[en] Thousands of operations involving the use of radioactive substances will end during the current century. While there is considerable regulatory experience in the 'front end' of the regulatory system for practices, the experience at the back end is more limited as fewer practices have actually been terminated. When a practice is terminated because the facility has reached the end of its useful life, action has to betaken to ensure the safe shutdown of the facility and allow the removal of regulatory controls. There are many issues involved in the safe termination of practices. These include setting criteria for the release of material and sites from regulatory control; determining the suitability of the various options for decommissioning nuclear facilities, managing the waste and material released from control (recycling, reuse or disposal), and the eventual remediation of the site. Some countries have put in place regulatory infrastructures and have developed programmes to manage the associated decommissioning and remediation activities. Other countries are at the stage of assessing what is involved in terminating such practices. The purpose of this Conference is to foster an information exchange on the safe an orderly termination of practices that involve the use of radioactive substances, including both decommissioning and environmental remediation, and to promote improved coherence internationally on strategies and criteria for the safe termination of practices

[en] The pilot nuclear power plant A-1 was a HWGCR (heavy water gas cooled reactor) with channel type reactor KS 150 (refuelling during operation) and power output of 143 MW_e. This NPP began operation in 1972 and was shutdown in 1977 after an integrity accident of the primary coolant system. The NPP A-1 has been under decommissioning since 1979 and extensive decommissioning works have been carried out since 1995. (author)

[en] This paper deals with the main activities and results of the Nuclear Power Plants Research Institute (VUJE) Trnava in the fields of development of remotely operated manipulators and robots for decontamination and dismantling. D and D of the Active Water Purifying Station (AWPS) of A-1 NPP Jaslovske Bohunice was chosen as a pilot project for the application of advanced CA technologies and manipulators for D and D tasks. The presence of radioactive, toxic or hazardous materials limits personnel access to facilities. Very often there are not enough up-to-date drawings of the installed technology. Therefore, in preparation phase of decontamination, a 3D Laser scanner and software 3Dipsos were involved as modelling technology and civil construction of the facility. Examples of acquired data and created 3D models are presented. Many D and D tasks have to be performed remotely. This paper describes the main features of developed remotely controlled manipulators. A movable manipulator MT-15 is dedicated for recognition and analysing tasks in hostile environment. A general purpose manipulator MT-80 is used for heavy duties in D and D. A long reach manipulator DENAR-41 was developed for the decontamination of underground waste storage tanks. Mock up tests of the afore-mentioned manipulators were performed before they were used in D and D tasks. Moreover the software EUCLID and IGRIP are used for simulation, analysing and optimisation of decontamination or dismantling tasks. This procedure leads to safe and more effective realisation of decontamination and dismantling tasks. The obtained results are also used for future development of suitable manipulators. The description of the initial and present state of contamination and radiation level in AWPS is presented in this paper. Experience with utilisation of advanced CA technology for acquiring as built models, development of manipulators and simulation of D and D tasks are described. (author)

[en] The VVR-S Romania research reactor was operated between 1957-1997, at 2 MW nominal power, for research and radioisotopical production. The detailed decommissioning plan was developed between 1995-1998, in the frame of the International Atomic Energy Agency Technical assistance project ROM/9/017. The proposed strategy agreed by the counterpart as well as international experts was stage 1. In 1997, an independent analysis performed by European Commission experts, in the frame of PHARE project PH04.1/1994 was dedicated to the 'Study of Soviet Design Research Reactors', had consolidated the development of the project emphasizing technical options of safe management for radioactive wastes and VVR-S spent fuel. The paper presents the main technical aspects as well as those of social impact, which lead to the establishment of strategy for safe management of decommissioning. Technical analysis of the VVR-S reactor and associated radwaste facilities (Radioactive Waste Treatment Plant - Magurele and National Repository Baita-Bihor) proved the possibility of the classical method utilization for dismantling of the facility and treatment-conditioning-disposal of the arrised wastes in safe conditions. The decommissioning plan at stage 2 has been developed based on radiological safety assessment, evaluation of radwaste inventory (removed as well as preserved on site), cost analysis and environmental impact. Technical data were provided by the R and D programme including neutron calculations and experiments, radiological characterizing (for facility and its influence area), seismic analysis and environmental balance during the operation and after shut down of the reactor. A special chapter is dedicated to regulatory issues concerning the development of decommissioning under nuclear safety. Based on the Fundamental Norms of Radiological Safety, the Regulatory Body defined the clearance levels and safety criteria for the process. The development of National Norms for the decommissioning of research reactors and other small nuclear facilities as well as for restoration of sites damaged by nuclear activities, is in progress. The correct information of the public regarding decommissioning using advanced methods provides the necessary transparency. (author)

[en] The BN-3590 reactor achieved first criticality in 1973. In 1998, the IAEA conducted a safety review of the facility. The Kazakhstan decree stated the intention to put the reactor into a radiological and industrially safe configuration within five years, a process adopted was called Safestor. The steps related to BN-350 shutdown include decontamination of residual sodium coolant, draining and deactivation of the bulk sodium coolant, and closure of the system. In parallel, the US in cooperation with the EU, UK, IAEA, and Japan are working together with the Kazakhstan to produce a detailed decommissioning plan to be presented to the IAEA. This work is at its final stage and the plan will be submitted to the IAEA for peer review before the end of 2002

[en] The compact sodium cooled reactor (KNK) was an experimental NPP build on the Karlsruhe research center. The entire fuel and all movable core internals have been already disposed of. The sodium coolant was removed except for some residues. The water stem loop with the turbine and the secondary sodium systems were dismantled. The ventilation system, electricity supply system and the reactor entrance and exit systems were adapted to the decommissioning steps to follow. The primary system, sodium dump tank, fuel element storage and the rotating top shield of the reactor vessel were dismantled. The work done so far has been based on eight decommissioning permits. Under the decommissioning concept the plant is to be decommissioned completely to green field in ten steps. To this day, nine decommissioning permits have been issued, the most recent in 2001

[en] From 1966 to 1972, under an Atomic Energy Commission (AEC) license, Nuclear Fuel Services (NFS) reprocessed 640 metric tons of spent fuel at its West Valley, New York, facility-, the only commercial spent fuel reprocessing plant in the U.S. The facility shut down in 1972, for modifications to increase its seismic stability and to expand its capacity. In 1976, without restarting the operation, NFS withdrew from the reprocessing business and returned control of the facilities to the site owner, the New York State Energy Research and Development Authority (NYSERDA). The reprocessing activities resulted in about 2.3 million liters (600,000 gallons) of liquid high-level waste (HLW) stored below ground in tanks, other radioactive wastes, and residual radioactive contamination. The West Valley site was licensed by AEC, and then the U.S. Nuclear Regulatory Commission (NRC), until 1981, when the license was suspended to execute the 1980 West Valley Demonstration Project (WVDP) Act. The WVDP Act outlines the responsibilities of the U.S. Department of Energy (DOE), NRC, and NYSERDA at the site, including the NRC's responsibility to develop decommissioning criteria for the site. The Commission published the final policy statement on decommissioning criteria for the WVDP at the West Valley site after considering comments from interested stakeholders. In that regard, the Commission prescribed the License Termination Rule (LTR) criteria for the WVDP at the West Valley site, reflecting the fact that the applicable decommissioning goal for the entire NRC-licensed site is compliance with the requirements of the LTR. This paper will describe the history of the site, provide an update of the status of the decommissioning of the site and an overview of the technical and policy issues facing Federal and State regulators and other stakeholders as they strive to complete the remediation of the site. (author)

[en] The 500 MWe gas graphite reactor Vandellos 1 is being decommissioned to a Stage 2 status. The Stage 2 in this particular case involves the dismantling of almost all structures and components outside the reactor vessel. The vessel itself will remain, after removal of fuel, with its internals, until the end of the dormancy period. By achieving Stage 2, about 80% of the site will be released. During the operation of the plant, the graphite fuel sleeves were stored in three concrete silos on site which included about 1000 tonnes of graphite and activated metal pieces. ENRESA started the decommissioning of the graphite silos in 2000. Decommissioning involves the dismantling and removal of equipment from each cell, the decontamination for the cell walls, ceilings and floors and the dismantling of the ventilation system. These activities were followed by a complete radiological monitoring in order to obtain the release of the remaining structures and proceed with its demolition. This paper provides an overview of the decontamination and decommissioning activities related to the graphite silos at Vandellos 1 and describes the efforts made to improve safety through the use of innovative technologies. In addition, the strategy to be followed for the safe management of the graphite waste is also described. (author)

[en] The Nuclear Power Plant of Vandellos 1, a gas-graphite reactor (GCR), started operation in the 70's after 17 years running the decommissioning process began in 1998, and is expected to finish at the end of 2002 with the level 2 of decommissioning with a practically total scope reached, except the concrete reactor vessel and its internals that will remain for another 25 years in surveillance state (dormancy) until their total dismantling. During the last four years the activities related to decontamination and disassembly of the power plant system as well as the management of all this material have been carried out. One of the last phases of the project that will be performed this year, without doubt, one of the most representative of the operative difficulty of the task is the disassembly of some buildings which are more than 80 meters high and with some structures weighing more than 3.000 t, an operation, which is spectacular in terms of volume and mass involved. However one has to keep in mind that it has been preceded by the of clearance process of all these structures to be disassembled this summer. Hundred of thousands of radiological measures will confirm with guarantee that the destination of the dismantled materials is the correct one, assuring the protection of people and the environment. This is a process which has to integrate the principles of radiological safety and industrial safety. First, it has to be guaranteed that structures and components are below the values authorised by authorities for their free release, and, secondly, that the planned sequence of the process and manoeuvres in the disassembly of these colossal structures assures safety. (author)

[en] Decommissioning of nuclear plants and components demands the proper management of the process, both for economic reasons and for retaining public confidence in the continued use of nuclear power. Surface decontamination has an important role to play in decommissioning. A new development, the EPRI DFDX process, produces secondary waste from decontamination in the form of powdered metal rather than ion exchange resin, thereby reducing the volume of secondary waste for storage and eventual disposal. The process has been patented and licensed and is due to be field-tested on a number of sites starting in 2002. Although the purpose of the process is to clean materials sufficiently to achieve unrestricted release, in practice there is some public unease at the prospect of formerly contaminated materials passing into unrestricted use. Greater public support for recycle can be achieved by recording the provenance of decontaminated materials and recycling them back into restricted uses in the nuclear industry. Because the materials have first been decontaminated to below free release levels, there is no objection to using non-radioactive facilities for the recycling and manufacturing activities, provided that the materials are properly tracked to prevent their uncontrolled release. (author)