Dr RK BajpaiHead,Repository Engineering SectionNuclear Recycle GroupBhabha Atomic Research CenterIndia

IAEA TM on Strategies and Opportunities for the Management of Spent FuelGCNEP, India, 25th-29th November, 2019

Long Term Strategy

Spent Fuel Used As A Resource Material

Long term strategy for HLW in India, is to

separate minor actinides & long lived fission

products

Reducing the need for their long term isolation

Such a strategy also favors recovery of useful

fission products (Cs-137,Ru-106,Y-90,Sr-90)

Novel matrices for immobilization of separated

radionuclide

Transmutation of long lived radionuclide

based on availability of state of art technology

Storage of Heat generating long lived wastes

Stainless steel 304L canisters used for vitrified HLWSpecific activity: 4000 Ci/lHeat generation rate : 12 W/lMaximum permissible glass temperature: 400 ˚C

Solid Storage Surveillance Facility, Tarapur(Operational)

Capacity :300 Te ( 1700 pits)Stack induced natural draft with cross flowUnderground double vaultSafety provisions for forced draft coolingPeak radioactivity of storage vault: 1.2 billion curies

generating 2-3 mw decay heat

Vitrified Waste Storage Facility, Kalpakkam

Capacity :1000 TeStack induced natural draft with axial flowAbove ground single vault, Multiple stackingSafety provision for induced cooling with Hepa filter

Canister

Handling Arrangement of SSSF

Heat Generating long lived waste needs continuous cooling to maintain

temperatures within acceptable limits

Schematic view of VWSF, Kalpakkam

Canister

Low Level RW Disposal Co-location of NSDF with NPP sites Safety periods/Institutional Control : 300 years Discharge of Radioactivity to Environment In Line with Principle of as Low

as Reasonably Achievable.

High Level RW Disposal India recognize the need of a DGR as final solution for permanent disposal of

long lived HLW and other waste A dedicated unit responsible for DGR and associated R&D has been created in

BARC as early as 1980 DGR requirement is slated after few decades Indian DGR is a Central Facility designed and developed to receives waste from

all its nuclear installations Granite host rocks in depth range of 500-700m have been given priority as host

rock/other host rocks also exist. DGR with a capacity of 10000 HLW loaded overpacks is under consideration

with provision to expand it further Very large scale involvement of national expertise in DGR Project Involvement of stakeholders/pubic awareness Participation in international collaborations/IAEA

Near Surface Disposal Facilities (Low and Intermediate Level Waste)

Earth Trench / Stone Lined Trench (ET/SLT)

Reinforced Concrete Trench (RCT)

Tile Holes (TH)

Seven such facilities are operating

Deep Geological Repository (DGR) for High Level WasteSite selection & CharacterizationLab scale experiments/sample testingSetting up URL in progressNumerical Modeling/Code Development

Stone Lined Trenches

(Potentially Active Solid Waste)

Category Surface

dose/activity

Disposal options Nature of waste

I < 2 mGy/h Stone Lined Earth

Trenches

Paper trash, concrete chips,

cotton mops, rubber items

etc.

These are shallow excavations in soil, 1 to 4 m deep and provided with stone lining for stability and integrity

RCC Trenches

2-20 mGy/h RC

Trenches

Contaminated

equipment,

hardware and

filters.

20-500 mGy/h RC

Trenches

Conditioned/pr

ocessed

concentrates,

sludges, spent

resins.

A typical trench is 4.8 m deep, 2.5 m wide and 15 m long. The outer containment wall thickness varies from 350 mm at the top to 750 mm at the bottom

Tile Holes

III >500 mGy/h Tile Holes Hardware from reactors,highly contaminatedequipment, conditionedspent resins etc.

IV Waste bearing alpha activity (< 4000 Bq/g)(> 4000 Bq/g)

RC Trench and Tile HolesTile Holes

Solidified alpha waste with activity.

Circular vaults, nearly 4 m below ground level Average inside diameter of 710mm. Made of 6 mm thick carbon steel shell 25 mm thick concrete lining on both sides

1. DGR should be capable of providing Protection of Health and Environment as

Per Regulatory Requirements ( Time scale: tens of thousands of years)

2. Design is KBS type with canister disposal in vertical pit mode

3. Allow Safe Handling of Waste Over packs ( transfer to 500m depth) &

Accommodate Variety of Waste ( ILW/Spent sources/Spent fuel/Vitrified)

4. Minimization of Mechanical, Hydraulic and Geochemical Perturbations

5. Control Release of Radionuclides ( to keep doses within permissible limits)

6. Design Should be Functional Flexible and Reversible ( Retrievability ?)

7. Avoid Site Complexities and Rely on More Simple High Confidence Models

8. Compliance of Operational and Transport Safety

9. The Facility should be economically viable and should not add adversely to cost

of per unit electricity

Deep geological repository at 500+m depth, with four disposal panels, two shafts, 250 disposal tunnels

Host rock : Granites/Argillites

Capacity : 10000 overpacks

Disposal mode : Pit type

Engineered Barrier : Glass-Canister-Overpack-Clay buffers-backfills-cement bulk head

Temp limit : <100 C

Focus area towards implementation of DGR in India

To locate a site with reasonable stability

To establish and demonstrate the site capacity to insure confinement/isolation over thousands of years

Setting up Underground Research Facility

To develop construction technology that can insure minimum additional damage to host media

To develop instrumentation and technology for measuring TMHRCB response

High end computational tools and technology to monitor fate of released RN over million year scales on kilometer size domain

Technology/tools for TSPA/Closure & decommissioning

Phase Years Activities

Pre Site Selection Studies 2015-2025 Evaluation of Granites/Argillites/Basalts, Lab scale sample characterization and mock up experiments, limited in situ exp. Numerical modeling/Generic URLFinalization of siting methodology

Siting 2025-2030 Geological,geophyical,hydraulicinvestigations and lab based studies

Site characterization/Site Specific URL Phase

2030-2050 In situ experiments to generate site specific data for safety assessment and licensing

Licensing/Regulatoryapprovals/Public Acceptance

2050-2055 Safety cases, approval by regulatory authority, public hearings

Design and Construction 2055-2070 Construction in phases and stages

Operation 2070- Emplacement of waste overpack

Monitoring/Closure

Reference Geological Disposal System under

Consideration in India

Man and Machine access Shaft

Diameter : 6m

Length : 400-500m

Shape : Circular

Ventilation Shaft :500m

Transportation Tunnels

Length :1000m each ( 4 Nos)

Capacity :63 disposal tunnels

Diameter : 5 m

Disposal Tunnels

Length :110m each ( 250 Nos) ie about 63 in each panel

Capacity :40 overpacks each

Diameter : 3-4m, should be minimum possible

Alignment : parallel to Max horizontal stresses

Disposal Pit

Total :10000

Depth : 2m

Diameter :09m-1m

Total available area : >1 million sq kms

Indigenously developed site selection methodology for Granite host rock

1. Siting approach: Systematic narrowing down from large regions to PCS

2. Stage and Phase wise attributes and criteria

3. Technologies used: GIS & Satellite Data/Ground Investigations/Non Invasive gravity/seismic/magnetic/electrical ,methods/Deep drilling/mathematical models

Comprehensive site data up to a depth of 1 km

Promising zones/Candidate sites delineation

Relative assessments in progress

Heat Intensity : 500 Watt /Over-pack

Total Heat Input : 1.25 M Watt/km2

Area of repository :4 km2,

No. of over-packs : 10000

Codes used : FLAC 3D/UDEC

2 KM

After 10 yearsGranite

After 500 years

1km

2km

Temp are well within design limit of 100 C

σ1 contours

Young’s Modulus E (GPa) Poisson's Ration Rock density (kg/m3) UCS c (MPa) Tensile Strength t (MPa)

29.23

2581

118 11

σ3 contours

σvσH σh

11.6

10.5

10.5

Code : FLAC 3DModel OutputMax σ1 25MPa

Max σ3 9 MPa

Single over pack in disposal pit in granite based disposal tunnel

Analyzed Case

FLAC3D 2.00

Central Mining Research InstituteRegional Centre, Roorkee

Step 8787 Model Perspective16:46:49 Wed May 14 2003

Center: X: 3.464e-001 Y: -9.921e-001 Z: 7.310e-001

Rotation: X: 10.000 Y: 0.000 Z: 50.000

Dist: 5.536e+002 Mag.: 19.5Ang.: 22.500

Contour of Temperature 7.8184e+001 to 8.2500e+001 8.2500e+001 to 8.5000e+001 8.5000e+001 to 8.7500e+001 8.7500e+001 to 9.0000e+001 9.0000e+001 to 9.2500e+001 9.2500e+001 to 9.5000e+001 9.5000e+001 to 9.7500e+001 9.7500e+001 to 1.0000e+002 1.0000e+002 to 1.0171e+002

Interval = 2.5e+000

Single Overpack Mock Up Disposal Exp. in Underground Facility

To develop methodology & Technology

For excavation of disposal pit

Canister transfer & emplacement

Design of heating system & monitoring

Numerical modeling of thermal & mechanical stresses

Validation of models

Depth : 1km

Host rock: Amphibolite

Duration : 6 years

Type of borehole

Dia(mm)

Depth

(m)

Total Nos

Heater borehole

368 4.5 5

Extensometer borehole

76 3.5 4

Stress meters borehole

38 3.5 6

Thermocouple boreholes

38 3.54.0

5292

Total no. of Borehole for Sensor

159

Main Heater Bore hole (4.5 m Depth)Auxiliary Heater Borehole (4.5 Depth)

Monitoring thermocouple Bore Hole (Varying depth)Stress Meters Bore Hole (7.00-8.50mDepth)

Extensometer Bore Hole (7.00m Depth)

Amphibolite Rock

Typical data profiles measured and modeled

Near perfect match was observed in measured and modeled temperature for a duration of 1400 days

Deviation observed in measured and modeled stress was due to overbreaks

•Canister transfer/emplacement• Long term TMRCHB response measurement/monitoring•Single overpack/Multiple overpacks experiments•Disposal Gallery Scale Experiment and demonstration•Proto type repository demonstration•Characterization method development

•Develop geological characterization methods /In situ stress/Hydraulic permeability measurement /Hydrogeological characterization methods

•Solute Transport/Gas Migration Studies for Safety Assessments•Parameters, mechanism, controls, modeling/RN Transport on cm, m and Deca meter natural fractures

•Design and Construction of Repository •Measurement of Excavation Damage Zone (EDZ)/Methodology to minimize EDZ/Development of Non blast excavation methods•Excavation methodology for large diameter disposal pits

•Pathway Sealing Experiments•Grouting experiments/Integrated tunnel sealing experiments•Excavation Damage Zones (EDZ) treatment

1) Hydration System

2) Heating System

3)Granite-Clay Barrier-Heater

4)Thermo- Hydro mechanical

instrumentation

5) DAS and HCS

To study complex thermal-hydraulic-mechanical-geochemical interaction among granite-clay-groundwater-waste canister

In progress

Excavation Response around disposal pits/galleries/shaft of DGR

Thermal Response around single canisters/multiple canisters

Radio Nuclide Transport through granites/smectite clays

Geochemical Modeling of glass, clay alteration

Coupled Mechanical, Thermal , Hydraulic Processes

Pre Experiment Modeling of lab and field scale experiments

Important themes and Ongoing studies

Codes in use: FLAC,3DEC,Modflow,Feeflow,Amber,Phase-II,Examine 3D and in-house lattice Bolzman method based codes on reactive transport

Current Focus Area

1 DGR/site evaluation/Lab based studies/modeling/identification of promising candidate sites

2 Setting up Underground Research Facility and experimentations

3 Investigations, design, analysis, costing, formulation of experiments etc

4 Development of analysis codes for Radionuclide transport, TMH coupling/Reactive transport

5 Development of Clay barriers for use in waste disposal facilities

6 Meter scale TMH Experiment to simulate disposal pit of DGR for design of Full Scale Exp

7 Alternate host rock TMH characterization to broaden the scope of final site selection

8 Sorption of actinides and FP on host rocks/clay barriers for use in safety assessments/petro mineralogy studies

9 Stability assessment under earthquake for improving design of underground excavations

10 Gas migration experiment through EBS for material qualifications/safety assessments

11 Long term performance assessment of clay barriers/glasses/Natural analgoues