CLASSIFICATION OF NUCLEAR REACTORS

TYPES OF FISSION• SLOW REACTORS OR THERMAL

REACTORS– REACTOR CORE IS LARGE AND

HEAVIER – THEY HAVE LONG NEUTRON LIFE

AND LOW POWER DENSITY SO CONTROL IS EASIER

– LOW FUEL LOADING– IT IS IMPOSSIBLE TO BREED – LOW COOLING PROBLEMS

• FAST REACTORS– FISSION CAUSED BY FAST

NEUTRON BUT THEIR SPEED REDUCED BY MODERATOR

– HIGH FISSION RATE AND HIGH BREEDING

– SMALL IN SIZE AND COMPACT– EASIER TO SHIELD– HIGH POWER DENSITY

( KW/m3)RESULTS IN COOLING AND HT PROBLEMS

TYPES OF FUEL• NATURAL URANIUM –

FISSIONABLE U 235 AND FERTILE U 238. SO PU 239 IS PRODUCED AND U 233 FROM THORIUM 232 ARE PRODUCED ARTIFICALLY FROM A FERTILE MATERIAL BY NEUTRON REACTION.

FUEL CYCLES• BURNER REACTOR - ONLY

HEAT IS PRODUCED WITHOUT CONVERSION

• CONVERTOR REACTOR –MATERIAL CONVERTED BY PUTTING FERTILE MATERIAL IN CORE U 238 TO PU 239.

• BREEDER REACTOR – PU 239 IS THE FUEL AND U 238 CONVERTED TO PU

Breeder reactor• r= no of fuel atoms formed/

no of original fuel atoms consumed in fission ; r<1 convertor if r > 1 then breeder ( 7 to 15 yrs to produce fuel for another reactor)

• Breeder generated energy and also produces fuel than it consumes.

STATE OF FUEL• SOLID OR LIQUID- MOSTLY SOLID

BUT MAY BE MIXED WITH URANIUM OXIDE TO FORM SLURRY IN WATER OR LIQUID METAL. SO ITS CALLED LIQUID METAL FUELED REACTOR( LMFR)-SGR –PERMITS HIGH TEMP, PRESSURIZATION SOLVED.

• POSITION OF FERTILE AND FISSILE MATERIAL

RELATIVE POSITION TO EACH OTHER IN REACTOR CORE.

CHOICE OF MODERATOR• TYPES OF MODERATOR ;

GRAPHITE , NATURAL WATER AND HEAVY WATER . GRAPHITE HAS HIGHER ATOMIC WEIGHT THAN WATER SO THEY ARE BULKY. NATURAL WATER GIVES A SMALL AND COMPACT REACTOR.

CORE COMPOSITION

METHOD OF COOLING

• DIRECT COOLING AND INDIRECT COOLING

• ORDINARY WATER IS USED WITH ENRICHED URANIUM AND HEAVY WATER WITH ORDINARY URANIUM DUE TO THEIR NEUTRON ABSORPTION CAPABILITY

• LOW NEUTRON ABSORPTION

GAS COOLED REACTOR

• GAS IS CIRCULATED THROUGH REACTOR CORE TO COOL THE REACTOR.AIR ,HE ,HYDROGEN OR CO2.

• POOR HEAT TRANSFER OF GASES REQUIRE HIGH PUMPING POWER.

• CORROSION PROBLEMS RESOLVED

• POWER DENSITY IS LOW

WATER COOLED REACTOR

• LIGHT WATER REACTOR- HAS GOOD THERMAL PROPERTIES, CHEAP COOLANT, BUT IT HAS CORROSION ISSUES AND DUE TO NEUTRON ABSORPTION MAY INTERRUPT CRITICALITY.

• BWR-BOILING WATER REACTOR

• WATER CONVERTS TO STEM AND DIRECTLY IMPINGES ON TURBINE

• STEAM LEAVING REACTOR MAY BE RADIOACTIVE AND PIPING AND STEAM TURBINE

PRESSURIZED WATER REACTOR

• WATER IS PRESSURIZED TO PREVENT BULK BOILING AT 150 ATM.

• HOT WATER FROM REACTOR FLOWS TO STEAM GENERATOR (HX)WHERE ITS HEAT IS TRANSFERRED TO FEED WATER TO GENERATE STEAM.

• STEAM IS PRODUCED AT 7.5 TO 8 Mpa AND 320 C.

• PWR ARE STABLE.• TURBINE LOOP SEPARATE

THAN PRIMARY SO LESS CHANCES OF RADIOACTIVE.

• THE LIQUID SHOULD BE HIGHLY PRESSURIZED TO REMAIN LIQUID AT HIGH TEMP.SO HIGH COST PIPE

COOLANT

• COOLANT PICKS UP HEAT AND KEEP FUEL ASSEMBLIES AT SAFE TEMP TO AVOID DESTRUCTION AND MELTING.

• AIR,HELIUM,WATER,CO2,H2,NA ,K,• IT SHOULD HAVE REALISTIC FLUIDITY FOR HT.• LOW ABSORTION OF NEUTRON• IF COMPOUND,STABILITY FROM DISASSOCIATION• SPECIFIC HEAT ANG K SHOULD BE HIGH TO HT.• NON CORROSIVE• THERMAL STABILITY

NEW TRENDS

• ORGANIC SUBSTANCE COOLED REACTORS ,OIL,PETROLEUM• CAN OPERTAE AT HIGH TEMP WITH MODERATE PRESSURE.SO

LIGHTER EQUP,DEVICES ,PIPES( ORDINARY STEEL ) AND REDUCED COST.

• LESS CORROSIVE THAN WATER • H2 CONTENTS MAKES THEM ACCEPTABLE AS MODERATORS• THESE DON’T BECOME RADIOACTIVE AS NEUTRON

BOMBARDMENT. • DON’T FREEZE AT LOW TEMP SO GOOD FOR USE IN COLD

REGIONS

FUEL CYCLE

GASES DIFFUSION

CENTRIFUGAL/ THERMAL DIFFUSION

ELECTROMAGNETIC DIFFUSION