HPT001.013
Revision 2
Page XXX of 32
NUCLEAR TRAINING
TRAINING MATERIALS COVERSHEET
Radiological Protection Technician TrainingPROGRAM
Fundamentals Training / HPT001
COURSE
/ COURSE NO.
Reactor Theory / HPT001.013
LESSON TITLE / LESSON PLAN NO.
INPO ACCREDITED / YES / X / NO
MULTIPLE SITES AFFECTED / YES / X / NO
PREPARED BY
C. Daphne Stephens / ______
Signature / Date
PROCESS REVIEW
Jim Lyon / ______
Signature / Date
LEAD INSTRUCTOR/PROGRAM MGR. REVIEW
Mike Peterson / ______
Signature / Date
PLANT CONCURRENCE - BFN / ______
Signature / Date
PLANT CONCURRENCE - SQN / ______
Signature / Date
PLANT CONCURRENCE- WBN / ______
Signature / Date
Receipt Inspection and Distribution:
Training Materials Coordinator /Date
Standardized Training Material
Copies to:
TVA 40385 [NP 6-2001] Page 1 of 2
SEQUOYAH NUCLEAR PLANTNUCLEAR TRAINING
REVISION/USAGE LOG
REVISION
NUMBER / DESCRIPTION
OF CHANGES / DATE / PAGES
AFFECTED / REVIEWED BY
0 / Initial Issue / All
1 / Program was inactive. Reviewed and revised to reactivate. / 3/22/90 / All
2 / General revision to update material for reactivation of initial training program. / All / C. Daphne Stephens
TVA 40385 [NP 6-2001] Page 2 of 2
I. PROGRAM: Radiological Protection Technician Training
II. COURSE: Fundamentals Training
III. LESSON TITLE: Reactor Theory
IV. LENGTH OF LESSON/COURSE: 8 hours
V. TRAINING OBJECTIVES:
A. Terminal Objective:
Upon completion of this course, the participants will demonstrate their knowledge of reactor theory, by scoring 80% on a written examination. The examination may be based on the enabling objectives in this lesson only, or it may be part of a comprehensive examination covering multiple lesson plans.
B. Enabling Objectives:
1. Define terms and definitions associated with reactor theory.
2. Describe the types of reactions that affect the structure of the atomic nucleus.
3. List methods by which neutrons are produced.
4. List the characteristics of neutrons and the classification energies for neutrons.
5. Differentiate between prompt and delayed neutrons.
6. Explain the importance of delayed neutrons on reactor operations.
7. List the properties of a good moderator.
8. Describe the different reactor states; subcritical, critical, and supercritical.
9. Explain Keff and relate it to the reactor states.
10. Define reactivity and list factors that affect reactivity.
11. Explain how reactivity is controlled.
12. Differentiate between the reactivity coefficients.
13. State the purpose of the control rods.
14. Explain the impact xenon-135 has on reactor operations.
15. Describe how reactor power can be controlled and adjusted.
16. Differentiate between the various types of commercial reactors and list the
properties of each type.
VI. TRAINING AIDS:
A. Computer, projector, screen, and associated software
B. White board and marker
VII. TRAINING MATERIALS:
A. Appendices
1. List for additional information
2. Summary of INPO Event Number 327-000401-1
3. Summary of INPO Event Number 318-951016-1
4. Data for Typical Reactors of Various Designs
B. Slides (p:/Training/Technical Programs and Services/Radcon/Initial Program/Lesson Plan Library/Library/HPT001.013r2.ppt)
1. Scattering Reactions
2. Absorption Reactions
3. Neutron Production
4. Neutron Energy Classifications
5. Prompt vs. Delayed Neutrons
6. Moderator Properties
7. Reactor States
8. Keff
9. Reactivity Coefficients
10. Neutron Absorbers and Poisons
11. Rx Power Control
12. Enrichment
13. Magnox
14. AGR
15. PWR
16. BWR
17. RBMK
18. CANDU
VIII. REFERENCES:
A. Cember, Herman, Introduction to Health Physics, 3rd Edition, McGraw Hill, New York, 1996.
B. General Electric Company, Basic Atomic and Nuclear Physics, BWR Academic Series, 1984.
C. Gollnick, Daniel A, Basic Radiation Protection Technology, 4th Edition, Pacific Radiation Press, Altedena, California. January, 2004.
D. INPO ACAD 93-008, Guidelines for Training and Qualifications of Radiological Protection Technicians. August, 1993.
E. Krane, Kenneth S., Oregon State University, Introductory Nuclear Physics, John Wiley & Sons, New York, 1988.
F. Lamarsh, John R., Introduction to Nuclear Engineering, 2nd printing, Addison-Wesley Publishing Company, Inc., June 1977, 74-4718.
G. NUREG-1123 Rev. 2, Knowledge and Abilities Catalog for Nuclear Power Plant Operators: Boiling Water Reactors, Division of Reactor Controls and Human Factors, Office of Nuclear Regulation, U.S. Nuclear Regulatory Commission, Washington, D.C., August, 1995.
H. Salem Nuclear Generating Station, Nuclear Control Operator Course, Reactor Theory Manual, September 1981.
I. Sequoyah Technical Training, Lesson Plan EGT202.803, Revision 2, Reactor Theory, November 5, 2001.
IX. INTRODUCTION:
A reactor is the nuclear equivalent of the furnace part of a steam boiler. By the same principle that a conventional boiler uses heat produced by burning a fuel, such as gas or coal, a reactor uses the heat produced by the fission process. This heat is removed from the reactor core by the coolant which then produces steam. The steam drives turbine generators which actually produce the electricity.
The purpose of the lesson plan is to familiarize health physics technicians with reactor theory. This lesson presents a brief overview of basic terms used in reactor physics. Also, neutron production, neutron classification, and neutron moderation is covered.
Neutrons cause fission in a nuclear reactor, and it is essential that neutron production be controlled. Though reactor physics is very mathematical in nature, a basic, simplified explanation is provided in this lesson plan. It is not the intent of this lesson plan to fully develop all of the equations and theory behind the operation of a nuclear reactor, but to introduce the concept and explain how this concept is utilized in order to safely operate a nuclear plant. The List for Additional Information, Appendix 1, is provided for students seeking additional information on reactor theory.
HPT001.013
Revision 2
Page XXX of 32
X. LESSON BODY: / INSTRUCTOR NOTESA. Terms and Definitions
1. Critical – a condition in the reactor when neutron
production is self sustaining.
2. Critical energy – the minimum excitation energy
required to split the nucleus.
3. Decay heat – produced by the radioactive decay of
fission and activation products.
4. Delayed neutron – a neutron produced after the
fission event by the beta decay of fission product
nuclides.
/ Objective 1
1 fission event yields
1 more fission event.
Produced 10-14 seconds
up to 89 seconds after
the fission event
5. Delayed neutron precursors – fission fragments
which result in a delayed neutron being produced.
6. Fast neutrons – neutrons with an energy > 0.1
MeV.
7. Fertile – a nuclide capable of being transformed,
into a fissile nuclide by neutron capture. / 232Th, 238U
8. Fissile – a nuclide capable of undergoing fission by
interaction with a slow neutron.
9. Fissionable- a nuclide capable of undergoing fission
by any process. / 233U, 235U, 239Pu
Any energy neutron
will cause fission
10. Fission fragments – elements resulting from the
fission process.
11. Intermediate neutrons – have an energy between 1.0
eV and 0.1 MeV.
12. Moderator – a material used to slow neutrons down.
13. Neutron flux – refers to the number of neutrons
passing through a unit area in unit time. It is a
measure of the neutron intensity.
14. Prompt Neutron – a neutron born at the time of the
fission event. / Most commonly
measured in
neutrons/cm2-sec.
Within 10-14 seconds
15. Reactivity – the change in neutron population from
one generation to the next.
16. Reactivity coefficients – quantify the effect of a
variation in parameters on the reactivity of the core.
17. Residual heat – heat remaining in the piping and
components after the reactor is shut down.
18. Slow neutrons – have an energy below 1.0 eV.
19. Subcritical – the number of neutrons in a generation
is less than the number of neutrons in the previous
generation.
20. Supercritical – the number of neutrons in a
generation is greater than the number of neutrons in
the previous generation.
21. Thermal neutrons – have kinetic energy that equals
the atoms of the materials around them.
B. Nuclear Reactions
1. Two basic types of nuclear reactions affect the
structure of the atomic nucleus, scattering and
absorption.
2. Scattering reactions – where the incident particle
collides with the target nucleus. / Objective 2
Slide 1
a. Elastic scattering is a collision between a
particle and nucleus where the kinetic
energy and momentum is conserved. / All energy remains in
the form of kinetic
energy of motion
b. Inelastic scattering is a collision between a
particle and a nucleus where a portion of
the kinetic energy is used to raise the target
nucleus to a higher energy level. / Excited state
3. Absorption reactions – where the incident radiation
transfers energy by becoming a part of the nucleus.
a. Radiative capture – incident particle is
captured by the target nucleus and excess
energy is carried off by gamma emission. / Slide 2
b. Particle emission – incident particle is
absorbed by the nucleus and the resultant
excitation energy is high enough that a
particle is ejected from the nucleus. / A new element is
formed
c. Fission – particle is absorbed by a heavy
target nucleus and the nucleus splits into
fission fragments and the emission of
neutrons.
C. Neutrons
1. Neutrons provide a method of chain reaction and
can be produced in several ways.
a. Neutrons are produced in the fission
process.
235U + 1n → 236U→ 2 FF + ν 1n + Q
Note: the average number of neutrons
released by fission of 235U is 2.42 / Objective 3, Slide 3
FF = fission fragment
Q = energy
ν = average number of
neutrons released
b. Neutrons can be produced by fission
fragments (delayed neutron precursors).
For example: the fission fragment 93Rb
has a 6 second half-life and decays by beta
to 93Sr, which left in a highly excited state
can decay by neutron emission to 92Sr. / Competes with gamma
and occurs only 1.4 %
c. Neutrons can be produced by alpha neutron
(α, n) reactions.
4α + 9Be → 12C + 1n
d. Neutrons can be produced by photoneutron
(γ, n) reactions.
γ + 9Be → 9Be* → 8Be + 1n / * excited state
2. Characteristics of neutrons include:
a. mass of 1.008665 amu
b. no electrical charge
c. wide range of energies, with average energy
of ~ 2 MeV / Objective 4
3. Neutrons are classified according to energy.
a. Fast neutrons have energies > 0.1 MeV.
b. Intermediate neutrons have energies
between 1.0 eV and 0.1 MeV.
c. Slow neutrons have energies below < 1.0
eV.
d. Thermal neutrons have kinetic energy that
equals the atoms of the material around
them.
Note: sources vary on neutron classification
energies and names. Other neutron classifications
include: cold, epithermal, intermediate, relativistic,
and spallation. / Slide 4
4. Prompt and Delayed Neutrons
a. When a fission event occurs, neutrons are
released.
b. Prompt neutrons are released when the
fission event occurs and
(1) have an average energy of 2 MeV
(2) are released in 99.36% of fission
events. / Objective 5, Slide 5
Within 10-14 seconds
c. Delayed neutrons are released after the
fission event from fractions of seconds up
to tens of seconds and
(1) have an average energy of 0.5 MeV
(2) occur in only 0.64% of fission
events. / 10-14 seconds up to 89
seconds
d. Delayed neutrons are essential to sustaining
the chain reaction because they allow the
power level to be controlled.
(1) Reactor period is the time to increase
reactor power by a factor of 2.718
times. / Objective 6
(2) For prompt neutrons, the reactor
period is 0.2 seconds.
(3) For delayed neutrons, the reactor
period is 17 seconds. / Prompt criticality led to
the explosion of the
Chernobyl reactor.
D. Neutron Absorbers and Leakage
1. Every neutron that is produced will either:
a. be absorbed into a non-fissionable material
and die or
b. be absorbed into a fissionable material and
cause a fission event or
c. leak out (escape) from the core.
2. Anything that affects the amount of non-fissionable
material in the core will affect the state of the
reactor. / No fission event.
E. Moderators
1. In power reactors most of the fission events that
occur are caused by thermal neutrons.
2. Most of the neutrons that are produced by fission
are fast neutrons.
3. Since most of the neutrons produced are born as
fast neutrons and most of the fission events are
caused by thermal neutrons, there must be a way of
slowing down neutrons.
4. In order to slow down (thermalize) neutrons, a
moderating material is placed in the reactor core.
5. Moderators provided something that neutrons can
collide with, giving up some of their energy. / Fast to thermal takes an
average of 19 collisions
6. The properties of a good moderator are:
a. atomic mass close to that of a neutron
b. small cross section for neutron absorption
c. large cross section for neutron scatter / Objective 7, Slide 6
d. chemically non-reactive with reactor
materials
e. provides a large energy loss per collision
f. stable isotope to avoid changing cross
section characteristics
7. TVA nuclear plants use water for a moderator.
F. States of a Reactor
1. Subcritical is when the number of neutrons in a
generation is less than the number of neutrons in
the previous generation. / Objective 8, Slide 7
2. Critical is when the number of neutrons in a
generation is equal to the number of neutrons in
the previous generation.
3. Supercritical is when the number of neutrons in a
generation is greater than the number of neutrons in
the previous generation.
4. The effective neutron multiplication factor, Keff, is
the relationship between the number of neutrons in
a generation to the number of neutrons in the
previous generation. / Objective 9, Slide 8
a. When Keff = 1, the reactor is critical.
b. When Keff < 1, the reactor is subcritical.
c. When Keff > 1, the reactor is supercritical.
G. Reactivity
1. Reactivity is the amount by which the reactor has
departed from criticality (how far away the reactor
is from Keff).
2. Reactivity is the fractional change in neutron
population per generation (how much did the
neutron population changer from one generation to
the next). / Objective 10
Can be affected by fuel
depletion, temperature,