Prof. Andrew C. Kadak, 2008Page 1Department of Nuclear Science & Engineering

Operational Reactor Safety22.091/22.903

Professor Andrew C. KadakProfessor of the Practice

Spring 2008

Overview

Prof. Andrew C. Kadak, 2008Page 2Department of Nuclear Science & Engineering

Course Learning Objectives

The course will focus on understanding the complete nuclear reactor system including the balance of plant, support systems and resulting interdependencies affecting the overall safety of the plant and regulatory oversight.

• Reactor Physics• Power Conversion• Safety Functions and Systems• Risk Assessment• Simulator Exercises• Technical Specifications• Safety Culture

Prof. Andrew C. Kadak, 2008Page 3Department of Nuclear Science & Engineering

Course Overview

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Course Overview Cont’d

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Grading Components

Homework 15%Quiz #1 20%Quiz #2 20%Quiz # 3 20%

Final Exam 25%

Late Homework will receive up to 1/2 full credit

Prof. Andrew C. Kadak, 2008Page 6Department of Nuclear Science & Engineering

Lecture 1: Overview of Nuclear Reactors

Learning Objectives:

Gain broad understanding of PWRs, BWRs, HTGRs

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Nuclear Fuel Cycle

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Prof. Andrew C. Kadak, 2008Page 9Department of Nuclear Science & Engineering

Calvert Cliffs - MD

Diablo Canyon

Prairie Island - MN

Indian Point - NY

Prairie Island site - MN

Robinson - SC

Surry - VA

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Prof. Andrew C. Kadak, 2008Page 10Department of Nuclear Science & Engineering

Objectives to Make Electricity

1. Make heat2. Remove heat using a fluid or gas3. Pass the fluid or gas through a turbine4. Turning an electric generator to make

Electricity

Prof. Andrew C. Kadak, 2008Page 11Department of Nuclear Science & Engineering

Removing Heat• Fluid (water or liquid metal) or gas is pumped through the

core to remove heat generated in fuel due to fissioning.

• Pumps needed to circulate coolant

• Transfer directly to turbines or to steam generators (PWRs)

• Condense steam to recirculate back to the core to provide cooling

Prof. Andrew C. Kadak, 2008Page 12Department of Nuclear Science & Engineering

Basics of Power Conversion

Boiling Water Reactor

Just like a coaloil or natural gas plant

ReplacesfossilBoilerbut nosmokestack

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Prof. Andrew C. Kadak, 2008Page 13Department of Nuclear Science & Engineering

Power Reactor Types

– Pressurized Water Reactor

– Boiling Water Reactor

– Natural Uranium Heavy Water Cooled Reactor (CANDU)

– RBMK - Russian Chernobyl Like - Water Cooled

– Fast Reactors - Liquid Metal (Sodium)

– Gas Reactors (CO2 or Helium Cooled)

– Molten Salt Cooled Reactors (Organic Coolants)

Prof. Andrew C. Kadak, 2008Page 14Department of Nuclear Science & Engineering

Making Heat

• Use the fissioning of uranium atoms (or plutonium) to release 200 Million electron volts per fission.

• Need to enrich natural uranium to 3 to 4 weight percent U-235 (from 0.7% found in nature.

• Need to fabricate uranium into pellets clad in zironium fuel assemblies which are placed into the reactor core.

Prof. Andrew C. Kadak, 2008Page 15Department of Nuclear Science & Engineering

Fission Event

Release of excess neutrons creates the potential for chain reaction.

The energy (mostly as kinetic energy of the fission fragments) is substantial.

n U-235 nn

FF2n

FF1

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Prof. Andrew C. Kadak, 2008Page 16Department of Nuclear Science & Engineering

Energy Release

1 fission = 200 Mev

1 gram U-235 fissioned = 8.6x1010 joules = 24,000 kwh

(Equivalent to lighting a small city for overnight)

24,000 kwh requires 3.2 tons of coal

12.6 bbls oil

Energy Density (energy / mass)

Energy Density of U-235 = 28,000 times energy density of coal

Prof. Andrew C. Kadak, 2008Page 17Department of Nuclear Science & Engineering

Pellets

Fuel Pins

Insertingpelletsinto pins

Fuel Assembly

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Creating the Reactor Core

• Need to model uranium fuel

• Reactor internals

• Coolant flow

• Apply Reactor Physics

• Develop neutron flux solutions

• Yields power distributions

• Creates heat that must be removedReactor Core

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Important Factors in Design• Reactor Core Design

– Fuel Design

• Reactor Physics - Core Power Distribution• Reactivity Control - Ability to shutdown plant• Safety Analysis - no fuel failure or melting

• Core Heat Removal

– Coolant - Heat Transfer

– Safety Systems (Emergency)

• Confinement of Radioactivity

• Electricity Production

Prof. Andrew C. Kadak, 2008Page 21Department of Nuclear Science & Engineering

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Boiling Water Reactors

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BWR Power Cycle

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Schematic Arrangement of a BWR

A.V. Nero, Jr., A Guidebook to Nuclear Reactors, 1979Source unknown. All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.

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BWR Fuel Assembly

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BWR Core Lattice

“BWR/6: General Description of a BWR,” GE, 1980.Source unknown. All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.

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Pilgrim Nuclear Plant

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Pressurized Water Reactors

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Schematic of Pressurized Water Reactor

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PrimaryCoolant Pump

PrimaryVessel

ControlRods

ReactorCore

292ÞC

PrimaryConcrete

Shield15.5 MPa

Pressurizer

324ÞC

SteamGenerator

Concrete and SteelContainment

Primary Side Secondary Side

Steam to Turbine6.9 MPa285ÞC

High-PressureHeaters

Low-PressureHeaters

FeedPump

CondensatePump

Turbine

Turbine Bypass

ElectricGenerator

Grid

Condenser

CoolingTower

-40ÞC-15ÞC

Pressurized Water Reactor Schematic

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Prof. Andrew C. Kadak, 2008Page 33Department of Nuclear Science & Engineering

Typical Four-Loop Reactor Core

ParametersTotal heat output ~3250-3411 MWTHeat generated in fuel 97.4% Nominal system pressure 2250 psia Total coolant flow rate ~138.4 x 106 lb/hr Coolant Temperature

Nominal inlet Average rise in vessel Outlet from vessel

557.5˚F61.0˚F618.5˚F

Equivalent core diameter 11.06 ft Core length, between fuel ends 12.0 ft Fuel weight, uranium (first core) 86,270 kg Number of fuel assemblies 193

Cross Section (193 Fuel Assemblies)

Masche, G., Systems Summary: W PWR NPP, 1971Source unknown. All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.

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PWR Fuel Assembly

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The Byron plant (photo courtesy Commonwealth Edison) is typical of a large US Pressurized Water Reactor plant. Each reactor is 1105 MWe and they came into commercial service in 1985 and 1987 respectively.

Prof. Andrew C. Kadak, 2008Page 36Department of Nuclear Science & Engineering

Gas Cooled Reactors

Fort St. Vrain - 330 MWe

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Power Cycle - Brayton

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Ceramic Fuel

L-029(5)4-14-94

Uranium OxycarbidePorous Carbon BufferSilicon CarbidePyrolytic Carbon

PARTICLES COMPACTS FUEL ELEMENTS

TRISO Coated fuel particles (left) are formed into fuel rods (center) and inserted into graphite fuel elements (right).

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Prof. Andrew C. Kadak, 2008Page 39Department of Nuclear Science & Engineering

Modular Pebble Bed Reactor

Thermal Power 250 MW

Core Height 10.0 m

Core Diameter 3.5 m

Fuel UO2

Number of Fuel Pebbles 360,000

Microspheres/Fuel Pebble 11,000

Fuel Pebble Diameter 60 mm

Microsphere Diameter ~ 1mm

Coolant Helium

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Prof. Andrew C. Kadak, 2008Page 41Department of Nuclear Science & Engineering

Reading and Homework Assignment

1. Read Knief Chapter 1

Problems: 1.9, 1.10, 1.12

2. Read Knief Chapter 2

Problems: 2.7, 2.12

3. Read Knief Chapter 4

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22.091 Nuclear Reactor SafetySpring 2008

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