This sample review copy provided for evaluation of the training material
from General Physics Corporation, at http://nucleartraining.gpworldwide.com/gfe.aspx
BWR/PWR Generic Fundamentals
SAMPLE QUESTIONS FROM THE
EXAM STUDY GUIDES
CHAPTER 1
FISSION CROSS SECTION (BARNS)
SAMPLE
10
4
10
3
10
Delayed neutron
Birth 0.5 MeV
(500,000 eV)
585 barns
2
10
U-235
1
10
-1
U-238
10
10
-2
0.025 eV
-3
10
-3
10
-2
10
-1
1
2
3
4
10
10
10
10
NEUTRON ENERGY (eV)
10
5
10
6
10
7
NRC Exam Bank Questions Study Guide (thru Dec2007)
Rev 4 (revised 2008)
©2006-2008 General Physics Corporation, Elkridge, Maryland
All rights reserved. No part of this book may be reproduced in any form or by
any means, without permission in writing from General Physics Corporation.
BP000Gr4_Sample Exam Study Guide Questions 08Nov08
THE FOLLOWING PAGES CONTAIN A REPRESENTATION OF A PORTION OF ONE EXAM
STUDY GUIDE CHAPTER AND SIX QUESTIONS FROM VARIOUS CHAPTERS.
The front matter from Reactor Theory Chapter 1 Neutrons is included to show the format and typical
information provided in each chapter.
Components Chapter 7 Sensors and Detectors
Components Chapter 8 Controllers and Positioners
Reactor Theory Chapter 6 Fission Product Poisons
Reactor Theory Chapter 8 Reactor Operational Physics
Thermodynamics Chapter 3 Steam
Thermodynamics Chapter 9 Thermal Limits
for more information contact
John Galamback - JGalamback @gpworldwide.com 410.340.3463
Sam Shoppell - [email protected] 803.295.5209
Jeff Klein - [email protected] 803.295.5210
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USING THIS DOCUMENT AS A STUDY GUIDE
BACKGROUND
This document was created from examination questions in the U.S. Nuclear Regulatory Commission’s
(NRC) Generic Fundamentals (GF) Examination question exam bank as of inclusion of the December
2007 exam. The NRC questions are written to address the knowledge and ability (K&A) statements
identified in NUREG-1122, Rev. 2 for PWRs or NUREG-1123, Rev. 2 for BWRs. This evaluation
process is in accordance with the Operator Licensing Examination Standards for Power Reactors
(NUREG-1021, Rev. 9). The specific procedure for administering the Generic Fundamentals
Examination Program is outlined in section 205. The K&A catalog statements associated with each
chapter follow the table of contents in this document. The NRC GF Examination, currently given four
times a year, has 50 multiple choice questions. Current regulations require that 40 questions be drawn
from the examination bank, five new questions be written every examination and five questions be
drawn from the examination bank and be revised before being added to the examination, for a total of 50
questions. The number of questions drawn from each chapter has been determined and set forth in
NUREG-1021 ES-205.
GP EXAM BANK MATERIALS
Questions drawn from the K&A catalog must have an importance rating of 2.5 or higher. Therefore,
although all of the K&As are addressed in the General Physics Corporation (GP) generic fundamental
training materials, only topics with an importance rating of greater than 2.5 will be on the NRC GF
examination. Those K&As with a rating of 2.5 or higher have been shaded on the accompanying list of
K/A – Objective Cross References; one list for PWR and one list for BWR.
A six digit topic number tracks the K&A sections; for example 192001. The first digit represents the
reactor type; 1 for PWR and 2 for BWR. The second and third digits represent the topic area 91 for
components, 92 for reactor theory, and 93 for thermodynamics (PWR and BWR are the same), and the
last three digits represent the chapter number 001-010. Thus 192001 would represent PWR reactor
theory chapter 1.
If the exam question was in the exam bank as a result of exams administered by December 2007 the
item will be discussed in this study guide. All exam questions have a unique question identification
number (QID). The QID number for a test item will begin with either the letter "B" (for BWR) or "P"
(for PWR). The QID number is a two, three, or four digit number that allows distinction between test
items having a common topic and knowledge. When two QID numbers are given for a single test item,
that test item appears in both the BWR and PWR question banks.
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Each page also provides supporting information to assist the candidate in finding additional information
about the question. The first box lists the QID and provides a general description of the question topic.
For short K/A topics it will list the K/A, in most it will show a shorter paraphrased topic title. In front of
the QID number is a 0 / 0 identifier. This was designed to be a quick reference in the Table of Contents
to identify if the question has appeared recently on an NRC exam. The first number represents BWR
exams and the second number represents PWR exams. Thus if the identifier in front of the QID is “2 /
1”, the question was used on two BWR exams and on one PWR exam. The identifier “0 / 0” represents
that the question was not used on any recent exams. Then the six digit K/A topic identifier and the K/A
number [to aid in searching the bank for specific K numbers these document identifies PWR K numbers
as PK and BWR K numbers as BK. Thus if searching for a question with a specific K number a PWR
user would search for PK1.02, while a BWR user would search for BK1.02] and importance rating is
shown [average importance on a 0-5 scale where 5 is high and a 2.5 average is need to be included as a
test topic]. Next is a listing of similar questions. If the exam bank has similar questions the additional
question QID(s) will be listed here. Some similar questions could be in other chapters (for example
water hammer questions could show up in the Components chapter on Pumps; the Components chapter
on Valves; or the Thermodynamics chapter on Fluid Statics and Dynamics). Finally the matrix shows
which NRC exams (if any) the question has been used on. Following the matrix, the multiple choice
question appears as it appears in the NRC GF exam bank, with any accompanying graphic.
Sample Question Matrix:
1 / 0 QID: P2145 (B2145) Neutron - prompt and delayed
PWR TOPIC: 192001
BWR TOPIC: 292001
KNOWLEDGE: PK1.02 [2.4/2.5]
KNOWLEDGE: BK1.02 [3.0/3.1]
Similar questions
P545 (B1845), P1245 (B2846), P2045 (B2046), P2645 (B2645), P2145 (B2145), P2545 (B2545),
P2445 (B3345), P2945, (B2945)
Recent BWR exams
Recent PWR exams
Oct2003
Not used in 2001 through 2007
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HOW TO USE THESE MATERIALS
The candidate studying for the GF examination should recognize that this is a sophisticated multiple
choice exam. The answers that are incorrect are designed to be plausible. Therefore the candidate might
arrive at an answer that is an option on the question but not have the correct answer if the candidate
makes the same common error.
The GF exam candidate should be aware that although studying the exam bank may be helpful, the
intent should be to understand the reasoning behind the correct answer rather than just memorizing the
exam bank. Knowing that 20% of the questions on the test (5 new and 5 revised out of 50 questions) are
not in the exam bank should give the candidate pause to realize that by just memorizing the exam bank
the candidate would only score an 80%. That leaves no room for error. It is imperative that the candidate
understands the concepts behind solving the questions.
The concept of a Generic Fundamentals exam is to ensure candidates entering a licensing program have
a background in general topics before studying system related topics. The skills and information that
candidates should learn to master the GF exam will provide candidates valuable information throughout
their career as an operator, and beyond. This study guide is not meant to be a stand-alone tool to pass the
NRC GF exam, but rather a complement to a classroom training program and self-study program. It is
far better to understand the principles behind the fundamentals than to just memorize a large number of
easily forgotten complex questions.
GF candidates studying for the exam should focus on questions with a QID representative of their
respective reactor. Many questions have applicability to both PWR and BWR reactors. However, there
are some questions that are only applicable to one or the other reactor type, primarily but not limited to
reactor theory questions.
This exam bank study guide was structured so that candidates studying for the exam can look at the
questions without seeing the answer. The question is on the front of a page and the answer and
explanation is on the back of the page. It is not always necessary to read the explanation on why the
answer is correct. If a candidate knows why the answer is correct and why the other answers are
incorrect they are doing well. The study guide was written for those that might need a little help
distinguishing between the correct answer and distracters that sound correct. If the candidate gets an
answer wrong it might be especially helpful to read the explanation as to why that answer is wrong and
then study the explanation as to why the correct answer is right.
In some cases there could be more than one way to explain why an answer is correct; typically the study
guide provides a single explanation. The staff at General Physics is open to including other reasonable
alternate correct explanations. The explanation section also sometimes provides some test taking
information that may be helpful to the candidate.
GP has attempted to justify every incorrect distracter. Occasionally a distracter was used because the
author thought the distracter might sound reasonable to an unqualified or borderline candidate and there
is no real justification for the answer; the answer is just wrong. Sometimes in calculation problems the
incorrect answer(s) are derived from common mathematical errors or assumptions. If the reason why a
distracter is wrong and/or was included is apparent this document attempts to point out the fallacy, but if
the incorrect reasoning is not apparent no justification is provided.
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TEST TAKING HABITS
Before the candidate begins, they should look at the standard equation sheet the NRC provides. If the
candidate recalls equations they think they will need that are not on the equation sheet, they should write
the equation (information) down as soon as the opportunity presents itself.
When solving any multiple choice question it is important to read the ENTIRE question. Although the
questions are not written to be tricky, it is easy to confuse a given test item with a question and answer a
candidate might have seen while studying. Read every word in the question and answer the question that
was asked. Use a highlighter to identify key parts of the question or underline (or circle) key parts. It
may also be helpful to write down key parts or additional key concepts. Identify exactly what the
question is really asking, then solve or determine the answer to the question before you look at the
answers given.
Then read the every multiple choice answer in its entirety. Again, look for key parts or concepts in each
answer. If the candidate reads an answer and the answer appears to be correct mark it with a +. If
something in the answer appears to be incorrect mark the section with an X.
When solving mathematical calculation problems the candidates should check their math carefully. They
also should ensure that the correct formulas were used and the data was entered in the calculator
correctly.
Examiners make every effort to make sure that an answer cannot be determined from information in
another question. However, sometimes another question or answer might jog the candidate’s memory
and help them answer a previous question or rule out a distracter. Do not waste time. Do not dwell too
long on a question; make sure you come back to any question you may skip. Make a list of the question
number and topics you skip to make sure you go back to the skipped question.
When using the SCANTRON forms, make sure you are filling in the correct blank for the correct
number question with the correct multiple choice options. Check! Use good self checking procedures.
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MULTI-PART QUESTIONS
Solving the basic GF exam questions involves determining which multiple choice answer is correct. If
one or more sections of a given answer are incorrect, the entire answer is incorrect and another answer is
correct. Thus, a candidate can sometimes determine the correct answer by ruling out all other options as
incorrect.
Example: (Note that the bold type was added by GP to point out the key words and phrases.)
Question:
As compared to a prompt neutron, a delayed neutron, born from the same fission event, requires
_______ collisions in the moderator to become thermal and is _______ likely to cause fission of a
U-238 nucleus. (Neglect the effects of neutron leakage.)
Rational:
Delayed neutrons are born at 0.5 MeV; prompt neutrons are born at 2.0 MeV. To reach thermal energies
the neutron must give up energy through collisions with other materials. Since the delayed neutron has
less energy to start with the delayed neutron must undergo fewer collisions to reach thermal energy.
Therefore, a delayed neutron requires FEWER collisions in the moderator to become thermal.
U-238 requires a neutron with 1.8 MeV of kinetic energy to undergo fast fission. Delayed neutrons are
born at 0.5 MeV. Therefore, a delayed neutron is LESS likely to cause fission of a U-238 nucleus.
Answer Analysis:
A. more (FALSE); more (FALSE)
Incorrect – both sections are false; if any sections are false, the answer must be incorrect
and another answer must be correct.
B. more (FALSE); less (TRUE)
Incorrect – one section is false and one section is true; if any section is false, the answer
must be incorrect and another answer must be correct.
C. fewer (TRUE); more (FALSE)
Incorrect – one section is true and one section is false; if any section is false, the answer
must be incorrect and another answer must be correct.
D. fewer (TRUE); less (TRUE)
CORRECT – all sections are true; if all sections are true the answer is correct, and all
other answer must be incorrect.
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TABLE OF CONTENTS
PWR K/A – OBJECTIVE CROSS REFERENCE .................................................................................. viii
BWR K/A – OBJECTIVE CROSS REFERENCE.................................................................................... ix
0 / 0 QID: P707 (B706) Operation of a flow D/P cell type flow detector.................................. 1
1 / 1 QID: B4609 (P4607) Operation of Pressure and Temperature Controller......................... 3
1 / 1 QID: B1361 (P1358) Xenon-135 versus time for startup with xenon-135 present............ 5
1 / 1 QID: B5334 (P5334) Period, Delayed Neutron Fraction and Power Rate of Change ....... 9
1 / 1 QID: B5438 (P5439) Specific work – turbine / Usefulness of Steam Tables .................. 11
1 / 1 QID: B1697 (P3395) Thermal conductivity and fuel centerline temperature .................. 13
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REACTOR THEORY: 192001
NEUTRONS
PWR K/A – OBJECTIVE CROSS REFERENCE
NUREG-1021 ES-205 1 question(s) on 50 question PWR GF Test
K/A
Quest.
in
NRC
bank
181
K/A STATEMENT
IMPORTANCE
RELATED
OBJECTIVE
NUMBER
RO
SRO
Define fast, intermediate, and slow
neutrons.
1.9*
2.0
19,20,22
Define prompt and delayed neutrons.
2.4
2.5
18,21,22
K1.01
0
K1.02
182
K1.03
0
Define thermal neutrons.
2.2
2.3
20,25
K1.04
0
Describe neutron moderation.
2.4
2.4
27
K1.05
0
Identify characteristics of good
moderators.
2.0*
2.1*
7a, 7b, 26, 28, 29, 30,
31
K1.06
0
Define neutron lifetime.
1.6*
1.6*
23
K1.07
0
Define neutron generation time.
1.6*
1.6*
23,24
K1.08
0
Describe fast flux, thermal flux, and
flux distribution.
1.9*
2.0
32
K1.09
0
Describe sources of neutrons.
2.3
2.4
18
The following objectives, while not cross referenced to specific K/As, ensure mastery of fundamental concepts: 1-6, 7a,
7c, and 8-17.
Note: Importance ratings that are marked with an asterisk (*) or question mark (?) indicate variability in rating responses
by reviewers. An asterisk (*) indicates that the rating spread was very broad. An asterisk (*) can also indicate that more
than 15% of the raters felt the knowledge or ability is not required for the RO/SRO position at their plant. A question
mark (?) indicates that more than 15% of the raters felt that they were not familiar with the knowledge or ability as
related to the particular system or design feature. A dagger (†) indicates that more than 20% of the raters indicated that
the level of knowledge or ability required by a SRO is different from the level of knowledge or ability required by a RO.
1
2
There are 18 questions in the NRC PWR exam bank through the December 2007 exam cycle.
All 18 questions in the NRC PWR exam bank are associated with K1.02, the statement with a rating over 2.5
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REACTOR THEORY: 292001
NEUTRONS
BWR K/A – OBJECTIVE CROSS REFERENCE
NUREG-1021 ES-205 1 question(s) on 50 question BWR GF Test
K/A
Quest.
in
NRC
bank
373
K/A STATEMENT
IMPORTANCE
RELATED
OBJECTIVE
NUMBER
RO
SRO
Define fast, intermediate, and slow
neutrons.
2.0*
2.1*
18, 21, 32
K1.01
0
K1.02
225
Define prompt and delayed neutrons.
3.0
3.1
20, 21, 23
K1.03
65
Define thermal neutrons.
2.7
2.7
25, 32
K1.04
75
Describe neutron moderation.
3.2
3.2
27
K1.05
25
Identify characteristics of good
moderators.
2.4*
2.6*
7a, 7b, 26, 28, 29,
30, 31
K1.06
0
Define neutron lifetime.
1.9*
1.9*
24
K1.07
0
Define neutron generation time.
1.9*
1.9*
22, 24
K1.08
0
Describe fast flux, thermal flux, and flux
distribution.
2.2*
2.4
19
The following objectives, while not cross-referenced to specific K/As, ensure mastery of fundamental concepts: 1-6,
7c, 7d, and 8-17.
Note: Importance ratings that are marked with an asterisk (*) or question mark (?) indicate variability in rating
responses by reviewers. An asterisk (*) indicates that the rating spread was very broad. An asterisk (*) can also
indicate that more than 15% of the raters felt the knowledge or ability is not required for the RO/SRO position at their
plant. A question mark (?) indicates that more than 15% of the raters felt that they were not familiar with the
knowledge or ability as related to the particular system or design feature. A dagger (†) indicates that more than 20% of
the raters indicated that the level of knowledge or ability required by a SRO is different from the level of knowledge or
ability required by a RO.
3
There are 37 questions in the NRC BWR exam bank through the December 2007 exam cycle. There are 4 K statements with
a rating over 2.5. K1.02 has 22 questions, K1.03 has 6 questions, K1.04 has 7 questions, and K 1.05 has 2 questions
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0 / 0 QID: P707 (B706) Operation of a flow D/P cell type flow detector
BWR TOPIC: 291002
PWR TOPIC: 191002
KNOWLEDGE:
KNOWLEDGE: PK1.05 [2.6/2.8]
Similar questions
P9; P1407; P2406 (B2206); P2606; P308 (B305); P3306 (B2010); P707 (B706); P907 (B1905);
B1108; B1307; B2112; B2607
Recent BWR exams
Recent PWR exams
Not used in 2001 through 2007
Not used in 2001 through 2007
A cooling water system is operating at a steady-state flow rate of 700 gpm with 60 psid across the
flow transmitter venturi. If cooling water flow rate is increased to 1000 gpm, differential pressure
across the flow transmitter venturi will be approximately...
A. 85.7 psid.
B. 122.4 psid.
C. 171.4 psid.
D. 244.8 psid.
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0 / 0 QID: P707 (B706) Operation of a flow D/P cell type flow detector
Explanation
A cooling water system is operating at a steady-state flow rate of 700 gpm with 60 psid across the
flow transmitter venturi. If cooling water flow rate is increased to 1000 gpm, differential pressure
across the flow transmitter venturi will be approximately...
•
A definition for volumetric flow rate is V ∝ D P . So, flow rate is directly proportional to the square
root of the differential pressure.
Set up a proportionality equations and for simplicity arrange it so that the unknown valve is in the top
of the fraction.
Final Flowrate
Final D / P
∝
Initial Flowrate Initial D / P
1000 gpm
Final D / P
∝
700 gpm
60 psid
2
 1000 gpm 
Final D / P

 ∝
60 psid
 700 gpm 
2
 1000 gpm 

 (60 psid ) ∝ Final D / P
700
gpm


2
(1.429) (60 psid ) ∝ Final D / P = 122.45 psid
A. 85.7 psid.
Incorrect -
700
60
=
, (60 × 1,000) ∝ (700 / x ) , X = 85.7 psid
1000
X
B. 122.4 psid.
CORRECT - 122.45 psid
C. 171.4 psid.
Incorrect -
700
60
=
, (60 ∗ 1000) = (700 / X ) , X = 85.7 ∗ 2 = 171.4 psid
1000
X
D. 244.8 psid.
Incorrect -
700
=
1000
60
X
,
(
)
60 ∗ 1000) = (700 / X ,
X = 11.065, X= 122.4 ∗ 2 =
244.8 psid
The correct answer is ANSWER B. 122.4 psid.
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1 / 1 QID: B4609 (P4607) Operation of Pressure and Temperature Controller4
BWR TOPIC: 291003
PWR TOPIC: 191003
KNOWLEDGE: BK1.04 [3.3/3.3]
KNOWLEDGE: PK1.04 [2.8/3.0]
Similar questions
Recent BWR exams
Dec2005
Recent PWR exams
Dec2005
Refer to the drawing of a temperature bistable in a bistable alarm circuit (see figure below).
The orientation of the bistable symbol indicates the characteristics of the bistable, as is normal for a
control circuit diagram. The bistable turns on to actuate an alarm at a temperature of 130°F. The
bistable has a 5°F dead band, or neutral zone.
If the current temperature is 150°F, which one of the following describes the alarm response as
temperature slowly decreases to 110°F?
A. The alarm is currently actuated and will not turn off.
B. The alarm will actuate at 130°F and will not turn off.
C. The alarm is currently actuated and will turn off at 125°F.
D. The alarm will actuate at 130°F and will turn off at 125°F.
TEMPERATURE
SIGNAL
A
BISTABLE
4
ALARM
08Jan22 new question added
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1 / 1 QID: B4609 (P4607) Operation of Pressure and Temperature Controller4
Explanation
Refer to the drawing of a temperature bistable in a bistable alarm circuit (see figure below).
The orientation of the bistable symbol indicates the characteristics of the bistable, as is normal for a
control circuit diagram. The bistable turns on to actuate an alarm at a temperature of 130°F. The
bistable has a 5°F dead band, or neutral zone.
If the current temperature is 150°F, which one of the following describes the alarm response as
temperature slowly decreases to 110°F?
Given a condition ABOVE setpoint alarm is extinguished (OFF). When parameter DECREASES to
setpoint, 130 units, alarm is actuated (ON). Alarm will remain actuated (ON) while parameter is
BELOW setpoint.
Example conditions
150 – OFF
140 – OFF
135 – OFF
TEMPERATURE
130 decreasing – ON
A
SIGNAL
125 – ON
120 – ON
110 – ON
BISTABLE
1100 – ON
120 – ON
130 increasing - ON
135 – OFF
140 – OFF
ALARM
125 – ON
150 – OFF
This bistable symbol represents a controller that turns off when the setpoint is reached. As the
temperature decreases the bistable turns on again at 130°F and stays on through out the problem.
A. The alarm is currently actuated (FALSE) and will not turn off (TRUE).
Incorrect – the alarm come on at 130 degrees decreasing not 150°F.
B. The alarm will actuate at 130°F (TRUE) and will not turn off (TRUE).
CORRECT – at 130°F decreasing the bistable is true and the alarm actuates and stays
on as long as the temperature is below 135°F.
C. The alarm is currently actuated (FALSE) and will turn off at 125°F (FALSE).
Incorrect – the alarm come on at 130 degrees decreasing not 150°F and stays on as
long as the temperature is below 130°F.
D. The alarm will actuate at 130°F (FALSE) and will turn off at 125°F (FALSE).
Incorrect – The alarm does actuate at 130°F but stays on until temperature rises above
135°F.
The correct answer is ANSWER: B. The alarm will actuate at 130°F and will not turn off.
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1 / 1 QID: B1361 (P1358) Xenon-135 versus time for startup with xenon-135 present
BWR TOPIC: 292006
PWR TOPIC: 192006
KNOWLEDGE: BK1.10 [2.9/2.9]
KNOWLEDGE: PK1.07 [3.4/3.4]
Similar questions
B1361 (P1358); B3861 (P3860)
Recent BWR exams
Recent PWR exams
Dec2005
Dec2006
A reactor has been operating at 75% power for two months. A manual reactor scram is required for a
test. The scram will be followed immediately by a reactor startup with criticality scheduled to occur
12 hours after the scram.
The greatest assurance that xenon reactivity will permit criticality during the startup will be attained if
the reactor is operated at ____________ power for 48 hours prior to the scram and if criticality is
rescheduled for ____________ hours after the scram.
A. 100%; 8
B. 100%; 16
C. 50%; 8
D. 50%; 16
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XENON - 135 REACTIVITY
(% ∆ k/k)
1 / 1 QID: B1361 (P1358) Xenon-135 versus time for startup with xenon-135 present
Explanation
A reactor has been operating at 75% power for two months. A manual reactor scram is required for a
test. The scram will be followed immediately by a reactor startup with criticality scheduled to occur
12 hours after the scram. The greatest assurance that xenon reactivity will permit criticality during the
startup will be attained if the reactor is operated at _50%_ power for 48 hours prior to the scram and if
criticality is rescheduled for _16_ hours after the scram.
SHUTDOWN
48 HRS AFTER
POWER
CHANGE
-4.7
-2.7
PEAK XENON 100% POWER
58 HRS AFTER POWER CHANGE
10 HRS AFTER SCRAM
100%
EQUILIBRIUM
XENON
XENON 8 HRS
AFTER SCRAM
XENON 16 HRS
AFTER SCRAM
75%
EQUILIBRIUM
XENON
XENON 24 HRS
AFTER SCRAM
-2.1
0 10 20
TIME (HOURS)
30
40
50 60 70 80 90 100 110 120
48 56 64 72 HRS AFTER CHANGE
0 8 16 24 HRS AFTER SCRAM
A. 100% (FALSE); 8 (FALSE).
Incorrect - the 100% peak xenon will be higher than 50% peak xenon. Waiting 8 hours
after the trip will put the xenon concentration at a point close to the peak (square root
of the power is equal to the number of hours to reach peak xenon 100% power means
peak at 10 hours after shutdown), where xenon concentration is still increasing, and is
well above the equilibrium value for 100% power.
B. 100% (FALSE); 16 (TRUE).
Incorrect - the 100% peak xenon is higher than 50% peak xenon. Waiting 16 hours will
put the xenon concentration after the trip at a point past the peak (square root of the
power is equal to the number of hours to reach peak xenon 100% power means peak at
10 hours after shutdown), where xenon concentration is decreasing rapidly, but still
above the equilibrium value for 100% power.
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BP000Gr4_Sample Exam Study Guide Questions 08Nov08
1 / 1 QID: B1361 (P1358) Xenon-135 versus time for startup with xenon-135 present
XENON - 135 REACTIVITY
(% ∆ k/k)
VALUE OF PEAK XENON 100% POWER
-4.7
PEAK XENON 50% POWER
SHUTDOWN 55.1 HRS AFTER POWER CHANGE
48 HRS AFTER 7.1 HRS AFTER SCRAM
POWER
XENON 8 HRS
CHANGE
AFTER SCRAM
-2.7
XENON 16 HRS
AFTER SCRAM
-2.1
50%
EQUILIBRIUM
XENON
0 10 20 30
TIME (HOURS)
40
XENON 24 HRS
AFTER SCRAM
50 60 70 80 90 100 110 120
48 56 64 72 HRS AFTER CHANGE
8 16 24 HRS AFTER SCRAM
0
C. 50% (TRUE); 8 (FALSE).
Incorrect - even though the 50% power peak xenon is lower than the 100% power peak
xenon, waiting 8 hours after the trip will put the xenon concentration at a point just past
the peak (square root of the power is equal to the number of hours to reach peak xenon
50% power means peak at 7.1 hours after shutdown), where xenon concentration is
higher than that at 16 hours after the trip. This choice is only partially correct.
D. 50% (TRUE); 16 (TRUE).
CORRECT – the 50% power peak xenon is lower than the 100% power peak xenon.
Waiting 16 hours after the trip will allow the xenon concentration to be well past the
xenon peak (square root of the power is equal to the number of hours to reach peak
xenon; 50% power means peak at 7.1 hours after shutdown), and will be at a lower
value than it would be at 8 hours.
The correct answer is ANSWER: D. 50%; 16
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1 / 1 QID: B5334 (P5334) Period, Delayed Neutron Fraction and Power Rate of Change5
BWR TOPIC: 292008
PWR TOPIC: 192008
KNOWLEDGE: BK1.08 [4.1/4.1]
KNOWLEDGE: PK1.10 [3.3/3.4]
Similar questions
Recent BWR exams
Sep2007
Recent PWR exams
Sep2007
Given:
•
•
•
Nuclear reactors A and B are identical except that reactor A has an effective delayed neutron
fraction of 0.0068 and reactor B has an effective delayed neutron fraction of 0.0052.
Reactor A has a stable period of 45 seconds and reactor B has a stable period of 42 seconds.
Both reactors are initially operating at 1.0 x 10-8 percent power.
The reactor that is supercritical by the greater amount of positive reactivity is reactor _______; and the
first reactor to reach 1.0 x 10-1 percent power will be reactor _______.
A. A; A
B. A; B
C. B; A
D. B; B
5
New question added 2008.
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1 / 1 QID: B5334 (P5334) Period, Delayed Neutron Fraction and Power Rate of Change5
Explanation
Given:
• Nuclear reactors A and B are identical except that reactor A has an effective delayed neutron
fraction of 0.0068 and reactor B has an effective delayed neutron fraction of 0.0052.
• Reactor A has a stable period of 45 seconds and reactor B has a stable period of 42 seconds.
• Both reactors are initially operating at 1.0 x 10-8 percent power.
The reactor that is supercritical by the greater amount of positive reactivity is reactor ___A___; and
the first reactor to reach 1.0 x 10-1 percent power will be reactor ___B___.
__
Using:
β− ρ
τ=
λeff ρ
Reactor A yields:
Reactor B yields:
.0068 − ρ
0.1ρ
4.5 ρ = .0068 − ρ
5.5 ρ = .0068
.0052 − ρ
0.1ρ
4.2 ρ = .0052 − ρ
5.2 ρ = .0052
ρ =1.12 × 10 −3 ∆k / k
ρ =1.0 × 10 −3 ∆k / k
45 =
42 =
The reactor with the greatest reactivity is the most supercritical, Reactor A.
t/τ
As far as the change in power, we can use: P = P0 e
For a given increase in power, P/P0, we can see that the value of the exponent decreases with
increasing period so it takes longer to achieve a given power. The longer the period, the longer it takes
for a given multiplication of power. Reactor B with the shorter period will achieve the higher power
level first.
A. A (TRUE); A (FALSE)
Incorrect – see above
B. A (TRUE); B (TRUE)
CORRECT – see above
C. B (FALSE); A (FALSE)
Incorrect – see above
D. B (FALSE); B (TRUE)
Incorrect – see above
The correct answer is ANSWER B. A; B
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BP000Gr4_Sample Exam Study Guide Questions 08Nov08
1 / 1 QID: B5438 (P5439) Specific work – turbine / Usefulness of Steam Tables6
BWR TOPIC: 293003
PWR TOPIC: 193003
KNOWLEDGE: BK1.23
KNOWLEDGE: PK1.25
Similar questions
B1377, B1577
Recent BWR exams
Recent PWR exams
Dec2007
Dec2007
An ideal auxiliary steam turbine exhausts to the atmosphere. The steam turbine is supplied with
saturated steam at 900 psia. Which one of the following is the maximum specific work (Btu/lbm) that
can be extracted from the steam by the steam turbine?
A. 283 Btu/lbm
B. 670 Btu/lbm
C. 913 Btu/lbm
D. 1,196 Btu/lbm
6
New question added 2008
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1 / 1 QID: B5438 (P5439) Specific work – turbine / Usefulness of Steam Tables6
Explanation
An ideal auxiliary steam turbine exhausts to the atmosphere. The steam turbine is supplied with
saturated steam at 900 psia. Which one of the following is the maximum specific work (Btu/lbm) that
can be extracted from the steam by the steam turbine?
In an ideal situation the maximum specific work is found by following an isentropic line straight
down from the starting pressure to the ending pressure. Pressure is already given in absolute so no
conversion from gage is needed. The maximum specific work is just the difference between the inlet
and exit enthalpy.
At 900 psia we can find the enthalpy of saturated steam from either the pressure table or looking on a
Mollier. From the pressure table we see that hg = 1196.4 Btu/lbm. (Note that the Mollier yields closer
to 1195 Btu/lbm).
Since the problem states and ideal expansion is occurring drop straight down along the entropy lines
until the entropy line intersects the constant pressure atmospheric line, 14.696 psia. There the specific
enthalpy is found to by ~912 Btu/lbm.
Take the difference of the value specific enthalpy at atmospheric and subtract it from the value
specific enthalpy at 900 psia. This is how much specific work is being performed by the turbine
(284.4 Btu/lbm, 283 if we use the Mollier number for 900 psia as well). Answer A. is correct.
A. 283 Btu/lbm
CORRECT – see above
B. 670 Btu/lbm
Incorrect – see above
C. 913 Btu/lbm
Incorrect – see above
D. 1,196 Btu/lbm
Incorrect – see above
The correct answer is ANSWER A. 283 Btu/lbm
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BP000Gr4_Sample Exam Study Guide Questions 08Nov08
1 / 1 QID: B1697 (P3395) Thermal conductivity and fuel centerline temperature
BWR TOPIC: 293009
PWR TOPIC: 193009
KNOWLEDGE: BK1.16 [2.4/2.8]
KNOWLEDGE: PK1.07 [2.9/3.3]
Similar questions
B394 (P895); P383 (B394); B495 (P495); B1594 (P1594); B1697 (P3395); B1995 (P1994); P1994
(B1995); P2395 (B2394); P2296 (B2696); P3195 (B3193)
Recent BWR exams
Recent PWR exams
Mar2006
Feb2002
Refer to the drawing of a fuel rod and coolant flow channel at the beginning of core life (see figure
below).
Given the following initial core parameters:
Reactor power = 50%
Tcoolant = 550°F
Tfuel centerline = 2,750°F
What will the fuel centerline temperature be if, over core life, the total fuel-to-coolant thermal
conductivity doubles? (Assume reactor power is constant.)
A. 1,100°F
B. 1,375°F
C. 1,525°F
D. 1,650°F
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1 / 1 QID: B1697 (P3395) Thermal conductivity and fuel centerline temperature
Explanation
Refer to the drawing of a fuel rod and coolant flow channel at the beginning of core life (see figure
below). Given the following initial core parameters:
Reactor power = 50%
Tcoolant = 550°F
Tfuel centerline = 2,750°F
What will the fuel centerline temperature be if, over core life, the total fuel-to-coolant thermal
conductivity doubles? (Assume reactor power is constant.)
The differential temperature is currently 2,200°F. If the thermal conductivity doubles, the differential
temperature will drop to 1,100°F. The new fuel centerline temperature will be 1,650°F
Q ∝ K (TCL − Tcoolant ) (BWR should use Tsurface; PWR should use Tbulk) for simplification this
calculation will use Tcoolant.
Q remains constant and Tcoolant remains constant
↔
Q ∝ K (TCL − Tcoolant )
↔
Q ∝ K (∆T )
↔
↑
↓
Q ∝ K (∆T )
↔
Alternately solving by calculations
↔
2 ↑ 0.5 ↓
Q ∝ K (∆T )
initially
Q ∝ K (TCL − Tcoolant )
Q ∝ K (2,750 − 550°F)
Q ∝ K (2,200°F)
based on arrow analysis
if K doubles ∆T must be reduced in half
Initially ∆T is 2,200°F
Finally ∆T would be 1,100°F
∆T = (TCL − Tcoolant )
(∆T + Tcoolant ) = TCL
TCL = 1,100°F + 550°F = 1,650°F
Q ∝ K (TCL − Tcoolant )
question states K doubles and since Tcoolant final is
equal to Tcoolant initial Tcoolant = 550°F
↔
Q ∝ 2K (TCL − 550°F)
substitute in for Q where Q ∝ K (2,200°F)
K (2,200°F) ∝ 2K (TCL − 550°F)
2K (TCL − 550°F)
K
(2,200°F) ∝ 2(TCL − 550°F)
(2,200°F) ∝
2,200°F ∝ (2TCL ) − 2(550°F)
2,200°F ∝ (2TCL ) − (1,100°F)
2,200°F + 1,100°F ∝ (2TCL )
3,300°F ∝ (2TCL )
3,300°F
∝ (TCL )
2
TCL α 1,650°F
A. 1,100°F
Incorrect – students could incorrectly select this answer since a common error is
starting to solve a problem and the first time a numbers is obtained that is a possible
answer the student stop and selects that answer. Here the common error is that 1,100°F
is the value of the final ∆T. The question asks for the final centerline temperature.
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1 / 1 QID: B1697 (P3395) Thermal conductivity and fuel centerline temperature
B. 1,375°F
Incorrect – this is a distracter. If the student has partial recall of the process she might
recall that if K doubles something must be reduced in half. 1,375°F is one half the
initial centerline temperature (2,750°F).
C. 1,525°F
Incorrect – this is a distracter. Sometimes it is difficult to come up with three incorrect
answers that have something to do with the problem. Students are reminded that just
because you come up with a number after the calculation, does not mean that you have
the correct answer. Question writers work hard at creating distracters that are based on
expected or previously observed errors.
D. 1,650°F
CORRECT – see calculation.
The correct answer is ANSWER: D. 1,650°F
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