Wednesday, October 13, 2010

Uranium Mining


Author: Gavin M. Mudd
energyscience.org.au

What is Uranium and How is it Mined?

Uranium is the heaviest, naturally occurring element. It consists of two principal isotopes – uranium-238 (238U) with 238 neutrons in its nucleus, and uranium-235 (235U) with 235 neutrons. The 235U isotope is the desired isotope for nuclear reactors or nuclear weapons due to its ability to fission or split apart and release vast quantities of energy in the process. Natural uranium consists of 99.3% 238U and about 0.7% 235U. Uranium is unstable – it decays into slightly lighter elements, which are also unstable and further decay. The process of decay releases energy and a small atomic particle, and is known as radioactivity.

There are two principal types of radioactive decay – alpha decay, the release of a charged helium atom, and beta decay, the release of an electron. This decay chain progresses through until a stable isotope is achieved (i.e. lead-206 or 206Pb from 238U and 207Pb from 235U). The rate at which an isotope decays is a characteristic of that isotope, and the time taken for 50% of an isotope to decay is known as its ‘halflife’.
The various decay products from uranium have half-lives ranging from fractions of a second to billions of years, shown in Table 1.

As uranium is mostly present in oxide form, it is commonly reported as either uranium (U) or its oxide ‘U3O8’. Averageconcentrations of uranium in typical soils and rocks are about 3 mg/kg U3O8 or parts per million U3O8 (ie. about 3 grams per tonne). This background uranium is partly responsible for natural background radiation. In order to mine uranium economically using existing technology, this concentration has to reach at least 300 mg/kg or 0.03% U3O8, with most uranium mines historically ranging between 0.1 to 0.5% U3O8. Due to uranium’s variable chemistry, it can be concentrated to mineable ore grades and deposits by numerous geologic processes. The most common types of mineable economic uranium ores are found in sandstone deposits, unconformity deposits, breccia complex deposits,
intrusive deposits, metamorhpic deposits and surficial deposits.

Uranium is mined using traditional techniques such as open cut or underground mining, but sandstone deposits can also be mined by ‘in situ leaching’ (also known as solution mining).Once the ore is mined it is finely ground and the uranium is chemically extracted through conventional processes involving leaching with acid or alkali, concentration and then purification to uranium oxide. Acid leaching is the most common. An oxidising chemical is commonly also used, such as pyrolusite (MnO2) or hydrogen peroxide (H2O2), to
ensure the leaching is rapid. For in situ leaching, the acid or alkali is injected directly into the ore zone and pumped back to the surface (no ore is excavated). After leaching from the ore, the uranium is further concentrated usingsolvent extraction or ion exchange, followed by chemical precipitation to an impure oxide using ammonia (this product is ‘yellowcake’). Finally, the yellowcake is heated at high temperature to remove the ammonia and leave relatively pure uranium oxide (>97% U3O8).

Is Uranium Mining Like Any Other Mining?

Uranium ore is significantly radioactive – a property that is very uncommon across the mining industry. There are some other mineral deposits that also contain elevated uranium or thorium (also radioactive), however these aregenerally very few. A uranium ore deposit may have outcrops at the surface, presenting a major localised radiological risk, although more commonly uranium deposits are not visible at the surface and hence have negligible radiological risk. The geologic structure that holds the uranium is relatively stable. The process of mining and milling uranium ore involves severe disturbance to this natural equilibrium, especially as crystalline rocks are broken up during mining, ground for milling and aggressively chemically treated to liberate the uranium. An ore grade of 0.3% U3O8 means that 99.7% of the ore is left as solid waste, known as tailings (the minor loss of uranium is easily made up by the amount of chemicals added during leaching). Uranium mill tailings retain about 85% of the original radioactivity of the ore, and must be managed so as to minimise releases of radioactive decay products such as radium and radon as well as heavy metals (eg. arsenic, copper, lead).

What are the environmental impacts of uranium mining?

The environmental impacts of uranium mining include the traditional impacts associated with gold or copper mining, as well as additional radiological impacts. Depending on the type of deposit and method of mining, the environmental impacts are associated with solid waste management, water management, and chemicals and emissions from milling.

In open cut mining large quantities of waste rock are excavated to access the ore, with much of this waste rock also containing low grade, uneconomic quantities of uranium. Additionally, this waste rock may also contain sulphide minerals such as pyrite. When undisturbed in situ this rock is stable. However, the process of mining increases the cracks present and allows water and oxygen to diffuse into the waste. The oxygen and water reacts with the sulphide to produce sulphuric acid. This in turn dissolves much of the heavy metals and radionuclides present in the waste, allowing it to leach out of the rock into the surrounding environment.

This leachate, known as acid mine drainage (AMD), is extremely toxic to aquatic ecosystems and will cause major, long-lasting environmental impacts. AMD is a major problem in the mining of many metals, but presents an additional problem when combined with uranium mining.

 Infamous sites where environmental impacts from AMD have been extensive include Rum Jungle, near Darwin in Australia, as well as the Elliot Lake district in northern Ontario, Canada.

Since the late 1970’s, in Australia at least, more stringent requirements have been placed on solid waste and water management at uranium mines.

At Ranger, all tailings will be required to be emplaced within former open cuts and all waste rock re-contoured to a landform which is intended to be stable. For Olympic Dam, however, the present planning is for all tailings to remain above ground and then covered with engineered soils to minimise erosion, infiltration and radiological releases.

Recent analyses have examined the energy and water costs and greenhouse emissions associated with uranium production.

Energy is measured in Joules, and a GJ is one thousand million Joules. (About 1GJ of heat would be produced by 500 typical electric radiator bars operating for an hour.) The analyses show that the energy cost of extracting uranium is between 170 to 350 GJ per tonne of U3O8with higher values from lower grade ores,

while for water it takes between 46,000 to 2,900 litres/t U3O8 (eg at Beverley, an acid leach mine, consumes an average 7.7 million litres of water per tonne of U3O8). The corresponding greenhouse emissions of carbon dioxide ranges from 8.5 to 51 t CO2/t U3O8. These environmental costs are particularly sensitive to ore grade, with higher values from lower grade ores.

How much radioactive waste does uranium mining produce?

The radioactive nature of uranium means that any mining leads to the production of significant quantities of
radioactive wastes – principally waste rock and tailings. The extent of waste will depend on the specifics of a
particular deposit and mine plan, but in general open cut mining produces significantly more waste than underground mining.

By December 2005 in Australia, on average, each tonne of uranium extracted has led to the production of 848 tonnes of mill tailings and 1,152 tonnes of combined low-grade ore and waste rock (excluding in situ leach production). The total quantity of tailings is about 128 million tonnes (grading about 0.03% U3O8) with about 175 million tonnes of combined low-grade ore and waste rock. In comparison to the volumes of radioactive waste in the nuclear fuel chain, the largest quantity is easily produced in the mining and milling of uranium.

What are the radioactivity releases from uranium mining?

The releases of radioactivity from uranium mining are sourced from tailings, low-grade ore and, to a lesser extent water management. The principal release is that of radon – a noble gas that is a radioactive decay product of uranium. Radon has a high rate of radioactivity per mass, and is implicated in lung cancers in long-term health studies of former uranium mineworkers.

Can uranium mines be operated safely?

The most recent experience of Australia’s operating uranium mines demonstrates the challenges involved in uranium mining, which are distinct and unique. There have been numerous incidents at the now closed Nabarlek mine and the operating Ranger, Olympic Dam and Beverley projects.

The most common examples include mismanagement of water, sometimes leading to unauthorised releases to adjacent creeks, significant risks to mine/mill workers, waste rock leaching, and ongoing seepage impacts from tailings. Some relatively recent examples include:

Ranger:
• despite being expected to operate under a “no-release” water management system, incidents involving misplaced low grade ores or failures in water control bunds have led on numerous occasions to contaminated runoff waters being leaked into adjacent creeks (especially Corridoor Creek, a tributary of Magela Creek).
• in early 2004 incorrect plumbing saw the process water circuit being connected to the potable drinking water circuit – leading to rapid and significant toxic process water being mixed with drinking water, and much of the Ranger workforce being potentially exposed to both acute chemical and radiological exposure.

Olympic Dam:
• after operating for nearly a decade, a major ongoing leak from the tailings dam was revealed, amounting to the loss of billions of litres of tailings water to groundwater.
• in March 1999, and again October 2001, major explosions and fires caused substantive damage to the mill and smelter complexes, including major releases of noxious fumes – though the extent of radiological releases
remains highly contentious, the fact that the uranium solvent extraction circuit in the 2001 incident was on fire
raises serious concerns about how these incidents are handled by current regulators.
Beverley:
• numerous spills and leaks from pipelines have occurred.

Nabarlek (now closed):
• due to the need to reduce the inventory of contaminated mine site waters, evaporation pond water was irrigated over an area adjacent to the mine/mill and led to significant tree deaths and lasting impacts on water quality in the adjacent creek which have taken nearly two decades to flush through.

Can uranium mines be satisfactorily rehabilitated?

The experience of rehabilitating uranium mines to date in Australia is questionable. The first generation of uranium mines from the Cold War, namely Rum Jungle, Radium Hill, Mary Kathleen and the South Alligator group of mines, all still present environmental and radiological management problems and require constant vigilence and maintenance.

Examples include:

• Rum Jungle – despite extensive remediation/rehabilitation works in the early 1980’s, including excavating
remnant tailings and disposal into former pits, re-contouring and engineering soil covers over low grade ore and waste rock dumps, acid mine drainage continues to pollute the Finniss River, and the complete site still urgently requires more remediation/rehabilitation works.

• Radium Hill – after being abandoned in early 1962, minimal earth works were undertaken in the early 1980’s, mainly just engineering soil covers over the tailings piles – erosion is a continual problem and tailings requires ongoing maintenance.

• Mary Kathleen – operating in both the Cold War phase of the late 1950’s to mid-1960’s as well as again in the commercial era of the late 1970’s, the mid-1980’s rehabilitation of the mine won an engineering excellence award for its perceived quality – despite internal concerns by the regulators about potential for long-term seepage from the tailings dam. Recent field studies in the late 1990’s have validated this concern and shown ongoing seepage of saline, metal and radionuclide rich waters from the tailings dam – well above the quantities predicted at the time of rehabilitation – impacting on the local creek.

Overall, the experience to date with uranium mining does not give rise to any sufficient degree of confidence, as past sites – even after significant rehabilitation works – are still showing problems with erosion and seepage and ongoing impacts on water quality.

About the author:

Gavin Mudd holds a PhD in Environmental Engineering and is a lecturer in the Department of Civil Engineering, Monash University. His research interest include the environmental impacts from uranium mining and milling in Australia.


http://www.energyscience.org.au/FS06%20Uranium%20Mining.pdf

28 comments:

  1. one of the downside of nuclear power is the effect of uranium mining to the environment, research nee to conduct to reduce it, for example i've read in physorg.com that researchers are using bacteria to convert the dissolve uranium in groundwater into solid form so the uranium is not susceptible to transport by water.... a lot more research like this need to be funded to decrease the effect of uranium mining to the ecology......

    mohd nor faris bin mohd nordin(me084035)
    reese_rico@yahoo.com

    ReplyDelete
  2. Nice article but i didnt understand a few terms mentioned such as 'U3O8'. Also, i've been googling if there is uranium in Malaysia but couldnt find any web site lead me to it. In addition for your informative article, here is one interesting fact about uranium....before the discovery of uranium's fissile nuclear properties, uranium was mainly used in small amounts to color glass and pottery..

    DZUL FADHLI B MOHD HUSIN SERIA
    ME083538
    dzulfadhli@yahoo.com

    ReplyDelete
  3. hi mr dzul. here are the explaination of Uranium 308. thx.


    Information concerning Uranium 308

    l. (U) Uranium 308 as stated Is a misnomer. What is meant Is U
    subscript 3, 0 (letter, not zero) subscript 8, or Uranium Oxide.
    0308 is basically Uranium ore after all the other dirt and rocks
    have been removed.

    2. (U) U3O8 is feedstock ore for all subsequent Uranium
    processing and applications.

    3. U308 Is not a weapon and, therefore, there are no delivery
    means.

    4. U3O8 has no basis for weaponizatlon. It could possibly be
    hazardous only after long term high level exposure in such
    activities as mining.

    5. Decontamination Is not applIcable in this situation.

    6. ChemIcal precursors are the intermediate chemicals needed to
    produce chemical warfare agents. Since there are many different
    ways of producing CW agents and many chemical processes to reach
    the end product, there are hundreds of chemical agents which can
    be considered precursors.

    7. DIA does not believe Iraq has the agent phosgene. Instead,
    they may have used phosgene oxime during the Iran-Iraq War.
    Phosgene oxime could be delivered by a number of artillery rounds
    or aerial bombs or rockets. Phosgene oxime is a vesicant and
    would be employed in manner similar to sulphur mustard. However,
    the primary blister agent in Iraq's inventory is still sulphur
    mustard and any quantities of phosgene oxime are limited.

    ReplyDelete
  4. so here we are,great explaination of uranium. from what i read,the process to get uranium is not easy and also uranium ore is significantly radioactive which are very uncommon across the mining industry. There are some other mineral deposits that also contain elevated uranium or thorium,however these aregenerally very few. The process of mining and milling uranium ore involves severe disturbance to this natural equilibrium, especially as crystalline rocks are broken up during mining, ground for milling and aggressively chemically treated to liberate the uranium. however,this situation should have the government concern which for the country who have nuclear plant, they must already made the plan for the safety of their country and generate uranium safely. Uranium actually more good things than harm if we can use it wisely.


    Ahmad Adam B Mohd Rozain
    Me086000
    aa_bencho@hotmail.com

    ReplyDelete
  5. ouh...so nuclear are not that safe actually...
    hurmmm...are the advantages of nuclear are worth it compare to its disadvantages???
    Amirul Hafez Bin Darobi
    Me084047
    apeh90@yahoo.com

    ReplyDelete
  6. Hey there. In my opinion, because uranium ore emits radon gas, uranium mining can be more dangerous than other underground mining, unless we are able install a system to solve that problem, like installing an adequate ventilation systems.

    Uranium has the potential to be a highly dangerous substance to us, human, when not treated in the proper manner, remaining radioactive for hundreds of thousands of years. My question is, how do they handle the uranium wastes? Since they are radioactive, there must be a proper way to handle them right?

    Thank You.

    LIM CHEE KEONG (ME 083567)
    eric9090@hotmail.com

    ReplyDelete
  7. after read through this article i notice that, this uranium mining gives us more harm than good. we know that Uranium is an unstable particle, it decays into slightly lighter elements, which are also unstable and caused further decay. As the result this process will release energy and a small atomic particle, which is known as radioactivity. so, the system should be improved in order to control this radioactivity safely..

    nik zakaria bin nik mustoffa
    me083873
    nik_nod32@yahoo.com

    ReplyDelete
  8. "Overall, the experience to date with uranium mining does not give rise to any sufficient degree of confidence, as past sites – even after significant rehabilitation works – are still showing problems with erosion and seepage and ongoing impacts on water quality."

    I'm sorry but now this statement really bothers me. After reading through the lines i thought this article is going to enhance my understandings about some safety measures taken into account when dealing with uranium. But as the article conclude, it has done the opposite thing. Could you please clarify on this matter.

    Thanks.
    Zulfadhli Bin Zahudin
    darhein_90@hotmail.com
    CE083466

    ReplyDelete
  9. As from my research,Uranium mill tailings retain about 85% of the original radioactivity of the ore,so my question here,will be is it this retain amount of nuclear will be still release radiation,and cause harm to man kind,but i think goverment should more stress on the effect of the nuclear milling rather than the good part of it

    KESAVAN S/O MOHANADAS
    CE083434
    kesavan712554@gmail.com

    ReplyDelete
  10. hi...
    can u tell me what is the average percentage abundance of the uranium element that can be found in the earth's crust?

    DARSHAN A/L NAMASIVAYAM
    ME 083535
    darshan.bigd@hotmail.com

    ReplyDelete
  11. salam..
    nice article but u have to mentioned more details about da disadvantages and advantages of uranium due to da nuclear energy..Uranium has the potential to be dangerous substances and what are the solution to conduct uranium waste in order to control this radioactivity safely?tq.

    wan khairi hakimi bin wan abdul aziz
    wankhairi_90@yahoo.com
    ce083464

    ReplyDelete
  12. hello,
    after reading so much on nuclear power plants and the advantages, the disadvantages that comes with mining uranium has really made me change my opinion on nuclear energy. i was starting to really agree that nuclear energy is a good solution but after reading the difficulties in mining uranium, we really should think about this before changing to nuclear energy in my opinion.

    YANG GUO XIAN
    ME083672
    iainygx@hotmail.com

    ReplyDelete
  13. HI,
    i just wondering,
    many people saying about the mining, uranium, power plant. how about the uranium price? is it cheap? or at least appropriate for the power it supply?
    (MD NAZRIN BIN MD NAZIR, nazrinnazir.90@gmail.com)

    ReplyDelete
  14. so to conclude, getting uranium is as hard and as dangerous as of getting rid of them.with all the claims that new nuclear power stations are safe and fool proof but from this article we see the dangers aand effects or uranium mining.and as i have learnt it is extremely costly to get rid of radioactive waste.I would like to know if even with all this major concerns it is still the better choice for our country to go with nuclear energy.and if so why

    Harsukhvir Singh Godrei
    me083547
    sukh_x@hotmail.com

    ReplyDelete
  15. Salam n Hi...
    Based on our country condition, how is it possible for us to built a NPP when there are too many incidents of collapse of building ESPECIALLY in malaysia even a stadium/ school the most basic facility is a failure n u guys are expecting to built a NPP...OMG
    "Rome wasn't built in a day"

    This is what GOD had said "The world is full of destruction cause by the greed n action from the human hands itself"

    Although Australia has a high mining production of uranium, they do implement more studies n construction on solar power..cause they knew it is far more worth it...

    mohamed nabeel b sidek
    me083582

    ReplyDelete
  16. hi...........
    everything has their own circumstances,so due to this topic.all we got to do is to take the chances and grab it.....
    although before that, we have to studies this sector briefly and deeply.
    doesn't mean that if we know there is a danger and obstacle,we have to give up.
    we wont know the scores,if we don't shoot right?
    think about it.........

    Fasnor hesyam faisal
    me086029
    ronsaf17@yahoo.com

    ReplyDelete
  17. what i think NPP have many benefit and can use this tcnlgy for other purpose
    alif ahnaf bin omar
    me084145
    alip04macro@gmail.com

    ReplyDelete
  18. Talking about Uranium Mining , i have heard more effects rather then the good side of it....especially on human health risk....What is the effect of uranium mining?

    As what i know, nuclear fuel from fresh uranium is cheaper than from recycled uranium or recycled plutonium (MOX), which is why there is a worldwide uranium rush.

    To produce the 25 tonnes or so of uranium fuel needed to keep your average reactor going for a year entails the extraction of half a million tonnes of waste rock and over 100,000 tonnes of mill tailings. These are toxic for hundreds of thousands of years. The conversion plant will generate another 144 tonnes of solid waste and 1343 cubic metres of liquid waste.
    Which can eventually lead to the contamination of local water supplies around uranium mines and processing plants ...........dear blogger could you pls explain to me the pros and cons of this uranium mining in detail???

    PAVANESVARAAN SUBRAMANIAM
    waraan_2@hotmail.com

    ReplyDelete
  19. salam..
    I think this blog should base on advantage of nuclear energy.rite?but now it seem opposite.I want to know what advantage from this uranium mining and how about uranium price?

    Ahmad Aizat B Arifin
    artseni14@gmail.com

    ReplyDelete
  20. using nuclear energy is really good for the environment and the economy also...But getting uranium for this process have devastating effect too, to the environment,Just like that electric car using electricity generated from fuel.

    Leon K
    ME084603

    ReplyDelete
  21. Hi there,from this article I've figured out the disadvantage of nuclear. Eventhough the protection and management in nuclear power plant is really good,but it is not really safe and secure when it comes to mining the uranium.

    Amiro Iqbal Bin Mohd Aminudin
    ME084618
    amiro_aminudin@yahoo.com

    ReplyDelete
  22. hye...

    what an informative articles...
    Right after I read this article, I think Malaysia needs to do lot more researches on how to handle uranium as it is a very unstable element to be used by NPP...

    tq

    Muhammad Fahmi bin Abd Talib
    ME083597
    fahmee107@gmail.com

    ReplyDelete
  23. hye..
    Very good article on uranium. Other than Australia and Canada, is there any other country that have Uranium Mines? If so, can you list them?

    ENGKU AHMAD AZIZAN
    ME083540

    ReplyDelete
  24. hallow....
    overall please allow me to give my opinion
    nuclear has bringing so much problems
    learn from history and current situation
    so dont let the others see Malaysia the same as Iran
    we should handle first democracy..
    then you can think of nuclear
    isnt that right?
    btw,Malaysia is Islamic country
    have to remember that

    ReplyDelete
  25. Mining of uranium is a difficult job. It must be conducted professionally in a way that it doesnt do any harm to any side is equally hard . We must however overcome this problem before resolving into using nuclear energy

    EYU ZHI MING
    ME083541
    invader81@hotmail.com

    ReplyDelete
  26. Nuclear energy is advertised as a "green" energy, green meaning it is sustainable and does not disrupt the surrounding flora and fauna. The generation of this energy may be clean and green, but if you look at the aspect of acquiring this energy (mining) it may cause a lot of pollution such as groundwater intrusion of the uranium that may lead to water poisoning and such. I am not against nuclear energy, but the public should be told of its pros and cons before deciding on building a plant in Malaysia.
    thank you,
    Muhamad Rifdy Bin Samsudin
    CE083444
    ed_dy12@hotmail.com

    ReplyDelete
  27. "The oxygen and water reacts with the sulphide to produce sulphuric acid. This in turn dissolves much of the heavy metals and radionuclides present in the waste, allowing it to leach out of the rock into the surrounding environment."the statement shows that the mining of uranium is very dangerous as we use oxygen and water as daily basis.in fact,we can never live without them.so,to prevent the uranium from affecting our health,what is the necessary strategy that can be taken.for example for iodine,they have iodine pills given to the citizens in advance to counteract the effects of such radiation..tq

    FIRDAUS BIN JULAIHI
    ME083542
    dozs73@gmail.com

    ReplyDelete
  28. Ok... A lot of information but the post is seriously too long. Does every nuclear power plant uses uranium for their reactor? Bcoz i have been reading and came across a few other elements being mentioned. It is green while operating the reactor but somehow it doesn't seem that green after reading this post. Hopefully in the future, no more accidents as those mentioned will happen, ppl will be more careful and be aware of this kind of thing especially when it's dealing with nature.

    Ang Jit Yong (ME083530)
    aplox3@hotmail.com

    ReplyDelete