance model and have the model and its conclusion approved by audit. One could envisage an iterative prediction-confirmation programme in the Olkiluoto characterisation work. Once sufficient understanding of the existing situation could be demonstrated, the exercise would evolve logically to predictions that could be tested in shafts and tunnels. Posiva should develop a basic data accessibility plan in consultation with STUK, in order to enable external review.

20 14 A Baseline Report on Olkiluoto is judged to be essential - the main argument here being that Baseline conditions need to be defined before construction of the ONKALO commences. The previously used wording that the ONKALO should confirm predictions made from the surface is misleading. The objective of the ONKALO is to allow the exploration of conditions underground and at scales unattainable from surface-based investigations. Some reviewers expressed a need for further regional studies, mainly motivated by a view to reassess the regional tectonic framework. There is a need to consider transport characterisation also in this phase of work. Quantitative flow and transport modelling forces one to address all-important issues from the outset and makes inconsistencies less likely to occur. There is a need to develop a better understanding of how the composition of the groundwater is changing and how it will change in the future and to take account of interactions between geochemical and hydrogeological processes. Special studies are also required on how the exposure of rock may result in it losing its reducing capability. Calculations are required that consider the primary porosity and not the whole rock in determining its redox buffering capacity. Copper corrosion in the chemical conditions prevalent at Olkiluoto may require additional attention. In this context special emphasis also needs to be placed on the occurrence and significance of ammonium at Olkiluoto. Interactions amongst barrier corrosion products involving copper and iron corrosion products and fuel need to be studied. Buffer and bentonite performance under the chemical conditions prevalent at Olkiluoto is also a potentially important issue. Since the main functions of bentonite are to limit water permeation and to help prevent mechanical deformation of the canister, it was also recommended that the bentonite should no longer be described by the somewhat inappropriate term buffer, as this could be misleading. Most of these RTD needs and general comments have been taken into account in the planning of current and future activities (although the term buffer has been retained). The programme for the ONKALO, as outlined in the UCRP report (Posiva 2003a), the Baseline Report (Posiva 2003b) and the Monitoring Programme (Posiva 2003c) address many of them. The purpose of this report, as is explained in Chapter 1, is to respond to the first point of criticism concerning the framework for programme planning. The framework for RTD programme planning is described in Chapter A key requirement is that of safety and, in Posiva's view, as explained in Posiva (2000), RTD needs and priorities should be based on the need to build support for the safety concept, which is the conceptual understanding of how safety as defined by the regulatory criteria is provided by a given technical concept. The safety concept corresponding to the current disposal concept is described in Chapter The strengths of this concept, and the potential weak points against which protection must be provided, are discussed in Chapter