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