Abdou 1 , P. Gierszewski 1,6 , M. Tillack 1 , M. Nakagawa 1,7 , J. Reimann 1,8 , D. Bartlit 3 , J. Grover 4 , R. Puigh 4 and R. McGrath 5. Nuclear Fusion , Volume 27 , Number 4. Get permission to re-use this article. Create citation alert. View access options below. You previously purchased this article through ReadCube. Institutional Login.
Log in to Wiley Online Library. Purchase Instant Access. View Preview. Learn more Check out. Abstract Abstract. Citing Literature. Volume 21 , Issue s2 December Pages Related Information. Close Figure Viewer. Browse All Figures Return to Figure. Previous Figure Next Figure. In addition, as long as fuel remains in the fuel storage pools, continuous manning of the unit with shift workers may be required, albeit with a reduced number. If consideration is given to adopting shorter refuelling cycles towards the end of the plant s life, the period required for cooling the fuel in the fuel storage pool is reduced.
Thus the pool can be emptied earlier than would otherwise be the case, reducing costs. As long as all infrastructure and provisions are in place, defuelling can be done as during plant operation. However, if removal of the fuel is delayed for a very long time, loss of qualified staff and necessary equipment could become a problem.
In some research and prototype reactors, defuelling is not a routine For example, depending on the reactor type: a b c No fuel storage pond may be available, Lifting equipment may not be capable of carrying fuel transport containers, Space may not be available for loading fuel elements into transport containers.
Developments worldwide have resulted in a situation where removal of spent fuel to off-site facilities may become a serious problem. For example, many NPPs and research reactors have been provided with fuel by a supplier from another country. Reactor operating organizations may have planned to return the spent fuel to the supplier which, however, in many cases will have become impracticable. As this situation was unforeseen, only a few of these reactor operating organizations have their own off-site spent fuel storage facilities.
In other cases, plans for a national fuel disposal facility have been seriously delayed [23, 24]. Therefore it is important for transition planning to consider what is to be done with the spent fuel. It may be necessary to consider constructing a spent fuel storage facility if no other alternative exists. This may have to be considered on a local, national or regional level.
Currently, some Member States consider the use of a spent fuel storage installation that is remote from the reactor and which uses dry or wet storage technology e. In addition to the removal of nuclear fuel it is very desirable to eliminate the possibility of criticality during the transition period. After removal, the systems should be flushed until residual contamination is below predetermined criteria and dried as appropriate. The criteria should be based on a regulations, b an assessment with respect to future decommissioning worker safety, or c limiting degradation e.
Experienced personnel are also needed to deal with radioactively or chemically contaminated solids. This is particularly important when the handling equipment is immediately available. Important examples are materials remaining in hot cells that have working manipulators, materials in storage that require such hot cells for handling, items that are in ponds for shielding reasons, and alpha emitting items that require glovebox handling. It is also important that such operations are not unduly postponed even when handling equipment is not immediately available or not working.
In such cases, devising alternate removal means during the transition period is a priority. Organic fluids or hazardous chemicals used during operation, e. Radioactively contaminated organic and flammable fluids, as well as non-radioactive hazardous fluids e. PCB transformer oil or solids e.
At the end of the operational life of a facility, effort is generally directed at the removal or reduction of any hazard in all areas of the plant to provide a passive safe environment during SE. The amount of work to be undertaken will depend on the operations that were carried out within the facility and the nature of the hazardous inventory associated with the process, that is radiological, toxic or non-hazardous.
Such removal or reduction is important for the transition period although historically this has frequently been delayed until the start of dismantling. However, it should be emphasized that if POCO is deferred until the dismantling phase the associated risks remain and are transferred to the future. Methods for assessing the overall requirements for cleanout, both in terms of the need for and extent of such operations, are given in Ref. Ultimately, if significant costs or personnel exposure are involved, the decision making process will be based on the overall net benefit. At final plant shutdown, all waste remaining from past activities is commonly removed from the plant for treatment, conditioning, packaging and storage or disposal.
Waste management includes not only process fluids Section The latter can comprise a significant number of items, e. Decontamination Installation of the cementation plant in preparation for decommissioning of the Salaspils IRT reactor, Latvia. The reactor block and experimental test apparatus of the IRT reactor, Georgia. At the end of operation, a research reactor s hall is typically full of experimental devices which are removed in preparation for decommissioning.
Fixing activity on accessible surfaces may be a viable alternative to its removal. However, implications for eventual dismantling and handling of such material require special consideration and specific recording Deciding on the need for and the extent of decontamination In general, decontamination that is carried out during the transition period is primarily aimed at dose reduction and is not intended for material clearance.
Aggressive decontamination methods can often be applied where the systems are no longer needed for operation. Within established constraints, the optimal decision will in general be based on a multiattribute analysis or an extended cost benefit analysis [28, 29]. The extensiveness of the decontamination will depend on the decommissioning strategy selected.
In a delayed dismantling scenario, natural decay will reduce radiation and contamination levels in plant systems and components as well as on surfaces and may render some decontamination superfluous. When the need remains after a long SE time, the effect of physicochemical mechanisms during SE may make decontamination less effective, e. If SE is planned, decontamination will be considered primarily for the areas that will be accessed during the transition period.
An alternative in some cases may be to fix contamination in place to reduce airborne resuspension and However, it is important that surface coatings do not overly complicate future decontamination and measurement System decontamination System decontamination may be performed on radioactive systems in order to reduce the general activity level within the systems in preparation for work during the transition period.https://ustanovka-kondicionera-deshevo.ru/libraries/2020-08-15/4768.php
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System decontamination should be carried out while qualified personnel with knowledge of the relevant systems are still available. Various decontamination methods are possible and it is important that the method and decontamination chemicals be chosen with a view towards available waste treatment installations and minimization of secondary waste. For example, a solution with a suitable composition and temperature for dissolution of the activity containing oxide layer on the surfaces of a system can be circulated in the system to transport the dissolved activity to a filter or ion exchange resin which is subsequently disposed of.
After decontamination has been completed, the systems are flushed and dried. A database can then be established which will provide significant input into the decommissioning planning process and the development of successful implementation plans. With this database, management may assess and decide on various options and their consequences such as: a b c Operating techniques: decontamination processes, dismantling procedures hands-on, semi-remote or fully remote and the required equipment; Radiological and industrial protection of the workers, the public and the environment; Waste management, waste classification and disposal options; At the beginning of the transition period, sufficient information should be collected to assess the radiological status of the facility and the nature and extent of any other hazardous materials present.
Data collected during this initial characterization period would generally be based on information available at the time of final shutdown, including historical operating records. A survey of the extent of contaminated land should be made early in the transition period. As work progresses during the transition period, the objectives of characterization move towards developing more detailed data concerning the physical, chemical and radiological conditions of the facility, including contaminated land.
This will include activation calculations, taking and analyzing of samples, as well as in situ measurements of dose rates Figs 8, 9 and contamination to fill the gaps in the available information. Information gathered during these phases serves as the technical basis for work and project decisions, including cost estimates, exposure estimates, risk evaluation, waste management, scheduling and workforce requirements, particularly with respect to radiological exposures. Since characterization requires time, money and dose commitment, it should be optimized to meet the above objectives.
Some considerations may require cost benefit analysis of: 1 Energy consumption, surveillance and maintenance requirements; 2 Replacement of complex systems with simpler ones; 3 The possible need to achieve a safer state; During planning of the transition period, decisions regarding systems and major equipment within a facility may need to consider the following options: i ii iii iv Operable as is: Systems that must remain operable and do not require modification for example, lighting where surveillance and maintenance is to be done.
Modified: Some systems will need to remain operable but, as a result of the above assessments, modifications are required. For example, building ventilation is needed to maintain control of remaining contaminated areas but its design capacity is excessive, or redundancy of systems and components is no longer required because the consequences of temporary failure are acceptable until repairs can be made.
Preserved for future use: A limited number of systems and equipment may be preserved for the future. For example, installed manipulators and cranes can be of use during dismantling, or radioactive waste treatment systems may be valuable for processing decontamination solutions. Decisions of this type will depend on the length of time until such use is expected as some ageing will occur even in systems that are not in operation.
Future refurbishment may be needed to bring these preserved systems and equipment to satisfactory levels of operability. New: In some cases system functions will be needed, but use of the installed system may not be feasible because it may be overly complex, be over capacity, have high levels of contamination, or entail difficulty of access for operation or maintenance. Installation of a new ventilation system is a typical example . Others include replacement of instrumentation because of obsolescence or the need for monitoring from a different or a remote location, and the installation of limited lighting for infrequent inspections where isolation of other unused circuits is not practical.
A third example is a new electrical distribution system to repower that equipment necessary to support the decommissioning work. In such situations, they are generally left in place and suitably isolated using standard safety practices, especially where there is internal radiological or hazardous chemical contamination or, in the case of electrical systems, the potential for short circuits or high voltage shocks. In some cases, complete removal of a system may be chosen, for example when the assets can be used at other facilities, or systems such as installed ventilation may be isolated where it is beneficial to use temporary or portable equipment when needed.
Industrial safety standards can be provided by either temporary, portable or permanent means. Ventilation, lighting and other safety measures are made available, although they are not necessarily in operation when the area is unoccupied. Walkthrough routes for periodic surveillance of unoccupied buildings are reviewed for industrial hazards and appropriate protection put in place e.
Contamination and radiation zones will be tightly controlled and delineated to prevent the migration of contamination. Services normally found in continuously occupied facilities e. No access anticipated: Access will not be required, or if so the need will be so infrequent that special entry procedures can be established. Isolated: Entry will not be required until demolition begins.
Decisions as to the type of access needed to specific rooms and buildings are closely tied to an evaluation of the surveillance and maintenance requirements. When the surveillance and maintenance routines are determined and This process may include significant modifications to building access and other infrastructure in preparation for decommissioning.
A detailed example is given in Ref. For example, a fire prevention strategy is intended to eliminate fire hazards to the greatest possible extent. Some likely problem areas may include oils and grease in systems and components which, although emptied and flushed, may still contain residual material.
Maintenance of good housekeeping standards and emergency access routes are key features in the implementation of such a strategy. Flood protection may be a concern after shutdown, depending on the geographical location and the climate, geology and hydrology of the area. For example, under US regulations, major dismantling activities are defined as any activity that results in permanent removal of major radioactive components, permanently modifies the structure of the containment, or results in dismantling for shipment of components which contain greater than class C waste, i.
Major radioactive components defined by these regulations could include the reactor vessel and internals, steam generators, pressurizers, large bore reactor coolant system piping and other large components that are radioactive to a comparable degree .
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Examples of decommissioning activities which are considered minor are: a b Normal maintenance and repair; Removal of certain, relatively small radioactive components such as control rod drive mechanisms, pumps, piping and valves; This can entail significant amounts of work and include major nonradioactive components such as cooling towers, transformers and control panels.
During the transition period, removal of readily movable equipment which is no longer needed can be considered. These items are either: 1 Packaged and disposed of; 2 Packaged after compaction and disposed of; 3 Decontaminated e.
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This section describes a number of activities to be carried out during the transition period. Decommissioning costs, including the costs of transition activities, are categorized in a proposed standardized list . The list, with a focus on the transition period, is shown in the appendix and includes the following groups: a b c d e f g h Pre-decommissioning actions, e. The prime costs of the transition period activities are related to labour and fuel removal activities, but also include the purchase of equipment and consumables, contract work, etc.
The costs are plant specific and dependent on whichever other activities are being pursued on the site. They are also dependent on the schedule chosen for shutdown of the plant and the start of decommissioning. Input data for decommissioning cost estimates are available from international organizations  as well as commercially, for example the parametric cost estimating database of the United Kingdom Atomic Energy Authority UKAEA outlined in Annex I Some of these systems have been developed for specific types of facility and should be used with caution for other types.
However, their continued use and collaborative data sharing will improve their applicability across the range of nuclear facilities. The costs for specific activities within the transition period should be clearly allocated to the operational or decommissioning base costs to establish an unambiguous boundary. Evaluating decommissioning cost according to a standardized list of cost items , including the costs of transition activities, would facilitate the comparison of costs for various decommissioning projects and the assessment of cost differences.
It is important that stabilization and other activities for facilities, systems and materials be planned and initiated prior to the end of operations. Carrying out these activities during the final stages of a facility s operational phase and during the transition period will be beneficial in that the operational capabilities of the facility and the knowledge of personnel will be utilized before they are lost. Actions taken at this time will pave the way to efficient and cost effective decommissioning by eliminating, reducing or mitigating hazards, minimizing uncertainty and maintaining steady progress.
The main conclusions of this report are that: a b c d e f g Early planning is the key to a smooth transition from operation to decommissioning and will avoid a no action scenario. Planning for transition requires timely allocation of dedicated human, technical and financial resources. Timely implementation of transition activities will reduce expenditures and hazards, simplify waste and material management and help to keep the workforce motivated. Significant cultural and organizational changes will occur during the transition from operation to decommissioning and need appropriate consideration and management.
The availability of relevant data and records is essential for smooth progress into and implementation of decommissioning. A database containing all relevant data needs to be established and maintained.
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This database should be kept up to date throughout the lifetime of the facility. Implementation of transition will require comparable management focus and workforce attention to detail as during normal operation. Good communication and involvement of all relevant stakeholders is essential for a successful transition from operation to decommissioning. Removal of special system fluids D 2 O, sodium, etc. Decontamination of systems for dose reduction Removal of waste from decontamination Removal of combustible material Removal of spent resins 5 Actions relevant to the transition phase appear in italics; actions partly or possibly relevant to it are in normal typeface, and actions not relevant to transition appear in bold italics.
WS-G- 2. Tucson, , WM Symposia, Inc. Chicago, , PennWell Corp. Decommissioning Symp. It is felt that both approaches are useful to provide practical guidance on how transition projects are planned and managed in various Member States. The examples given are not necessarily best practices nor do they necessarily reflect the views of the IAEA; rather, they reflect a wide variety of national legislations and policies, social and economic conditions, nuclear programmes and traditions.
Although the information presented is not intended to be exhaustive, the reader is encouraged to evaluate the applicability of these schemes to a specific transition project. Introduction This section describes the decommissioning of nuclear installations in the Czech Republic, with emphasis on the period of transition from operation to decommissioning.
Except for one zero power reactor, no nuclear installation has been decommissioned in the Czech Republic. The operating organizations in the Czech Republic are now preparing for the future decommissioning of their nuclear installations in accordance with relatively new legislation on the peaceful utilization of nuclear energy and ionizing radiation. One research reactor has already been decommissioned. There are also other non-reactor nuclear installations in the Czech Republic, e. Only those installations of significance from the point of view of decommissioning are mentioned.
The process of decommissioning installations such as irradiation facilities is very simple and does not pose a significant problem. Licensing requirements related to transition The main legislation applicable to the transition phase is Law No. Decree No. This regulation details the method and extent of the assurance of radiation protection at decommissioning installations and workplaces with significant 1 or very significant ionizing radiation sources. The regulation also includes requirements to make financial provision for the decommissioning of nuclear installations.
Decommissioning of nuclear installations will be up to the operating organizations, whose legal responsibility is to create a financial reserve for this purpose. Decommissioning, according to Czech legislation, means those activities aimed at releasing nuclear installations or workplaces with ionizing radiation sources for use for other purposes following the end of operations, or exempting them from the requirements of the Atomic Law.
The Atomic Law identifies the need for a specific licence to cover decommissioning work. The issue of a licence for individual stages of decommissioning of a nuclear installation or workplace with a significant or very significant ionizing radiation source requires specific documents to be produced. However, there is no danger of a radiation accident associated with the source. A case-by-case system is used for decommissioning with the decay period also being dependant on the nature of the installation. Decommissioning of nuclear installations to green field status is not obligatory.
Article 3 of Decree No. The scope of essential decontamination, dismantling and demolition work, of environmental monitoring and the possible reuse of land influence which of the following options can be adopted: 1 Direct decommissioning, when from a radiation protection perspective it is not necessary to carry out decontamination, dismantling and demolition work.
In such circumstances, neither ionizing radiation sources nor equipment contaminated by the ionizing radiation sources remain at the site, or other ionizing radiation sources are switched off and isolated to preclude restart. In this situation, equipment is left in place, confined by protective barriers to prevent radionuclide leakage into the environment until these have decayed to a level stipulated by special regulations. Description of the transition period The transition period from operation to decommissioning is not defined by the regulations, nor is the term transition used in the field of decommissioning.
However, some activities could be regarded as transitional, e. Section I 1. The following is paraphrased from Art. The end of operation shall be reflected in changes to documentation, mainly in the determination of the decommissioning strategy, the demarcation of the controlled zone, the definition of the monitoring programme and emergency plans. In the case of a workplace with sealed ionizing radiation sources the operational period ends with the removal of the radiation sources. Description of the transition period of nuclear installations in the Czech Republic I Nuclear power plants The Dukovany NPP was constructed between and , with a break between and due to a change in the type of reactor being built type V instead of V The second is in trial operation.
Two basic options are considered with respect to the decommissioning of Czech NPPs: 1 Immediate decommissioning after the termination of operation. The decommissioning activities are carried out immediately after the end of operation. Defuelling is done immediately and the spent fuel is transferred to the at-reactor pool. The duration of the cooling period depends on the spent fuel parameters. The fuel is then transported to the spent fuel storage facility. After defuelling, the primary circuit is decontaminated. Dismantling of non-contaminated equipment and buildings is started immediately.
Pre-dismantling decontamination, dismantling and post-dismantling decontamination of equipment for handling radioactive wastes are carried out in contaminated buildings. Following the final decontamination of the buildings, demolition is started. The decommissioning activities are postponed. The following activities are carried out simultaneously throughout the NPP except on the nuclear island: predismantling decontamination, dismantling of equipment, postdismantling decontamination and related processing of generated radioactive waste, final decontamination and demolition of active buildings.
The nuclear island is the only remaining area of the NPPs. After the period of SE the remaining buildings and systems will be decommissioned. No other decontamination or dismantling operations are carried out. The buildings are maintained to provide physical containment. The NPP buildings are closed and kept under surveillance physical protection, checking and maintenance of Safe enclosure is the preferred option for the decommissioning of Czech NPPs. Four buildings will remain on the site. Two buildings will remain on the site for about 50 years.
The reactor was operated at a maximum power of 2 MW from until when the power was increased to 4 MW. Following a change in fuel type in it operated at a maximum power of 6 MW. In the reactor was reconstructed and recommenced operations in at a maximum power of 10 MW. The reconstruction comprised replacement of the reactor vessel, primary circuit, reactor control system and ventilation system.
Because of the design of the reactor, the reactor system and equipment are all contaminated. Immediate dismantling has been selected as the appropriate decommissioning strategy. There are, however, some steps that could be considered parts of the transition process: a b c d e f g h i Planning of the decommissioning; Defuelling and removal of the beryllium reflector and reactor internals; Dismantling of parts below the reactor lid; Dismantling of research loops, probes, irradiation channels and rabbit systems; Dismantling of the upper reactor lid; Draining of systems; Surveying and mapping of radiological conditions; Processing of radioactive wastes; Preliminary decontamination if needed.
The final disposal method for the fuel reprocessing or disposal in a future deep geological repository has not yet been decided on. The above mentioned actions will require about two years. Then proper decommissioning will start and take about three years. Decommissioning will not include the demolition of the reactor building, which will be used for other purposes. LR-0 research reactor LR-0 is an experimental light water zero power reactor used to establish the core neutron physics characteristics and shielding requirements of the WWER type reactor.
The TR-0 reactor was commissioned in as a heavy water zero power reactor. The LR-0 reactor began operation in Its maximum power is 5 kw Fig. A strategy of immediate dismantling has been selected. Decommissioning is expected to be relatively simple because the reactor design makes contamination of the reactor equipment unlikely. The reactor will be dismantled immediately. The following steps can be considered to be part of a transition period: 1 Planning of decommissioning, 2 Defuelling the slightly irradiated fuel will either be used for fabrication of new fuel or be disposed of in a future deep geological repository , 3 Draining of systems, 4 Surveying and mapping of radiological conditions, 5 Processing of potential radioactive wastes, 6 Decontamination if needed.
Decommissioning does not include demolition of the reactor building, which will be utilized for other purposes. The above mentioned activities will FIG. The LR-0 research reactor hall. Decommissioning will then begin and is expected to take about two years. VR-1 training reactor The VR-1 training reactor is a pool type light water reactor which uses enriched uranium fuel.
Its rated power is W thermal. The decommissioning process for the reactor will be similar to the decommissioning of the LR-0 research reactor. The decommissioning does not include demolition of the reactor building, which will be utilized for other purposes. Refurbishment of the reactor vessel and the shielding was planned. However, in it was decided to decommission the reactor instead.
The selected strategy for these facilities is also one of immediate dismantling. Decommissioning does not include the demolition of buildings, which will be utilized for other purposes.
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Issues in planning for decommissioning In the past it was not necessary for operating organizations of nuclear installations to prepare a preliminary decommissioning plan as is now required by legislation. Now the decommissioning planning is an important part not only of the operation, but also of the planning and construction of a nuclear installation.
When the preliminary decommissioning plans of the operational nuclear facilities were prepared, some required data were either unavailable or unknown. This mainly related to research facilities which had been built many years previously. There was a lack of data available to assess the amounts of material arising from decommissioning including information regarding the composition of materials, the level of contamination, etc. Thus it was necessary to collect the necessary data by measurement of actual dimensions, from the operational history or even from the construction data , perform measurements and carry out the calculations.
Of course, the continuous collection of data will be used to prepare and update the final decommissioning plans. Conclusions No nuclear facility except a zero power reactor has been decommissioned in the Czech Republic. The operating organizations of the other facilities are now preparing for the decommissioning of their nuclear installations. The transition period from operation to decommissioning of nuclear installations is not defined by the regulations and the term transition is not formally used in this context.
However, some activities can be regarded as transition activities such as defuelling, management of spent fuel, decontamination, drainage of systems and preparation for SE or storage with surveillance. Nevertheless these activities, which constitute the interface between the end of operation and the start of decommissioning activities, are very important and have a great impact on the safe and successful implementation of the decommissioning programme. The reactor started operation at full power on 26 August Until 31 October it operated with three shifts per day, five days per week.
From 1 November until its final shutdown on 31 October its operation was reduced to one shift per day, five days per week. The total integrated power during its operation was MW th d. However, since there was some doubt as to whether this was correct, it was decided that the reactor should be shut down in such a way that it could be restarted easily. The initial transition activities After final shutdown of DR-2 its core was dismantled and placed on the storage rack in the reactor tank.
Two months later the fuel elements were moved to the fuel storage pool of the DR-3 from where they were sent to the USA. The beryllium reflector elements were left in the grid plate. The shimsafety rods were placed on the storage rack in their guide tubes, while the regulation rod was left hanging in its extension rod in the tank. After removal of the fuel, the primary circuit, including the DR-2 tank and the holdup tank, was drained, as was the secondary circuit.
It was discussed whether the primary system should be dried, but it was decided that this was not necessary. To provide the necessary radiation shield at the top of the reactor tank once the water in the tank had been removed, a steel plate was placed on top of the reactor carrying a 5 cm thick layer of lead bricks. Since this meant that the reactor hall had to be transformed into a clean area a number of additional measures were taken. The control rod drive mechanisms at the reactor top were removed and the thickness of the lead brick shield was increased to 10 cm.
In addition, a 40 cm thick concrete shield plate was placed on top of the reactor All beam and irradiation tubes were, where needed, provided with additional shielding and steel plates were welded over the tube openings. Other openings to the reactor were sealed with a plastic material. The interior of the primary circuit and the tank were connected to the outside atmosphere through a filter.
The staircase to the top of the reactor was removed and so were most railings. The secondary circuit was dismantled. For the next 20 years the reactor was left in SE with little need for maintenance. Regular inspections and yearly radiation surveys were carried out. They indicated that the activity of the tank was decaying with a half-life of seven to eight years. The project planned to open the various parts of the reactor and to assess the remaining activity level, the radionuclides involved and where the activity was placed.
However, before the reactor could be opened a number of activities had to be carried out. The reactor hall had been used for chemical engineering experiments between and and much equipment from these had been left and had to be removed before work could start. The walls and floor had to be cleaned and repainted, the staircase to the top of the reactor had to be reinstated, the reactor hall crane had to be re-licensed, etc. To permit handling and measurement of radioactive components stored in the reactor, two facilities were built in the reactor hall. One, made from concrete blocks, was for the storage of radioactive components taken from the reactor.
The other was a measuring facility, again made from concrete blocks and lead bricks, in which long components placed on a flat vehicle could be moved past a lead collimator where the activation distribution along the component could be measured. In addition, since the status of the reactor had to be changed from a sealed to an open facility new safety documentation for the reactor had to be prepared, submitted to and approved by the nuclear and radiation safety The new documentation included a safety assessment of the project activities. To obtain the necessary information on the reactor the DR-2 archive, in particular drawings, had to be brought up to date.