New Ways of Uranium Mining in Northern Saskatchewan€¦ · energy production. Figure 1: World production of uranium About half of the fuel currently used in U.S. nuclear reactors

New Ways of Uranium Mining

in Northern Saskatchewan

by

Dipl. Ing. Holger Itzeck

BAUER Resources Canada Ltd, Edmonton, Canada

Dipl. Ing. (FH) Joachim Urs Müller

BAUER Resources GmbH, Schrobenhausen, Deutschland

for

6. Hans Lorenz Symposium

Technical University of Berlin

Department of Soil Mechanics and Foundation Engineering

October 7, 2010

Berlin, Germany

Introduction

A significant portion of the world‟s uranium stocks is located in the province of

Saskatchewan in Canada. According to current research, the world‟s richest deposits

occur in sandstone formations of the Athabasca Basin in the transition zone to the

underlying crystalline rocks of the Canadian Shield.

The classic mining methods involve a number of disadvantages: underground mining

represents per se a considerable risk for workers involved and open pit mines are

characterized by significant interventions in nature and landscapes, which reverberate

often decades after completion of the mining operation.

Therefore the French energy company AREVA and BAUER Resources Canada Ltd.

have joined to develop, design and test an entirely new mining process. The technically

very demanding combination of nozzle jet and airlift (reverse circulation) technology

allows cutting the material in great depth, carrying it to the surface and immediately feed

it into the processing plant. This article explains the specific characteristics of the

uranium deposits at McClean Lake and demonstrates how a smart combination of

knowledge and experience from different departments, disciplines, and regions can

contribute significantly to the development of future technologies.

2 H. Itzeck, J.U. Müller

1. Uranium in Canada

1.1 Uranium Deposits in Canada

The upper part of the earth's crust contains approximately 2.7g/t of a substance that

equally fascinates and frightens mankind: uranium. The heaviest natural metal

(19.16 g/cm3) occurs in a variety of forms. The most important is the uranium

pitchblende; a uranium oxide named after its colour. Uranium is a radioactive element

and appears naturally combining the isotope U-238 (99.3 per cent) and U-235 (0.7 per

cent). The latter is the only known substance occurring in nature able to produce a

fission chain-reaction. With the discovery of nuclear fission in 1938, a development

began that like hardly any other demonstrates both, the blessing and the curse of

science. After the end of the Cold War, today uranium is mainly used as a primary fuel in

nuclear power plants, gaining enormous economic importance. One uranium pellet

(weight: 7 g) contains the energy equivalent of 850 kg coal or 560 litres of oil. In 2007,

65,000t of Uranium were used worldwide in 436 nuclear reactors; approximately 23 per

cent of the annual production (41,000t) comes from Canada. The gap between

production and demand is filled by using former nuclear weapon material recycled for

energy production.

Figure 1: World production of uranium

About half of the fuel currently used in U.S. nuclear reactors is made of former Soviet

nuclear warheads – a rather great example of historic irony. The United States are the

largest consumers of nuclear energy as well, using 31 per cent of the world‟s production.


Deposits vary considerably in their ore grade. Besides formations in the range of per

mille uranium grade, deposits with 20 per cent uranium and even “rich ore zones” with

50 per cent uranium content exist. These significant differences result from the different

conditions under which the ores form; high-grade ores develop only under specific

conditions.

The following will focus on the so-called discordance (inconformity) deposit type,

because not only do they make up the lion's share of Canadian uranium resources, but

currently only in Canada, the economic and technical conditions are suitable to use the

newly developed mining

method.

Ore accumulations are

primarily caused by

hydrothermal procedures.

With their relatively high

uranium contents, the

granite and gneiss under

the Athabasca sandstone

form the uranium

reservoir. The high

solubility of uranium under

oxidizing conditions (U6+)

and its strongly limited

mobility (U4+) in a

reducing environment

plays a significant role. In the area of fissured base structures, uranium mostly

precipitates as pitchblende. Weathering processes often lead to the formation of clay

caps and quartz strings near the deposit. As a result, pitchblende deposits with

extremely high uranium levels in a reachable depth and in a mechanically relatively

easily detachable form exist in northern Saskatchewan. A typical discordance deposit

can be found in Figure 2.

One can imagine the uranium deposits of the test site as lentil-shaped entity within

weathered sandstone. The typical ore bodies have horizontal dimensions of 20x50m and

reach a thickness of 10m. The first test drillholes will aim for depths between 150 and

Figure 2: A typical discordance deposit from Canada


180m; at a later stage, AREVA plans to drill down to a depth of 300m and more. The first

test drills are limited to fringe areas of the ore lenses with lower uranium grade to leave

options for other mining methods in case of an unsatisfactory outcome. There seems to

be a link between the uranium content of the ore and its ability to be removed by a jet

nozzle beam, i.e. if it works in the fringe areas with lower uranium content, the procedure

will work even more efficiently at the high-grade center. The formations lie under

consistently hard, resistant sandstone with high silica content, which will be addressed

later.

1.2 AREVA McClean Lake Operation

The French AREVA Group is a leading energy company with over 70,000 employees

and a strong industrial presence in more than 43 countries. The AREVA Group provides

technical solutions for nuclear but also conventional energy production to its customers.

AREVA emerged from a fusion of CEA-industries, Cogema, Framatome ANP,

Framatome Connectors International (FCI), and Siemens. AREVA NP GmbH with

headquarters in Erlangen is a Joint Venture. AREVA holds 66 per cent of the shares,

Siemens 34 per cent. In Germany alone, 5,100 employees work for the company.

Subsidiary AREVA Resources Canada Inc. is a partner and shareholder in several Joint

Ventures in the area of the Athabasca basin in the Canadian province Saskatchewan,

which runs open pit and underground operations for mining uranium ore. In the

processing plants the ore is enriched to the uranium concentrate "Yellow Cake".

Since the first uranium discovery at McClean Lake in 1979, the area grew to the world‟s

largest and most modern material-handling and production facilities for uranium ore.

Besides the mill, which also processes the uranium of surrounding mines for other

companies to the “Yellow Cake” concentrate, in McClean Lake itself uranium is fetched

from three open pit operations. Strict legal restraints regarding the environment, health,

and safety requirements, rising labour costs, and at times very difficult geological

conditions for ore mining brought AREVA to consider alternative methods. In a very

extensive research and development project, the company analysed, tested, and tried

alternative mining techniques to increase extraction. Thus reducing the intervention in


nature, AREVA attempts to keep its environmental footprint to a minimum. On behalf of,

Figure 3: Uranium production in Canada (World Nuclear Assn. 2010)

and together with, AREVA Resources Canada Inc., BAUER Resources Canada Ltd. has

developed a mining system that avoids many negative side effects of conventional

uranium mining and makes smaller uranium deposits economically more viable. In a

nutshell, it is a successful combination of high-pressure jet cutting with an airlift (R/C)

system.

2. Basic ideas to develop a new ore extraction methodology

2.1 Principle of High Pressure Injection

Injection works performed in the construction industry aim to improve the ground for a

particular purpose. By using an adequate drilling technology, adapted to the respective

soil conditions, existing cavities - such as pores in the gravel or unconsolidated soils -

will in most cases be filled with self-hardening slurry to solidify the foundation or to seal

the ground. If, due to the nature of the soil, classical injections are impossible or

ineffective, a jet grouting method (high pressure injection) is required. The ground is

dissolved from its natural structure by a high-energy cutting beam and mixed with a

slurry, usually consisting of cement and bentonite, whereby the soil is solidified and

sealed. High-pressure injection can be applied to underpin and deepen existing


foundations or - as a precautionary measure in the construction of tunnels and galleries -

function as horizontal sealing soles or vertical sealing walls for lakes or dams.

According to DIN (German Standard) 12716, there are three different methods for jet

grouting: During the single-phase process, the ground is cut by a high-pressure jet and

simultaneously mixed with the cement-bentonite suspension. The hardening of the

cement suspension solidifies the soil. The cement cutting beam in the dual-phase

procedure is additionally shrouded with compressed air to create larger column

diameters at greater depths. In contrast, the triple-phase procedure uses an air-

shrouded water jet to cut the ground; a separate nozzle at lower pressure provides the

cement suspension necessary for grouting the soil. For years, BAUER successfully

applied the different techniques of high-pressure injection on construction sites in

Germany and abroad, continuously improving the procedures.

2.2 Principle R/C Operation

The airlift or R/C (reversed circulation) method is characterized by reversing the classical

way of directing the drilling fluid. The drilling tool breaks the soil or rock and extracts it

via the inner liner pipe of the drilling rod. Blowing compressed air below the borehole‟s

groundwater or slurry levels

generates an upwards-flowing

motion inside the liner pipe,

lifting the mixture of drilling fluid

and cuttings up to the surface.

In contrast to the direct rotary

drilling method, the reverse

circulation method is

characterized by the drilling fluid

descending through the annular

space between pipe wall and

drill hole wall to the drill bit.

There it mixes with the cuttings

and is brought back to the

surface via the liner pipe of the

drill rod. The backflow treated in

Figure 4: Principle reverse circulation drilling


either a settling pond or tank alternatively to a recycling unit, to remove the solids out of

the fluid and then returned to the hole. In most cases it is sufficient to use water as a

flushing and support medium for the drilling process. Occasionally bentonite or polymer

based drilling fluids are used. There are three different techniques for blowing

compressed air into the standpipe: An injection valve in the standpipe, connected to a

separate air pipe attached on the outside of the drilling rod, produces the necessary

pressure difference in the pipe to keep the circulation running. Another option is the use

of double-walled drill rods, where air is pressed into the annulus between outer and inner

tube. The third option is putting an air tube into the standpipe down to a certain depth.

The compressed air entering the standpipe of the drill rod creates a suction, which

flushes the drill material to the surface. The position of the air inlet in the drill string

depends on the drill depth, geology and the provided slurry treatment. Positioning the air

inlet too low can lead to instability of the borehole, because of strongly fluctuating fluid

levels. In addition, there is a risk that the water/soil mixture brought to the surface can no

longer be collected in the sedimentation tanks or be handled in a drilling fluid filter

system, which will then overflow. Especially in cases where samples need to be exactly

classified and complete (e.g. diamond exploration), this is unacceptable. On the other

hand, an air inlet too high in the drill string might not develop enough suction to clean the

drilling tool and the drill face sufficiently. There are countless theoretical studies and

methods of calculation about the correct positioning; however, Bauer‟s practice expertise

has proven that finally the drill teams in the field are most competent in determining the

final and correct position.

R/C drilling is effective in a large variety of soil formations. Usually a short casing

suffices to stabilize the upper layers of soil; the main line of the hole is drilled mostly

supported by a drilling fluid. The achieved real diameters are usually very consistent with

the theoretical calibres.

The drilling depths and diameters are primarily determined by the diameter of the liner

pipe and the compressor performance installed for the drill. The so-called direct

circulation operations are limited to maximum drilling diameters of 400mm, as the energy

used to produce the necessary flushing volume and speed inside the annular space

would be far too high. This is why the R/C or airlift method over the years has become

the most economical way to install deep wells for the extraction of potable or mineral

water, but also for drilling of larger diameters for exploration. Based on BAUER‟s


historically grown expertise, drilling rigs specifically designed for this purposes are

successfully used worldwide. This includes the BAUER BBA series, BG 36 RC (see

3.HLS 2007), or the rotary drilling rigs manufactured by PRAKLA drilling technology. The

development of the HPRC system was built on this extensive knowledge.

3. The Task

The development of the BAUER High Pressure Reversed Circulation (HPRC) mining

system is based on the basic idea of the triple-phase jet procedure described in 2.1: to

dissolve the soil in its

structure with an air-

shrouded high-pressure

water jet. The client

requirements for the

development of the HPRC

system were focused on

the task of removing ore at

a depth of 150-180m

under ground level; bring it

to the surface and to

deliver it directly to the

processing plant on site.

The high-pressure jet

used had to be of at least 525bar pressure on the surface and should be led to the

nozzle with minimum pressure loss. Various development projects in Europe, the USA,

and Russia have been engaging with this topic extensively; however, nothing was

developed for marketability.

3.1 A New Mining System

To mine ores using high-pressure injection and airlift technology, the basic principle the

process builds on must be clarified first. For once, there were considerations to lower the

drilling tool, with a built-in Jet-R/C system -commonly the mining head- freely suspended

into the drilling hole, supplied by a hose package. However, a rigid connection using a

continuous drill string proved to be the most practical solution, especially with regards to

the necessary rotation of the mining head. To mine ores using a drill string with mining

Figure 5: Combination of high pressure jet and reverse

circulation (principle)


head based on high-pressure water jet technology for the required depth of 150-180m, it

is important to develop an appropriate connection system, which has little pressure

losses, satisfies the required features, and allows short trip times. The familiar types of

multiple rod connectors are based on the principle of centric arrangement of the pipes.

This technique, however, was not applicable, since the client required us to lead six

different lines with different functions to the mining head. Two high-pressure water

channels, two air channels, and a return pipe Ø 100mm were therefore built into an

external pipe of Ø 244mm. The remaining space inside the pipe was developed as a

sixth channel producing an upward-facing flow at the bottom of the hole, preventing an

accumulation of uranium at the bottom of the so-called quiver bore. The connection of

the external pipes was resolved by a connector system developed at BAUER and

already known in the field of the Continuous Flight Auger (CFA) drilling technique. The

rod ends are stuck together, and connected torsion-resistant by indenting and force-fit

via a chain coupling. The internal pipes are only put together via plug-in connection; the

entire power transfers through the external linkage.

The complete development and construction contract for BAUER Resources Canada

Ltd. included the following services:

BAUER HPRC swivel power rotary head with six flushing heads to mount on a

drilling rig of third-party manufacture

BAUER HPRC Mining System control unit connected to the hydraulic power of

that drilling rig

36 HPRC mining drill rods, each with six inner conduits

HPRC mining head (in four different versions/configurations)

HPRC air inlet assembly

Since this assignment is a research and development project, the system has been

under continuous supervision since it was brought into service in April 2009. With each

completed drill hole, AREVA and BAUER use the acquired knowledge to optimize

processes, increasing productivity and output per bore.

3.2 Site Installation and Test Program at McClean Lake

In 2009, AREVA prepared four drill holes for the primary field test to raise uranium using

the newly developed procedure. Initially, all four bores were drilled to final depth using

the classic R/C method in a diameter of 17.5" (444.5mm). Then, a permanent steel tube


of 13 3/8" (339.7mm) the production casing was cemented into the bore, ending above

the uranium deposits. At the experimental stage of the system, it was necessary, after

sinking the conductor pipe, to modify the drill rig from conventional drilling setup to the

BAUER HPRC system. Ideally, after a successful conclusion of the development phase,

for the subsequent production these two steps will be separated and operated

independently. The combination of the two steps in the BAUER HPRC System required

the design of a control unit that works independently from the carrier drill rig. The rig with

its mast serves as carrier for the HPRC rotary head and as generator of the hydraulic

energy necessary to operate the rotary drive and additional functions.

The carrier device, the HPRC system, and data acquisition from various sensors on the

HDI pumps, compressors, and

the HPRC system itself, are

controlled via a control board

separate from the machine. After

the adaptation to the HPRC

system, the mining head,

together with the HPRC rotary

head, and the HPRC drill rod are

installed in the bore and lowered

down to the ore body. The

course of action regarding the

jetting process was much

discussed during the design and

specification of the HPRC

system. In the first field trial of

2009, an upward directed nozzle

direction and mining starting

from the lower end of the ore

body were still preferred.

According to the results and the

experience of the first study,

however, some components were modified in 2010 and the nozzle direction was

reversed. Whether this fundamental change in procedure enables a larger ore discharge

cannot be confirmed at this time.

Figure 6: Principle HPRC System


3.3 Production monitoring and quality insurance

While traditional high-pressure injections operate with working pressures of 380-420bar,

the client requested working pressures of 525bar for the development of the BAUER

HPRC mining system. To ensure a smooth operation of the system at the mine, special

attention to use

components and devices

for the development of the

high pressure grouting

components that have

proven to be reliable in the

day-to-day business at

lower pressures was paid.

Those could be adapted to

the new requirements of

higher pressures by

modifications. For most

remaining items of the

HPRC system, the design team was able to combine parts that have been successfully

used in other devices at BAUER for years. They could be adapted to the new system by

small modifications.

Before shipment to Canada, every single channel of the HPRC rods was tested over a

certain period with a specially developed testing device using at least 1.5 times of the

normal working pressure to test the connector system, weld seams and deflecting blocks

for their leak and compression resistance. This pressure, however, was limited to 1000

bar for the two high-pressure channels. At the final assembly stage, this test load for the

high-pressure channels and HDI blocks could have been effectuated only under

increased health and safety arrangements, because failure of one of the components at

this pressure level would generate great risks for the operator. Although connectors and

linkages have been welded together mechanically using one for the most demanding

procedures defined by oil and gas industry standards, additionally welding seams

between outer tube and connectors were checked via ultrasound.

For the five single channels next to channel 6 (internal space), very high standards for

the dimensional accuracy of parts and manufacturing tolerances had to be set. While

Figure 7: Control board in operator’s cabin


connecting the rods, the tripping process, the connectors have to link together, as a

malpositioning of the rods inevitably damages the inner joints. Special welding fixtures

during production guarantee that all indoor pipe positions can be welded accurately into

place within the system.

3.4 Challenges

In the course of test preparation and implementation at the McClean Lake mine, a range

of technical and logistical tasks had to be solved. These will be briefly sketched here:

Drilling accuracy:

Besides great hardness and high silica content, the sandstone was characterized

by jointing and layering of great degree. The horizontal gradient of 15 per cent

was not adjuvant for the targeting of drills and several attempts by different

drilling companies were needed to meet the high standards. The third attempt

then met the required 0.2 per cent maximum deviation from the vertical.

Casing installation:

To avoid any radioactive contamination of the water-bearing stratum close to the

surface, and to reduce the risk of losing the valuable mining head, the entire drill

had to be cased from the top edge of the ore body up to the surface. Only after a

couple of attempts, the ideal compromise between a most economic drilling

diameter and a worry-free annual space distance was found.

Continuous operation of high-pressure pumps:

During ore mining, the European high-pressure pumps provided by AREVA run

on performance limit. To create realistic test conditions, even at this early stage

the equipment was operated at for the mining industry typical 24/7 schedule. This

HPRC operation, combined with the harsh Canadian winter, leads to a strong

strain of all components in a non-stop operation. The US-representative of the

pump manufacturer was initially completely overextended supplying spare parts

and service.

Compressors:

Similar difficulties were experienced here, since permanently relatively large

amounts of air have to be produced with high pressure to maintain a continuous

flow out of 180m depth. Service and spare parts supply, however, was much

better, because compressors generally are more common in Saskatchewan.


Material Mix:

Development of a material mix and a procedure which ensures a refill of mined

out ore chambers with a homogeneous mass of defined strength. This is

supposed to create sound conditions during the production of the neighbouring

cavity, avoiding leaks to other aquifers and giving the theoretical possibility to

mine the neighbouring areas, using different mining methods, later.

The real challenge, however, was to adapt, install and operate a completely newly

developed mining device. The device had to be transported over 8,500km from the

production plants in Germany to this secluded part of the world and be adapted to the

very basic unit of a third-party manufacturer and a large number of peripheral equipment.

In addition, the drill team on-site was used to working with hydraulically controlled drilling

equipment. The electronic pilot control with digital display and touch screen as main

control used in the BAUER HPRC mining system represented huge change, which could

not be handled without initial problems.

3.5 Questions

In addition to the yearlong discussions among nozzle jet specialists concerning nozzle

diameter, nozzle geometry, and material issues, several other questions were clarified,

or at least classified as relevant or irrelevant, in the course of the test program. Even

long-standing users of the nozzle jet technique are repeatedly surprised by how many

points had to be put to the test over and over again, because conditions or tasks

changed. Questions related to the topic pulsation of the cutting beam or enrichment of

the cutting beam with solid particles were discussed already in advance of the attempts

and rejected. During the development stage, diverse ideas were continually discussed

with AREVA. Many new points were highlighted during testing.

These include:

Inclination of cutting nozzles to the horizontal depending on the direction of work

Location of the cutting nozzle in the mining head in relation to the suction inlet for

the airlift channel

Form and design of the grate in front of the suction inlet

Installation and operation of a sonar tool integrated in the mining tool for checking

the actual diameter of the cavity (a sonar log should be possible w/o an extra

tripping process).


Performance of the high pressure flushing head under realistic conditions

Which cutting program (maximum pressure, rotational speed, time of exposure,

etc.) produces the biggest possible extraction in the particular different ore

qualities?

How t to achieve not only large but also very specific cavity diameter to establish

a later mining plan.

Wear characteristics of all relevant components under extreme working and

weather conditions.

Some of these questions lack, even after the trial program, a sure answer. Subsequently

generations of engineers will have an opportunity to prove themselves.

4. Current Situation and Future Opportunities

While in the first summer (2009) the main objective was to prove that the process is able

to generate economical ore production, during the second summer (2010), emphasis

was placed on tests targeting at the later use in a mining plan. It was worked on the

nuances of control, sonar survey, and improvements in detail. The test program was

completed with great success. The achieved production levels of uranium ore in the

northern Saskatchewan proved to meet the criteria of economic viability. Contrasting

previously described disadvantages of other mining methods, the new procedure gains

the full approval of the Canadian authorities and has great chances to become the

Figure 8: Drilling at McClean Lake MED site in summer 2010


preferred method for uranium mining for this and similar deposits. The prospective

avoidance of environmental damage, the exclusion of risks associated with underground

mining - especially in connection with exposing minors to radon - and the possibility to

improve workers protection leads us to expect very positive future developments. After

the usual creative break for prefeasibility studies, feasibility studies, and the lengthy

approval process, we believe to soon be able to start the actual production at McClean

Lake. Currently, the HPRC procedure„s future is promising.

5. References

Itzeck, Holger; Mielenz, Peter; Schwank, Stefan [2007]: „Spezialtiefbau anderswo -

Großbohrungen zur Diamantenexploration in Saskatchewan” in.: Vorträge zum 3.

Hans Lorenz Symposium, hrsg. vom Grundbauinstitut der Technischen

Universitaet Berlin, Heft 41, S.: 33-47.

Homrighausen, Reiner; Lüdeke Ulrich [1995]: „Rotary-Spülbohrverfahren im Vergleich

und ihre Durchführung“ in: BBR (9/95).

Jefferson, C.W. et al. [2007]: „Unconformity-associated uranium deposits of the

Athabasca Basin, Saskatchewan and Alberta”, in: Goodfellow, W.D., ed., Mineral

Deposits of Canada: A Synthesis of Major Deposit-Types, District Metallogeny,

the Evolution of Geological Provinces and Exploration Methods: Geological

Association of Canada, Mineral Deposits Division, Special Publication No. 5, pp.

273-305.

Lehmann, Bernd [2008]: „Uran-Lagerstaetten“, in: Advanced Mining Solutions (AMS

online), Volume 2, No. 2, pp. 16-26.

N.N.: [2009]: “Report on responsible growth” AREVA in 2008.

www.wikipedia.de

www.bauer.de

www.arevaresources.ca

www.cameco.com

http://www.wikipedia.de/

http://www.bauer.de/

http://www.arevaresources.ca/

http://www.arevaresources.ca/

Documents

New Ways of Uranium Mining in Northern Saskatchewan€¦ · energy production. Figure 1: World production of uranium About half of the fuel currently used in U.S. nuclear reactors