PRASANTH KP SEMINAR REPORT

8/13/2019 PRASANTH KP SEMINAR REPORT

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CARMEL POLYTECHNIC COLLEGE

ALAPPUZHA

DEPARTMENT OF ELECTRICAL AND ELECTRONICS

ENGINEERING

SEMINAR REPORT

ON

PEBBLE BED REACTORS:-

A FUTURE FOR NUCLEAR ENERGY

SUBMITTED BY :

PRASANTH.K.P

Reg No : 11030175


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CARMEL POLYTECHNIC COLLEGE

ALAPPUZHA

DEPARTMENT OF ELECTRICAL AND ELECTRONICS

ENGINEERING

CERTIFICATE

This is to certify that the seminar report entitled PEBBLE BED

REACTOR:- A FUTURE FOR NUCLEAR ENERGY presented by

PRASANTH.K.P of fifth and sixth semester diploma in Electrical and

Electronics Engineering, Carmel polytechnic college, Punnapra, Alappuzha in

partially fulfillment of the requirement for the award of Diploma in Electrical

and Electronics engineering under the Board of technical Education, during the

year 2013-2014


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ABSTRACT

Pebble Bed Reactors offer a future for new nuclear energy plants. They are small,

modular, inherently safe, flexible in design and operation, use a demonstrated nuclear

technology and can be competitive with fossil fuels. Pebble bed reactors are helium

cooled reactors that use small tennis ball size fuel balls consisting of only 9 grams of

uranium per pebble to provide a low power density reactor. The low power density and

large graphite core provide inherent safety features such that the peak temperature

reached even under the complete loss of coolant accident without any active emergency

core cooling system is 2 significantly below the temperature that the fuel melts. This

feature should enhance public confidence in this nuclear technology. With advanced

modularity principles as described, a new way of thinking and building nuclear plants is

proposed that would improve quality by factory fabrication of space frame modules and

site assembly similar to legos would speed the time to operation. It is expected that

this type of design and assembly could lower the cost of new nuclear plants such that the

biggest impediment to new nuclear construction namely the capital cost of new nuclear

plants is removed. This would allow nuclear plants to support the goal of reducing global

climate change in an energy hungry world.


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INTRODUCTION

One of the major challenges of the reintroduction of nuclear energy into

the world energy mix is the development of a nuclear power plant that is competitive

with other energy alternatives, such as natural gas, oil or coal. The environmental

imperative of nuclear energy is obvious. No greenhouse gases emitted, small amounts of

fuel required and small quantities of waste to be disposed of. Unfortunately, the capital

costs of new nuclear plants are quite large relative to the fossil alternatives. Despite the

fact that nuclear energys operating costs in terms of operations and maintenance and,

most importantly, fuel are much lower than fossil alternatives, the barrier of high initial

investment is a significant one for utilities around the world.

Definitive resolution of the numerous open technical issues is likely

to take quite some time. This is time that Exelon --- which hopes to obtain a license from

NRC in only two-and-a-half years --- is not inclined to expend. The increased flexibility

that utilities need to compete in a deregulated market limits their timelines for decision-

making, and may well be incompatible with the caution and rigor that advanced nuclear

reactor development requires.


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PEBBLE-BED REACTOR (PBR)

The pebble-bed reactor(PBR) is a graphite-moderated, gas-

cooled,nuclear reactor.It is a type ofvery-high-temperature reactor(VHTR), one of the

six classes of nuclear reactors in theGeneration IV initiative.The basic design of pebble-

bed reactors features spherical fuel elements called pebbles. These tennis ball-sized

pebbles are made ofpyrolytic graphite(which acts as the moderator), and they contain

thousands of micro-fuel particles calledTRISOparticles. These TRISO fuel particles

consist of a fissile material (such as235

U)surrounded by a coated ceramic layer ofsilicon

carbidefor structural integrity and fission product containment. In the PBR, thousands of

pebbles are amassed to create a reactor core, and are cooled by a gas, such

ashelium,nitrogenorcarbon dioxide, which does not react chemically with the fuel

elements.

This type of reactor is claimed to be passively safe;[1]

that is, it removes the

need for redundant, active safety systems. Because the reactor is designed to handle high

temperatures, it can cool by natural circulation and still survive in accident scenarios,

which may raise the temperature of the reactor to 1,600 C. Because of its design, its

high temperatures allow higher thermal efficiencies than possible in traditionalnuclear

power plants(up to 50%) and has the additional feature that the gases do not dissolve

contaminants or absorb neutrons as water does, so the core has less in the way of

radioactivefluids.

The concept was first suggested byFarrington Danielsin the 1940s, butcommercial development did not take place until the 1960s in theGermanAVR

reactorbyRudolf Schulten.[2]

but this system was plagued with problems and political

and economic decisions were made to abandon the technology.[3]

The AVR design was

licensed toSouth Africaas thePBMRandChinaas theHTR-10,the latter currently the

only such design operational. In various forms, other designs are under development

byMIT,University of California at Berkeley,General Atomics(U.S.),
http://en.wikipedia.org/wiki/Neutron_moderatorhttp://en.wikipedia.org/wiki/Neutron_moderatorhttp://en.wikipedia.org/wiki/Neutron_moderatorhttp://en.wikipedia.org/wiki/Nuclear_reactorhttp://en.wikipedia.org/wiki/Nuclear_reactorhttp://en.wikipedia.org/wiki/Nuclear_reactorhttp://en.wikipedia.org/wiki/Very-high-temperature_reactorhttp://en.wikipedia.org/wiki/Very-high-temperature_reactorhttp://en.wikipedia.org/wiki/Very-high-temperature_reactorhttp://en.wikipedia.org/wiki/Generation_IV_reactorhttp://en.wikipedia.org/wiki/Generation_IV_reactorhttp://en.wikipedia.org/wiki/Pyrolytic_carbonhttp://en.wikipedia.org/wiki/Pyrolytic_carbonhttp://en.wikipedia.org/wiki/Pyrolytic_carbonhttp://en.wikipedia.org/wiki/TRISOhttp://en.wikipedia.org/wiki/TRISOhttp://en.wikipedia.org/wiki/TRISOhttp://en.wikipedia.org/wiki/Uranium-235http://en.wikipedia.org/wiki/Uranium-235http://en.wikipedia.org/wiki/Uranium-235http://en.wikipedia.org/wiki/Uranium-235http://en.wikipedia.org/wiki/Silicon_carbidehttp://en.wikipedia.org/wiki/Silicon_carbidehttp://en.wikipedia.org/wiki/Silicon_carbidehttp://en.wikipedia.org/wiki/Silicon_carbidehttp://en.wikipedia.org/wiki/Heliumhttp://en.wikipedia.org/wiki/Heliumhttp://en.wikipedia.org/wiki/Heliumhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Pebble-bed_reactor#cite_note-1http://en.wikipedia.org/wiki/Pebble-bed_reactor#cite_note-1http://en.wikipedia.org/wiki/Pebble-bed_reactor#cite_note-1http://en.wikipedia.org/wiki/Nuclear_Powerhttp://en.wikipedia.org/wiki/Nuclear_Powerhttp://en.wikipedia.org/wiki/Nuclear_Powerhttp://en.wikipedia.org/wiki/Nuclear_Powerhttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Farrington_Danielshttp://en.wikipedia.org/wiki/Farrington_Danielshttp://en.wikipedia.org/wiki/Farrington_Danielshttp://en.wikipedia.org/wiki/Germanshttp://en.wikipedia.org/wiki/Germanshttp://en.wikipedia.org/wiki/AVR_reactorhttp://en.wikipedia.org/wiki/AVR_reactorhttp://en.wikipedia.org/wiki/AVR_reactorhttp://en.wikipedia.org/wiki/AVR_reactorhttp://en.wikipedia.org/wiki/Rudolf_Schultenhttp://en.wikipedia.org/wiki/Rudolf_Schultenhttp://en.wikipedia.org/wiki/Pebble-bed_reactor#cite_note-2http://en.wikipedia.org/wiki/Pebble-bed_reactor#cite_note-2http://en.wikipedia.org/wiki/Pebble-bed_reactor#cite_note-2http://en.wikipedia.org/wiki/Pebble-bed_reactor#cite_note-3http://en.wikipedia.org/wiki/Pebble-bed_reactor#cite_note-3http://en.wikipedia.org/wiki/Pebble-bed_reactor#cite_note-3http://en.wikipedia.org/wiki/South_Africahttp://en.wikipedia.org/wiki/South_Africahttp://en.wikipedia.org/wiki/South_Africahttp://en.wikipedia.org/wiki/PBMRhttp://en.wikipedia.org/wiki/PBMRhttp://en.wikipedia.org/wiki/PBMRhttp://en.wikipedia.org/wiki/Chinahttp://en.wikipedia.org/wiki/Chinahttp://en.wikipedia.org/wiki/Chinahttp://en.wikipedia.org/wiki/HTR-10http://en.wikipedia.org/wiki/HTR-10http://en.wikipedia.org/wiki/HTR-10http://en.wikipedia.org/wiki/Massachusetts_Institute_of_Technologyhttp://en.wikipedia.org/wiki/Massachusetts_Institute_of_Technologyhttp://en.wikipedia.org/wiki/Massachusetts_Institute_of_Technologyhttp://en.wikipedia.org/wiki/University_of_California_at_Berkeleyhttp://en.wikipedia.org/wiki/University_of_California_at_Berkeleyhttp://en.wikipedia.org/wiki/University_of_California_at_Berkeleyhttp://en.wikipedia.org/wiki/General_Atomicshttp://en.wikipedia.org/wiki/General_Atomicshttp://en.wikipedia.org/wiki/General_Atomicshttp://en.wikipedia.org/wiki/General_Atomicshttp://en.wikipedia.org/wiki/University_of_California_at_Berkeleyhttp://en.wikipedia.org/wiki/Massachusetts_Institute_of_Technologyhttp://en.wikipedia.org/wiki/HTR-10http://en.wikipedia.org/wiki/Chinahttp://en.wikipedia.org/wiki/PBMRhttp://en.wikipedia.org/wiki/South_Africahttp://en.wikipedia.org/wiki/Pebble-bed_reactor#cite_note-3http://en.wikipedia.org/wiki/Pebble-bed_reactor#cite_note-2http://en.wikipedia.org/wiki/Rudolf_Schultenhttp://en.wikipedia.org/wiki/AVR_reactorhttp://en.wikipedia.org/wiki/AVR_reactorhttp://en.wikipedia.org/wiki/Germanshttp://en.wikipedia.org/wiki/Farrington_Danielshttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Nuclear_Powerhttp://en.wikipedia.org/wiki/Nuclear_Powerhttp://en.wikipedia.org/wiki/Pebble-bed_reactor#cite_note-1http://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Heliumhttp://en.wikipedia.org/wiki/Silicon_carbidehttp://en.wikipedia.org/wiki/Silicon_carbidehttp://en.wikipedia.org/wiki/Uranium-235http://en.wikipedia.org/wiki/TRISOhttp://en.wikipedia.org/wiki/Pyrolytic_carbonhttp://en.wikipedia.org/wiki/Generation_IV_reactorhttp://en.wikipedia.org/wiki/Very-high-temperature_reactorhttp://en.wikipedia.org/wiki/Nuclear_reactorhttp://en.wikipedia.org/wiki/Neutron_moderator


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theDutchcompany Romawa B.V.,Adams Atomic Engines, andIdaho National

Laboratory.

Pebble bed reactors were developed in Germany over 20 years ago. At the

Juelich Research Center, the AVR pebble bed research reactor rated at 40 MWth and 15

MWe operated for 22 years demonstrating that this technology works. The reactor

produced heat by passing helium gas through the reactor core consisting of uranium

fuelled pebbles. A steam generator was used to generate electricity through a

conventional steam electric plant. Germany also built a 300 MWe version of the pebble

bed reactor but it suffered some early mechanical and political problems that eventually -

-led to its shutdown. In December 2000, the Institute of Nuclear Energy Technology of

the Tsinghua University in Beijing, China, achieved first criticality of their 10 MWth

pebble bed research reactor. In the Netherlands, the Petten Research Institute is

developing pebble bed reactors for industrial applications in the range of 15 MWth. The

attraction to this technology is its safety, simplicity in operation, modularity and

economics. Advances in basic reactor and helium gas turbine technology have produced

a new version of the pebble bed reactor concepts. Instead of using less efficient steam

cycles to produce electricity, new designs as going to direct or indirect cycle helium gas

turbines to produce electricity. These designs have target thermal efficiencies in the

range of 45% compared to 32% for steam cycles. By avoiding the use of high

temperature water, all the difficulties associated with maintaining high temperature water

systems are eliminated. The optimum size for a pebble bed was concluded to be about

250 MWth thermal to allow for rapid and modular construction as well as maintaining its

inherent safety features. These designs do not require expensive and complicated

emergency core cooling systems since the core cannot melt. These advances have led the

ESKOM and the MIT team to independently conclude that the modular pebble bed

reactor can meet the safety and economic requirements for new generation. Currently,

the South African design has been upgraded to 400 MWth and 165 MWe electric. It is in

the final design stage with construction to begin in 2007 and commercial operation in

2010.
http://en.wikipedia.org/wiki/Netherlandshttp://en.wikipedia.org/wiki/Netherlandshttp://en.wikipedia.org/wiki/Netherlandshttp://en.wikipedia.org/wiki/Adams_Atomic_Engineshttp://en.wikipedia.org/wiki/Adams_Atomic_Engineshttp://en.wikipedia.org/wiki/Adams_Atomic_Engineshttp://en.wikipedia.org/wiki/Idaho_National_Laboratoryhttp://en.wikipedia.org/wiki/Idaho_National_Laboratoryhttp://en.wikipedia.org/wiki/Idaho_National_Laboratoryhttp://en.wikipedia.org/wiki/Idaho_National_Laboratoryhttp://en.wikipedia.org/wiki/Idaho_National_Laboratoryhttp://en.wikipedia.org/wiki/Idaho_National_Laboratoryhttp://en.wikipedia.org/wiki/Adams_Atomic_Engineshttp://en.wikipedia.org/wiki/Netherlands


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SCHEMATIC OF A PEBBLE BED REACTOR


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COMPONENTS OF PBR

The components of PBR are :-

The reactor unit system The fuel handling The reactor control system The heat transfer system The Generator and Compressors The fuel pebbles

The Reactor Unit

The reactor unit consists of the 3 meter diameter core filled with fuel spheres and

surrounded by the graphite reflector. The functions of the reflector are to: Reflect

escaping neutrons back into the core, to keep the neutron losses as low as possible;

Provide paths for the control rods and the reserve shutdown system absorbers to

enter the core region to shut down the reactor, and To provide a heat transport path

for the decay heat from the fuel to the Reactor Pressure Vessel so that passive

cooling of the core is possible by radiating this heat to a suitable heat sink called

the Reactor Cavity Cooling System (RCCS). Provide the volume in which the fuel

spheres can move through the core but remain in a well defined geometry. Provide

a flow path for the cold gas to be returned to the top of the core.

The reactor core contains approximately 360,000 uranium fuelled

pebbles about the size of tennis balls. Each pebble contains about 9 gm of low

enriched uranium in 10,00015,000 (depending on the design) tiny grains of sand-

like microsphere coated particles each with its own a hard silicon carbide shell..

The unique feature of pebble bed reactors is the online refuelling capability in

which the pebbles are recirculated with checks on integrity and consumption of

uranium.


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REACTOR CROSS SECTION


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