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nuclear
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MECHANICAL PROPERTIES OF ADVANCED NUCLEAR REACTOR
MATERIALS
WHAT IS NUCLEAR REACTOR
EVOLUTION OF NUCLEAR REACTOR WHAT ARE ADVANCED REACTORS
CHALLENGES FOR MATERIALS IN ADVANCED REACTORS
NEED FOR MECHANICAL PROPERTIES IN ADVANCED REACTORS
CANDIDATE MATERIALS FOR ADVANCED REACTORS AND THEIR MECHANICAL PROPERTIES
FUTURE SCOPE
CONCLUSION
CONTENTS
Nuclear Reactor is a device designed to maintain a steady chain reaction, and thus producing enormous amount of energy
it maintains steady flow of neutrons, which are generated by the fission of heavy nuclei
based on the purpose they serve, they are classified into research reactors and power reactors
WHAT IS A NUCLEAR REACTOR
Research reactors are operated at universities and research centres in many countries,
. These reactors generate neutrons for multiple purposes,
INCLUDING
medical diagnosis and therapy,
testing materials and
conducting basic research.
Power reactors are usually found in nuclear power plants.
Dedicated to generating heat mainly for electricity production,
nuclear reactor technology has been under continuous development since the first commercial exploitation of civil nuclear power in the 1950s.
this evolution is what we study as generations of nuclear reactor
each generation is advanced from its earlier generations either in term of cost, technology or safety
generation i nuclear reactors first commercialised reactors of various designs (gas-cooled / graphite moderated, or prototype water cooled & moderated),
generation ii nuclear reactorsthe standard light-water reactor pressurized water reactors and boiling water reactors in operation today
EVOLUTION OF NUCLEAR REACTOR
generation iii nuclear reactors
these are now in construction in several countries. the generation-iii designs are an evolution of current light-water reactor (lwr) technology with improved performance extended design lifetimes and more favourable characteristics in the extreme events such as those associated with core damage. a typical example is the epr - the european pressurised-water reactor
generation-iv - reactor designs that could be commercially deployed from 2040.
some of them doesn't require neutrons to slow down to thermal level
Hence are able to 'burn' fuel without first slowing down the neutrons, and are therefore termed fast neutron reactors.
fast reactors are not new - they have existed for decades though have never been widely exploited commercially.
they have the advantage that they can 'breed' large amounts of fissile material (pu-239) from fertile material (u-238) and can therefore extract at least 50 times more energy than current reactors from a given quantity of uranium
what are advanced reactors
Incorporate safety improvements and are simpler to operate, inspect, maintain and repair
The new generation of reactors have:
a standardised design toreduce capital cost and reduce construction time
higher availability and longer operating life, will be economically competitive in a range of sizes, further reduce the possibility of core melt accidents
higher burn‑up to reduce fuel use and the amount of waste
More 'passive' safety features which rely on gravity, natural convection to avoid accidents
The main requirements for the materials to be used in these reactor systems are the following:•The in-core materials need to exhibit dimensional stability under irradiation, whether under stress (irradiation creep or relaxation) or without stress (swelling, growth).•The mechanical properties of all structural materials (tensile strength, ductility, creep resistance, fracture toughness, resilience) have to remain acceptable after ageing, and•The materials have to retain their properties in corrosive environments (reactor coolant or process fluid).
THESE REQUIREMENTS HAVE TO BE MET UNDER NORMAL OPERATING CONDITIONS, AS WELL AS IN INCIDENTAL AND ACCIDENTAL CONDITIONS
Mechanical and thermal CHALLENGES FOR MATERIALS IN ADVANCED REACTORS
Severe Environment Conditions during operation
–Temperature
–Irradiation Levels
–Coolant compatibility
mechanical strength.strength is the property that enables a metal to resist deformation under load.
hardness hardness is the property of a material to resist indentation and scratching.
there are several methods of measuring hardness, hence the hardness of a material is always specified in terms of the particular test that was used to measure this property. rockwell, vickers, or brinell are some of the methods of testing
toughnesstoughness is the property that enables a material to withstand shock and to be deformed without rupturing. toughness may be considered as a combination of strength and plasticity
MECHANICAL PROPERTIES of materials
Creep
Creep is a time-dependent deformation of a material while under an applied load that is below its yield strength. It is most often occurs at elevated temperature, but some materials creep at room temperature. Creep terminates in rupture if steps are not taken to bring to a halt.
Fatigue
Load on the material is not constant in actual conditions
It fluctuates under the operating conditions
The mechanical property that comes into picture under fluctuating load conditions is called fatigue
Fatigue mode of failure is extremely dangerous for a component as it doesn’t give prior warning and failure is sudden