the French experience

Transcription

1 VLLW disposal and management of large volume of slightly contaminated materials the French experience Nicolas Solente

2 Very Low Level Waste disposal in France The CIRES facility in Morvilliers

3 VLLW waste in France VLLW disposal concept principles The CIRES disposal facility in Morvilliers Facility design Waste forms and packaging Waste acceptance Criteria Operations Improvements

4 VLLW in France: National Context A significant decommissioning program Nuclear research facilities : by dismantling worksites and 15 sites completely decommissioned including one enrichment plant, 2 reprocessing plants and 9 Power Reactors No clearance level for waste release from regulatory control Waste zoning implemented in nuclear facilities Nuclear wastes and conventional wastes Nuclear wastes and conventional wastes About 650,000 m3 of waste with very low specific activity (1 to 10 Bq/g) or potentially radioactive only to be disposed of before 2030 A need for a safe and cost effective disposal solution

5 VLLW in France: waste forms metallic waste, uncompactable Waste forms Inert waste; 52% Metallic waste for compaction Non-metallic waste for compaction hazardous waste requiring stabilization Sludge requiring solidification

6 VLLW repository in Morvilliers The CIRES disposal facility

7 VLLW disposal facility in Morvilliers Close to Centre de l Aube facility dedicated to LIL-SL waste Very low level waste disposal facility started up in 2003 Expansion of activities with the creation in 2012 of a storage facility and a grouping/transit facility for institutional waste

8 Facility concept

9 VLLW in France: CIRES capacity Disposal capacity (currently licensed): m 3 Total disposed volume: (2012) Currently used: 35% Annual disposal volume: approx m3

10 VLLW disposal facility: operational phases 2- Construction 3- Operation 1 - Preparation 4- Implementation of the capping system

11 Cover details Soil Coarse material sand Antierosion geotextile Drainage geogrid Clay Antipuncture/anti UV geotextile Geomembrane Antipuncture geotextile Strengthening geotextile Waste wrapping

12 Capping phases

13 Capping: final capping in place

14 Waste packaging Closed, open and uncontainerized items accepted, based on waste radiological characteristics

15 Waste Acceptance Criteria: radiological criteria Acceptation Index (IRAS): IRAS = Am: specific activity for RN i (in Bq/g) Am 10CCCCC i Class i is the Class Number (0, 1, 2 or 3) corresponding to RN i IRAS shall be: < 1 for the waste stream of the package <10 for the waste package Threshold applies, under which RN needn t be declared U and Th-232 are specific case treated separately Class numbers are listed in WAC annex: ex

16 Waste Acceptance Criteria: non-radiological criteria Chemical criteria: maximum admissible content in dangerous waste: ex: Pb, Cr, Zn Prohibited waste: liquids, explosive, easily flammable, PCBs, containing gas, corrosive, non-treated fines, pathogens, FOODSTUFF; Putrescible waste is limited. Soluble fraction < 10% Leaching tests are performed on accepted dangerous waste to verify that waste remains compliant.

17 VLLW on-site waste treatment

18 On-site treatment 85% of the waste delivered to the CIRES has already been processed and packaged and can be disposed of without further processing. Treatment available on-site includes: Soft waste compaction (plastics ) Scrap metal compaction Sludges and liquid waste solidification

19 Compaction Wastes after compaction COMTRADSP /01/2011

20 Sludges treatment SOLIDIFICATION FOR SLUDGES STABILIZATION FOR HAZARDOUS WASTES COMTRADSP /01/2011

21 CIRES VLLW disposal facility Improvements

22 CIRES disposal facility improvements Cell geometry longer cells (2x) with 1 ramp Deeper cell Steeper walls Waste emplacement Optimization of waste packages emplacement Uncontainerized items now accepted (heat exchangers.) Mobile roofs rail transfer replaces crane handling (expensive, hazardous)

23 Disposal of Large Volume of Radioactive Waste The CODIR-PA project

24 Main principles of design Concept adapted from the VLLW disposal facility Concept allow the use of transport containers for waste storage Passive barrier of VLLW disposal facility replaced by engineered barrier New active barrier types implemented

25 Project boundaries Waste is inert (or has been made inert: compost ) Rubbles, metal scrap, soil. May be conditioned or not Hazardous waste regulations apply Waste packaging rules are similar to what is used at Morvilliers VLLW disposal site No pre-required characteristics for local geology However, the selected site must exhibit several characteristics (mechanical strength ) The concept is modular and the facility capacity may be extended by adjunction of new modules Construction is quick

26 French legal framework As applies to hazardous waste storage: Geological context must be a confinement barrier. The required level of passive safety is achieved with 5m of material thickness of natural or re-worked terrain. The permeability of this material must be < ms -1 A water collection system limited at its bottom by a geomembrane is an active barrier system The passive barrier may be engineered with re-worked natural materials. The engineered barrier, of a given thickness and permeability, must display the same level of protection relative to the protection of soil, surface and underground water, as defined above; the thickness of the engineered barrier cannot, however, be less than 0.5m

27 Passive and active barriers Active barrier Passive barrier Function Drain Active sealing Passive sealing Sorption, attenuation material Gravel, synthetic materials Geomembrane Natural clay, GSB, reworked materials clay French regulations require the presence of an attenuation layer at least 0,5m thick below the engineered low permeability barrier; Low permeability passive engineered barrier (as GSB) is used with, not instead of, a clay barrier

28 Barriers equivalence 2 passive barriers are considered equivalent if the same level of protection is achieved towards underground water; The criterion used for comparison is concentration in the aquifer. Examples Engineered barrier : Argile : e= 1 cm, K< m.s-1 e = 2 m, K< 10-9 m.s-1

29 Barrier equivalence: sorption capability Radioactive pollutant Concentration = 1 Radioactive decay Radioactive pollutant Concentration = 0 When sorption is considered, the thickness of the engineered barrier controls in part the flow of pollutant at the bottom of the barrier. Several equivalent combinations of thickness-permeability parameters may be considered, for specific RNs, to study the effect of diffusion: Studies have demonstrated that below a given permeability of the clay, diffusion does not limit the clay thickness required to confine a specific RN (Cs137 in Andra study)

30 Selecting a mineral barrier Natural clay Bentonite, as adjuvant to natural clay: improves permeability characteristics natural/re-worked barriers cannot achieve better than Engineered materials: ms -1 due to risks of heterogeneity containing polymers (commercial product containing sand + bentonite + polymer). Significant decrease in thickness required. Permeability achieved: ms -1 after aging. But these materials are not yet qualified for the proposed use.

31 Active barrier - Geomembrane/geotextile - May include drainage layer - Must be protected from: - Tear following subsidence of waste pile - Puncture due to waste packages

32 Site selection No prerequired geological criterion but No risk of flooding Stable site, with sufficient soil mechanics properties Plane surface, with typically a 2% slope

33 2 concepts 2 disposal concepts were developed for 30 containers Other types of containers

34 Stacks (30 maritime containers) Containers stacked on a slab made of Sub-base in sand type material, located immediately above the passive barrier. thickness: 0,5m Asphalt and concrete base, resistant to shearing as induced by waste container load during operations Each 44*42m zone holds 6600m 3 of waste

35 Cells (other containers) Retaining wall Passive barrier Drain Active barrier Length: 67m, holds 5000m 3 of waste Design include retaining walls

36 General lay-out of the disposal site Non-containerized waste extension zone Cells Non-containerized waste extension zone (prefered) Storm Basin Stacks Containerized waste extension zone Storm basin extension zone Cells: holds m3 on 12ha Containerized waste stacks: holds m3 on 6,2 ha

37 Temporary capping Cells at least 0,5m of materials, protecting the geomembrane from waste package (risk of puncture) A geogrid, in the backfilling layer, to limit the geotextile tear in case of waste subsidence A geomembrane, protected by a anti-puncture geosynthetic material (doubling as a UV filter) Stacks At least 0,8m of materials (to protect from puncture on the containers corners) A geogrid to protect from subsidence due to degrading containers

38 Final capping Geomembrane protective layer (sand, 0.5m) Safety layer (clay, >1m, permeability < ms -1 ) Drainage layer Shaping backfill (backfill material, >1m, slope 2,5 to 1) Drainage layer below vegetal cover (0,5m, coarse or other draining materials)+ filtering geotextile Geotextile, providing grip for soil cover Soil cover (vegetal layer, 0,5m to 0,3m)

39 Operations Operations: 12 years Cells Disposal capacity: m3 each year Staff: 11 (7 truck operators) Stacks Disposal capacity: m3 each year Staff: 7 (3 truck operators)

40 Costs Estimated to 450 /m3 in cells 1100 /m3 for stacks (400 /m excluding containers costs)

41 Conclusions Concepts of VLLW were transposed, with no strong constraint on geology 0,5m passive barrier, providing same performance as 5m of undisturbed clay Safety assessment necessary, with due consideration for geology and hydrogeology ISO 20 containers may be used for convenient storage and transport Cells are analogous to VLLW, but built above surface with retaining walls Containers are stacked on a simple platform Optimization possible with new, not yet approved materials for the barriers

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