1. Site characterization and data requirements for implementing the BDC
This talk comes before the one on borehole completion and design
Presenter Name
School of Drafting Regulations for Borehole Disposal of DSRS
2016
Vienna, Austria

2. Outline Step by step development of the BDC
The nature of site characterization
Site characterisation techniques
Site characterization data and their uses 2

3. Main references TECDOC 1644 Requirements for disposal
Guidance for borehole disposal
TECDOC 1644
Technology of the BDC

4. Step by step development of the BDC
This section aims to put site chn in context – to show where it appears in the overall BDC development process 4

5. Possible Borehole programme
3. Pre-disposal -site specific
1. Pre-requisites
4. Disposal
DECISION POINT
approve site
Borehole construction
Collection and transfer of sources from store
Source containerization
Emplacement & backfilling
Casing removal, seal emplacement
Site decommissioning
DECISION POINT
–license disposal at recommended site i
Regulatory framework
Regulator, implementer established
Define national inventory
HOLD POINT i
Characterise favoured site
Site-specific design & safety assessments
Retrieve, transfer, condition and store sources i i
This is an example of what a BDC programme could look like. It has two main decision points – one to decide on the site (mostly a govt decision in this case) and a second to approve borehole construction and (in principle) source disposal. There is also a hold point (shown in red) that follows borehole construction. The aim is to give the regulatory body an opportunity to inspect the borehole before any waste is put into it. The diagram is a condensed form of the prgm shown in TECDOC After decommissioning the site. The diagram does not show what happens after decommissioning, which could be followed by immediate delicensing of the site or delicensing following a period of post-closure institutional control. Such delicensing would need regulatory approval.
2. Pre-disposal generic i
Define inventory for disposal adapt design to suit i
Define site selection process
Site screening
Site walkover & evaluation
Draw up ranked shortlist i i
Government decisions and inputs i
Waste management implementer actions
Regulatory Body decisions & inspections i
Cuba 18 Feb 2009
Crossl

6. Decision points First decision: site approval. Supporting information:
preliminary safety case based on IAEA generic safety assessments
inventory
Site data based on existing information/ desk studies
Second decision: approval for borehole construction and disposal of sources but with hold point following construction.
Supporting information:
Site specific safety case
Inventory
Site characterization data
Step-by-step development
This diagram shows essentially the same thing except that in this case we emphasize the need for a safety case and aproach its development also in two main steps: a preliminary safety case and a site-specific safety case. The first is based on existing information and desk studies and its purpose is to obtain approval for site investigations. The site specific safety case uses information from the site investigations and is used to obtain permission for borehole construction and disposal of sources but with a hold point at which regulatory approval is obtained to emplace the sources in the borehole 6

7. The nature of site characterization7

8. Multi-disciplinary DISCIPLINE TOPIC MAIN RELEVANCE Geology
Geotechnical properties
Hydrogeology, chemistry, seismic
Borehole construction/ stability
Geochemistry
Chemistry of host rocks
Chem’try of groundwater
Sorption properties, groundwater chem.
Corrosion of containers
Hydrogeology
Hydraulic properties/ flow regime
Transport of radionuclides in groundwater
Seismology
Earthquake magnitude and probability
Impact of earthquakes on engineered barriers
Surface properties
Erosion/ hydrology Topography
Reduction of cover / loss of isolation
Inadvertent human intrusion
Ecology
Plant and animal life/ farming
Conversion of radionuclide flux to annual dose
Resources
Scope for resource exploration & exploitation
Site chn will be a multi-disciplinary exercise and this table lists the main disciplines that will be involved
Describe the first two or three rows in the table
The fact that the task is multi-disciplinary raises the importance of coordination – it is the operator’s job to bring all this information together and make is useable by the safety case. If the work does not inform or advance the SC in some way you should ask why you are doing it. 8

9. Use of safety assessment
Safety assessment is the main driver for research and development (R&D) and site characterization
Identify key uncertainties
R&D/ Site characterization to resolve uncertainties
Update
data
Safety assessment
Facility design
design
Safety assessment plays an important role in site chn – essentially it is the main driver for the work because it is the means by which key uncertainties are identified and, therefore, the work to resolve these uncertainties is defined. So we see that we have an iterative process in which SA identifies the uncertainties, SC is performed to resolve these uncertainties by creating new information, this information is then fed back into the SA and/or the facility design which then feeds back into the SA. The SA is then run again to decide whether we have made a strong enough case or whether the process needs to be repeated. 9

10. Site characterization techniques
In this next section we describe the main techniques used in site chn 10

11. Use of existing information
It is likely that a great deal will already be known about the properties of the site, especially
Geology/ hydrogeology
Hydrology
Meteorology From national institutes etc
Ecology
Transport & utilities
All existing information needs to be collected
Local centres of expertise consulted and integrated into the project
Identify key missing data /inconsistencies
It is likely that a great deal of information will exist about the site and its environs. This can usually be obtained from national institutes and includes data on geology (and possibly hydrogeology), hydrology, meteorology, ecology, transport routes and available utilities (electricity, gas and water). Centres of expertise (local and national) need to be consulted and, if possible, brought into the project, so that all this information can be collected. Missing data can be identified by considering the needs of safety assessment 11

12. Scope of Site Investigations
Scope defines activities to be undertaken, e.g.
How many investigation boreholes?
How deep?
Type and amount of sampling and testing, etc?
Scope of required investigations depends on:
The geological environment eg how complex is it?
The inventory of wastes for disposal - esp. mobility and longevity of radionuclides;
The national regulations and approaches to authorisation;
The local availability of resources

13. Investigation Strategy
Take maximum advantage of existing information;
Use techniques for site investigations that are:
Best suited to obtain the required information; and
Are available locally at reasonable cost.
Use of specialist contractors, hence the need to specify the work ie technical specifications
The site investigations should take maximum advantage of existing information and use techniques that are best suited to obtain the required information; and are available locally at reasonable cost. Such investigations will normally be performed by contractors and this entails a need for technical specifications

14. Technical Specifications
The generic TS define generic requirements that need to be followed for undertaking the different investigation activities;
Responsibility for providing more detailed information on how activities are undertaken rests with the implementing organisation
These detailed requirements should take account of:
Local regulations and approaches to undertaking site investigations;
Available local resources; and
Local language
IAEA has prepared tech specs for the investigatory and disposal boreholes. Obviously, these are generic (non-site specific).
They define the generic requirements that need to be followed for undertaking the different investigation activities.
They place the responsibility for providing more detailed information on how activities are undertaken with the implementing organisation. This is so that the detailed requirements can take account of:
Local regulations and approaches to undertaking site investigations;
Available local resources; and
Local language

15. Activities included in Generic Technical Specifications
Surface-based geophysical surveys;
Exploratory boreholes:
Interpretation;
Investigation management (if above activities are undertaken by multiple contractors)
Ecological survey
The types of work that will need to be covered by the tech specs include:
Surface-based geophysical surveys;
Drilling and testing of exploratory boreholes:
Interpretation of results;
Investigation management (if above activities are undertaken by multiple contractors)
Ecological survey will also be needed and this may be included as part of the site characterization programme

16. Important Considerations
Investigations are designed to gather the information needed for the project - it is important to keep focus;
Multidisciplinary – may require collaboration between a range of contractors; and
Contractors may need to wait whilst other activities are being undertaken, e.g.:
Drilling halted whilst testing is being carried out
Investigatory drilling is not like drilling a water well
Some important considerations are
Investigations are designed to gather the information needed for the project - it is important to avoid getting side-tracked;
The Investigations will be multidisciplinary and you may require there to be collaboration between a range of contractors – this requires active coordination; and
Contractors may need to wait whilst other activities are being undertaken, e.g.:
Drilling halted whilst testing is being carried out. The contractor needs to know this from the outset because it will affect his costs. It follows that investigatory drilling is not like drilling a water well

17. Surface-based geophysical surveys
Provide data and information on the subsurface environment:
lithological contrasts;
Geological structures (e.g. faults); and
Depth to groundwater.
Identify prospective locations for siting:
Investigation boreholes (one or more); and
Disposal boreholes (one or more).
Use of seismic surveys, ground penetrating radar
Surface-based geophysical surveys are used to provide data and information on the subsurface environment, in particular, lithological contrasts, geological structures such as faults and the depth to groundwater.
These surveys may be used to identify prospective locations for siting:
Investigation boreholes (one or more); and
Disposal boreholes (one or more).
The most commonly used techniques are seismic surveys and ground penetrating radar,

18. Exploratory boreholes
Are likely to be smaller diameter than the disposal borehole
Define geological succession;
Define characteristics of the geological materials, e.g. geo-mechanical, geochemical and hydrogeological properties;
Define groundwater chemistry;
Establish groundwater pressures/ flow directions; and
Provide information to calibrate geophysical surveys
At least one exploratory borehole will be needed. Exploratory boreholes are likely to be smaller diameter than the disposal borehole and they are used to:
Define the geological succession. Here one might use diamond drilling to extract rock core for subsequent examination. If percussion drilling is used, cuttings should be collected at metre intervals for examination
Define the characteristics of the geological materials, e.g. geo-mechanical and hydrogeological properties;
Define the groundwater chemistry;
Establish groundwater pressures/ flow directions; and
Provide information to calibrate the surface-based geophysical surveys

19. Core drilling

20. Specific down-hole techniques
Geophysical wireline logging
Hydrogeological Testing
Groundwater sampling and testing
Many down-hole techniques are available. Geophysical wireline logging is performed using a range of tools lowered into the hole on wire. This provides a continuous record of rock properties with depth. Typical properties measured are electrical resistivity, porosity, permeability, natural gamma radioactivity, borehole diameter (calliper log) all of which may then be correlated with the lithology of the extracted core. This allows changes in the character of the lithology to be more easily brought to light.
Hydrogeological Testing applies when the borehole contains water (ie saturated conditions). It is done by isolating (“packering”) a length of borehole and then measuring the response when water is pumped into or extracted from the isolated portion. In simple terms one wishes to know how easily water can flow in and out of the isolated portion – it is a measure of permeability and, thus, of the ease with which contaminants might migrate away from a disposal
Groundwater sampling and testing is important for two main reasons . First because of its effect on the corrosion of the waste packages. We especially need to know the oxidation potential and the concentrations of ions that could cause accelerated corrosion or degradation of concrete (eg chloride and sulphate). That makes it clear that we should take steps to avoid contamination of the extracted water. The mineralogy of the host rock will be an important determinant of the groundwater chemistry. The second reason is to provide for an understanding of the origin of the water and its age. If it transpires that the extracted water has been in position for hundreds of thousands of years, for example, we can have some confidence that groundwater movement is very slow. Thus groundwater chemistry provides information about the origin of the water and its flow.

21. Typical wireline log
Example of a wireline log that provides data (bottom to top) for borehole diameter (calliper log), density and resistivity

22. Interpretation Critically evaluate the results of the investigations;
Establish characteristics of site, including geological materials present and associated uncertainties;
Identify and describe information related to geological evolution/ change; and
Define geological conditions that may influence:
Borehole construction
Depth of borehole disposal; and
Location of disposal borehole
A SC prgm will yield an enormous quantity of information and interpreting the results is a specialist job and a tech spec will be needed to explain to the contractor what needs to be done. The regulator will expect the licensee to have a good understanding of the characteristics of the site so the contractor will provide a description of, for example, the geological formations found at the site and the way these have evolved. Any uncertainties will need to be described. In relation to the disposal borehole you will be looking for information that might influence its location, its construction (principally rock competence – strength and in-situ stress) and the geological formation in which the disposal zone is to be located

23. Uses of site characterization data
In this next section we describe the main techniques used in site chn 23

24. Site characterization – possible data uses
Site selection
Borehole design optimization
Borehole construction
Post-closure safety
Understanding the geological evolution of the site

25. Site selection
Site location may be determined by site properties but is more often a political decision

26. Design Optimization
Necessary adaptation to individual country/ site conditions:
number of packages, hence length of disposal zone determined by inventory
geometry of borehole(s) tuned to optimize use of the site
Aim to
dispose at depth of at least 30m
Avoid phreatic surface
Avoid any heavily weathered rocks near the surface
Aim to preserve isolation, taking account of long-term erosion
An important task is to optimise the design to make best use of the site. The number of disposal packages (and hence the length of the disposal zone) derives from the number of sources (the inventory) and the package-to-package spacing but where, within the site, the disposal borehole is to be located and where, within the borehole, the disposal zone is to be placed will depend on the site properties. This is discussed further in the lecture on borehole design and completion

27. Disposal borehole construction
Construction of the disposal borehole will be facilitated by the presence of competent rock ie rock that does not lose cohesion or fracture heavily when the borehole is drilled
Such effects can be caused by the presence of low strength rocks caused, perhaps, by extensive weathering rocks (often near the surface) or by high rock stresses at depth causing breakout
Warning of such possibilities will be provided by site characterization

28. Post-closure safety
Strong reliance on long-term physical containment - hence key inputs relate to groundwater chemistry
Longer term radionuclides will escape – hence key inputs relate to flow and transport of contaminants into the human environment

29. Geological evolution
The licensee will be expected to have a good overall understanding of the geological evolution of the site because it is this that informs about its likely future evolution
Hence key inputs could relate to past climate conditions, seismicity, geomorphology etc

30. Summary The presentation has covered
Step by step development and implementation of the BDC
The nature of site characterization
Site characterization techniques
Uses of site characterization data

31. Thank you!