Operational Reactor Safety

22.091 /22.903

Professor Andrew C. Kadak Professor of the Practice

Spring 2008

Overview

Prof. Andrew C. Kadak, 2008 Page 1

Department 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, 2008 Page 2

Department of Nuclear Science & Engineering

Course Overview

Department of Nuclear Science & Engineering

Prof. Andrew C. Kadak, 2008 Page 3

Source un kn own. All right s re se rved. T his c ontent is exclud ed fro m our Creativ e Comm on s

Course Overview Cont’d

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Prof. Andrew C. Kadak, 2008 Page 4

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Grading Components

Final Exam 25%

Late Homework will receive up to 1/2 full credit

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Department of Nuclear Science & Engineering

Lecture 1: Overview of Nuclear Reactors

Learning Objectives:

Gain broad understanding of PWRs, BWRs, HTGRs

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Department of Nuclear Science & Engineering

Nuclear Fuel Cycle

Calvert Cliffs - M D

Diablo Canyon

Prairie Island - M N

Indian Point - N Y

Prairie Island site - M N

Robinson - S C

Surry - V A

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Department of Nuclear Science & Engineering

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Objectives to Make Electricity

1. Make heat

2. Remove heat using a fluid or gas

3. Pass the fluid or gas through a turbine

4. Turning an electric generator to make Electricity

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Department 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

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Department of Nuclear Science & Engineering

Basics of Power Conversion

Replaces fossil Boiler but no

smokestack

Boiling Water Reactor

Just like a coal oil or natural gas plant

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Power Reactor Types

– P ressurized Water Reactor

– B oiling Water Reactor

– Natural Uranium Heavy Water Cooled Reactor (CANDU)

– RBMK - R ussian Chernobyl Like - W ater Cooled

– F ast Reactors - L iquid Metal (Sodium)

– Gas Reactors (CO 2 or Helium Cooled)

– M olten Salt Cooled Reactors (Organic Coolants)

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Department 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.

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Department of Nuclear Science & Engineering

Fission Event

n U-235 n

Release of excess neutrons creates the potential for chain reaction.

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

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Energy Release

1 fission = 200 Mev

1 gram U-235 fissioned = 8.6x10 10 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 Energ y Densit y (energ y / mass)

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

Department of Nuclear Science & Engineering

Prof. Andrew C. Kadak, 2008 Page 16

Pellets

Inserting pellets into pins

Fuel Pins

Fuel Assembly

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Creating the Reactor Core

Reactor Core

• Need to model uranium fuel

• Reactor internals

• Coolant flow

• Apply Reactor Physics

• Develop neutron flux solutions

• Yields power distributions

• Creates heat that mu st be removed

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Important Factors in Design

• Reactor Core Design – F uel Design

• Reactor Physics - Core Power Distribution

• Reactivity Control - A bility to shutdown plant

• Safety Analysis - n o fu el failure or melting

• Core Heat Removal

– C oolant - H eat Transfer

– S afety Systems (Emergency)

• Confinement of Radioactivity

• Electricity Production

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Prof. Andrew C. Kadak, 2008 Page 20

Prof. Andrew C. Kadak, 2008

Boiling Water Reactors

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BWR Power Cycle

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Schematic Arrangement of a BWR

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A.V. Nero, Jr. , A Gu ideboo k to Nuc lear R eacto r s , 1979

BWR Fuel Assembly

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Prof. Andrew C. Kadak, 2008 Page 27

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BWR Core Lattice

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“ B W R / 6: General Des c r iption of a BW R,” GE, 1980.

Pilgrim Nuclear Plant

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Pressurized Water Reactors

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Schematic of Pressurized Water Reactor

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Department of Nuclear Science & Engineering

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Pressurized Water Reactor Schematic

Co n c r e t e a n d S t e e l C o nta inme n t

P r i m a r y S i d e S e c o nd a r y S i de

Pr ima r y Co n c r e t e Sh ie ld

15 .5 M P a

Co n t r o l Rod s

P r e s s u r i z e r

32 4 Þ C

S t e a m to T u r b ine

6. 9 M P a

2 85 Þ C

St e a m Gen e r a t or

Tu r b i n e

Tu r b i n e B y p a s s

Co n d e n ser

- 40 Þ C

- 15 Þ C

Gr id

Re a c to r Co r e

Pr ima r y Ve s s e l

29 2 Þ C

Pr ima r y Co o l a n t P u m p

Fe e d Pump

Co o l i n g To w e r

Co n d e n s a t e Pu m p

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Department of Nuclear Science & Engineering

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Typical Four-Loop Reactor Core

Cros s Sectio n (19 3 Fue l Assemblies)

Parameter s

Total heat output ~3250-3411 MWT

Heat gener ated in fuel 97.4%

Nominal s ystem pressure 2250 psia

Total coolant flow rate ~138.4 x 10 6 lb/hr Coolant Temper ature

Nominal inlet Average rise in vessel Outlet from vessel

557.5 ˚ F

61.0 ˚F

618.5 ˚ F

Equivalent core diameter 11.06 ft Core length, betwee n fuel ends 12.0 ft Fuel weight, uranium (first core) 86,270 kg Number of fu el assem blies 193

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Masche, G., Syst ems S u mmary: W PWR NPP, 1971

PWR Fuel Assembly

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Prof. Andrew C. Kadak, 2008 Page 34

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The Byron plant (photo courtesy Commonw ealth Edison) is typical of a large US Pressurized Water Reactor plant. Each reactor is 1105 M W e a nd they came into commercial service in 1985 and 1987 respectively .

Prof. Andrew C. Kadak, 2008 Page 35

Department of Nuclear Science & Engineering

Gas Cooled Reactors

Fort St. Vrain - 330 MWe

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Department of Nuclear Science & Engineering

Power Cycle - Brayton

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Ceramic Fuel

Py roly tic Carbon Silicon Carbid e Porous Carbon Buffer Uranium Oxy carbide

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

PARTICLES COMPACTS FUEL ELEMENTS

Prof. Andrew C. Kadak, 2008

Department of Nuclear Science & Engineering

Page 38

L - 029(5 ) 4-14-94

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Modular Pebble Bed Reactor

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

Department of Nuclear Science & Engineering

Prof. Andrew C. Kadak, 2008 Page 41

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22.091 Nuclear Reactor Safety

Spring 2008

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