View source for Whiteshell Nuclear Research - Used Fuel Disposal Program

This article was originally published with the following title:  "'''Thirty years of geoscience-geotechnical research for safe storage/disposal of high level nuclear waste in underground repository.'''” 

==Introduction== 
Canada initiated a research program in the mid-1970s to develop and demonstrate the technology for safe disposal of nuclear fuel waste generated by nuclear electric generating stations in Canada. In 1978 Atomic Energy of Canada Ltd (AECL) was assigned responsibility for researching and developing the immobilization and disposal of radioactive wastes under the Canada/Ontario Nuclear Fuel Waste Management Program. AECL’s mandate was to develop, demonstrate and document technology for safe disposal of used nuclear fuel. By 1989, AECL had developed a repository concept that was referred to an Environmental Assessment Panel, the Seaborn Panel<sup>1</sup>. 
After a series of workshops, open houses, and public hearings held over 10 years, the Seaborn Panel concluded in 1998 that, from a technical perspective, the safety of Deep Geological Disposal had been on balance adequately demonstrated, but from a social perspective it had not. The Panel recommended that a Nuclear Fuel Waste Management Agency be established to manage and coordinate the full range of activities relating to the long-term management of nuclear fuel wastes.  As a result, the Government of Canada passed the ''Nuclear Fuel Waste Act'' in 2002, which led to the establishment of the Nuclear Waste Management Organization (NWMO) by the owners of used nuclear fuel in Canada.  AECL’s program focused on the concept of deep disposal in plutonic rocks of the Canadian Shield, which are abundant in Ontario with the Whiteshell/Lac du Bonnet Batholith being the western limit of the exposed Precambrian rocks.  The AECL, under its Canadian Nuclear Fuel Waste Management Program (CNFWMP), initiated assessment of the concept with some assistance from the Geological Survey of Canada. As part of this assessment, a broad program of geoscience and geotechnical research was started to investigate the plutonic rocks at several areas of the Canadian Shield<sup>3</sup>.  The major geoscience efforts ultimately focused on the Lac du Bonnet Batholith field research areas (Figures 1 and 2). The main focus of the work was to develop and test site screening/evaluation and characterization techniques to investigate progressively smaller areas of plutonic rocks to depths of 1000 m. The intent was to understand and define design needs of an underground repository.


[[File:Figure 1 Lac du Bonnet batholith, URL and subsurface geologic domains investigated ver1.jpg|thumb|centre|750x750px|Figure 1: Lac du Bonnet Batholith, URL and subsurface geologic domains investigated. Figure courtesy of Ganpat Lodha.]]

==Geoscience Studies==
The Lac du Bonnet Batholith lies in the southern part of the English River Subprovince of the Winnipeg River batholith zone.  The batholith is in sharp contact with the Bird River Greenstone Belt to the north and in gradational contact with foliated tonalite-granodiorite gneisses and migmatite.  The batholith trends east-northeast, with about 1500 km<sup>2</sup> of exposed rocks east of the Paleozoic rock cover.  The initial fault/fracture identification shown in Figure 2 is partly based on several types of satellite data, airborne geophysical data, airphoto data and available bedrock geology maps.  This is followed by detailed surface geological mapping, ground geophysics, surface hydrological and associated studies.  The geology of the Underground Research Laboratory (URL) site is representative of the batholith.  The gross structure, the variations in its large-scale litho-structural components, and the orientation of smaller scale fabric elements affect the distribution of some of the fractures and low-dipping fault zones.  AECL mapped the batholith for type, lithology, and fracture frequency at a scale of 1:50,000 and the URL site for lithology and fracture characteristics and distribution at a scale of 1:1000.  Detailed geoscience studies at the URL site and five other smaller grid areas 'A', 'B', 'D', 'G’ and 'J' shown in Figure 2 were continued, until the completion of the environmental review process in 1998 and the transfer of the program to the Nuclear Fuel Waste Management Organization (NWMO) in 2002. 

[[File:Figure 2 Location of Grid, Sample and Detailed Study Areas Shown with simplified geology of Lac- du Bonnet Batholith within Whiteshell Research Area (WRA)..jpg|thumb|center|971x971px|Figure 2: Location of Grid, Sample and Detailed Study Areas Shown with simplified geology of the Lac-du Bonnet Batholith within the Whiteshell Research Area (WRA). Figure courtesy of Ganpat Lodha]]

The geotechnical studies were initiated simultaneously by construction of an Underground Research Laboratory (URL). In practice the construction of an underground repository will begin after detailed surface site evaluation and characterization (including extensive borehole studies), but for this research the construction of the URL started early, after initial evaluation of the Lac-du Bonnet Batholith.

==Underground Research Laboratory==
The Underground Research Laboratory (URL) was constructed in the Canadian Shield 18 km east of Lac du Bonnet, Manitoba (Figures 1 and 3).  Its purpose was to study the safety and feasibility of long-term containment and isolation of Canada’s used nuclear fuel in a deep geologic repository.  The laboratory timeline began with siting investigations in 1978 and ended with shaft closure in 2010.  The URL was unique in Canada and was only one of a few facilities of its kind in the world.  The quality of the research program and a unique variety of crystalline rock environments attracted international attention.  International research participants at the URL included the USA, Japan, France, Korea, Sweden, and Finland.  Engineers Geoscientists Manitoba awarded the 1990 Team Achievement Award to the URL project for contributions to geoscience and engineering. In the early 2000’s, the URL was designated as one of the International Atomic Energy Association’s (IAEA) centres of excellence for training in and demonstration of, technologies for radioactive waste disposal.  

<li style="display: inline-block;">[[File:Figure 3a Photo showing surface URL facilities..jpg|thumb|left|400x400px|Figure 3a:  Photo showing URL facilities at the surface. Figure courtesy of Neil Chandler.]]</li>
<li style="display: inline-block;">[[File:Figure 3b Photo underground URL facilities..jpg|thumb|right|400x400px|Figure 3b: Facilities underground at URL. Figure courtesy of Neil Chandler.]]</li>

==URL Siting and Construction== 
A small set of screening criteria was established for selecting the URL site.  The site had to be larger than 1 km<sup>2</sup>, be predominantly outcrop, and be undisturbed by previous excavations.  The site had to be within, but not close to, well-defined hydrologic boundaries. The location of the URL shaft was specified in a region of moderate fracture zone permeability to allow access to proposed areas of future underground experiments.    The site had to be accessible, near power, near AECL’s Whiteshell Laboratories and available for lease.  Shaft collar excavation and construction of the surface facilities began in 1982 (Figure 4).  The shaft was sunk to a depth of 255 m, followed by excavation of a loop of horizontal tunnels at 240 m below surface (the 240 Level).  The shaft was extended to a depth of 443 m in 1988.  This was followed over the next three years by the excavation of the lateral inclined tunnel at the 420 Level and boring a one meter diameter ventilation shaft from surface to this level in compliance of mining regulations for safety.  (Explanation: A ventilation shaft separate and within a few metres from the main shaft which moves people and equipment up and down, was needed to provide a survival/communication alternate pathway for trapped underground workers in case of accidental collapse or closure of the main shaft due to a rock slide etc.)  

<li style="display: inline-block;">[[File:Figure 4a URL Excavations schematic.jpg|thumb|left|400x400px|Figure 4a: URL Excavations schematic. Figure courtesy of Neil Chandler.]]</li>
<li style="display: inline-block;">[[File:Figure 4b Controlled blasting on the 240 Level.jpg|thumb|right|400x400px|Figure 4b: Controlled blasting on the 240 Level. Figure courtesy of Neil Chandler.]]</li>

The URL construction phase adhered to the observational method, following a design process similar to that followed on many large geotechnical construction projects. Design specifications were based on evolving characterization information. The primary objective was always to provide a safe and efficient underground research facility. The design-as-you-go method (an efficient design modification process responding to observed geological and ground conditions as well as revised experimental requirements) was aimed at minimizing the costs of construction and operation, providing underground access to a variety of hydrogeologic and geo-mechanical environments, and accommodating development and evaluation of characterization techniques during construction. Research activities generally had priority over construction activities. The guiding principle was to maximize the benefit to the research program in order to best achieve the URL objectives.

==Regional and Site-Scale (URL) Characterization==

One program objective was to study the character and distribution of fracturing, at all scales, in several types of plutonic rock.  A second objective was to develop ways to analyze this information to infer conditions at depths of 500 to 1000 m to aid in the siting of a future deep geologic repository.  Area-scale, site-scale, and excavation-scale characterization methods were developed and tested from detailed study of fractures and lithology from core logging, geophysical logging, hydrogeological monitoring and testing in over 30 vertical and inclined boreholes drilled up to one-kilometre deep in some of the research areas of this batholith (Figure 2).  A multi-disciplinary approach to data collection and interpretation used input from geology, geophysics, hydrogeology, hydro-geochemistry, and later with URL construction and excavation-scale geotechnical studies. 

The Satellite data, airborne geophysical data, airphoto data and available bedrock geology maps were used to provide initial regional-scale fault/fracture identifications of the batholith.  Airborne magnetic and electromagnetic surveys combined with LANDSAT 5 data were helpful in identifying boundaries of the plutonic rocks, overburden thicknesses, major lineaments that might be geological structures and lithological contacts. The surface gravity data along with magnetic data were useful to model the depth (root) of the batholith (Figure 5).  Surface geological mapping of exposed rock outcrops, combined with VLF/EM, radar and seismic reflection surveys data, were useful in identifying the orientation and depth continuity of low-dipping fracture zones beneath rock outcrops to a depth of 1000 m.

The research areas including URL site-scale studies by geological mapping, radar surveys, core logging combined with borehole geophysical logging, TV/ATV logging, flowmeter logging and full waveform sonic logging confirmed the location of hydro-geologically important fractures and was used to infer the relative permeability of some fracture zones. Single-hole radar and crosshole seismic tomography surveys were useful to establish the continuity of fracture zones away from the boreholes to distances of 50 to 400 metres (WB1-WB2: Figures 6 and 7). Mr. John Hayles, P.Geo. (MB) & P.Eng. (ONT) was presented with the “Technical Excellence” award of Engineers Geoscientists Manitoba (EGM), in 2014 for his pioneering work on geophysical tomography during this research work at the WRA.

[[File:Figure 5 Subsurface Models of Gravity & Magnetic Data from Whiteshell Research Area..jpg|thumb|centre|750x750px|Figure 5: Subsurface models of gravity & magnetic data from Whiteshell Research Area. Figure courtesy of Ganpat Lodha.]]

[[File:Figure 6 Integrated Cross-Hole and Surface Radar Surveys at Grid Area ‘B’.jpg|thumb|centre|750x750px|Figure 6: Integrated cross-hole and surface radar surveys at Grid Area ‘B’. Figure courtesy of John Hayles.]]


[[File:Figure 7 Crosshole Seismic Image of the P-Wave Velocity between Borehole WB1 and WB2.jpg|thumb|centre|750x750px|Figure 7: Crosshole seismic image of the P-wave velocity between borehole WB1 and WB2 shown with hydraulic test correlations and fracture histogram. Figure courtesy of John Hayles.]]

Single-hole hydraulic tests using straddle packer testing in multiple-interval casing systems and large-scale crosshole pumping tests provided estimates of the in-situ permeability (Figure. 8).  Crosshole tracer tests were performed in several of the major fracture zones to estimate the solute transport properties and to provide information to scale up the properties to the regional modeling scales. Geochemical and hydrogeochemical characterization of host rock fracture-infilling minerals, groundwaters and porewaters provided data for flow modelling as well as obtaining information on groundwater ages, sources of salinity and rock-water interactions.

The detailed characterization revealed three low-dipping fault zones and associated fracture zones (moderate to sparsely fractured) that controlled the large-scale patterns of groundwater movement and groundwater chemistry within the URL rock mass.   


[[File:Figure 8 Hydraulic Testing Equipment; Workover Rig and or Umbilical Cable.jpg|thumb|centre|750x750px|Figure 8: Hydraulic testing equipment; workover rig and/or umbilical cable. Figure courtesy of Ganpat Lodha.]]

==URL Research Program==
Over thirty experiments, or experimental programs, were conducted at the URL, with each experiment composed of several sub-projects.  Experiments were conducted in parallel with numerical modelling to develop tools for assessing the safety of a used fuel repository millennia into the future.  Potential engineering designs and construction methods for excavations and repository seals were often tested at full scale (Figure 9).  Advances in geotechnical and cement-based material sciences, material testing, instrumentation, in situ investigation, rock fracturing and fracture characterization led to hundreds of publications in international journals, conference proceedings, book chapters and peer-reviewed and publicly-accessible reports.  Interim results of URL characterization and initial experimentation contributed to a comprehensive ten-volume Environmental Impact Statement submitted for the review of Canada’s conceptual design for long-term used fuel management<sup>1,2</sup>.  

The following are examples of studies performed within the different regions of the URL:
# Surface hydrology:  A hydrogeologic network of over 130 shallow and deep boreholes was established to monitor hydraulic head caused by construction of the URL.  Included within this network was monitoring dedicated to understanding local-scale run-off and infiltration in a granite outcrop. 
# Highly fractured rock (fracture zones): Extensive characterization was performed to determine the hydraulic and solute transport properties of the fracture zones that cross the URL site, and to test our ability to predict the transport of solutes through the geosphere using available numerical tools. 
# Moderately fractured rock: A comprehensive study of solute transport through rock having between one and five fractures per linear metre was performed.  URL shaft sinking included a study of the effect of excavation on the hydraulic and mechanical response in the moderately fractured rock near the surface.  Ultimately, sealing of URL shaft was conducted in this region.  The seal continues to be monitored as the groundwater in the surrounding rock recharges.
# Low stressed and sparsely fractured rock: The excavations on the 240 m Level of the URL were stable with little excavation related damage.  Experiments at this level studied the performance of engineered sealing materials in the absence of rock damage. Another project to improve excavation methods used controlled blasting to minimize blast-related fracturing.  The existence of a single water-bearing fracture at this level allowed the study of the hydro-mechanical response of the fracture to excavation and the study of radionuclide transport in an isolated block taken from the fracture.
# High stressed and sparsely fractured rock: The rock at the 420 m Level of the URL was stressed to the point of fracturing in the roof and floor of excavations.  In some cases, the fracturing resulted in small, but continuous, regions of highly-damaged rock.  Experiments examined rock response to excavation, including choosing tunnel cross-sections to minimize fracturing.  The effectiveness of tunnel seals at full-scale was studied in tunnels with much near-surface rock damage (Figure 9).  The high pore water salinity at this depth also provided an environment for testing the effect of salinity on clay and cement-based sealing materials.  Diffusion of solutes through unfractured, low-porosity rock could also be studied. 

<li style="display: inline-block;">[[File:Figure 9a Full-scale tunnel seal excavation.jpg|thumb|left|400x400px|Figure 9a: Full-scale tunnel seal excavation. Figure courtesy of Neil Chandler.]] </li>
<li style="display: inline-block;">[[File:Figure 9b Heater - container in an in-floor borehole.jpg|thumb|right|400x400px|Figure 9b: Heater - container in an in-floor borehole. Figure courtesy of Neil Chandler.]]</li>

==URL Closure Project==

As part of the URL decommissioning activities, a large, engineered seal constructed of high-strength concrete bulkheads sandwiching a dense clay layer ensured that deep saline groundwater never mixes with fresher water at shallow depths. Monitoring this seal is being funded by the NWMO and organizations from Finland, France, and Sweden.  Data will provide information on the performance of an engineered seal in a repository application. All underground facilities were removed and the URL shaft was permanently sealed in 2010.  Surface buildings have since been dismantled. 

==Summary==

The detailed geoscience/geotechnical investigations completed at WRA and experiences from other studies provide enough support to suggest that reasonably large volumes of sparsely fractured plutonic rocks are present in the Canadian Shield.  The knowledge gained in the WRA and URL clearly demonstrated that these sparsely fractured rocks, enveloped by low dipping and occasional vertical fractures at shallow depths can have low permeability at depth. The studies in Whiteshell Research Area demonstrated that long residence time of ground water in sparsely fractured volumes of plutonic rock can potentially provide suitable environment for siting a safe underground repository.  The Whiteshell Research Area and URL contributed greatly to our technical and practical understanding of issues related to the geoscientific characterization of rock masses at varied scales and to the engineering design and construction of a future geologic repository for used nuclear fuel.

The URL garnered international recognition and positioned Canada at the leading edge of technological developments related to the disposal of radioactive waste.  It was an important geoscientific and engineering project in Manitoba between 1978 and 2010. The geoscience research and URL project were useful for the economy of Eastern Manitoba, supporting local business and services, with approximately 100 people employed and living in the area for more than 30 years.  

Today, the long-term management of Canada’s used nuclear fuel is under the responsibility of the Nuclear Waste Management Organization. This organization is pursuing the eventual development of a deep geological repository and is implementing a community driven site selection process to seek an informed and willing host with a suitable geological formation<sup>5</sup>.

==Acknowledgements==

This paper has been compiled by the authors from the public domain reports available from AECL and CANDU Owners Group work related to the used nuclear fuel disposal program (1978-2010).  The initial review and input about early stages of the program from Dr. Nash Soonawala is appreciated. Final review and editing by Dr. M. Ben Belfadhel, Ryan Bernier and Glen Cook are gratefully acknowledged.

==References==
# Executive Summary: Summary of the Environmental Impact Statement on the Concept for Disposal of Canada’s Nuclear Fuel Waste, Atomic Energy of Canada Limited Report, 1994. AECL-10721, COG-93-11
# Davison, C.C., Brown, A., Everitt, R.A., Gascoyne, M., Kozak, E.T., Lodha, G.S., Martin, C.D., Soonawala, N.M., Stevenson, D.R., Thome, G.A., Whitaker, S.H., 1994. The disposal of Canada's nuclear fuel waste: Site screening and site evaluation technology. Atomic Energy of Canada Limited Report, AECL-10713, COG-93-3.
#Dormuth, K.W., Nuttall, K., 1987. The Canadian nuclear fuel waste management program: Radioactive waste management and the nuclear fuel cycle, Vol. 8 (No. 2-3), 93-104
#Simmons, G, Baumgartner, P, 1994. The disposal of Canada's nuclear fuel waste: Engineering for a Disposal Facility. Atomic Energy of Canada Limited Report, AECL-10715, COG-93-5.
# Nuclear Waste Management Organization. www.nwmo.ca

==Compiled by==
# Ganpat S. Lodha, PhD, PGeo (SM), FGC, Honorary Life Member (Geoscientist)-EGM. 
# Neil A. Chandler, PhD, PEng (SM), FEC <br><br>

<br>Editing
# James A. Burns, PhD.
<br>

Posted by Glen N. Cook, PEng (SM), FEC

If you have feedback on this article please contact the webmaster at APEGM.heritageeng@gmail.com.

==Photo Gallery==

<li style="display: inline-block;">[[File:Gary Simmons with Colin Allen and Ken Dormuth on completing 30 years of service at URL.jpg|thumb|none|300px|Left to right: Gary Simmons with Colin Allen and Ken Dormuth on completing 30 years of service at URL. Photo courtesy of Ganpat Lodha.]] </li>

<li style="display: inline-block;">[[File:Whiteshell Community Reporter Dec 1994 Vol 2 no 2 - photo of Sid Whitaker, Ken Dormuth & Phyllis Gillespie with EIS submission.jpg|thumb|none|300px|Whiteshell Community Reporter Dec 1994 Vol 2 no 2 - Sid Whitaker, Ken Dormuth & Phyllis Gillespie with EIS submission. Photo courtesy of Ganpat Lodha.]] </li>

<li style="display: inline-block;">[[File:Applied Geoscience Branch staff with branch manager Cliff Davison in the middle.jpg|thumb|none|300px|Applied Geoscience Branch staff with branch manager Cliff Davison in the middle. Photo courtesy of Ganpat Lodha.]] </li>

<li style="display: inline-block;">[[File:3-D fracture mapping at URL Radar Survey scientist Art Hollaway, Gary Simmons, Japanese visitor and Cliff Davison.jpg|thumb|none|300px|3-D fracture mapping at URL Radar Survey.  Left to right: Art Hollaway, Gary Simmons, Japanese visitor and Cliff Davison, Photo courtesy of Ganpat Lodha.]] </li>

<li style="display: inline-block;">[[File:Underground Research Laboratory (URL) staff..jpg|thumb|none|300px|Underground Research Laboratory (URL) staff. Photo courtesy of Neil Chandler.]] </li>