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High Temperature Gas-Cooled Reactor (HTGR)

ENGR 5301-35 Nuclear Reactor Kinetics & ControlInstructor

Dr. Wendell C. Bean

The Phillip M. Drayer Department of Electrical Engineering

Fall 2011

Presented by:- Group E

Charanpreet Singh

Karandeep Singh Randhawa

Zaki Ahmed Abbasi

8/27/2012 Lamar University 1


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Outline

Introduction

PC Tran Simulator for HTGR

Simulation Results and Diagrams References



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History of Gas Reactors in US

Peach Bottom (40 MWe) 1967-1974

-First Commercial (U/Thorium Cycle)

-Generally Good Performance (75% CF)

Fort St. Vrain ( 330 MWe) 1979-1989 (U/Th)

-Poor Performance

-Mechanical Problems

-Decommissioned



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Fort St Vrain



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History First proposed by the Staff of the Power Pile

Division of the Clinton Laboratories (knownnow as Oak Ridge National Laboratory) in1947

Professor Dr. RudolfSchulten in Germany alsoplayed a role in development during the 1950s

The Peach Bottom reactor in the United Stateswas the first HTGR to produce electricity

Fort St. Vrain Generating Station was oneexample of this design that operated as anHTGR from 1979 to 1989



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Peach Bottom- First HTGR in US



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High Temperature Gas-cooled Reactor

(HTGR) Also called Very High Temperature Reactor

(VHTR)

Generation IV reactor concept that uses agraphite-moderated nuclear reactor with a once-through uranium fuel cycle

Can conceptually have an outlet temperature of1000C

The reactor core can be either a prismatic blockor a pebble-bed core

The high temperatures enable applications suchas process heat or hydrogen production via thethermo-chemical sulfur-iodine cycle.



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Nuclear reactor design Neutron moderator- graphite. The reactor

core is configured in graphite prismatic blocks

or in graphite pebbles

Nuclear fuel- Coated fuel particles, such as

TRISO fuel particles. Coated fuel particles have

fuel kernels, usually made of uranium dioxide,

uranium carbide or uranium oxycarbide

Coolant- Helium. Helium is an inert gas, so it

will generally not chemically react with anymaterial



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Prototype HTGR generates anywhere from 10MW for an experimental device up to 600 MWper module for a multi-modular power plant

The reactor outlet temperature is in the orderof 700C to 1000C

The helium pressure is from 3 to 8 Mpa

The core helium flow is driven by a circulatorand regulated by variable speed

There are graphite reflectors in both the

annular and central column regions A neutron source is provided for the initial flux



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Operators pull the control rods to reach criticality

Fission energy is transmitted from either

prismatic fuel assemblies or TRISO balls to thehelium coolant

The fuels color changes during its temperature

rise

Heat transfer is by a combination of conduction,

convection and radiation to the containment air

By natural convection of the air and use of

cooling water at heat exchangers secondary side,

heat is removed to the atmosphere



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After reactor shutdown the Shutdown Cooling

System (SCS) is turned on that draws a small

amount of the helium gas from the vesselbottom and cooled by a heat exchanger

In addition to the rod control, the unit power

production can be controlled byBypass valve of the circulating helium flow to

the power conversion unit

Helium temperature controlExtraction and addition of helium



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To reach a given power level

Bypass is the fastest because it directly returns aportion of circulating helium back to the reactor(without going through the power conversionunit)

Temperature control is the slowest because the

large core fuel and moderator heat capacity An extraction valve from the circulating system to

a tank is for extraction and another valve withpump is for pumping helium into the system

A proportional plus integral logic is used tocontrol these valves on the helium pressure



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Since the power conversion system is open to

various designs, a simple pressurized-water

heat exchanger is used for now in thisprototype as heat sink

Super heated steam is generated to drive the

turbine/generator High temperature helium can also be used for

hydrogen production.



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Naturally Safe Fuel

Shut Off All Cooling

Withdraw All Control Rods

No Emergency Cooling

No Operator Action



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Safety features and other benefits The graphite has large thermal inertia. The core is

composed of graphite, has a high heat capacityand structural stability even at high temperatures

The helium coolant is single phase, inert, and hasno reactivity effects.

The fuel is coated uranium-oxycarbide whichpermits high burn-up (approaching 200 GWd/t)and retains fission products

The high average core-exit temperature of theVHTR (1,000C) permits emissions-freeproduction of process heat



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Advantages & Disadvantages of Gas

Cooled Reactors

High Efficiency (45% -50%) Lower Waste Quantity

Higher Safety Margins

High Burnup-100 MWD/kg

Poor History in US

Little Helium Turbine Experience

US Technology Water Based

Licensing Hurdles due to different designs



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Safety Advantages

Low Power Density

Naturally Safe

No melt down

No significant radiation release in accident

Demonstrate with actual test of reactor



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Types of HTGRs Pebble bed reactors (PBR)

The pebble bed reactor (PBR) design consists of fuel inthe form ofpebbles, stacked together in a cylindricalpressure vessel, like a gum-ball machine

Prismatic block reactors (PMR)

The prismatic block reactor refers to a prismatic blockcore configuration, in which hexagonal graphite blocksare stacked to fit in a cylindrical pressure vessel

Both reactors may have the fuel stacked in an annulusregion with a graphite center spire, depending on thedesign and desired reactor power



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What is a Pebble Bed Reactor ?

360,000 pebbles in core

About 3,000 pebbles

handled by FHS each day

About 350 discarded daily

One pebble discharged

every 30 seconds

Average pebble cycles

through core 10 times

Fuel handling most

maintenance-intensive part

of plant



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TRISO Fuel Particle --Microsphere



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Pebble Bed Advantages Low excess reactivity-online refueling

Homogeneous core (less power peaking)

Simple fuel management

Potential for higher capacity factors -no annual

refueling outages

Modularity-smaller unit

Faster construction time -modularity

Indirect cycle -hydrogen generation

Simpler Maintenance strategy-replace vs repair



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AVR in Germany-Pebble Bed



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International Activities

Countries with Active HTGR Programs China -10 MW Pebble Bed -2000 critical Japan -40 MW Prismatic

South Africa -400 MW Pebble -2012

Russia -290 MWe-Pu Burner Prismatic 2007

(GA, Framatome, DOE, etc)

Netherlands -small industrial Pebble

Germany (past) -300 MW Pebble Operated



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Key Technical Challenges

Materials (metals and graphite)

Code Compliance

Helium Turbine and Compressor Designs

Demonstration of Fuel Performance

US Infrastructure Knowledge Base

Regulatory System



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Technology Bottlenecks

Fuel Performance

Balance of Plant Design Components

Graphite

Containment vs. Confinement Air Ingress/Water Ingress

Regulatory Infrastructure



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Simulator-PCTRAN-HTR

PC-based Simulator for High Temperature Gas

Cooled Reactor

Version 0.1 (Beta)

Developed by Micro-Simulation Technology

located at 10 Navajo Court, Montville, New

Jersey 07045, USA

http://www.microsimtech.com/downloads/do

wnload2.asp


A h t f th PCTRAN HTR


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A screenshot of the PCTRAN HTR

reactor



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PC-based Simulator

For

High Temperature Gas-Cooled

Reactor (HTGR)


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PC TRAN HTGR A prototype PC-based simulator for High Temperature Gas-

Cooled Reactor (HTGR) successfully developed byMicro-Simulation Technology USA.

Using Microsoft Visual Basic language and operates under

Windows operating system.

The input and output are in Access database and its operation

is done by graphic user interface.

Reports and plots can be generated by the program and later

accessed by user.

The run-speed can be used to speed up simulation for 2, 4, 8up to 64 times.

This helps in understanding both the reactor core and the

power conversion system.


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About the Reactor

This prototype can generate anywhere from 10 MW to 600

MW per module for a multi-modular power plant.

The power production can be controlled by

1) bypass valve of the circulating helium flow to the power

conversion unit(fastest way).

2) helium temperature control(slow method). 3) extraction and addition of helium.

A d t b fil


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Access database filesListData.mdb

It has basic plant data and tells us about the status of

control buttons of all initial conditions, heat exchangers,pumps, Trip, malfunctions & gives us a list of initialconditions.

BackData.mdb it contains all backtrack conditions.

OptData.mdb has tables fora:-TimePlotOut which has output time record interval

for PlotData recording.

b:- TimeBackOut which has time interval for writing abacktrack record.

PlotData.mdb stores all the calculated variables in it.

It lists all variable names and their units for plotting. Alsoit has Actual plot data values in it.


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Reactivity

Run-Time

Transient time clock

Heat Exchanger

pump

Hx- capacity

Initial condition no.

Valve

run

Reactor Cavity Cooling

System


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Component Operation P for power control to S for rod control.

Code Control :- Run & Freeze.

Pumps are started and stopped by pressing the left mouse

button when the cursor is on the pump.

Valves can be opened to any position from 0-100% .

Backtrack- can be used to go back to a previous state of

reactor.

Position Dmd-The Rod position can be changed from 0-100%

by it.

Power Dmd- The value of power required at a time can be set

here.

SCRAM- It causes emergency shutdown of the nuclear

reactor by releasing the control rods into reactor core.


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Initial Conditions



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To edit basic data

Data values can be put

manually as-well :-

Gas Pressure(MPa)

Total Fuel Mass(Kg)

Rated Thermal Power(MW)

Avg Fuel Temperature(C)

He Flow Rate (kg/sec)



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Raising Power to 100%

In order to set reactor to give max power

following changes need to be done:-

Rod position needs to be at 89%(withdrawn).

Gas outlet needs to be around 844 C.

Coolant needs to be at 250 C.

Pump for HX 2nd IN needs to be at 100%.

Helium circ pump should be 100%.


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For a Rated Power of 50%

In order to set reactor to work at 50% power

level following changes need to be done:-

Rod position needs to be at 88%.

Gas outlet needs to be around 639 C.

Coolant needs to be at 104 C.

Pump for HX 2nd In needs to be at 63%.

Helium circ pump should be 51%.


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Advantages

Japan and South Africa have been using these simulators fortheir reactors.

All the transient and accident analysis cases are wellreproduced in this simulator.

This PC-based tool can even be used for demonstration of thegas-cooled reactors unique features and its advantages inefficiency and reliability.

Safe characteristic for HTGR can be obtained by it.

The fast run function of PCTRAN up to 64 times faster thanreal-time is valuable in training and analysis.

Reports and plots can be generated by the program and laterprinted by user.


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High Temperature Gas-Cooled Reactor

(HTGR) by Micro Simulation Technology.


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Contents

Introduction1

Simulation

2

Cases3

Click to add Title4


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Transient Verification Runs

Four Cases were selected for PCTRANHTR-10 verification from the followingpaper.

Commissioning and Operation Experience andsafety Experiments on HTR-10

3rd International Topical Meeting on High

Temperature Reactor Technology.

October 1-4, 2006,Johannesburg, South Africa.


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Transient Verification Runs

Model is brought to Critical.

Maintained near 100%Power.

Operating Variables are:

Toutlet = 703.7C

Tinlet = 252.1 C

He Circulation flow = 4.28 kg/sec Core Power = 10 MW

He Pressure = 2.96 MPa


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Design Parameters


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Text

Text


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Case I: He Circulator Trip ATWS Test

Reactor Started at 100% power steady state.

Switch from P to S.

Rod Speed set to zero to prevent its movement.

The He Circulator is tripped without incurring areactor scram.

The transient key plots are follows:


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Case I: He Circulator Trip ATWS


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Case I: He Circulator Trip ATWS


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More Cases

A steady state at 30% power is created forbenchmark of three operational transients.

Rod Withdrawal from 30% power.

Varying Helium Circulation Rate.

Feed water Alterations.


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References

[1] Operation and Control Simulation of a Modular

High Temperature Gas Cooled Reactor Nuclear Power

Plant, Haipeng Li, Xiaojin Huang, and Liangju Zhang ,

IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 55,NO. 4, AUGUST 2008

[2] http://www.microsimtech.com

[3] http://www.cti-simulation.com

http://www.microsimtech.com/http://www.cti-simulation.com/http://www.cti-simulation.com/http://www.cti-simulation.com/http://www.cti-simulation.com/http://www.microsimtech.com/


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