Safe disposal of VLLW and LILW. Experience gained in 20 years of operation of El Cabril disposal facility February 2015

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1 Safe disposal of VLLW and LILW. Experience gained in 20 years of operation of El Cabril disposal facility February 2015 Inmaculada López ENRESA, Emilio Vargas 7, Madrid, Spain

2 Content Background Past and ongoing challenges Future challenges 2

3 Background El Cabril disposal facility project was launched in 1986, for LILW, based on barriers and disposal units of concrete Construction begun in January 1990 and Operation in October 1992 The project for the complementary facilities for VLLW was launched in 2000, based on clay and HDPE barriers and different types of disposal units Construction begun in February 2006 and operation started in October Existing facilities today: Disposal areas for LILW and VLLW Treatment and Conditioning systems Concrete containers manufacturing plant Characterization laboratories Ancillary installations Interim storage 3

4 Background Total surface: 35 Ha. The buildings and LILW disposal area occupy 20 Ha and the rest is occupied by VLLW disposal area. LILW Internal disposal capacity 100,000 m 3 (28 vaults), with occupancy level of 70 % VLLW Internal disposal capacity 130,000 m 3 (4 cells), with occupancy level: of 20 % Annual waste reception: around 1700 m 3 Interim storage capacity: 6,200 drums (220 l.) The present authorization was updated in 2001 and further complemented in 2008 (for VLLW). Is valid until the available disposal capacity will be completed. Two Safety Periodic Review have been presented to the regulator (every 10 operation years) 4

5 The most relevant past and on going challenges Management of wastes arising from incidents involving the smelting of Cs-137 sources. Development and operation of the complementary VLLW disposal facilities, for the separated disposal of this sub-category of wastes. Capillarity phenomena observed in LILW vaults, with generation of free water inside New configurations of disposal units that best suit new needs arising from the dismantling of nuclear facilities and to optimize the available disposal volume. Disposal of disused sealed sources with a half-life between those of Co-60 and Cs-137. Continuous updating of the safety case based on the knowledge acquired and also in keeping with the requirements imposed by the Authorities. 5

6 Waste arising from incidents involving the smelting of radioactive sources (Cs-137) Several incidents occurred. The most relevant was in The total waste generated was around 2500 m 3. An action plan was required by the regulatory authority to receive, storage, treat and conditioning the produced waste. Several design modifications were necessary and carried out in order to : Provide additional interim storage capacity. Initially waste was placed in existing storage buildings. Additional capacity was needed for waste arrived in ISO containers. These containers are stored in three disposal vaults. Add new treatment and conditioning capacities, taking into account the optimization of the available disposal volume. The arid waste conditioning consists in the incorporation to mortar to lock them into containers. Before, segregation, trituration and chloride reduction is needed. 6

7 Complementary facilities for VLLW. Licensing The needs arise from the decommissioning of NPP as well as from the non-nuclear industrial incidents above, and from the recognition that the strategic value that the existing high tech concrete vaults for LILW had to be maintained for those higher activity waste Political parties in Parliament reached consensus in promoting the development of such facility specifically for VLLW disposal ( ) After discussions with the regulator, the Safety objectives and safety technical options for a VLLW disposal were approved in May 2003 The licensing was conducted as a design modification. Some documentation was required as for a new installation: the safety report and the general project A formal Environmental Impact Statement was required, with public participation. A few relevant dates: Municipal planning license - January 2003 Construction authorization - February 2006 Operational authorization July

8 Complementary facilities for VLLW. Description Objectives and criteria Same basic safety objectives and criteria accepted for the existing LILW facility at El Cabril. Dose constraint of 1 msv/y. Surveillance period of 60 years. Technical design based on the regulations for disposal facilities for non-radioactive hazardous waste in Europe (Upgraded due to specific regulatory requirements). Disposal area Four disposal cells authorized. Only the first cell (nº 29) built and in operation. The next cell (nº 30) in construction. Adapted to site topography. Surrounded by intercepting drainage ditch. Cells closed by a seismic resistant stones dike. Treatment building Stabilization of chemically toxic VLLW Void backfilling of disposal units Interim Storage capacity 8

9 Capillarity phenomena observed in LILW vaults The disposal system has an inspection gallery, beneath each row of disposal vaults, with a seepage system provided with individual vault collection thanks. After 10 years, we begun to collect small amounts of water in the control tank of vault16 (the first constructed, filled up and sealed), in winter time. Years after we also collected small amounts of water in some other vaults, and also in summer. An in depth initial investigation was immediately launched to verify potential water ingress pathways by several ways. Nothing was found. After significant efforts evaporation-condensation-capillary absorption cycles, inside the vaults, was finally determined as the origin of the process. Thermo-hydraulic model developed matches pretty well the appearance and the pattern and volumes of water collection, and its dependence of the time of the year and the outside temperature. No correlation at all to rainfall conditions. 9

10 New configurations of disposal units The generation of wastes of higher density, as metallic pieces, from the decommissioning of NPPs, leads to use new disposal unit of different dimension than the ones already approved. A new container CE-2b was licensed, with the same horizontal dimensions as container CE-2a, but half height. The management of metallic pieces required a new procedure for conditioning the waste directly into the concrete container (CE-2a, CE-2b) and the adaptation (and approval) of the acceptance process for the resulting disposal unit. The adaptation of the acceptance process was also required because now such disposal unit can be generated directly at producer s facilities. 10

11 Disposal of disused sealed sources (up to Cs-137) Since the beginning of operation the disposal of disused sealed sources with half-life until Co-60 was admitted. In order to manage sources with longer half-life (up to Cs-137) Enresa applied in 2011 for a design modification. The additional specific risks associated were studied and the conditions to ensure the safety of the disposal system were established. The specific study is based on the methodology and scenarios considered in IAEA document: Dangerous quantities of radioactive material (D-Values) (2006). In 2014 the disposal authorization was granted, but the activity of the sources acceptable for disposal was limited to that generating waste packages of level 1 activity. 11

12 Safety Case. Updating The safety case has been periodically updated using the knowledge gained since the very beginning, throughout the different phases of the project. The safety case has also been improved as a result of the Safety Periodic Review requirements. The main improvements are: Adaptation to the basic trends developed by the IAEA Better integration of the engineering barriers specifications and the waste acceptance requirements Enhancement of assessment tools and/or use more detailed models A great effort and attention have been given to the modelling on specific issues Potential water table rise Potential water tub effects Influence of capillarity phenomena observed in vaults The safety case is used to support and justify: The design modifications in the facility, either big such as the addition of VLLW disposal cells, or small, such as the use of different types of disposal unit in LILW vaults. The waste acceptance criteria. The safe disposal of specific waste such as disused sealed sources. 12

13 Future challenges Disposal of VLLW large components. Coordination of efforts with the producers to minimize waste generation, along with the optimization of the occupation of the available disposal volume. Update the need of disposal capacity for LILW, considering the potential life extension of NPPs, and the experience gained in their decommissioning. Optimization of the long term cover design through the results of the ongoing large scale experiments. Promote specific R&D lines associated with the characterization, behavior and durability of confinement materials and systems based on concrete and clay materials as key components of the isolation and confinement barriers. Continuous updating the safety case based on the new acquired knowledge and also in keeping with new requirements imposed by the Authorities. 13

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