Shankar Menon
Programme Co-ordinator
OECD/NEA Co-operative Programme on Decommissioning

The OECD Nuclear Energy Agency’s Co-operative Programme on Decommissioning was established in 1985 to share the experience and information emerging from on-going decommissioning projects. The main aim of the Programme is to gather and collate such data, which can then provide the basis for planning the future industrial phase of decommissioning of commercial nuclear plants. After the first two five-year periods, the Programme Agreement has been extended for another five-year period in 1995.

Starting with 10 decommissioning projects in 1985, today the Programme has 35 participating projects from 13 countries. Apart from exchanging information, task groups have been set up within the Programme for in-depth analysis and studies of areas of common interest. Among the areas now being studied by such groups are the recycling of material from decommissioning projects and decommissioning costs.

This paper will describe the structure of the Programme and the manner in which it operates. The main characteristics of some typical projects are given to illustrate the variety and breadth of the information being generated. Some of the results of the work in the task groups will be presented.

The Co-operative Programme on Decommissioning was established by the Nuclear Energy Agency (NEA) of the OECD in 1985. The basic scope of the Co-operative Programme is the exchange of scientific and technical information obtained from major decommissioning projects in member countries of the OECD.

Since its start in 1985 with 10 projects from 9 countries, the Programme has grown considerably and now covers 35 projects and has 25 participating organisations from 13 countries. In addition, the Programme is actively supported by a number of international organisations.

The Programme is carried out under an agreement between the participating organisations. The original agreement in 1985 was for a five year period. It was renewed for a second period in 1990 and again for a third five year period in 1995. The Co-operative Programme has been described in two major reports [1, 2], issued at the end of the first and second five year periods respectively.

The countries and the respective organisations participating in the Programme are listed in Table 1. As will be noted, the membership represents a wide range of types of organisations in the nuclear field, such as research institutions, power companies, governmental departments, waste management companies and power plant suppliers. The characteristic common to these organisations is that they all are engaged in or are actively planning decommissioning of nuclear plants. The Commission of the European Communities is a member of the Programme. The International Atomic Energy Agency and UNIPEDE participate as observers, providing a reciprocal exchange of information as well as avoiding an unnecessary duplication of efforts.

The Programme is executed under the general direction of the Radioactive Waste Management Committee of the NEA and the Programme agreement is implemented by the Liaison Committee (LC), where all the participating organisations are represented. The Chairman of the LC is elected by its members, while the NEA is responsible for the functions of its secretariat. Sweden has undertaken the responsibilities of co-ordinating the Programme.

The central forum for the exchange of information between the participating projects is the Technical Advisory Group (TAG), where the Programme Co-ordinator functions as the secretary. For making in-depth studies of specific topics of interest, the Programme has established a number of task groups of specialists.

The projects in the Co-operative Programme represent a wide variety of decommissioning projects, ranging from experimental or demonstration nuclear reactors and commercial scale power plants to pilot or full size fuel reprocessing plants.

The full list of the projects in the Programme is shown in the tables in Table II. Of the 35 projects listed, 12 projects have been completed. Of these eight have been decommissioned to Stage 3, while the other four are in a dormant state (Stage 1 or a variant thereof or Stage 2).

A perusal of the list of projects shows that:

• the Programme covers 24 reactors, seven reprocessing plants, two fuel material plants, one isotope handling facility and one fuel storage/transfer pond,
• the reactors represent a wide selection of types such as BWR, PWR, PHWR, Gas-cooled/D2O-moderated, water-cooled/D2O-moderated, GCR, AGR, VVER and HTGR, as well as sodium cooled FBR,
• 21 of the 35 are to be, or have been, decommissioned to Stage 3, namely total dismantling.

Many of the earlier projects in the Programme had to do with experimental or prototype plants. The projects which have joined the Programme at a later date have, for understandable reasons, concerned plants of a more standardised and commercial character. Even so, there are still significant differences that can be seen in the planning and execution of decommissioning projects. Apart from the differences that can be expected due to the variation in type of plant, the organisational, economic, regulatory and other circumstances prevailing at each site can strongly influence the decommissioning projects. This is illustrated in the following brief descriptions of some of the projects in the Programme.

The plant was originally owned by a 13-nation consortium but was transferred in stages to Belgian ownership after shutdown in 1975. The site has been transformed into a centralised waste processing facility and is also being used as a centralised interim storage for conditioned radioactive waste. The company Belgoprocess was established to take charge of activities on the site, including the decommissioning project.

Some of the features characterising the project are:

• It is being planned and executed by an in-house team over a relatively long period.
• Before embarking on the major project of dismantling the reprocessing plant itself, a pilot project was carried out to check techniques and costs and to train personnel. This involved the emptying and decontamination to release limits of 2 small storage buildings.
• There is on-going purpose-oriented development work on techniques for solving project problems. This has resulted in significant advances in areas such as
• Concrete decontamination: The early work was concentrated on scabbling and then, when the productivity figures with scabbling were lower than expected, with shaving using a diamond tipped rotary cutting head. This latter technique gives a smooth surface (easier for release measurement), is faster, produces less secondary waste and is more comfortable for workers.
• Decontamination of metallic components by dry abrasive blasting. About 85 % of the metallic structures and components are expected to be decontaminated to unconditional release levels.
• Ventilated suits and associated equipment for worker protection in alpha contaminated areas.

BR3 was the first European (West) PWR and its decommissioning is an EU supported project. The first phase (1989-92) of the project involved:

• the chemical decontamination of the primary loop for dose reduction,
• testing of three different cutting techniques on the thermal shield in the reactor vessel.

Decontamination of the primary loop was completed in April 1991. The Siemens CORD process was used in three cycles and achieved a total average decontamination factor of 10 (40 in the steam generator). The decontamination resulted in 1.3 m³ of cation and anion resin as secondary waste.

The three cutting methods tested were:

• mechanical sawing,
• electro-discharge machining (EDM),
• plasma arc cutting (in a flooded cutting chamber).

Phase 2 of the project (1993-94) covered the removal and segmentation of all the other vessel internals. The main lesson learnt from the comparison of cutting methods was that mechanical cutting produced less secondary waste than plasma arc cutting or EDM and that its cutting speed was acceptable. So various types of mechanical cutting were used to dismantle and segment the reactor internals, including:

• circular saw,
• band saw,
• reciprocating saw,
• hydraulic shears.

EDM was used as a back-up technique and for "surgical" work.

As a complement to Phase 2, the first set of vessel internals (replaced in 1964) was segmented to gain experience on material with a 30-year cooling period.

The project is also developing methods for the decontamination of contaminated metals to (unconditional) release levels. Both chemical and wet abrasive methods have been tested. Decontamination and dismantling techniques for concrete are also tested and compared on slightly activated pieces.

A Phase 3 has been started to dismantle the primary system, including segmenting of the reactor vessel and the surrounding neutron shield tank.

G2 and G3 were two gas-graphite reactors that operated between 1958 and 1980. The decommissioning project resulted in a Stage 2 decommissioning, with the core and other internals enclosed in the concrete pressure vessels while the steam generators and the external circuits were dismantled and removed.

The main activity in the project was the dismantling and recycling of the material in the external circuits consisting of 1500-2000 t of carbon steel in each reactor. The INFANTE electric arc melting facility was built at the G2/G3 site for melting the contaminated material from the circuits. Graphite and ferro-silicium were added for producing cast iron in the form of 25 kg ingots or 3.8 t blocks.

A total of about 4600 t of scrap steel was melted at INFANTE between April 1992 and the middle of 1994. The ingots and blocks are stored at the facility awaiting dispatch to a very low level waste facility (yet to be built) or for a recycling project within the nuclear industry. INFANTE is being decommissioned. A new electric induction furnace is being built adjacent to the INFANTE site.

AT-1 was the pilot plant for reprocessing fast breeder fuel from Rapsodie and Phénix. The plant was shut down in 1979. The decommissioning project, which is part-funded by the EU, was started in 1982 and is expected to be completed in 1999.

A reusable modular alpha-tight workshop was used in dismantling the lightly shielded cells and gloveboxes. After this followed the dismantling of the accessible hot cells, with direct access work using biological shielding.

The most interesting aspect of this project was the use of the remote dismantling machine, the ATENA, for work in the high active cells. ATENA was installed on the floor of the dismantled accessible hot cells, from where it used its 6 m long articulated arm for dismantling work in the "blind" hot cells, with suitable manipulators. This phase, which was carried out between 1990 and 1992, was followed by the dismantling of the storage and workshop cells, including the ATENA maintenance cell.

Since 1995, the general clean-up of the cells has been going on, including the decontamination of the concrete walls. This has included taking drilled out core samples in some cells, to check the penetration of contamination in the walls.

Comparisons have been made using the acquired data between manual and robot dismantling, taking into account the doses to personnel, discomfort factors in ventilated suits as well as costs.

The KKN Niederaichbach plant was a 100 MWe gas cooled, heavy water moderated reactor. It operated from 1972 to 1974 and was placed in a safe storage status in 1981. Due to long drawn-out processes and objections by intervenors, the license for dismantling to a Stage 3 status was granted only in 1987.

A main feature of the decommissioning project was the use of a purpose designed, remote controlled dismantling machine for removing the activated components in the core. The high precision, rotary mast type machine with its manipulator used many techniques for dismantling all the internals of the vertically oriented pressure tube assembly. Among the techniques used were:

• grinding,
• plasma torch,
• abrasive disc cutters,
• screw removal,
• vacuum cleaning.

The remote dismantling of the core region and segmenting these components took place between November 1990 and March 1993. These components amounted to 522 t with a total activity of 8.6 x 10¹² Bq. They were packaged into 139 containers ready for disposal at the Konrad repository when it becomes operational. About 20 per cent of this metal is below 200 Bq/g. This fraction has been sent to the Siempelkamp melting facility for recycling within the nuclear industry.

The next project activity was the removal of all activated structures during the period April-November 1993. All the surfaces in the building were then decontaminated, about 200 000 surface measurements made, checked by the inspection and environmental authorities, after which the site was released from "atomic" regulation. The building and stack were demolished and the site achieved "green field" status in July 1995.

An interesting feature of the KKN project was that it was performed on a turnkey contract with a main contractor.

The MZFR was a 200 MWt PHWR that operated at Karlsruhe from 1965 to 1984. The plant is being decommissioned to a Stage 3 status in consecutive stages, each stage being required to be licensed separately.

The dismantling of the MZFR will involve the removal of about 72 000 t of concrete and 7200 t of metal. About 1000 t of the concrete and 1680 t of metal will have to be classified as radioactive waste.

Five stages of the project have been completed to date, including the dismantling of the conventional plant. The 150 t turbine and the 130 t generator will be reused.

The fourth license covered the dismantling of systems in the auxiliary building as well as the decontamination of the primary circuit. The aim of the decontamination was to bring as much as possible of the contaminated material under 200 Bq/g. This is currently the upper limit for material that can be melted at the Siempelkamp CARLA facility in Germany. Material under such activity levels will be recycled within the nuclear industry.

The licence for the sixth stage has been granted in April 1997. This will cover the dismantling of the primary systems and all reactor support systems inside the reactor building. On the completion of this stage in 1999, only the reactor pressure vessel and its internals will remain in the reactor hall. The remote removal and segmenting of the reactor vessel and its internals will be covered by the seventh licence, which is currently under preparation. The eight and final licence will cover the decontamination, release measurements and demolition of the buildings.

There are eight Russian pressure water reactors type VVER at the nuclear power station, owned by Energiewerke Nord (EWN), Greifswald. Four had been in operation, one was in start-up, one ready for start-up and two under construction when the decision was taken in 1990 to decommission and dismantle the station.

The reactors are built as double-units with each pair of reactors having common secondary systems and one turbine hall for all the reactors. The secondary heat was used for the district heating system of Greifswald town.

The Greifswald decommissioning project is very significant for several reasons including the following:

• It involves the decommissioning to site release without radiological restrictions of a nuclear power station that had delivered about 17 000 MW-years of electricity.
• There are today already a number of similar reactors (VVERs) ready for decommissioning.
• A central idea in the project is to cut out and remove large integral components from the reactor building into an intermediate storage, where they can be treated (decontaminated or segmented) later.
• The power station had earlier been the biggest source of employment in the district. With the termination of both construction activities and power generation, there has been a drastic reduction in the work force. This has also led to the adoption of the philosophy of executing as much as possible of the decommissioning work with in-house capabilities.

The intermediate storage facility for fuel and decommissioning waste is being constructed. Storage hall Nr 7 has been taken into operation for receiving low active (<100 Bq/g) metallic components removed from the plants.

When the reactors were shut down, there was fuel in three of the reactors, in four of the fuel pools as well as in the central wet storage facility. As all fuel will have to be in castor casks at the interim storage facility by the end of June 2000, the casking of fuel has been one of the high priority tasks in the project.

The Japan Power Demonstration Reactor (JPDR) was a 90 MWt BWR that operated between 1963 and 1976. The aims of the decommissioning project, which was started in 1981, were to gain hands-on experience on dismantling, develop/demonstrate suitable technologies and to obtain project-based data on certain practical aspects such as radiation exposure, waste arisings, costs, etc.

The project started with a 5-year research and development programme on various techniques of interest and the preparation of a decommissioning plan. The development work continued even after decommissioning activities started on site in 1986, now concentrating on large scale mock-up tests on various techniques.

The JPDR decommissioning project was characterised by the number of techniques that were used and demonstrated during the various operations. The internals of the reactor vessel were removed using a plasma torch. The pipes connected to the reactor vessel were cut using shaped explosive charges and disc cutters. An arc saw was used to segment the reactor vessel. Diamond sawing and coring techniques, abrasive jets and controlled blasting were utilised when demolishing the biological shield. A variety of techniques was used in the decontamination of concrete surfaces.

The JPDR was decommissioned to a Stage 3 green field condition in 1996. The database collected and accumulated during the project is now being analysed and used in a research and development programme for the future decommissioning of commercial nuclear power plants.

The Windscale Advanced Gas-Cooled Reactor (WAGR) was a 100 MWt prototype reactor that operated between 1962 and 1981. Its decommissioning, which is part-funded by the EU, is being run as a demonstration project for United Kingdom reactors.

The high specific activity vessel internals will be dismantled by a remote controlled, centrally placed dismantling machine (RDM). A waste transfer route has been established by jacking up two steam generators thus allowing the transport of dismantled components from the reactor cavity to a purpose-built waste packaging building.

The four heat exchangers were lifted out of the station as single units, taken on high-technology transporters to the Drigg repository, where they were grouted in situ, internally and externally.

The execution of the project has been significantly affected, first by the withdrawal of CEGB financial support in 1988 and later by the re-organisation of the UKAEA during the last few years. AEA-Technology has been floated as a private company on the stock market and were appointed managing agents for the owners, UKAEA, on the WAGR project. Later the Remote Dismantling Operations contract has been let to Magnox Electric plc. Quite recently, the project management has been transferred from the AEA-T Management Agency to a UKAEA team with Magnox Electric as the prime contractor.

The B204 plant at Sellafield was built for reprocessing uranium metal fuel and later converted to reprocess oxide fuel. It operated between 1952 and 1973. The current decommissioning project is aimed at placing the plant in a Stage 2 decommissioning status, where the primary plant will be dismantled, the structures will be decontaminated to meet low level waste disposal criteria and left for demolition at a later date.

The project is characterised by its division into nine phases, funding for each of which has to be sanctioned separately. The project is managed by the BNFL Decommissioning Unit, where each phase is divided into project packages which are awarded by competitive tender.

The first three phases of the project have been completed:

• Phase 1: Construction of a waste handling facility/provision of decommissioning equipment for the Medium Activity Cell North (MAN).
• Design studies for remaining project phases.
• New filtered cell ventilation.

Currently, the MAN cell is being dismantled from the upper levels downward (Phase 4) and the active commissioning of the equipment for emptying the stainless steel hulls silo (Phase 5) has been started.

The Fort St Vrain plant was a 330 MWe high temperature gas cooled reactor and was therefore the first and only one of its kind to be operated as a commercial reactor. It operated between 1976 and 1989. The owners of the plant, Public Service Company of Colorado, decided to immediately decommission to a Stage 3 status after comparison with the option of safe storage over 55 to 60 years.

The decommissioning activities were started in July 1992 after defuelling to a purpose-built intermediate storage facility on site. The project was completed in November 1995. Some of the interesting features of the Fort St Vrain decommissioning project were:

• Fixed price contract based on competitive bidding.
• Removal of the head of the prestressed concrete pressure vessel in twelve wedges using a diamond wire saw.
• Filling of the pressure vessel with water after sealing of all vessel penetrations.
• Segmenting/dismantling of internal components under water.
• Its short dismantling period (39 months).
• Its success in its relations to the public by effective communication with the local community, the media, state government and regulatory officials.

The site has been converted into a thermal power plant with a gas fired boiler.

The Co-operative Programme covers 35 decommissioning projects. The characteristics of 11 of these have been briefly described above. The projects described have been chosen to illustrate the varying circumstances and the variety of problems facing the projects. Each of the other projects has also its special aspects affecting the way in which that project is executed.

As mentioned earlier, the main function of the Co-operative Programme is the exchange of information and experiences between decommissioning projects. This takes place at meetings of the Technical Advisory Group, which is made up of project managers or senior technical representatives of projects. The Programme Co-ordinator is the secretary.

The TAG meets twice a year, generally at the site of one of the projects. Each meeting lasts at least 2 days, allowing full and open reports from projects. The reporting covers technological, economic as well as political aspects. As is illustrated in the previous chapter, there is a sufficient variety of projects to cover most types of problems than can be encountered in decommissioning.

Due to the wide variety of projects and also because of the different prevailing circumstances and needs at the various projects sites, the type of information produced and reported is quite diverse. In order to facilitate the exchange of such diverse information, the projects are encouraged to report their technical progress under the following headings:

• activity inventory,
• decontamination methods,
• cutting techniques,
• remote operations,
• radioactive waste management,
• health and safety.

During its 12 years of operation, the number of projects in the Programme has increased from 10 to 35. This has not (yet) become a problem at meetings of the TAG. Firstly, 12 projects have been completed. The intensity of work in certain other projects is not very high. So, by a suitably planned organisation of the meetings, it has been possible to cope. It is indeed conceivable that the Programme can continue to expand.

It was apparent, after the first few meetings of the TAG, that there were a number of specific issues of general interest that required in depth concentrated analyses for which the TAG was not the most suitable forum. This was both due to the limited time for the TAG meetings and due to the fact that such issues required the work of specialists.

Special groups (Task Groups) were therefore established for making such studies/analyses. These have been on:

• costs,
• recycling and reuse,
• decontamination in connection with decommissioning.

These function very differently from the TAG. They are strictly "working" groups, so they do not have too large a number of members. Their work is not limited to exchange of information for mutual benefit but can sometimes also include the formulation of common opinions. One instance of this is taking place in the work of the Task Group on Recycling and Reuse. The projects in the Programme jointly represent the largest group of "producers" of candidate material for recycling. The Task Group has become a voice for collectively expressing its views on the criteria that are being discussed today for the release of material without radiological restrictions.

The work of two of these task groups is briefly described below:

It was noted that costs were being calculated on widely varying bases for the various projects. During a first study, cost data from 12 projects were used to establish a basis for the comparison of costs [3]. From this comparison it was possible to gain a better understanding of the distribution of costs in decommissioning projects. Another important achievement of the first study was the production of a "standardised" list of cost items and cost groups that can be used as a framework for all decommissioning projects.

The work of this group was re-started recently to broaden the scope of the study by including many major cost studies made on commercially operating power plants. An interesting development has been the co-operation that has developed between the NEA Task Group and similar groups at the International Atomic Energy Agency and the European Commission as well as the US Departments of Energy and Defence and the US Environmental Protection Agency, with the aim of achieving an internationally accepted ("standardised") listing of decommissioning cost items. The NEA Task Group and its listing is acting as the hub of this co-operation.

This Group was established to examine the means for minimising wastes for disposal arising from decommissioning operations together with maximising the recovery of valuable materials. The study has been completed with regard to metallic materials and is to be continued looking at non-metallic materials.

It has been concluded that, after treatment, significant quantities of materials generated from decommissioning can be recycled and reused. Indeed, recycle and reuse options provide a cost effective solution to the management of materials arisings. The most significant impediment to the use of recycle and reuse is the absence of consistent release standards within the nuclear industry. Several international organisations, like the IAEA and the EC, have proposed interim of draft standards with the object of agreeing to an internationally accepted set of release levels.

The current recommendations of international organisations are aimed solely at minimising radiological risks. No other risks have been considered. The NEA task group has attempted to view recycling in a broader context, evaluating both radiological and non-radiological detriments as well as social, economic and environmental aspects. This is seen to be fully in harmony with the ICRP concept that the justification of a practice should take into account the total detriment and not only the radiation detriment. The Task Group has found that the non-radiological risks associated with the replacement of material are much higher (nearly twice) than those associated with recycling. Moreover, the Task Group has considered the beneficial aspects of recycling, such as conservation of natural resources and protecting the environment [4].

In the last few years, there has been an increased recognition of the need for the regulation of industries, where naturally occurring radioactive material (NORM) is handled, in many cases leading to the technological enhancement of the concentration of radioactivity in the products or by-products of various industrial processes to significantly high levels. One of the main aims of the continued activities of the Task Group will be the adoption of internationally recognised, consistent rules for regulating release standards for radioactivity in the fields of both nuclear power and NORM.

The International Co-operative Programme was established to promote the industrialisation of the decommissioning of nuclear facilities, by providing a forum for the exchange of information and applications related experience between major decommissioning projects.

During its 12 years of operation, it has grown from a programme covering 10 projects at start to 35 today. It is conceivable that the Programme can cope with a few more projects without overstraining the TAG, which is the forum for the information exchange.

During its first 12 years, the Programme has seen a progressive move from a phase of development and technical demonstration towards a more routine industrial-scale application of the technologies used. In spite of the extreme heterogeneity of the projects in the Programme, there has developed a considerable commonality between the various projects as regards sequence and methods for the decommissioning process. The work in the various Task Groups has shown that, in spite of widely varying local conditions, there is much to be gained by co-operation and common action, specially in such areas as waste treatment and waste minimising.

The increase in the number of participating projects in the Programme has made it one of the major forums today for the collection and dissemination of decommissioning information. The Programme has also developed into being a channel for the collective expression of the views of nuclear facility decommissioners, with hands-on experience of problems to be solved in the field.

The continued expansion of the Co-operative Programme is a recognition of the value of international co-operation for ensuring the safe, environmental friendly and cost effective decommissioning of nuclear facilities.

1. International Co-operation on Decommissioning
Achievements of the NEA Co-operative Programme, 1985-1990.
OECD Nuclear Energy Agency Paris 1992.

2. The NEA Co-operative Programme on Decommissioning.
The First Ten Years, 1985-95.
OECD Nuclear Energy Agency Paris 1996.

3. OECD/NEA Co-operative Programme on Decommissioning.
Report from the Task Group on Decommissioning Costs.
CPD/DOC (91) 4, June 1991 Paris 1991.

4. OECD NUCLEAR ENERGY AGENCY
Nuclear Decommissioning.
Recycling and Reuse of Scrap Metals.
OECD Nuclear Energy Agency Paris 1996.