The main features and operating experience of Fastneutron reactors
Report of the student N. Kakhanov
December 3
2018
The first fast neutron reactor
In 1955, the first research fast
reactor of zero power was
launched in the USSR - in the
Physics and energy Institute
(Obninsk) under the leadership of
A. I. Leypunsky. In the same
Institute two years later launched
a research reactor BR-2 with
mercury coolant.
A. I. Leypunsky
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What is fast neutron reactor?
A fast neutron reactor is a nuclear
reactor in which the fission chain
reaction is sustained by fast neutrons.
That means the neutron moderator in
such reactors is undesirable. This is a
key advantage of fast reactors, because
fast reactors have a significant excess
of neutrons, unlike PWRs (or LWRs).
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Scheme of FR
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Breed and Burn (BB) Principles
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Inherent Safety Approach
Superior thermophysical properties of liquid metals allow:
• Operation at high power density and high fuel volume
fraction
• Low pressure operation with significant margin to boiling
• Passive decay heat removal
The fast neutron spectrum leads to long neutron path lengths
• Neutron leakage is enhanced (25% at moderate sizes)
• Changes in power level effects impact the reactor as a
whole, not locally
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Fast reactor operating experience (BN-350)
In the Soviet Union, BN-350 fast
neutron reactor was operated for 25
years. In addition to generating
electricity, BN-350 provided heat for a
desalination plant to produce clean
fresh water from the sea in the
amount of 200 thousand tons per day,
which used about half of its capacity.
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Fast reactor operating experience (BN-600)
− Long-term
tests
of
the
equipment working in sodium
were carried out;
− Operating modes of the power
unit have been worked out and
optimized;
− Technology of replacement
and repair of sodium equipment,
including pumps and steam
generators, has been mastered;
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Fast reactor operating experience (BN-600)
− Obtained a unique experience
in sodium leak, which showed the
effectiveness
of
protective
systems for the localization of the
consequences of leaks;
− Experience of processing of
isotopes of high concentrations;
− The installed capacity usage
time is about 7000 hours per year.
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Fast reactor operating experience (BN-800)
− BN-800 assumes a transition to
practically non-waste nuclear energy
and the possibility of a wide
expansion of the fuel base;
− It will be used to develop
industrial technologies for the
reprocessing of irradiated fuel and
the manufacture of new fuel
elements (recycling technology);
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Fast reactor operating experience (BN-800)
− BN-800 has an advanced
protection system. In case of
deviation from the normal mode of
operation, reactor itself shuts down
the nuclear reaction;
− The reactor has an integrated
layout: all the equipment of the
primary circuit exposed to radiation
is enclosed inside its body.
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Comparison of light water reactor and fast reactor
Characteristics
LWR
FR
786
(U‐235)
556 (Pu
fissile)
Power density (MWt/m3)
102
300
Rod outer diameter (mm)
9.5
7.9
Enrichment (%)
~4.0
~20
40
100
Specific power (kWt/kgHM)
Average burnup (MWd/kg)
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Comparison of light water reactor and fast reactor
Characteristics
LWR
FR
Average linear heat rate (kW/m)
17.5
27.1
pressure (MPa)
15.5
0.1
inlet temp. (°C)
293
350
outlet temp. (°C)
329
500
pressure (MPa)
7.58
15.2
temperature (°C)
296
455
Coolant
Steam
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Conclusion
− FRs have improved neutron
economy;
− FRs can recycle nuclear waste;
− FRs can produce fuel for thermal
reactors;
− FRs liquid metals have superior
heat transfer properties;
− FRs do not use pressure vessel.
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Conclusion
− FRs must use superior control
system;
− FRs can have positive reactivity
feedback from void coefficient;
− Liquid metals require special
technology and handling;
− Fast reactor technology can be
more expensive.
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THANK
FOR YOUR
ATTENTION!
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