Lecture Notes for Environmental and Non-radiological concerns
1. Introduction
The purpose of this presentation is to introduce the students to the broad array of environmental and non-radiological issues involved in siting a borehole disposal facility.
The objectives of the lecture are:
1.
Provide the primary environmental factors to be reviewed during the development of the borehole disposal facility.
2.
Provide the non-radiological factors (technical and non-technical) involved during the review of the proposed facility.
3.
Provide examples of environmental factors first obtained in the exploratory phase of a site development that continually sampled during the operations of a low-level radioactive waste disposal facility.
2. Scope/Structure
This scope of this presentation focuses on environmental and non-radiological factors affecting the siting of a borehole disposal facility. A brief review of the regulatory framework for siting a radioactive waste disposal site is also provided.
The environmental factors are: geology, landform evolution (e.g., erosion)/topography/climate change, geochemistry, hydrology and hydrogeology and biosphere, land use and human activities.
The primary environmental factor is the site geology where at least one exploratory borehole is drilled at the site: to obtain rock samples, measure the drill penetration rate, and record at what depths water is seen and its (volume) yield.
The non-radiological factors are divided into technical and non-technical categories.
Each category is further broken into “suitable” and “unsuitable” siting characteristics.
Examples of suitable and unsuitable technical factors are geological stability and volcanic activity respectively. In the non-technical category, government owned land is suitable, but if it is a national park (land reserve), the land is not suitable for a disposal site.
The structure of this lesson is a brief lesson introduction, a review of the site selection regulatory framework, a discussion of the environmental concerns (e.g., geology, hydrology, climate), and non-radiological issues such as land ownership. Real-life examples of non-radiological sample items is provided for the benefit of the inexperienced student/regulator. The lesson is concluded with a summary slide.

3. Concepts
The overall aim of site characterization is to gain a general understanding of the site in terms of its regional setting, its past evolution and likely future natural evolution over the assessment time frame.
Site characterization for a borehole facility is assumed to be accomplished using standard mineral and water resource exploration techniques. Among the information to be gathered, baseline information on environmental and non-radiological factors (e.g., geology, hydrology, hydrogeology, fauna and flora, human activities including population densities) should be collected.
The key part of the geological (the study of the earth's physical structure and substance) investigations is the drilling of at least one investigatory borehole. The depth of the borehole should extend tens of meters below the anticipated maximum disposal depth (or to the water table unless this is known to be at least 200 m deep). Information gathered and logged from these boreholes include a core for professional examination, drill penetration rate as indicative of rock hardness, the depth where water is encountered (can happen more than once) and the volumetric yield and other drilling information such as sharp color changes.
In some cases fractured or creep of the host rock may require a well casing. Monitoring the rock in the investigatory wells could prove useful in planning the construction of the disposal borehole. It may be helpful to measure rock stress within the investigatory borehole.
Faults within the facility footprint need to be evaluated as they could act as pathways to groundwater for radionuclide transport. Geologically recent (< 100,000 years old) faults are of particular interest as they may suggest activity within the timescale of interest.
Boreholes would generally avoid crossing a fault.
A geomorphological study ( the study of the physical features of the surface of the earth and their relation to its geological structures) should be conducted to see if erosive processes and any land movements have occurred in the recent past. If discovered, this may indicate similar events could occur in the timescale of interest. The site’s topographical layout should be documented as excessive steep slopes could lead to erosion in the vicinity of the disposal boreholes.
A geochemistry ( the study of the chemical composition of the earth and its rocks and minerals study needs to be accomplished at the facility. Oxidation/reduction (redox) is probably the most important parameter due to its potential effect on metal corrosion and thus radionuclide migration. Unfortunately, this is a difficult parameter to measure directly with any accuracy so that it will usually have to be inferred from host rock observations
(mineral assemblages and surfaces that have been in contact with water). In general there

is an expectation that the host rock environment will become more reducing as depth increases. As such, more than one estimation of redox will need to be performed (e.g., at least at the top and bottom of disposal zone).
Groundwater samples should be obtained and analyzed. The groundwater pathway is the most likely pathway for human exposure to leaking waste containers. Standard water preservation techniques should be used. If the water is undrinkable, this effectively rules out this pathway, adding to the safety of the disposal site.
Hydrology and hydrogeology is the study of surface and sub-surface water. Water is a primary mobility agent for leaking radionuclides. Important information to be collected is:
 the amount of rainfall,
 estimates of evapotranspiration, and
 any indication of previous flooding at the site.
A key item to be noted is whether the disposal zone transitions between the unsaturated and saturated zones. To ensure this situation is avoided, seasonal groundwater levels need to be obtained and recorded. If the radioactive waste will be disposed in the saturated zone, tests need to document the flow properties of the host rock.
Other environmental data, such as biosphere uses and human activities need to be obtained for use in the site performance assessment model. This model will be used as a predictive tool for the post-closure timeframe.
The environmental concerns, along with other non-radiological factors, can be categorized in many ways. One potential method is breaking the factors into technical and non-technical issues. Each of these types of factors can then be further broken down into “suitable” and “non-suitable” as they impact the site characterization. This breakdown may be beneficial where regulatory bodies are located in the member nation’s public health agency and its environmental protection agency.
The presentation also includes actual environmental concerns from a member nation.
The material illustrates how pre-operational sampling will be useful during the disposal phase of the facility lifetime.
4. Definitions
Disposal borehole: a borehole this is specially located, drilled and constructed for the disposal of disused SRS and other small volume wastes.
Geochemistry : the study of the chemical composition of the earth and its rocks and minerals.
Geology: the study of the earth's physical structure and substance.

Geomorphology: the study of the physical features of the surface of the earth and their relation to its geological structures.
Hydrogeology: the branch of geology concerned with water occurring underground or on the surface of the earth.
Hydrology: the branch of science concerned with the properties of the earth's water, especially its movement in relation to land.
SRS: sealed radioactive source
Timescale of interest: post-closure modeling timeframe needed for the decay of the radionuclides to levels below public health concerns (e.g., nominally 1,000,000 years is used)
5. Additional information
Case study of work done in preparation for a disposal facility in South Africa:
Raubenheimer, E., Dzanga, P.K., Borehole Disposal Facility: Generic Site Selection and Characterization , Report No. GEA-1622, South Africa Nuclear Corporation (LTd),
Pretoria (2005).
6. References
BOSS: Borehole Disposal of Disused Sealed Sources – A Technical Manual, IAEA-
TECDOC-1644, Vienna (2011).
Borehole Disposal Facilities for Radioactive Waste – Specific Safety Guide; IAEA
Safety Standards Series No. SSG-1, IAEA Vienna (2009).
7. Summary of the Lesson

Overall goal of site characterization & techniques used

Environmental concerns o Geological investigations

Need at least one borehole to obtain vadose zone properties o Faults and fractures o Geomorphological study o Geochemistry study (e.g., redox potential)

Groundwater sample is needed o Hydrology and hydrogeology

Transition across unsaturated and saturated zones

Pre-operations site characterization can be characterized in many ways

Example of actual non-radiological environmental monitoring

8. Questions and Answers
Question #1: What is the primary purpose for characterizing the borehole disposal facility?
Answer: to gain a general understanding of the site in terms of its regional setting, its past evolution and likely future natural evolution over the assessment time frame.
Question #2: What are the four main objectives of the geology investigation at the proposed site? Briefly describe each.
Answer: The four main geology investigation objectives are:
1.
gather rock samples -- lab analysis for radionuclide transport properties
2.
drill penetration rate – hardness of the rock type
3.
depth to water – document at what depth water is encountered (more be more than once), depth of water in the finished borehole and to obtain a water sample.
4.
Blow yield – volumetric flow of water from well (yield of well).
Question #3: What is the minimum number of exploratory boreholes that need to be drilled? What is the purpose of these boreholes?
Answer: The minimum number of boreholes in one. More can be drilled. The purpose of the borehole is:
1.
Determine the nature of any chemical reactions between the barrier system and the surrounding environment.
2.
Find the water table and gather necessary data to be able to model water flow at the facility.
3.
Gather data to determine if the facility can be constructed and if a borehole casing is needed.
Question #4: What type of climate is preferred for a borehole disposal facility? Why?
Answer: Arid climate is the preferred climate for a facility. Water is most important item in contaminant transport. By limiting the amount of water available
(little or no precipitation), the possibility of radionuclide migration is reduced.
Question #5: What is probably the most important geochemistry analysis to be performed during the site characterization process? Why?
Answer: Oxidation/reduction (redox) potential is probably the most important parameter. This analysis is critical due to its effect on metal corrosion and radionuclide migration.