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
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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