Sudan Academv of Science(sAs)

Atomic Energy ResearchesCoordination Council

Extraction and Purification ofYellow Cake

A Dissertation Submitted in Partial Fulfillment of theRequirement for Diploma Degree in Nuclear Science

(Chemistry)

ByElshafeea Hassan Yousif

(B.Sc.)

Supervisor:Dr. Adam Khatir Sam

J

January 2006

-'

Sudan Academy of Science(SAS)

Atomic Energy ResearchesCoordination Council

Extraction and Purification ofYellow Cake

A Dissertation Submitted in Partial Fulfillment of theRequirement for Diploma Degree in Nuclear Science

(Chemistry)

ByElshafeea Hassan Yousif

(B.Sc.)

Supervisor:Dr. Adam Khatir Sam

January 2006

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ACKNOWLEDGMENT

I would l ike to thank honorable supervisor D.Adarn Khatir Sanr fcrr his

contitiuous support and guidance, support. and valuable instructions from

which I have benefi ted nruch in executing this rvork.

And also I would l ike to thank every one who aided me in this rvork.

Elshafeea Hassan Yousif(High Diplorna Student)

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ACKNO\VLEDGMENT

I would like to thank honorable sllpervisor D.Adam Khatir Sam for his

continuous support and guidance, support and valuable instructions from

which I have benefited much in executing this work.

And also I would like to thank everyone who aided me in this work.

Elshafeea Hassan Yousif(High Diploma Student)

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ABSTRACT

' l ' l t is disscrtat ion has rcvicrved curre nt studies on productiorr and

puri l icat ion ol 'yel lorv cake l ionr uranium ores by both aci<J ancl alkal ine

leaclr ing processcs. l t cotnprises three chapters, the f i rst one r jeal wit |

uranium minerals, uraniunr deposits, geology of uranium and uranium

isott lpes. ' l 'hc

secottd clrapter covers nrining and mil l ing methods,

uraniurn leaclt i r tg chernistry, precipitat ion, and puri f icat ion of uraniunr

cotlccntrate by solvent extractiotr and possible impurities that contmonlyt

interl'ered rvith yellorv cake. "t'he last chapter presented ongoing literature

review.

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ABSTRACT

This dissertation has reviewed current studies on production and

purification of yellow cake from llranium ores by both acid and alkaline

leaching processes. It comprises three chapters, the first one deal with

uranium minerals, uranium deposits, geology of uranium and uranium

isotopes. The second chapter covers mining and milling methods,

uranium leaching chemistry, precipitation, and purification of uranium

concentrate by solvent extraction and possible impurities that commonly,

interfered with yellow cake. The last chapter presented ongoing literature

review.

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Subject Page

Ack t to l v l cdg t r t c t r t

Abstract

Abstract (Arabic)

Table of contents

List of tablcs

List of firgures

CI{AI'T'BIT ONtr

Uraniurn and it 's deposits

l . l In t roduct ion . . .

1.2 Uraniunr minerals

L3 Geology o[ Uraniurn

1.3.1 Unconformity related deposits

1.3.2 Sandstone deposits

1.3.3 Quartz pebble conglonrerate deposits . . .

1 .3 .4 Vein deposi ts

1.3.5 l l reccias cornplex deposits

1.3.6 ln t rus ive deposi ts

I .3 .7 Phosphor ic deposi ts

t.3.8 Col lapsc breccias pipe deposits

1.3.9 Volcanic deposi ts

I .3 . I 0 Surhc ia l dcposi ts

1.3.1 I Metasonrat i te deposits

| .3.12 Metamorphic deposits

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Acknowlcdgmcnt ..

Abstract (Arabic) .

Table of contents .

List of tables .

List of figures ' " '"

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Subject

Abstract

TABLE OF CONTEN'rS

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Uranium and it's deposits............................................... 2

1.1 Introduction...................................................... 2

1.2 Uranium minerals............................................... I 2

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CHAPTER ONE

1.3 Geology of Uranium ..

1.3.1 Unconfonnity related deposits .

1.3.2 Sandstone deposits ..

1.3.3 Quartz pebble conglomerate deposits .

1.3.4 Vein deposits .

1.3.5 Breccias complex deposits ..

1.3.6 Intrusive deposits ..

1.3.7 Phosphoric deposits .

1.3.8 Collapse breccias pipe deposits .

1.3.9 Volcanic deposits .

1.3.10 Surficial dcposits .

1.3.11 Metasomatite deposits .

1.3.12 Metamorphic deposits .;

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I .3. I 3 l igrites deposits

1.3. I 4 I l lack shale deposits

I . I 5 Other type of deposits

1.4 Uranium isotopes

CIIAP'TBITTOIV

Nuclear fuel cvcle

2.1 Uranium mining

2.2 Uranium nr i l l i r ig

2.3 Uranium Leaching

2.3. t Acid leach chemistrv for uranium

2.3.2 Alkaline leach chemis[ry for uranium

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2.6 Stripping

2.7 Precipitation

Literature Review

CHAI'TBIt 'THTTBE

2.5 Solvent extraction

2.4 Purification

Conclusiort

Reflerences

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CHAPTER TO\V

Literature Review .

Conclusion .

2.6 Stripping ..

2.7 Precipitation .

CHAI1TER THREE

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•••••••••••••••••••••••• 11 .References

Nuclear fuel cycle " .

2.1 Uranium mining .

2.2 Uranium milling .

2.3 Uranium Leaching ..

2.3.1 Acid leach chemistry for uraniurn .

2.3.2 Alkaline lea~h chemistry for uranium .

2.4 Purification .

2.5 Solvent extraction .

1.3.13 ligrites deposits .

1.3.14 Black shale deposits ' .

1.15 Other type of deposits .

1.4 Uranium isotopes .

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Table ( l . l ) : l ist of sonre contnron uraniunr nr inerals 3

Table (1.2): uraniunr isotopes

L[ST'OF FICURIS

Figurc (1 .1) : Uranium decay senes

Figurc (1 .2) : Uraniunr Act in ium decay ser ies l0

Figure (2.1): General ized process for uranium extract ion . . . . . . J 9

Figure (2.2): Schernatic flow sheet of purihcation by

Solvent extraction 20

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Table (1.1):

Table (1.2):

Figure (1.1):

Figure (1.2):

Figure (2.1):

Figure (2.2):

LIST OF TABLES

list of some common uranium minerals .J

uranium isotopes ..

lISI' OF FlCURES

Uranium decay series .

Uranium Actinium decay series ..

Generalized process for uranium extraction ......

Schematic flow sheet of purification by

Solvent extraction ..

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CHAPTER ONE

URANTUM AND IT'S DEPOSITS

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CHAPTER ONE

URANlUM AND IT'S DEPOSITS

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UIIANIUI \ l r \ND lT 'S DEI 'OSIT-S

l . l In t ro t luct iou:

Irollowing the developrnent of the nuclear industry during and

immediately after World War II, attention was focused on developing

technologies, which could be used to upgrade and purify uranium from

low-grade sources. Initially the nuclear industry had relied on high-grade

uraniunr ores ltorn the Belgiurn Congo and Canada. One of the main

part icipants in this developnrcnt \ \ ,as Union of South Afr ica. The

production of yel lorv cake was an essential step in this cleveloprnentr.

1 .2 Ur ln iurn rn inera ls :

An urrdcrstanding of rnineral izat ion concepts o{ 'uranium lead to better

undcrstanding of expected leaching behavior. In nature exist mainly in

the valcncc state Ua* l tetravalent) and U6* (hexavalent).The mineralogy

and geochernistry of the vale nce states dissirnilar. Tetravalent uranium is

readily oxidized and is stable only under reducing conditions. llexavalent

uraniurn forms a cornplex uranyl ion (UO2 )2" that cornbines with other

elentents in oxides, silicates, sulphates, vanadates, arsenates, carbonates,

phosphates and molybdatesz.

Uraniurn minerals may be tenned prirnary or secondary, depending upon

their degree of oxidation and origin. The comrnon Uranium minerals are

l isted in T'able ( l . l ) .

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The nrost inrportant primary ore minerals are uraninite, an oxide,

coffinite, a silicate. Pitchblende, also a primary mineral, is a caliform

variety of uraninite.

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URANIUM AND IT'S DEPOSITS

1.1 Introduction:

Following the development of the nuclear industry during and

immediately after World War Il, attention was focused on developing

technologies, which could be used to upgrade and purify uranium from

low-grade sources. Initially the nuclear industry had relied on high-grade

uranium ores from the Belgium Congo and Canada. One of the main

participants in this development was Union of South Africa. The

production of yellow cake was an essential step in this development 1•

1.2 Uranium minerals:

An understanding of mineralization concepts of uranium lead to better

understanding of expected leaching behavior. In nature exist mainly in

the valence state U4' (tetravalent) and U<J+ (hexavalent).The mineralogy

and geochemistry of the valence states dissimilar. Tetravalent uranium is

readily oxidized and is stable only under reducing conditions. Hexavalent

uranium forms a complex uranyl ion (U02 )2+ that combines with other

elements in oxides, silicates, sulphates, vanadates, arsenates, carbonates,

phosphates and molybdates2•

Uranium minerals may be termed primary or secondary, depending upon

their degree of oxidation and origin. The common Uranium minerals are

listed in Table (1.1).

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The most important pnmary ore minerals are uraninite, an oxide,

coffinite, a silicate. Pitchblende, also a primary mineral, is a caliform

variety of uraninite.

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The secondary minerals may be fornred fi 'onr elenrents and ions derived

tiom the prirnary nrinerals fl 'orn the intrinsic hosl constituents, or from

migrat ing ground water, ur ider varying pl l condit ions. The translbrnrat ion

lrom primary to secondary minerals is gradual and conrplex.

The most conrnron and widespread secondary minerals are carnotite,

tyuyamurite, metatyuyamurite, saleeite, sklodowskite, torbernite,

metatorbemite, autunite, rnetaautunite, uranophate, schroeckingari te and

zeuneri te. Minerals pref ixed by Meta are chemical ly aird physical ly the

same but have lorver \\,ater content2.

Table ( l . l ) : l ist of some comnron uraniun-t nr inerals

lvlirrerals

F.irn'ury

Cort rpos i t ior r

l j ran i te - l tu , . , t ' u t t )o ;

Pitchblcnde

8..qr',r',*lite

B^.erterit"

Da"i,tite

UrOs

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Coffinite U(SiOr)r.,_(OH).*

Secondary

uranophate Ca(UOz)z(SiO3)2(OH)2.5H zO

sklodowskite (FI 3O)2M g(U02)2(Si04).211 2O

sclqoeckingarite NaCar(UOzXCOTXSOT)F. I 0 l I2O

autunlte Ca(UO:) : ( l 'Or)2. I 0- I 2 l l rO

zeunente Cu( [JO:) : (AsOr) : . I 0- I 2 l l rO

tort lerni te Cu(UO: ) r (POr )2 . I 2 l l ?O

sa lcc i te Mg( UOu ):( l 'Or)2. I 0l lrO

cam()t l te K2(UO2XVOl ) .1 -3H20

lvuvamul ' l te Ca( UOz )(V O.r ). 5 -8 l l 20

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The secondary minerals may be formed from elements and ions derived

from the primary minerals from the intrinsic host constituents, or from

migrating ground water, under varying pH conditions. The transformation

from primary to secondary minerals is gradual and complex.

The most common and widespread secondary minerals are carnotite,

tyuyamurite, metatyuyamurite, saleeite, sklodowskite, torbernite,

metatorbernite, autunite, metaautunite, uranophate, schroeckingarite and

zeunerite. Minerals prefixed by Meta are chemically ahd physically the,

same but have lower water content~ .

Table (1.1 ): list of some common uranium minerals

~lineralS =r-- -Composition-----~-------~~._-----------Primary

- -_.- ----- .j ------6----------- --~

Uranite (l)I-, ' U,)t ) 0 21 ,.--_._+

Pitchblende U,O~

Becqllurelite 7U02.11 H2O- - -

Barrenerite (U,Ca,Fe,Th,Y)(Ti,Fe)20 c>

Davidite UFe5Tilj025

Coffinite U(SiO.j)I_x(OH).h

Secondary

uranophate Ca(U02h(Si03)2(OHh.5H 2O

sklodowskite (H30hMg(U02)2(Si04).2H 2O

schfoeckingari te NaCa3(U02)(C03)(SO.j)F.10H20-----

alltunite Ca(U02h(PO.j)2.10-121120---_. -------

zellnerite ClI( U02b( As04b·1 0-1211 20---'-- ----,-".

torbernite ClI(U0 2)2(P04h. 12H2O---

saleeite Mg(U02b(PO.jh.101hO_._----- ----------_.-.

camotite K2(U02)(V04).1-3H2O

tyuyamurite Ca(U02)(VO.j).5-8IhO-- -.

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1.3 Geolugy 0f Uranium

According t t-r the gcological sett ing, the rnajori t l 'of the uralr ium resources

in the rvorld catr be assigrrecl to one of the fol lorving types of cleposits2'6.

1 .3.1 LJnconlor r r r i ty re la te t l deposi ts

Uttcott lbrrnity-rclated deposits ar ise fronr gcological change occurr irrg

closc to nrajor uttcotr lbrnri t ie s. Belou, the unconforty, the nreta-

scdirt tcntary rocks r,vhich host the nrineral izat ion are usual ly faulted and

brecciated.

Uncontbrrnity- related deposits constitute approximately 33% of the

worltl Urattiurn rLrour.., and they inclu<le some of the largest and richest

deposits. Mirrerals are uraninite and pitchblende. The main deposits occur

in Canada, such as; I{abbit Lake, Key Lake and those in the Alligator

River area in qorthern Australia. The <lre of sonre of these deposits

contain in addit ion to the Uranium other elernents such as: As. Ni. Mo.

and trace of Au.

1,3,7 Sandstone t leposits

Most of tlre sandstone deposits are contained in Sedimentary rocks*that

were deposits under fluvial or, marginal marine conditions, the host rocks

are almost always relatively friable, medium to coarse grained sandstone

containing pyrites and organic matter of plant origin. The sediments are

comnronly associated with tufls or other volcanic material. Unoxidized

ores in these types of deposits contain Uraniurn minerals pitchblende and

confljnite. ln weathered, that are oxidized ores, secondary uranium

tliuerals suclt as cornotite, tyuyanrunite and uranophane are fonled.

In addit ior-t to uraniurn, ores of sandstone deposits can contain Mo, Se,

Cu and V, rvhich are occasional ly recovered as by or Co- product.

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1.3 Geology of Uranium

According to the geological setting, the majority of the uranium resources

in the world can be assigned to one of the following types of deposits 2,6.

1.3.1 lJ nconformity related deposits

Unconlormity-related deposits arise from geological change occurring

close to major unconlormities. Below the unconforty, the meta­

sedimentary rocks which host the mineralization are usually faulted and

brecciated.

Unconformity- related deposits constitute approximately 33% of the,

world Uranium resources and they include some of the largest and richest

deposits. Minerals are uraninite and pitchblende. The main deposits occur

in Canada, such as; Rabbit Lake, Key Lake and those in the Alligator

River area in nprthern Australia. The ore of some of these deposits

contain in addition to the Uranium other elements such as; As, Ni, Mo,

and trace of Au.

1.3.2 Sandstone deposits

Most of the sandstone deposits are contained in Sedimentary rocks \that

were deposits under fluvial or, marginal marine conditions, the host rocks

are almost always relatively friable, medium to coarse grained sandstone

containing pyrites and organic matter of plant origin. The sediments are

commonly associated with tuffs or other volcanic material. Unoxidized

ores in these types of deposits contain Uranium minerals pitchblende and

conflinite. In weathered, that are oxidized ores, secondary uranium

minerals such as cornotite, tyuyamunite and uranophane are fonlled.

In addition to uranium, ores of sandstone deposits can contain Mo, Se,

Cu and V, which are occasionally recovered as by or Co- product.

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1.3.3 Quartz pebble conglonterate deposits'l 'hcse typcs of dcposits are restricted to low'cr protereozoic rocks, whic|

were dcpositcd and oxygen deficient condit ions. The deposits from whic|1

uraniutt t was producecl are locatecl in El l iot Lake distr ict of Ontario in

Canada. In the Witrvatersrattd basin in South Afr ica uranium is beinc.

recovcred as a by- product of gold production.

1.3.4 Vein deposi ts

In this deposits uraniurrr rninerals,

elements, such as Ag, Ni, Co, Bi,

brecc ias . . . e tc .

generally associated with other

Fe, and Mo, fill fracture cracks,

1.3.5 l l reccias cornplex deposits

These deposits were developed in proterozonic continental regimes

during an organic period. The host rocks include quartz rich

volcanoclastics and seditrtentary rocks. The main representative of this

type of deposit is at Roxby Dorvns in South Australia where uraniunr

occurs associated with Cu, Ag, And Au. I

1.3.6 Intrusivedeposits

These deposits include those uranium deposits that are associated with

intrusive or anatectic rocks of different chemical compositions. Examples

of Uranium deposits include Rossing in Namibia and palabora is South

Africa, which are associated rvith alaskitic and carbonatitic intrusive,

respectively.

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1.3.3 Quartz pebble conglomerate deposits

These types of deposits are restricted to lower protereozoic rocks, which

were deposited and oxygen deficient conditions. The deposits from which

uranium was produced are located in Elliot Lake district of Ontario in

Canada. In the Witwatersrand basin in South Africa uranium is being

recovered as a by- product of gold production.

1.3.4 Vein deposits

In this deposits uranium minerals, generally associated with other,

elements, such as Ag, Ni, Co, Si, Fe, and Mo, fill fracture cracks,

breccias ... etc.

1.3.5 Breccias' complex deposits

These deposits were developed in proterozonic continental regImes

during an organic period. The host rocks include quartz rich

vo1canoclastics and sedimentary rocks. The main representative of this

type of deposit is at Roxby Downs in South Australia where uranium

occurs associated with Cu, Ag, And Au.

1.3.6 Intrusive deposits

These deposits include those uranium deposits that are associated with

intrusive or anatectic rocks of different chemical compositions. Examples

of Uranium deposits include Rossing in Namibia and palabora is South

Africa, which are associated with alaskitic and carbonatitic intrusive,

respectively.

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1.3.7 I 'hosphor icdeposi ts

Thesc types ol' deposit contaitr lorv concentration of uraniunr, and

uraniutn is produced as by- product fronr phosphoric and production

deposits in North Alr ica and N,l iddle East.

1.3.8 Col lapse breccias pipe deposits'fhesc

deposits occur in circular vertical pipes rvith dorvn dropped rock

h'agnrents. Uradiurn and other elements such as Mo, and Ag are

conccntrated in the permeable breccias fil l ing of the pipe and in the

arcuate fracture zones enclosing the pipe. Deposits of this type are mined

in the Arizona ship in the USA.

1.3.9 Volcanicdeposi ts

These types are strata bound and structure bound concentrations in acids

volcanic rocks. Uranium is usual ly associated rvi th Mo, Fe etc.

Examples of this type are deposits of Michelin in Canada, Nopa$ in

Chihuahua Mexico, Macusani in Peru and numerous deposits in China

and the former USSR.

1.3.10 Surf icial deposits

This type broadly defined as uraniferrous sedinrents, usually very young

to recent age that ltave not been deeply buried and may or ntay not been

calcificd to some degree. The Uranium deposits associated with calcified

sedimerrts, relerred to as calcrete, rvhich occur in semiarid areas of

Australia, Namibia and Sornalia are included with this type, also include

peats, bogs and Karst caverns as rvell as pedogenic and structural fi l ls.

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1.3.7 Phosphoric deposits

These types of deposit contain low concentration of uramum, and

uranium is produced as by- product from phosphoric and production

deposits in North Africa and Middle East.

1.3.8 Collapse breccias pipe deposits

These deposits occur in circular vertical pipes with down dropped rock

fragments. Uranium and other elements such as Mo, and Ag are

concentrated in the permeable breccias filling of the pipe and in the

arcuate fracture zones enclosing the pipe. Deposits of this type are mined

in the Arizona s~ip in the USA.

1.3.9 Volcanic deposits

These types are strata bound and structure bound concentrations in acids

volcanic rocks. Uranium is usually associated with Mo, Fe ... etc.

Examples of this type are deposits of Michelin in Canada, Nopa~ in

Chihuahua Mexico, Macusani in Peru and numerous deposits in China

and the former USSR.

1.3.10 Surficial deposits

This type broadly defined as uraniferrous sediments, usually very young

to recent age that have not been deeply buried and mayor may not been

calcified to some degree. The Uranium deposits associated with calcified

sediments, referred to as calcrete, which occur in semiarid areas of

Australia, Namibia and Somalia are included with this type, also include

peats, bogs and Karst caverns as well as pedogenic and structural fills.

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1.3.1 I N letasornat i te deposi ts

In this type uraniunr conccrttrates in nretasomati tes commonly intruded

by nricrocl ine granites. E,xarnples of this type are the deposits at Ross

Adarns in Alaska in the USA, Zheltye Vody in Kriroy Rog in Ukraine

and l3sl l inbaras in Brazi l .

t

1.3 .12 Metanrorph icdepos i ts

This type occurs in metasediments and rnetavolcanics generally without

direct evidence of post metarnorphic mineralization. Example of this type

is at forstau. Australia.

1.3.13 l igr i tes deposits

This type is generally classihecl as an unconventional uranium resource,

occurs in lignites. E,xanrples of uraniferous lignites are located in the

serres basin, Greece, in north ancl South Dakota and deposit at melouJe,

Kazakhstan.

1.3.14 Black shale deposits

Uraniurn of this type of deposit also considered unconventional resources.

Examples: challanooga shale in the USA and chanziping deposits in

china.

1.3.15 Other type of deposi ts :'Ihis type includes the deposits not classified under the above deposits.

Examples are deposits in l 'odilto, Limestone, Grant's district, New

Mexico, USA.

1.4 Uraniurn isotopes

ln nature uranium atoms exist in several forms called isotopes 238U, 2lsu

and tiou. tn typical natural Uranium, most of the mass (99.2739%) would

-.IIII

•••••••••••••••

1.3.11 lVletasomatite deposits

In this type uranium concentrates in metasomatites commonly intruded

by microcline granites. Examples of this type are the deposits at Ross

Adams in Alaska in the USA, Zheltye Vody in Kriroy Rog in Ukraine

and Espinbaras in Brazil.

1.3.12 Metamorphic deposits

This type occurs in metasediments and metavo1canics generally without

direct evidence of post metamorphic mineralization. Example of this type

is at fOt"stau, Australia.

1.3.13 Iigrites deposits

This type is generally classified as an unconventional uranium resource,

occurs in lignites. Examples of uraniferous lignites are located in theI

serres basin, Greece, in north and South Dakota and deposit at melovoe,

Kazakhstan.

1.3.14 Black shale deposits

Uranium of this type of deposit also considered unconventional resources.

Examples: challanooga shale in the USA and chanziping deposits in

china.

1.3.15 Other type of deposits:

This type includes the deposits not classified under the above deposits.

Examples are deposits in Todilto, Limestone, Grant's district, New

Mexico, USA.

1.4 Uranium isotopes

In nature uranium atoms exist in several forms called isotopes 238U, 235U!

and 234U. In typical natural Uranium, most of the mass (99.2739%) would

7

;

;

I;

llllIltII

I

I

lI

hI

IIInrt

corlsist of atorns of 2r8U. A very small port ion of total mass (0.7204%)

consists of atorns of 2r5U ancl (0.00 57%) consist of atorns of 230U. Thet"U i t a parent of uranium series (4n+2) and 2lsu is a parent of uranium

act i t t iunr ser ies (4n+3;6. ' l 'hese ser ies are shorvn in F ig ( l . l ) and (1.2) ,

respcct ivelya. '

There also artificial Uranium isotopes produced in reactor by neutron

induce such as t'ou, t"u, t"U, tIu and 213u. 'the Table (1.2) shows the

natural ancl artificial Uraniunr isotopes a'6.

' table ( 1.2): uranium isotopes

isotope Hal f l i fe Atottt nercentsTo Spccif ic activity Bq/g) 7 )-"-u 72v

233uI . 62* 105 v

234u2.47*105 v

0.0057 231 .30

235u7. l0* 108v

0.7204 80 .01 I

236u2.39*107 v

237u 6.750 y

238u4 .5 t r 109 y

99.2739 12.445

?39u 23.5 min

Ii•11

••••l1lil1li

•III

consist of atoms of 2J8 U. A very small portion of total mass (0.7204%)

consists of atoms of 2J5 U and (0.0057%) consist of atoms of 2J4U. The

2J8 U is a parent of uranium series (4n+2) and 235 U is a parent of uranium

actinium series (4n+3t These series are shown in Fig (1.1) and (1.2),

respectivel/.

There also artificial Uranium isotopes produced in reactor by neutron

induce such as 236 U, 237 U, 239 U, 232 U and 233 U. The Table (1.2) shows the

natural and artificial Uranium isotopes 4,6.

Table (1.2): uranium isotopes

isotope Halflife Atom percents% Specific activity Bq/g232

U72y - -

233U l.G2*10

5y - -

234U 2.47*10

5y

0.0057 231.30

235U 7.10* 10

8y

0.7204 80.011

236U 2.39*10

7y - -

237U

6.750 y - -

238U 4.51 * 10

9Y

99.2739 12.445

239U

23.5 min - -

8

The Uranium-238

The lour natural

nZlS -U U Sones

n t" Trr series

Docay Sories

gf i:u

I z]i

lIIlllIlItttIItItTIII

I i igurc ( l . l ) Uraniur r r -238 decal ' ser ies:

^j1 5 Cv ,f ?38 U?s mrrt44

142

t40

(}":"irji r I(25d '

\i__ _.' r\6.7 lrI pa-Nis;l-

- --- i-lt

o* u

U Srries

NP Series

l3B " - '- i i een o*Al3[tt3 kyl"t-*-l r IL\._J'\1,,. I _.

22 nn /.__l! Iy.*j*_l-- .3,Bd | 1 i | . ,

' ?3oTh v, ?3 ll1,

7 tl l

?l8n,[JTi"l i t

?18 Rn

rarlioactive series

8,"txe rJ val':eslor hai l- lr le arefc,r rnultiple ,

d*cay pi-llhs

2

I0

lsP

z,L-q).oE

Il,

g

col-

50)z

2t4 Pb13227 n,

214 Bit30210 Tl| 2Bl ,. i rtt

i, ti Jrroo,f26, , )?0s Tl

124 4.2 tn

zro Pb zz v

[ zta ,0.1 iiO prs .

?10 Po,140 d

{IIiiIlII

a - -

I

20fiPt'B0 81 82 83 84 85 86 87 88 89 g0 9t 92 93 94Hgn Pb 8i Po Al RnFr Ra AcTh Pa U NpPu

{-2li;n

Lead.206 is theslable end

9

Figure (1.1) U.oanium-238 decay series:

80XErj valJes

for hall-hIe arefor multiple j

docay paths

'81' ; 45Gy 123B Ue a 234 Th I 1 . I

144 I I . Decay t··wt·· " 25 dill !

···-·t-'··-r-· _- --_.. ..-.. 234- 6.7 h

142 .+--..; ..- ··-.1----.------- P<l.+- 234 u, :. j.... I I

J . 230 Th 023 My1J~ O· I ~ , ". , •

i i I It • r t of·, .. '. 9' ~

138 -"- ·-..··t-· ."l·t-- ,226 Ra- •+l3 ~Y 1

1

.'-"--

-------t-- '.' _. -L .. I ~ ~ : •

~E[(31:.1m~t~1'81' '1

222

R~_ 3.·8-··-d~ kY-'i-~ -:--:The four natural", I

radioactive series:) i' ' , Po 218 At 1.3 s , ..~ 214 Pbb ~ ~ ,~- -~ i ~~

g 132 27 rn •. • ..

~ 214 Si ~ 1Z 130' . . .

i210 TI ' "'. j . .1281.3 m ... " •... £ ••

~)d }/10 Bi . 11

••

126 I .' 210 Po ·,..-J--.....e.-.a.......a...--I...-~

206 TI' ·-t o

• • 1·10 d - Lead·206 is the1244.2 rn : - 206 Ph- stable end roduct

8081 828384 85 8687 88 899091929394

HgTl Pb Bi Po At RnFr Ra Ac Th Pa UNpPu

The Uraniurn..238Decay Series

O 235USeries

O 232Ttl Series

d')-'k\l!J . - -U Series

o 2JlNp Series

•II

••••••I

••••••I

••••

gr tm u senes

EqltIIItIItIIIII

?

IIIIII

Figurc ( | .2) : Uraniunr Act in iunr decay ser ies:

The Uranium.23SDecay Series

144

t42

f40

138

r36

l3, l

r32

r l

25h

II*t '--

i

227

i t?3t Pa

nnn

tttTh series

?38U Senes

il:l/ Np serias

The four naturafradroactive series

Thrs ss6gs ;strff Cl't ron&l ly cnrle<lthe Actinium senBS.

. - - . . - l . -

I

l i

| 32ky?1: 227 Ac

zoJ)E:)ccot-e l- t l

6l 'z

223

iztI lL)s

I

?15

2lt po0,5 s

'l ,t) rJt

- - - HA '

fjoxerJ valuesfor half -tlfe arefor nrultipled*"ay paths B0 8t 8? 83 84 85 86 87

HgTl PbBi PoAr HnFr

9RnII

BB 89 90 gt Ea 93 94Fa Ac Th Ps U Nppu

' l

215

I

0. I rns

i

II

' ' t , , . , .ii

l 0

Figure (1.2): Uranium Actinium decay series:

10

- .... -- - ,

BetaDecay144

z

ThIS series istraditionally calledthe Actinium senes.

~ 136l1> I

The four natural DE ' 219 At . i

13,1 1 'f 223 Rn .radIoactive series:::> • .. .c: 215.~ 11 d ~~_c 81

1 I" r-e 132 j. , t219 Rn" 'II,~fl nrJls]21S Po 39 s .••.

Z 130 211 Pb It· 1 .:.. t·~.H") m 215 At 'f"

·L22 rTl;~~Bj~_ °2\ ::: -.I~-r,Boxed values 126

1 0.5 s Lead-207 is thefor half·llfe are '1.8 rn 207 Pb' I stable end roductfor mUltiple 124 I .L..J_..L _L -_.r..-__ J

d&f.i\y paths 8081 82 8384 85 86 87 88 8990 9192 9394HgTI Pb Si Po At AnFr Ra Ac Th Pa UNpPu

~2:.J5U Se~s

O 232Th Series

0:>38. U Senes

O "'1/.... N S .penes

The Uranium·235Decay Series

•••••..••••IIIIII•..•••••

CHAPTER TWO

NUCLEAR FUEL CYCLE

;

*

IIIltIITIIItIIITIII

•,•••••..11

••III

III

••••.'•

CHAPTER TWO

NUCLEAR FUEL CYCLE

llTtIIIItt

t

tTtIIIItIII

NUCLEAR FUBL CYCLB

2.1 Uraniurn nr i r r ing:

Mining is f l rst step in truclcar fLrel cycle and i t carr ied out depending on

the orc depth and environrnental condit ions, through either open pit or

underground rnining. - l 'he Fig (2.1) shorvs the diagram of General ized

process for uraniunr extraction.

Open pit minirrg operat iorts, can be appl ied to sedimentary and vein type

ore bodies. And i t used for near surlace deposits. Open pit mining is

preferred to under.ground operation because a high productivity beller ore

recovery, easier delvatering and safer mining can have greater

environmental impact than underground rnining. Underground mining

used lbr depths from 50-200 m or more and the selected method and

loading operation depend on the type of the ore. Safety is very important

from radiation hazarrj come lrom direct radiation. dust and radon2.

2.2 Uraniur t rn t i l l ing:

The second step of nuclear fuel cycle is rni l l ing. This step involves

crushing and grinding operation to produce a sized or suitable for aciql or

alkaline leaching.

2.3 Uranium Leaching:

Leaching is an important step in the processing of uranium ore. The

leaching process controls the following2:

a) The proportion of uranium solubilized from the ore

b) The quantities of reagent, which are major operating cost, required to

maintain suitable leaching condit ion.

c) The concentrat ion of impuri t ies in leach solut ion.

d) The grinding requirenrents.

12

NUCLEAR FUEL CYCLE

2.2 Uranium milling:

The second step of nuclear fuel cycle is milling. This step involves

crushing and grinding operation to produce a sized or suitable for aci9 or

alkaline leaching.

2.3 Uranium Leaching:

Leaching is an important step in the processing of uranium ore. The

leaching process controls the following2:

a) The proportion of uranium solubilized from the ore

b) The quantities of reagent, which are major operating cost, required to

maintain suitable leaching condition.

c) The concentration of impurities in leach solution.

d) The grinding requirements.

2.1 Uranium mining:

Mining is first step in nuclear fuel cycle and it carried out depending on

the ore depth and environmental conditions, through either open pit or

underground mining. The Fig (2.1) shows the diagram of Generalized

process for uranium extraction.

Open pit mining operations, can be applied to sedimentary and vein type

ore bodies. And it used for near surface deposits. Open pit mining is

preferred to under ground operation because a high productivity beller ore,recovery, easier dewatering and safer mining can have greater

environmental impact than underground mining. Underground mmmg

used for depths from 50-200 m or more and the selected method and

loading operation depend on the type of the ore. Safety is very important

from radiation hazard come from direct radiation, dust and radon2•

111111JI-

•••••••••t.

••••IIIIII•••L _

12

lIIItIIilt

I

*

IIilI

I

lfrttIIt

Uraniurn ores are treated by either acid or alkal ine reagents t 'u. A lot of

f'actors tnust be considerccl to select acitl or alkaline reagent such as

carbotratc contertt to ore, el ' f ic iency of uranium extract ion rvater usage,

energy cottsutnption, prclduct qual i ty requirenrents and errvironrnental

considerat ion. Although acid leach is used in majori ty of uraniunr nr i l ls,

alkal irre lcaching has nurrrber of funclanrental advantages these a.e t .

a) ' l ' l te

solut ion is r t tore specif ic for uraniunr minerals, leaving most of

thc gangue unattacked.

b) Uranium cah be directly precipitated lrom leach liquor.

, c) ' i lre carbonate solution can be easily regenerated,

'I 'hcse characteristics also lead to a number of disadvantages that

include the fol lowing:

a. Fine grinding is required to expose the uraniunr minerals.

b. Some gangue minerals (such as calciurn sulphate and pyrite) can

react with alkaline reagent resulting in high consumption.

c. ' l 'he more relractory uraniunr minerals are not dissolved under

alkal ine condit ions. rAfter selection of reagent, there are five-leaching systems2:

l. Agitation leaching (acid and alkaline)

2. Pressure leaching (acid and alkaline)

3. Strong acid pugging and curing (acid)

4. Heap leaching (acid)

5. lnsitu leaching (nrainly alkal ine)

The choice of technique depends on the above lactors.

2.3,1 Acid leach cl ternistry ' of urart iurn'fhere are two valency states in rvhich uranium occurs naturally,

hexavalent forrn the oxide of rvhich is UOr. and tetravalent from.

the

tl-re

13

IIIII

•••--

I.-..

Uranium ores are treated by either acid or alkaline reagents 2,6. A lot of

factors must be considered to select acid or alkaline reagent such as

carbonate content to ore, efficiency of uranium extraction \vater usage,

energy consumption, product quality requirements and environmental

consideration. Although acid leach is used in majority of uranium mills,

alkaline leaching has number of fundamental advantages these are 2:

a) The solution is more specific for uranium minerals, leaving most of

the gangue unattacked.

b) Uranium cah be directly precipitated from leach liquor.

c) The carbonate solution can be easily regenerated,

These characteristics also lead to a number of disadvantages that

include the following:

a. Fine grinding is required to expose the uranium minerals.

b. Some gangue minerals (such as calcium sulphate and pyrite) can

react with alkaline reagent resulting in high consumption.

c. The more refractory uranium minerals are not dissolved under

alkaline conditions.

After selection of reagent, there are five-leaching systems2:

1. Agitation leaching (acid and alkaline)

2. Pressure leaching (acid and alkaline)

3. Strong acid pugging and curing (acid)

4. Heap leaching (acid)

5. Insitu leaching (mainly alkaline)

The choice of technique depends on the above factors.

2.3.1 Acid leach chemistry of uranium

There are two valency states in which urat1lum occurs naturally, the

hexavalent form the oxide of which is U03, and tetravalent from, the

13

. . ' ,

;

ttttItttt+

L

tI

ttttttt

L .--,nr

oxide ol ' ,uvhiclr is Uoz. rn i lexavalent fornr uraniurn goes cl i rect ly i ' toso lu t ion:

-+ UOz' . -+ l lzo ( l )

after oxidat ion to l lexavalent as shorvn.

UO, + 211'' l 'hc tctravalent goes into solutiorr

UO2 + UOrtt + 2e' (2)

This oxidat ion ca4 be achievecl by ferr ic ion in the leach solut ion as sivenby this equation

UO, + 2Fer* -r Uor* + 2Fe2n (3)

To maintain the dissolution of Uoz the Fer* must be renewed bysubsequent oxidaiion of Fe2* formed in eq.(3). tf manganese dioxide isused as the oxidant, the fol lowing react ions take place.

2Fe2'+ Mnoz + 4H* -) 2Fe3, + Mn2' + 2]lzo

2Fe2r +l/3clor + 2Fl '-+ Fer* + l/3cl-+ Huo

2Fe2* +HzSos + zH* -+ 2Fel* + HzSoa+ Hzo

(4)

(s){.

(6)The consumption of acid required to achieve the equivalent oxidation offerrous is reduced by s0%. tf sodium chlorate or caro,s acid are usedinstead of pyrolusite in the above eq.(5) (6).

By using sulphuric acid in presence of an oxiclizing agent which providesleach oxidation reduction potentials of 400-500 mV relative to saturatedcalonlcl electrode, being present in hexavalance form as uranyl ion thisreact ion occurs:

Uort' + 2soq2- -+ LJo2(so4)2-

UO2 (SO4)r ' -+ SO. t - -+ UO2(SO4)34-

The uranyl sulphate anion cotnplexes are species, rvhich are extracted bysolvent. Unfortunately the oxidizing sulphuric acid leach, rvhich is o{ten

(7)

(8)

l 4

oxide of which is U02. In Hexavalent form uranium goes directly into

solution:

The tetravalent goes into solution after oxidation to Hexavalent as shown.

U02~ UO/+ + 2e- (2)

This oxidation car} be achieved by ferric ion in the leach solution as given

by this equation

U02+ 2FeJ +~ UO/ + 2Fe2+ (3)

To maintain the dissolution of U02 the Fe3+ must be renewed by

subsequent oxidation of Fe2+ formed in eq.(3). If manganese dioxide is

used as the oxidant, the following reactions take place.

2Fe2++ Mn02 + 4H+ ~ 2FeJ++ Mn2

+ + 2H20 (4)

2Fe2++ 1/3CIOJ + 2H+ ~ Fe3++ 1/3Cr + H20 (5)

+2Fe

2+ +H2SOs + 2H+ ~ 2Fe3

+ + H2S04+ H20 (6)

The consumption of acid required to achieve the equivalent oxidation of

ferrous is reduced by 500/0. If sodium chlorate or caro's acid are used

instead ofpyrolusite in the above eq.(5) (6).

By using sulphuric acid in presence of an oxidizing agent which provides

leach oxidation reduction potentials of 400-500 mY relative to saturated

calomel electrode, being present in hexavalance form as uranyl ion this

reaction occurs:

UO/f

+ 2S0/- ~ U02(S04)2- (7)

U02 (S04)/-+ S04 2- ~ U02(S04)/- (8)

The uranyl sulphate anion complexes are species, which are extracted by

solvent. Unfortunately the oxidizing sulphuric acid leach, which is often

14

In addition sulphuric acid dissociates in water as follow:

IlttIItilil

1

tilililIItIttilI

carr ied out at tentperature of 40-80 oC is aggressive and non-select ive

result ing in ntatry other species besides uranium being leachedr. l -hese

prcscnt problcrns in uraniunr solvent extract ion. Sorne of the rnost

important species involved arer:

Soluble si l ica

I ungsten

Antimony

Arsenic

Molybdenurn

Vanadium'l' itaniurn

Zirconiunr

I'hosphate

si(oFr)4 sio2

(Woo)t '

( sbo4 ) r-

( AsO3)r'

(MoOa)2'

(vo'')(t' i03)2-

(ZrO)2'

( Poo ) ' -

HzSOo -+ HSO4- + H* k : 4x 10-r

HSO+--+ H* + SO+2- k: I .27x10'2

Chloride (Cl-) and nitrate (NO:-) anions may be present in the leach

l iquorr .

2.3,2 Alkal ine leach cherrr istry of uraniurn

The rcagent used in alkaline leach is carbonate and bicarbonate (sodium

carbonate - sodiurn bicarbonate). In solution the uranyl ion forms stable

complex with carbonate ion, thus.

UOrt' + 2(Cor)2- -+ [Uoz (COr)r]' ' (9)

Uort* + 3(Co:)2- -) [Uoz (Co:)r]o- (10)

For reaction (1) id alkaline process, the hydrogen ion is supplied by

bicarbonate, with inust be present for this purpose.

l 515

For reaction (1) iri alkaline process, the hydrogen ion is supplied by,

bicarbonate, with must be present for this purpose.

(9)

(l0)

[UOz(C03hf[UOz(C03)3t

Soluble silica Si(OH)4 SiOz,

(W04) z·Tungsten

Antimony ( Sb04 )3.

Arsenic ( As03)3.

Molybdenum (Mo04/'

Vanadium (V03')

Titanium (Ti03{

Zirconium (Zr03)2-

Phosphate ( P04 ) 3-

UOzz+ + 2(C03)z- --)

UOZ2

+ + 3(C03)2- --)

2.3.2 Alkaline leach chemistry of uranium

The reagent used in alkaline leach is carbonate and bicarbonate (sodium

carbonate - sodium bicarbonate). In solution the uranyl ion forms stable

complex with carbonate ion, thus.

In addition sulphuric acid dissociates in water as follow:

H2S04 --) HS04. + H+ k = 4x 10.1

HS04' --) H+ + solo k = 1.27x10.2

Chloride (Cr) and nitrate (NO)") anions may be present in the leach

I" Ilquor .

carried out at temperature of 40-80 QC is aggressive and non-selective

resulting in many other species besides uranium being leached!" These

present problems in uranium solvent extraction. Some of the most

important species involved are l:

••••••

IlIl

UO, + l l2O2

UO., + (( 'Or)r

-) UOr

+ 2( | I( 'Or ) ' +

( l l )

[UO2(CO,) , ] ' - + I l rO (12)

2.4 l tur i f icat ion ' |

A nunrber ol ' rrrethods dcpending upon type of solut ion can accomplish

thc puri f icat ion of the clar i l led leading solut ion. The variables include2:

a. Concentrat ion of Uraniunr.

b. ' i l re

arrrount and concentrat ion of i rnpuri t ies.

c. '[ 'he desired final purity of tl ie uraniunr product.

The lcading so lu t ion conrpos i t ion rv i l l essent ia l ly be dependent upon the

nrirrerlkrgy of the ore, attd leadirrg nrediurn. '[ 'hus.

a number of

puri f icat ion cornbinations nray be appl icable, For example, the

alternative can include the follorving, depending upon the feed solution

analysis and grade of procluct demanded2:

l. direct precipitation from alkaline and some acid liquors

2. lon exchange, elution and precipitation.

3. Solvent extract ion, str ipping and precipitat ion.

4. Ion exchange fol lorved by solvent extract iort .

2.5 Solvertt Extract iort

The rccovery of uraniurrt f i 'ortr orcs by using solvent extract ion since

1955 rvi th the use of diethyl hcxylphosphericacid (DEI-IPA) the (DAPE,X

process) attd since 1957 secondary or part icular ly the tert iary amines (the

AMEX process) lras bcen polrular extractions. A conrnron organic

phosphate tri-rr-butyl phosphate (TBP) is rvidely used for separating

Uranium (VI) fronr co-existirrg elernents in a nitric acid medium. 'fhe

Fig.(2.2) shows the flclw sheet of purification by solvent extraction 2'6.

'fhe distribution coefficient is considerably large over an acid range from

pH 3-6 M nitr ic acid.

l 6

puri tication combinations may be applicable.

16

(I I )

[U02(CO:dJ( + H20 (12)

For example, the1.

alternative can include the following, depending upon the feed solution

analysis and grade of product demamled2:

1. direct precipitation from alkaline and some acid liquors

2. Ion exchange, elution and precipitation.

3. Solvent extraction, stripping and precipitation.

4. Ion exchange followed by solvent extraction.

The recovery of uranium from ores by uSll1g solvent extraction slI1ce

1955 with the use of diethyl hexylphosphericacid (DEHPA) the (DAPEX

process) and since 1957 secondary or particularly the tertiary amines (the

AMEX process) has been popular extractions. A common organic

phosphate tri-n-butyl phosphate (TBP) is widely used for separating

Uranium (VI) from co-existing elements in a nitric acid medium. The

Fig.(2.2) shows the -flow sheet of purification by solvent extraction 2,6.

The distribution coefficient is considerably large over an acid range from

pH 3-6 M nitric acid.

2.5 Solvent Extraction

b. The amount and concentration of impurities.

c. The desired final purity of the uranium product.

The leading solution composition will essentially be dependent upon the

mineralogy of the ore, and leading medium. Thus, a number of

A number of methods depending upon type of solution can accomplish

the purification of the clm-ilied leading solution. The variables include2:

a. Concentration of Uranium.

2.4 Purit1cation t

••••-.

III*

tIIIIIIIIIIIt

The advantage of, ( ' t 'BP) is non-volat i l i ty (boi l ing point 289 "C) alcl i ts

stabi l i ty with c<lncentrated nitr ic acid. The disadvantage of i t , i ron,

thoriurn and protact inium are co-extracted rvi th uranium in nitr ic acid, so

if there are olte of tlrent tnust be separatecl prior to extracting uranium.

The extract ion of Uor2+ by (TBp) from sl ight ly acicl rnedium can,be

described as:

Uo2t*(oor+zNo3 rool

* 2TBo,ou .* Uo2No3)z .2TBP,"' (13)

Due to the large alkyl groups of TBp (cr2t{27o4p) the complex

conrpounds are readily soluble in organic solvents (e.g. kerosene). The

distr ibut ion coeff ic ient for the TBP extract iorr is siven as6:

D_

The appl icat ion of the lorv o[ nrass act ion to equation ( l 3) gives

D_[nq[, lrn\ (16)

From equation ( 16) i t can be seen that

increases with decreasing nitrate content.

luo,(rvo,) r.zra r,",)( l4 )

L, luo, (N o,) r.zrn rr.,, l^=6 (ls)

Where, K is the. equilibrium constant. Thus the distribution coefficient

finally becomcs;

K

t7

the distribution coeffiaient

17

(14)

(15)

( 16)

D=

From equation (16) it can be seen that the distribution coeffioient

increases with decreasing nitrate content.

Where, K is the, equilibrium constant. Thus the distribution coefficient

finally becomes;

U022

+ +2N03 + 2TBP +-+ U02(N03)2.2TBP (13)(aq) (aq) (or) (or)

The appl ication of the low of mass action to equation (13) gives

Due to the large alkyl groups of TBP (C HOP) the complex12 27 4

compounds are readily soluble in organic solvents (e.g. kerosene). The

distribution coefficient for the TBP extraction is given as6:

The advantage of (TBP) is non-volatility (boiling point 289 DC) and its

stability with concentrated nitric acid. The disadvantage of it, iron,

thorium and protactinium are co-extracted with uranium in nitric acid, so

if there are one of them must be separated prior to extracting uranium.

The extraction of U022+ by (TBP) from slightly acid medium can~be

described as:

Following extract ion the loaded solvent is usual ly contacted rvi th a scrub

solut iotr to retnove impuri t ies l iorn solvent pr ior to recovery of uranium6.

2.6 St r ipp ing: r

After scrubbing, the solvent passes to the stripping circuit where uranium

is recovered in aqueous solution by contact of solvent rvith acidified

aqueous solution such as sodiunt or ammonium carbonate.

2.7 Precipitat ion

The result strip solution is treated in a precipitation circuit, rvhich it is

precipitated by anrmonia or hydrogen-peroxide produce (yellorv cake).

The IIZOZ used for precipitat ion of uranium peroxide from str ip solut ion

after acidi fred by FINO3 to pl l3.5 in 70"C rvi th st irr ing according to the

fbl lowing react ion:

UO2(NO1) +tl2o2 +HrO -) UO4.2fl,O + 2HNOr (17)

The Uoo is convprted to Uo, by heating at 450'C or by reducing it by

NurSrO, solution as fol low:

2NaS O +UO +H O ->2 3 ' 4 2

NurSoOo *UO_, +2NaOH ( l 8)

anunonium

C and then

By using anrmonia the yellow cake is precipitated as

diuranate (NH4)U2O', which it dried in an oven at 100'

clacined at 350' C to obtain UO, 6 .

r8

Following extraction the loaded solvent is usually contacted with a scrub

solution to remove impurities from solvent prior to recovery ofuranium6.

.-i.­..•-­.-..

2.6 Stripping:

After scrubbing, the solvent passes to the stripping circuit where uranium

is recovered in aqueous solution by contact of solvent with acidified

aqueous solution such as sodium or ammonium carbonate.

2.7 Precipitation

The result strip solution is treated in a precipitation circuit, which it is

precipitated by ammonia or hydrogen-peroxide produce (yellow cake).

The 11 2°2 used for precipitation of uranium peroxide from strip solution

after acidified by HN03 to pH 3.5 in 70 QC with stirring according to the

following reaction:

2NaS 0 +UO +H 0 ~ Na S 0 +UO +2NaOH (18)23' 4 2 246 3

Na S 0 solution as follow:, 2 2 3

(17)UO .2H ° + 2HNO4 2 3

The UO is conv,erted to UO by heating at 450'C or by reducing it by4 3

By using ammonia the yellow cake is precipitated as anUTIomum

diuranate (NH )U ° , which it dried in an oven at 100' C and then427

clacined at 350' C to obtain UO 6.3

..••..

18

I

IIIIIIIIIIIIIFIItII

I Fig (2.1): Ceneral izecl process for uranium extract ion

OreI

IMining

I

IV

Crushing and grinding

II

Le aching

I+

I'uri hcation and c<lncentrationII

t ' i 'ecipitation ancl solid - l iquid separation

IV

Drying and calciningI+

Uraniunr concentrate (yellorv cake)I

IRefining

It

Uol

Sol ic l - l iqu id

ISeparat ion and rvashing tai l ings

I

IY

l 9

IIII

•••••••••••

•..III

Fig (2.t): Generalized process for uraniuIll extraction

Ore

1Mining

1Crushing and grinding

1Leaching

1Solid - liquid

1Separation and washing tailings

1Purification and concentration

1pj-ecipitation and solid - liquid separation

1Drying and calcining

1Uranium concentrate (yellow cake)

1Refining

1u03

19

llIIIIIlI

Fig (2.2): Schematic f lorv sheet of pur i f icat ion by solvent 'extract ion.

Raffinate

To rvaste or tofurther

Str i l lped su lventStr iDoins NarCO.

Precioitatio

IIIIIIIIIItII

Feed solut ion to solvent extract ion

(NH4)2U2O7

Extract io

Acidificatio Scrubbins

U. oroduct

20

Raffinate

Na..,C0l.

'aste or tourther

Feed solution to solvent extraction

..J Extractio : 1

TonI Acidificatio I IScrubbinQ I- f

I St' . IStripped solvent I

nOOIlH! I

l\

Nil'} .IPrecinitatio I":

I U.oroduct I

Fig (2.2): Scheluatic flow sheet of purification by solvent ~

extraction.

IIIIII

•••••,

••11

••••20

, CFIAPTER THREE

LITERATURE REVIEW

;I

IIIIIIIIIil*

*

Ii

ItI

I

II

III

1111.­~

,..•• , CHAPTER THREE

LITERATURE REVIEW

IItt

l

ttiIil

LITERATURE REVIEW

'fhere are nlany studies have been conducted on extraction of uranium.

El-t lazek arrd El-Sayed ( 2003)r have proposecl a new l iquid emulsion

llcnrbranc (t.[,M) proccss lor urarriutn extraction from either dehydrate

28-30"/u I'zOs (DII) or hcrni-dihydrate 42-45oh P2O5(HDI'I) rvet process

plrosphoric acid. ln this proccss, the organic component of the LE,M is

cornposed of a synergist ic nt ixture of 0.1M di-2-ethyl hexyl phosphoric

acid (DE,FIPA) and 0.0251v1 tr ioctyl phosphine oxide (TOPO) rvi th 4%

Span 80. ' l 'hc

internal or the str ip acid phase is contposed of 0.5M citr ic

acid. 'ftre prepared LEM was proved to be stable in 42-45o/o PzOs acid

concentration rarrge and can, lherefore, be applied to the phosphoric acid

produced by the henri-dihydrate process. After breakdorvn of tlre loaded

emulsion, the uranyl citrate in the internal strip phase is separated by

adding methanol followed by its calcination to the orange oxide. Most of

the reagents used are recycled. The proposed process is characterized by

simplici ty, pract ical ly closed operat ion cycle in addit ion to lower capital

and operating costs.

Awwad (2002)'s userl TOPO to extract uraniurn (Vl) fi 'om aqueous

nitrate medium, it was found that uranium extraction by TOPO was

suitable in toluene as diluent than cvclohexane and chloroform. Sodium

hydroxide solution is suitable for striping uranium from TOPO in toluene.

Mohammed and Eltayeb (2003)t6 used 25%TBP in kerosene to exffact

uranium from Uro phosphate ore. For this purpose first, the phosphate ore

samples have been decomposed rvith sulphuric acid. The resulting

phosphoric acid has been filtered off, and pretreated with pyrite and

activated charcoal. The chemical analysis of the obtained grain

phosphoric acid sholved ttrat about9S% of uraniunr

22

•-- LITERATURE REVIE\V

There are many studies have been conducted on extraction of uranium.

EI-Hazek and El-Sayed ( 2003)3 have proposed a new liquid emulsion

membrane (LEM) process for uranium extraction from either dehydrate

28-301Yu P20S (OH) or hemi-dihydrate 42-45% P20s(HOH) wet process

phosphoric acid. In this process, the organic component of the LEM is

composed of a synergistic mixture of 0.1 M di-2-ethyl hexyl phosphoric

acid (OEHPA) and 0.025M trioctyl phosphine oxide (TOPO) with 4%

Span 80. The internal or the strip acid phase is composed of 0.5M citric

acid. The prepared LEM was proved to be stable in 42-450/0 P20S acid

concentration range and can, therefore, be applied to the phosphoric acid,produced by the hemi-dihydrate process. After breakdown of the loaded

emulsion, the uranyl citrate in the internal strip phase is separated by

adding methanol followed by its calcination to the orange oxide. Most of

the reagents used are recycled. The proposed process is characterized by

simplicity, practically closed operation cycle in addition to lower capital

and operating costs.

Awwad (2002)15 used TOPO to extract uramum (VI) from aqueous

nitrate medium, it was found that uranium extraction by TOPO was

suitable in toluene as diluent than cyclohexane and chloroform. Sodium

hydroxide solution is suitable for striping uranium from TOPO in toluene.

Mohammed and Eltayeb (2003)16 used 25%TBP in kerosene to extract

uranium from Uro phosphate ore. For this purpose first, the phosphate ore

samples have been decomposed with sulphuric acid. The resulting

phosphoric acid has been filtered off, and pretreated with pyrite and

activated charcoaL The chemical analysis of the obtained grain

phosphoric acid showed that about 98% of uranium

22

Content of the phosphate ore was rendered soluble in the phosphoric acid.

A thrcc stage extracticln at a phase ratio (aqueous/organic) of l:2,

ful lowcd by trvo stages str ippirrg using 0.5 N,l sodiunr carborrate solut ion

at a pltasc rat io (A/O) of l :4 have been found to be t l re opt inrunt

corrditions to report ntore than 98",'" of uranium content in green

phosphoric acid to thc aqLreoLrs phase as uranyl tr icarbonate complex

(UOz (C'Or)r) t ly applying socl ica decornposit iorr upon t lre str ipping

cat 'bonatc solut ion usirrs 5091, socl iurn hvdroxide. about 98% of uraniunr

contcrrt was [)recipi tated as sodiunr diuranate concentrate (Naz Uz Or).

The clternical anplysis using atonric absorption spectrometry (AAS)

showed a good agreement betrveen the specifications of the obtained

uraniutn concentrate lvith the standard commercial specification of

sodium diuranate concentrate. Further purification was achieved for the

yellow cake by s"elective precipitation of uranium from the solution as

uranium peroxide (UO4.2l ' l20) using 30% hydrogen peroxide. Final ly the

uraniurn peroxide precipitated rvas calcined at 450 degree C to obtain the

orangc powcler uraniunr tr ioxide (UOr).The chernical analysis of the f inal

uraniutu trioxide product has proved its nuclear purity and nteets the

standard conlnrercial specification. According to the obtained results', it

can be concluded that nuclear grade uranium trioxide can be successfully

produced with an overall uranium recovery percentage of 93o/o from Uro

phosphate ore.

El-Kamash and El-Sayed (2003)s used extraction chromatography to

study the extraction oI both U(VI) and U(lV) frorn nitric acid solutions

using' l 'BP solvent impregnated polyacryl ic acid polymer (SM-7) as inert

supporting tnaterial. Batclt kinetic and breakthrough column experirnents

were carried out to explain tlie nrechanistic aspects of the extraction

process obtain therrnodynarnic parameters and simulate its applications.

23

Content of the phosphate ore was rendered soluble in the phosphoric acid.

A three stagc extraction at a phase ratio (aqueous/organic) of 1:2,

followed by two stages stripping using 0.5 tvl sodium carbonate solution

at a phase ratio (A/O) of 1:4 have been found to be the optimum

conditions to report more than 98% of uranium content 111 green

phosphoric acid to the aqueous phase as uranyl tricarbonate complex

(U02 (COjh) By applying sodica decomposition upon thc stripping

carbonate solution using 50% sodium hydroxide, about 98% of uranium

contcnt was precipitated as sodium diuranate concentrate (Na2 U2 0 7),

The chemical anplysis using atomic absorption spectrometry (AAS)

showed a good agrcement between the specifications of the obtained

uranium concentrate with the standard commercial specification of

sodium diuranate concentrate. Further purification was achieved for the

yellow cake by selective precipitation of uranium from the solution as

uranium peroxide (U04.2H20) using 30% hydrogen peroxide. Finally the

uranium peroxide precipitated was calcined at 450 degree C to obtain the

orangc powder uranium trioxide (UOj). The chemical analysis of the final

uranium trioxide product has proved its nuclear purity and meets the

standard commercial specification. According to the obtained resultsl, it

can be concluded that nuclear grade uranium trioxide can be successfully

produced with an overall uranium recovery percentage of 93% from Uro

phosphate ore.

EI-Kamash and E1-Sayed (2003)5 used extraction chromatography to

study the extraction of both U(VI) and U(IV) from nitric acid solutions

using TBP solvent impregnated polyacrylic acid polymer (SM-7) as inert

supporting material. Batch kinetic and breakthrough colunm experiments

were carried out to explain the mechanistic aspects of the extraction

process obtain thermodynamic parameters and simulate its applications.

23

Based or-r thc experinrental results, an approximate and simplified first

order kinet ic expression lras been used to interpret the metal deplet ion in

the l iquid phase. A mathernatical nrodel, consists of nretal ion mass

trattsler and colunur nlass balance equations, \! 'as proposed to predict the

breaktlrrough curves of both metal ions on an extraction column. The

predicted breakthrough curves were in a good agreentent with the

Experirnental clata'. These results suggested that the proposed models are

applicable to the interpretation o[ kinetic data, the prediction of

breakthrough curves and can be used as design tool for extraction

chromato graphic process.

Thompson ( 2002 )7 usecl solvent extraction process to recover uranium

and technetiurn fronr solutions of irradiated commercial reactor fuel wlrile

sending the plutoniunr to rvaste rvith the fission products and higher

actinides was tested with actual luel solution. I-le found the process meets

all goals for recovery and decontamination. Babain et al (2001)8 usecl $as

extraction of actinide complexes rvith beta-diketones prepared beforehand

and analogous ones synthesized in-situ. tt was determined that

tributylphosphate in supercritical carbon dioxide can to extract

macroquantities of uranyl nitrate efficiently. Experiments on preparation

of uranyl complexes in-situ sholv that in the case of low excesses beta

diketones do not permit to extract uranium lrom uranyl nitrate. In the

same time uranyl carbonate is extracted efficiently by fluorine-containing

beta-diketones in the same conditions. Introduction of additional neutral

ligand permits to increase elficiency of extraction. Introduction of

pyridine into solutions of beta-diketones in supercritical carbon dioxide

leads to increase of uranium extraction efficiency from uranyl nitrate and

does not affect on uranyl carbonate extraction. Data obtained confirmed

74

Based on the experimental results. an approximate and simplified first

order kinetic expression has been used to interpret the metal depletion in

the liquid phase. A mathematical model, consists of metal ion mass

transfer and column mass balance equations, was proposed to predict the

breakthrough curves of both metal ions on an extraction column. The

predicted breakthrough curves were in a good agreement with the

Experimental data'. These results suggested that the proposed models are

applicable to the interpretation of kinetic data, the prediction of

breakthrough curves and can be used as design tool for extraction

chromatographic process.

Thompson ( 2002 )7 used solvent extraction process to recover uranium

and technetium from solutions of irradiated commercial reactor fuel while

sending the plutonium to waste with the fission products and higher

actinides was tested with actual fuel solution. He found the process meets

all goals for recovery and decontamination. Babain et al (2001)8 used gas

extraction of actinide complexes with beta-diketones prepared beforehand

and analogous ones synthesized in-situ. It was detennined that

tributylphosphate in supercritical carbon dioxide can to extract

macroquantities of uranyl nitrate efficiently. Experiments on preparation

of uranyl complexes in-situ show that in the case of low excesses beta

diketones do not permit to extract uranium from uranyl nitrate. In the

same time uranyl carbonate is extracted efficiently by fluorine-containing

beta-diketones in the same conditions. Introduction of additional neutral

ligand permits to increase efficiency of extraction. Introduction of

pyridine into solutions of beta-diketones in supercritical carbon dioxide

leads to increase of uranium extraction efficiency from uranyl nitrate and

does not affect on uranyl carbonate extraction. Data obtained confirmed

24

that basic f i rnct ion of pyridine is binding of ni tr ic acid escaping during

Ibrnrat ion ol ' corrrplcxes of bcta-diketones.

Ptrgct et al (2002 )e used solvent extract ion process for treat ing a

rvastcwater cott taining dissolved uranium is considered. They usecl

Aluntina 336 (a qrrixtr-rre of tri-octyl and tri-decyl an'rines) as extractant in

tltis process. '[ 'he result showed that it is possible to reach an efficiency of

about 95u/u l'or the uraniunt extraction, for ntetal concentration in the feed

of l0 ppnl. Furthermore, an effrciency of about 50% is reached for ntetal

concentration in the feed of I pprn u,lten the liquid florv rate is equal 1200

Lih.

Zi l 'bcrntan et al (2001)r0used 30% tr ibutylphosphate ( ' fBIr) in ciodecane

ttndcr corrditions of the second organic phase to extract uraniurn(4) ancl

uraniurrr(6) li 'onr nitric acid solutions. By conrparing extraction for \he

elemettts lor similar cottditions, when using non-stratified extraction

systenl (30% TBP in hexachlorobutadiene), it was shown that during

uranium extraction lrom aqueous phase for both systems noticeable

differences are pointed out. Study of absorption spectra of the light and

heavy organic phases suggested the assumption that solvate forms in both

organic phases differ both for uraniunt (lV) and uranium

Cao et al (2002)" have proposed florv-sheet for obtaining yellorv cake

from Sandstone ores corttainirtg uraniunr in Nong Son area to recover

uraniunr in the fiortn of MDU. 'l 'hese ores have been classified into 3

categories dependillg on tlte u'eathcring degree, giving different chenrical

composit ion as shorvn. ' l 'he arnount of calciurn carbonate (g CaCO3 /100g

of ore) reacted with HCI under different conditions of ternperature and

time showed that stirring rnettrod requires high acid consumption. The

results obtained from static leaching of the 3 ore categories showed that

25

that basic function of pyridine is binding of nitric acid escaping during

formation of complexes of beta-diketones.

Puget et al (2002)9 used solvent extraction process for treating a

wastcwater containing dissolved uranium is considered. They used

Alumina 336 (a ~llixture of tri-octyl and tri-decyl amines) as extractant in

this process. The result showed that it is possible to reach an efficiency of

about 95% for the uranium extraction, for metal concentration in the feed

of 10 ppm. Furthermore, an efficiency of about 50% is reached for metal

concentration in the feed of I ppm when the liquid flow rate is equal 1200

L/h.

Zil'bcrman et al (2001 )10 used 30% tributylphosphate (TBP) in dodecane

under conditions of the second organic phase to extract uranium(4) and

uranium(6) from nitric acid solutions. By comparing extraction for \he

elements for similar conditions, when using non-stratified extraction

system (300/0 TBP in hexachlorobutadiene), it was shown that during

uranium extraction from aqueous phase for both systems noticeable

differences are pointed out. Study of absorption spectra of the light and

heavy organic phases suggested the assumption that solvate forms in both

organic phases differ both for uranium (IV) and uranium

Cao et al (2002)11 have proposed flow-sheet for obtaining yellow cake

from Sandstone ores containing uranium in Nong Son area to recover

uranium in the form of MDU. These ores have been classified into 3

categories depending on the weathering degree, giving different chemical

composition as shown. The amount of calcium carbonate (g CaC03 11 OOg

of ore) reacted with HCI under different conditions of temperature and

time showed that s,tirring method requires high acid consumption. The

results obtained from static leaching of the 3 ore categories showed that

25

leaching efficiency largely depends on the rveathering degree and particle

II

size of ore. ' l 'he lowest lcaching efficiency was observed for non-

weatltcred orc. In order to increase uranium extraction this ore was

grourtd to tlrt: size of max. 2.5nrrn. arrd then iricubated by 40"to HuSOa for

48 hoLrrs with the addit ion of KC'lO 3 (3 kg/tone of ore) as oxidant. The

results of acid pugging shorved that uraniurn extraction efficiency reached

min.92u/u The leaching experiments were carried out under the following

conditions: Particle size of ore: Weathered: max. 30mm, Semi-weathered:

max. lOmm, Non-weathered: max. 2.5mm (incubated by 40% FI2 SOa);'l-empcrature 25-30 deg. C; Redox potential; pH l, acid consumption: 40-

50 kg/ore tone. Leaching efficiency reached 90%. Uranium concentration

in tlre solution after 8-stage counter-current leaching was min. 4 glL,

uraniunr contcnt in sol id rvastc 0.0l%r. Lcaching solut ion was f i l tered and

directly neutralized through t\r,o stages to precipitate yellowcake.

Experirnental data shorved that the uranium recovery reached 90%.

Yellorvcake product nret the relevant specifications and had UlOa content

of nrininturnT6u/u.

Fyoclorov (2002)r2 used [n Situ Leaching (tSL) method to production

uraniurn from open-pit and underground mines in Kazakhstan; they found

this method has a number of economical and ecological advantages.

Faizal et al (2000)rr used solvent extraction TBP/ kerosene to Rirang ore

uranium extraction to produce ADU from rare earth and they recovered

98.75 u/o of U with yellow cake (ADU) rvhich contents U : 67.55 o/o and

RE2Or : not detected.

Wisnubroto ( I gg7)t4 used diethyl hexyl phosphoric acicl (HDEHP) and

Tri-octylamine for U recovery from sulfuric acid solution and he found

that the later compound is easier to use, and also has a good selectivity on

recovery uranium.

26

leaching efficiency largely depends on the weathering degree and particle

size of ore. The lowest leaching efficiency was observed for non­

weathered ore. In order to increase uranium extraction this ore was

ground to the size of max. 2.5rmn, and then incubated by 40% H2S04for

48 hours with the addition of KCIO 3 (3 kg/tone of ore) as oxidant. TheI

results of acid pugging showed that uranium extraction efficiency reached

min. 92%. The leaching experiments 'Nere carried out under the following

conditions: Particle size of ore: Weathered: max. 30mm, Semi-weathered:

max. 10mm, Non-weathered: max. 2.5mm (incubated by 40% I-h S04);

Temperature 25-30 deg. C; Redox potential; pH I, acid consumption: 40­

50 kg/ore tone. Leaching efficiency reached 90%. Uranium concentration

in the solution after 8-stage counter-current leaching was min. 4 g/L,

uranium content in solid waste 0.0 I%. Leaching solution was filtered and

directly neutralized through two stages to precipitate yellowcake.

Experimental data showed that the uranium recovery reached 90%.

Yellowcake product met the relevant specifications and had U30 8 content

of minimum 76%.

Fyodorov (2002)12 used In Situ Leaching (ISL) method to production•

uranium from open-pit and underground mines in Kazakhstan; they found

this method has a number of economical and ecological advantages.

Faizal et al (2000)13 used solvent extraction TBP/ kerosene to Rirang ore

uranium extraction to produce ADU from rare earth and they recovered

98.75 % of U with yellow cake (ADU) which contents U = 67.55 % and

RE20 3 = not detected.

Wisnubroto (1997)14 used diethyl hexyl phosphoric acid (HDEHP) and

Tri-octylamine for U recovery from sulfuric acid solution and he foundI

that the later compound is easier to use, and also has a good selectivity on

recovery ural1lum.

26

Bascd on this rcvierv

conccntratc (ycl loiv cake)

can bc drawn:

Conclusion

on extract ion and puri f icat ion of uranium

fronr uraniurn ores the belorv concluding points

l. Open pit mining is preferred to under ground operation because a high

productivity beller ore recovery, easier dewatering and safer mining

can have greater environmental impact than underground mining.

2. Alkaline leaching is prefened for high carbonate rocks because the

solution is more specific for uranium minerals, leaving most of the

gangue unattacked, uraniunr can be directly precipitated from leach

l iquor and the carborrate solut ion can be easi ly regenerated.

3. Acid leaching is preferred over alkaline leaching for low carbonate

rocks and ntore relractory uranium nrinerals rvhich, not dissolved

under alkal ine condit ions.

4. Particle size about 2.5 mnt increases uranium leaching efficiency and

suitable for f i l t rat ion.

5. Potassium chlprate used as an oxidant is very efficient in increasing

leaching eflficiency.

6. In Situ Leaching (lSL) method is superior over other methods because

it has a number of economical and ecological advantages.

7. TBP is considered the most suitable extractant for uranium because it

is non-volatile and stable rvith concentrated nitric acid.

8. Kerosene is the most widely used di luent because i t is easi ly avai lable

and inexpensive.

9. Hydrogen peroxide the best precipitant because gives more pure+product.

27

Conclusion

Based on this reVIew on extraction and purification of uramum

concentrate (yellow cake) from uranium ores the below concluding pointsI

can be drawn:

I. Open pit mining is preferred to under ground operation because a high

productivity beller ore recovery, easier dewatering and safer mining

can have greater environmental impact than underground mining.

2. Alkaline leaching is preferred for high carbonate rocks because the

solution is more specific for uranium minerals, leaving most of the

gangue unattacked, uranium can be directly precipitated from leach

liquor and the carbonate solution can be easily regenerated.

3. Acid leaching is preferred over alkaline leaching for low carbonate

rocks and more refractory uranium minerals which, not dissolved

under alkaline conditions.

4. Particle size about 2.5 mm increases uranium leaching efficiency and

suitable for filtration.

5. Potassium chlprate used as an oxidant is very efficient in increasing

leaching efficiency.

6. In Situ Leaching (ISL) method is superior over other methods because

it has a number of economical and ecological advantages.

7. TBP is considered the most suitable extractant for uranium because it

is non-volatile and stable with concentrated nitric acid.

8. Kerosene is the most widely used diluent because it is easily available

and inexpensive.

9. Hydrogen peroxide IS the best precipitant because gIves more pure

product.

27

2.

-t

J .

4.

5 .

Re [e rell ces

t . M. w. lVlakenzie: Uraniurn sorvent extraction using tertiaryarnines uraniunr ore yellorv cake. seminar, Melbourne

Austral ia (1997).

IAEA (1993): Uranium extract ion technology, Teclmical reportser ies No. 359, V ienna.

El- l Iazek,-N. 'r . ; El-Sayed,-fvr.S: t f i rect uraniunr extract ior l

l iorn dihydrate and henri-clihyclrate \\,et process phosphoric

acids by liquid emulsion ntenrbrane. J. Raclioanalt,tical_arrrcl_

l,'luclectr-Cltentistry V . 257 (2), 347 -352 (2003 )InLernet web site rvww.uic.com

El-Kamash,-A.M.; L,i-Sayed,-A.A.; Aly,-H.F. Thermodynamics

of uranium extraction from nitric acid solution by TBp loadett

on irrert supporting material. Journal of Ratlioanalytical-and-

Nucleur-Chemistr.y', V 2S3 (3) 489-495 (2002).

Nasscr s. z.:Production of yel lorv c'ake from Rock phosphate

&lt 's Characterizat ion, M.Sc. 'r 'hesis, Karary Acaclenry ofl 'echnology, Sudan (2004 ).' l 'hornpson,-M.c:

Denronstrat ion of the uREX solventExtraction Process rvith Dresclen lteactor Fuel Solution(Report), (2002\.

8. Babain,-V.; Kantachev,-V.; Murzin,-A.; Shadrin,_A:

Supercritical gas extraction of microquantities of metals bybeta-diketones Russian Federation (200 1 ).

9. Puget,-Flavia-P: Altemative process for treating radioactive

effluents.lnternational nuclear Atlantic conference (INAC); 13.Braz i l ian (2002) .

6.

2828

Extraction Process with Dresden Reactor Fuel Solution

References

Shadrin,-A:Murzin,-A.;

Demonstration of the UREX Solvent

Kamachev,- V.;

(Report), (2002).

8. Babain,-V.;

7. Thompsoll,-M.C:

Supercriqcal gas extraction of microquantities of metals by

beta-diketones Russian Federation (200 I).

9. Puget,-Flavia-P: Alternative process for treating radioactive

effluents.International nuclear Atlantic conference (INAC); 13.

Brazilian' (2002).

5. EI-Kamash,-A.M.; Ei-Sayed,-A.A.; Aly,-H.F. Thermodynamics

of uranium extraction from nitric acid solution by TBP loaded

on inert supporting material. Journal of Radioanalytical-and­

Nuclear-Chemist,)'. V 253 (3) 489-495 (2002).

(L Nasser S. Z.:Production of Yellow Cake from Rock Phosphate

&It's Characterization, M.Sc.Thesis, Karary Academy of

Technology, Sudan (2004 ).

I. M. W. Makenzie: Uranium solvent extraction usmg tertiary

amllles Uranium ore yellow cake. Seminar, Melbourne

Austral ia (1997).

2. IAEA (1993): Uranium extraction technology, Technical report

series No. 359, Vienna.

3. E1-Hazek,-N.T.; EI-Sayed,-M.S: Direct ural11um extraction

from dihydrate and hcmi-dihydrate wet process phosphoric

acids by liquid emulsion membrane. J. Radioanalytical-a~ld­

Nuclear-Chemistry V. 257(2), 347-352 (2003)

4. Internet web site www.uic.com

I 0.Zi I 'bcrnran,-8. Ya. ; [ ;ed.rov,-yu.S. ; Arkhipov,-S.A. ; BI azheva,-I .v.;clekov,-R.G: Extract io. of Ua' ancl U6* uricler co.cl i t ionsof tlre second orgarric phase fbrrnation J. Rartiokhi,rit,o.. v. 43(2) lss- | se (2001 1.

I I .Cao,- l I .1 ' . ; Le, -Q. ' l ' . ; D inh, -M. ' l ' . ; 1 'han,_V.L. ; Le,_K.D:Ura.ium leaching a.d recovery frorn sandstone ores of NongSon Badirr (viet Nanr) lnternational symposiurn on theuranium productio. cycle and the environment, vienna (2000).

l2.Fyodorov,-G.V: Uraniunr production and the environment inKazakhstan (Report); r. The uranium productio' cycle and theenvrronment. Proceedings 571 l9l_l9g (2002).

I 3 .Faiza l , -R; FIa ln i , -L .N. ; Budi , -S. ; sugeng,-w. ;sus i lan ingtyas:

Rirang uranium ore processing using base methocl rvi thprrril ication of uraniurn hydroxitle fi-onr rar.e earths . FiftltScictrtiJic Presentotiotr otr Nucleqr Fttel C),cle: Nuclear FuelElements Developnre.t centre, National Atomic EnergyAgency 332 102- 108 (2000).

l4.wisnubroto,-D.-S: Uranium extraction from sulfuric acidsolution, National Atomi Energy Agency, serpong Indonesia(2r2) 6-12 (1997\.

l5.Awwad,-N.s: Equi l ibr ium and kinet ic studies on the extract ionof uranium (vl) l roln nitr ic acid medium into tr i -phenylphosphi 'e oxide using a single drop column technique.J. Nucleur-science.s-urtd-Appticat iorts, v. 36 (3),151-160

(2003)

l6.Mohanrnred,-A.-A.; Eltayeb,-M.-A.-H: uraniurn extract ionfrom uro area phosphate ore, Nuba mountains, Sudan .6,h Arabconlerence on peaceful uses of atonric energy cairo (Egypt)(2003) . '

79

IO.zil'bcnnan,-B. Ya.; Fcdorov,-Yu.S.; Arkhipov,-S.A.; Blazheva,­I.V.;Glekov,-R.G: Extraction of U4

+ and UG+ under conditions

of the second organic phase formation J. Radiokhimiya., V. 43(2) 155-159(2001).

I I.Cao,-H.T.; Le,-Q.T.; Dinh,-M.T.; 1'han,-V.L.; Le,-K.D:

Uranium leaching and recovery from sandstone ores of Nong

Son Basin (Viet Nam) International symposium on the

uranium production cycle and the environment, Vienna (2000).

12.Fyodorov,-G.V: Uranium production and the environment in

Kazakhstan (Report); K. The uranium production cycle and the

environment. Proceedings 571 191-198 (2002).

13.Faizal,-R; Hafni,-L.N.; Budi,-S.; Sugeng,-W.;Susilaningtyas:Rirang uranium ore processing using base method with

purification of uranium hydroxide from rare earths . Fifth

Scientific Presentation on Nuclear Fuel Cycle: Nuclear FuelI

Elements Development Centre, National Atomic Energy

Agency 332 102-108 (2000).

14.Wisnubroto,-D.-S: Uranium extraction from suIfuric acid

solution, National Atomi Energy Agency, Serpong Indonesia

(212) 6-12 (1997).

15.Awwad,-N.S: Equilibrium and kinetic studies on the extraction

of uranium (VI) from nitric acid medium into tri­

phenyl phosphine oxide using a single drop column technique.1. Nuclcar-Scicnccs-and-Applications, V. 36 (3) ,151-160

(2003 )

16. Mohammed,-A.-A.; Eltayeb,-M.-A.-H: Uranium extraction

from Uro area phosphate ore, Nuba mountains, Sudan .6th Arab

conference on peaceful uses of atomic energy Cairo (Egypt)

(2003). '

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