INTRODUCTION TO NUCLEAR FUELS.pptx

7/21/2019 INTRODUCTION TO NUCLEAR FUELS.pptx

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INTRODUCTION

TO NUCLEARFUELSBASICS AND WORLD RESERVES

BY:MUKUL BHANDARI


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INTRODUCTION

Nuclear fuel is a material that can be 'burned' by nuclear

fission or fusion to derive nuclear energy.

Nuclear fuel can refer to the fuel itself, or to physical

objects (for example bundles composed of fuel rods)

composed of the fuel material, mixed with structural,

neutron moderating, or neutron reflecting materials.

Most nuclear fuels contain heavy fissile elements that are

capable of nuclear fission.

hen these fuels are struc! by neutrons, they are in turncapable of emitting neutrons when they brea! apart. "his

ma!es possible a self#sustaining chain reaction that

releases energy with a controlled rate in a nuclear reactor

or with a very rapid uncontrolled rate in a nuclearwea on.


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NUCLEAR FISSIONNuclear fission is either a nuclear reaction or a radioactive

decay process in which the nucleus of an atom splits into

smaller parts (lighter nuclei), often producing free neutrons

and photons (in the form of gamma rays), and releasing a

very large amount of energy, even by the energetic standards

of radioactive decay.


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NUCLEAR FUSION

Nuclear fusion is a nuclear reaction in which two or more atomic

nuclei join together, or $fuse$, to form a single heavier nucleus.

%uring this process, matter is not conserved because some of the

mass of the fusing nuclei is converted to energy which is

released.


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COMMON RAW MATERIALFOR NUCLEAR FUELS

URANIUM

PLUTONIUM


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NUCLEAR FUEL CYCLE

"he nuclear fuel cycle is an industrial process involving

various activities to produce electricity from uranium in

nuclear power reactors.

"he cycle starts with the mining of uranium and ends

with the disposal of nuclear waste.

"he raw material for today&s nuclear fuel is uranium..


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Contd.

"he nuclear fuel cycle includes the front end&, i.e.

preparation of the fuel.

"he service period& s that in which fuel is used during

reactor operation to generate electricity.

"he bac! end&, i.e. the safe management of spent

nuclear fuel including reprocessing and reuse and

disposal.

f spent fuel is not reprocessed, the fuel cycle is referred

to as an open& or once#through& fuel cycle,if spent fuel is

reprocessed, and partly reused, it is referred to as a

closed& nuclear fuel cycle.


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Nucle! "uel c#cle


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E$%LORATION

deposit of uranium, such as uraninite, discovered by

geophysical techni*ues, is evaluated and sampled to

determine the amounts of uranium materials that are

extractable at specified costs from the deposit.

+ranium reserves are the amounts of ore that are

estimated to be recoverable at stated costs. +ranium in

nature consists primarily of two isotopes, +#- and +#

-/.


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MININ&

"here are three ways to mine uranium0

1pen pit mines, underground mines and in situ leaching

where the uranium is leached directly from the ore.

N 2"+ 3456N7 0uranium is leached from the in#place ore through an array of regularly spaced wells and

is then recovered from the leach solution at a surface

plant.


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MILLIN&

Milling is generally carried out close to a uranium mine.

"he mined uranium ore is crushed and chemically treated

to separate the uranium.

"he result is yellow ca!e&, a yellow powder of uranium

oxide (+-1). n yellow ca!e the +ranium concentration

is raised to more than 89.

fter milling, the yellow ca!e concentrate is shipped to a

conversion facility.


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URANIUM CONVERSION

Natural uranium consists primarily of two isotopes,

::.-9 is +#- and 8.;9 is +#-/.fission process by

which heat energy is released in a nuclear reactor, ta!es

place mainly in +#-/. Most nuclear power plants re*uire

fuel with +#-/ enriched to a level of -


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yellow cake is converted into gas for enrichment


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ENRICHMENT

+ranium is enriched in +#-/ by introducing the gas in

fast#spinning cylinders(centrifuges&),where heavier

isotopes are pushed out to the cylinder walls.

+ranium can also be enriched using older technology by

pumping +=> gas through porous membranes that allow

+#-/ to pass through more easily than heavier isotopes,

such as +#-.


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FUEL FABRICATION !nriched "rani"m #U$%& cannot 'e directly "sed in

reactors( as it does not withstand high tem)erat"res or

)ress"res It is therefore converted into "rani"m o*ide

#UO+&

$"el )ellets are formed 'y )ressing UO+( which issintered #'aked& at tem)erat"res of over ,-../0 to

achieve high density and sta'ility

The )ellets are cylindrical and are ty)ically 12,3 mm in

diameter and ,.2,3 mm long

They are )acked in long metal t"'es to form f"el rods(

which are gro")ed in 4f"el assem'lies5 for introd"ction

into a reactor.


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FUEL %ELLETS


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ELECTRICITY &ENERATION

1nce the fuel is loaded inside a nuclear reactor,

controlled fission can occur.

=ission means that the +#-/ atoms are split. "he

splitting releases heat energy that is used to heat water

and produce high pressure steam.

"he steam turns a turbine connected to a generator,which

generates electricity.

"he fuel is used in the reactor for - years.

bout once a year, /9 to -89 of the fuel is unloaded

and replaced with fresh fuel.


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S%ENT FUEL STORA&E

"he spent fuel assemblies removed from the reactor are

very hot and radioactive. "herefore the spent fuel is

stored under water, which provides both cooling and

radiation shielding.

fter a few years, spent fuel can be transferred to an

interim storage facility. "his facility can involve either

wet storage, where spent fuel is !ept in water pools, or

dry storage ,where spent fuel is !ept in cas!s.

?oth the heat and radioactivity decrease over time. fter@8 years in storage, the fuels radioactivity will be about

a thousand times lower than when it was removed from

the reactor.


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S'ent "uel (to!)e


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RE%ROCESSIN&

"he spent fuel contains uranium (:>9), plutonium (A9)

and high level waste products (-9)."he uranium, with

less than A9 fissile +#-/ and the plutonium can be

reused. 2ome countries chemically reprocess usable

uranium and plutonium to separate them from unusablewaste.

Becovered uranium from reprocessing can be returned to

the conversion plant, converted to +=> and subse*uently

re#enriched. Becovered plutonium, mixed with uranium, can be used

to fabricate mixed oxide fuel(M1C).


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S%ENT FUEL AND HI&HLEVEL WASTE DIS%OSAL 2pent nuclear fuel or high level waste can be safely

disposed of deep underground, in stable roc! formations

such as granite, thus eliminating the health ris! to people

and the environment."he first disposal facilities will be in

operation around 88.

aste will be pac!ed in long#lasting containers and

buried deep in the geological formations chosen for their

favourable stability and geochemistry, including limited

water movement. "hese geological formations havestability over hundreds of millions of years,far longer

than the waste is dangerous.


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W(te d*('o(l


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FUELS

1C%4 =+43

=or fission reactors, the fuel (typically based on uranium) is

usually based on the metal oxide the oxides are used rather

than the metals themselves because the oxide melting point

is much higher than that of the metal and because it cannot

burn, being already in the oxidiDed state. +1C(uranium dioxide)0

M1C(Mixed xide fuel)


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UO$+URANIUM DIO$IDE,

+ranium dioxide is a blac! semiconducting solid.

t can be made by reacting uranyl nitrate with a base

(ammonia) to form a solid (ammonium uranate).

t is heated (calcined) to form +-1 that can then be

converted by heating in an argon E hydrogen mixture (;88

F5) to form +1.

"he +1 is then mixed with an organic binder and

pressed into pellets, these pellets are then fired at a much

higher temperature (in 6Er) to sinter the solid.

"he aim is to form a dense solid which has few pores.


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MO$+MI$ED O$IDE FUEL,

Mixed oxide, or M1C fuel, is a blend of plutonium and

natural or depleted uranium which behaves similarly

(though not identically) to the enriched uranium feed for

which most nuclear reactors were designed.

M1C fuel is an alternative to low enriched uranium

(34+) fuel used in the light water reactors which

predominate nuclear power generation.

2ome concern has been expressed that used M1C cores

will introduce new disposal challenges, though M1C isitself a means to dispose of surplus plutonium by

transmutation.


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METAL FUELS

Metal f"els have the advantage of a m"ch higher heat

cond"ctivity than o*ide f"els '"t cannot s"rvive e6"ally

high tem)erat"res.

Metal f"els have the )otential for the highest fissile atom

density.. Metal f"els are normally alloyed( '"t some metal f"els

have 'een made with )"re "rani"m metal.

Metal f"els have 'een "sed in water reactors and li6"id

metal fast 'reeder reactors( s"ch as !7R8II

T9O T:P!;! $U!L


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TRI&A FUELS

"B7 fuel is used in "B7 ("raining, Besearch,

sotopes, 7eneral tomics) reactors.

"he "B7 reactor uses uranium#Dirconium#hydride

(+Gr6) fuel, which has a prompt negative temperature

coefficient, meaning that as the temperature of the core

increases, the reactivity decreasesHso it is highly

unli!ely for a meltdown to occur.

Most cores that use this fuel are $high lea!age$ cores

where the excess lea!ed neutrons can be utiliDed forresearch.


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ACTINIDE FUEL

n a fast neutron reactor, the minor actinides produced by

neutron capture of uranium and plutonium can be used as

fuel.

Metal actinide fuel is typically an alloy of Dirconium,

uranium, plutonium and the minor actinides.

t can be made inherently safe as thermal expansion of

the metal alloy will increase neutron lea!age.


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CERAMIC FUELS

5eramic fuels other than oxides have the advantage of

high heat conductivities and melting points, but they are

more prone to swelling than oxide fuels and are not

understood as well.

"6424 B 1= "1 "IJ42

+BN+M 5B?%4

+BN+M N"B%4


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URANIUM CARBIDE

"he high thermal conductivity and high melting point

ma!es uranium carbide an attractive fuel.

n addition, because of the absence of oxygen in this fuel

(during the course of irradiation, excess gas pressure can

build from the formation of 1 or other gases) as well as

the ability to complement a ceramic coating (a ceramic#

ceramic interface has structural and chemical

advantages). uranium carbide could be the ideal fuel candidate for

certain 7eneration K reactors such as the gas#cooled fast

reactor.


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URANUIM NITRIDE "his is often the fuel of choice for reactor designs that

N2 produces, one advantage is that +N has a better

thermal conductivity than +1.

+ranium nitride has a very high melting point. "his fuel

has the disadvantage that unless A/N was used (in place

of the more common A@N) that a large amount of A@5would be generated from the nitrogen by the (n,p)

reaction.

s the nitrogen re*uired for such a fuel would be so

expensive it is li!ely that the fuel would have to bereprocessed by a pyro method to enable to the A/N to be

recovered. t is li!ely that if the fuel was processed and

dissolved in nitric acid that the nitrogen enriched with

A/N would be diluted with the common A@N.


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LI-UID FUELS

Li6"id f"els are li6"ids containing dissolved n"clear f"el

Li6"id8f"eled reactors generally have large negative

feed'ack mechanisms and therefore are )artic"larly

sta'le designs? however the li6"id f"el form also has the

disadvantage of 'eing easily dis)ersi'le in the event ofan accident( s"ch as a leak in the )rimary system

MOLT!N ;ALT;

A@U!OU; ;OLUTION; O$ URAN:L ;ALT;


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COMMON %HYSICALFORMS OF NUCLEAR FUEL Urani"m dio*ide #UO+& )owder is com)acted to

cylindrical )ellets and sintered at high tem)erat"res to

)rod"ce ceramic n"clear f"el )ellets with a high density

and well defined )hysical )ro)erties and chemical

com)osition. A grinding )rocess is "sed to achieve a "niform

cylindrical geometry with narrow tolerances ;"ch f"el

)ellets are then stacked and filled into the metallic t"'es

The metal "sed for the t"'es de)ends on the design of

the reactor ;tainless steel was "sed in the )ast( '"tmost reactors now "se a irconi"m alloy which( in

addition to 'eing highly corrosion8resistant( has low

ne"tron a'sor)tion


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The t"'es containing the f"el )ellets are sealed< these

t"'es are called f"el rods The finished f"el rods are

gro")ed into f"el assem'lies that are "sed to '"ild ")

the core of a )ower reactor

0ladding is the o"ter layer of the f"el rods( standing'etween the coolant and the n"clear f"el It is made of a

corrosion8resistant material with low a'sor)tion cross

section for thermal ne"trons( "s"ally Bircaloy or steel in

modern constr"ctions( or magnesi"m with small amo"nt

of al"mini"m and other metals for the now8o'soleteMagno* reactors

0ladding )revents radioactive fission fragments from

esca)ing the f"el into the coolant and contaminating it


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%WR FUEL

Press"ried water reactor #P9R& f"el consists of

cylindrical rods )"t into '"ndles

A "rani"m o*ide ceramic is formed into )ellets and

inserted into Bircaloy t"'es that are '"ndled together

The Bircaloy t"'es are a'o"t , cm in diameter( and thef"el cladding ga) is filled with heli"m gas to im)rove the

cond"ction of heat from the f"el to the cladding

There are a'o"t ,CD8+%- f"el rods )er f"el '"ndle and

a'o"t ,+, to ,DE f"el '"ndles are loaded into a reactor

core =enerally( the f"el '"ndles consist of f"el rods'"ndled ,-F,- to ,CF,C P9R f"el '"ndles are a'o"t -

meters long


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%WR FUEL

In %WR "uel undle(/ cont!ol !od( !e *n(e!tedt0!ou)0 t0e to' d*!ectl# *nto t0e "uel undle. T0e"uel undle( u(ull# !e en!*c0ed (e1e!l 'e!cent*n 234U.

T0e u!n*u5 o6*de *( d!*ed e"o!e *n(e!t*n) *ntot0e tue( to t!# to el*5*nte 5o*(tu!e *n t0ece!5*c "uel t0t cn led to co!!o(*on nd0#d!o)en e5!*ttle5ent.

T0e 7*!clo# tue( !e '!e((u!*8ed 9*t0 0el*u5 to

t!# to 5*n*5*8e 'elletcldd*n) *nte!ct*on 90*c0cn led to "uel !od "*lu!e o1e! lon) 'e!*od(.


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BWR FUEL

In 'oiling water reactors #79R&( the f"el is similar to

P9R f"el e*ce)t that the '"ndles are GcannedH that is(

there is a thin t"'e s"rro"nding each '"ndle

This is )rimarily done to )revent local density variations

from affecting ne"tronics and thermal hydra"lics of thereactor core

In modern 79R f"el '"ndles( there are either D,( D+( or

D% f"el rods )er assem'ly de)ending on the

man"fact"rer A range 'etween E%1 assem'lies for the

smallest and 1.. assem'lies for the largest U; 79Rforms the reactor core !ach 79R f"el rod is 'ack filled

with heli"m to a )ress"re of a'o"t three atmos)heres

#E.. kPa&

CANDU FUEL+CANADA


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CANDU FUEL+CANADADeute!*u5 U!n*u5, CANDU "uel undle( !e out 0l" 5ete! lon)

nd ;< c5 *n d*5ete!. T0e# con(*(t o" (*nte!ed+UO2, 'ellet( *n 8*!con*u5 llo# tue(/ 9elded to8*!con*u5 llo# end 'lte(.

Ec0 undle *( !ou)0l# 2< =)/ nd t#'*cl co!elod*n) *( on t0e o!de! o" >4


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URANIUM RESERVES

Urani"m reserves are reserves of recovera'le "rani"m(

regardless of isoto)e( 'ased on a set market )rice

The reserves fig"res consists of reasona'ly ass"red

reso"rces #RAR& )l"s inferred reso"rces recovera'le at a

cost range of 'elow ,E. U;>kg The amo"nt of "ltimately recovera'le "rani"m de)ends

strongly on what one wo"ld 'e willing to )ay for it

WORLD RESERVES


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WORLD RESERVES

country Tonnesu Worldspercentage

AUSTRALIA ;/?@3/


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WORLD RESERVESCOUNTRY TONNES U Worlds

percentageNI&ER 2@2/

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INTRODUCTION TO NUCLEAR FUELS.pptx