ML25247A192

Examination Report Letter No. 50-326/OL-26-01, University of California - Irvine

ML25247A192
Person / Time
Site:	University of California - Irvine
Issue date:	01/26/2026
From:	Michael Brown NRC/NRR/DANU/UNPO
To:	Shaka A University of California - Irvine
References
50-326/OL-26-01 OL-26-01
Download: ML25247A192 (0)

Text

Dr. A.J. Shaka, Reactor Director University of California-Irvine 231A Rowland Hall Irvine, CA 92697-2026

SUBJECT:

EXAMINATION REPORT NO. 50-326/OL-26-01, UNIVERSITY OF CALIFORNIA-IRVINE

Dear Dr. Shaka:

During the week of January 5, 2026, the U.S. Nuclear Regulatory Commission (NRC) administered an operator licensing examination at your University of California-Irvine research reactor. The examination was conducted according to NUREG-1478, "Operator Licensing Examiner Standards for Research and Test Reactors," Revision 2. Examination questions and preliminary findings were discussed with those members of your staff identified in the enclosed report at the conclusion of the examination.

In accordance with Title 10 of the Code of Federal Regulations, Section 2.390, a copy of this letter and the enclosures will be available electronically for public inspection in the NRC Public Document Room or from the Publicly Available Records component of NRC's Agencywide Documents Access and Management System (ADAMS). ADAMS is accessible from the NRC website at http://www.nrc.gov/reading-rm/adams.html. The NRC is forwarding the individual grades to you in a separate letter which will not be released publicly. Should you have any questions concerning this examination, please contact Amy Beasten at 301-415-8347 or via email at Amy.Beasten@nrc.gov.

Sincerely, Tony Brown, Chief Non-Power Production and Utilization Facility Oversight Branch Division of Advanced Reactors and Non-Power Production and Utilization Facilities Office of Nuclear Reactor Regulation Docket No. 50-326

Enclosures:

1. Examination Report No. 50-326/OL-26-01

2. Written examination cc: w/enclosures to GovDelivery Subscribers January 26, 2026 Signed by Brown, Tony on 01/26/26

ML25247A192 NRR-079 OFFICE NRR/DANU/UNPO/CE NRR/DANU/UNPO/OLA NRR/DANU/UNPO/BC NAME ABeasten NJones TBrown DATE 1/26/2026 1/26/2026 1/26/2026 U. S. NUCLEAR REGULATORY COMMISSION OPERATOR LICENSING INITIAL EXAMINATION REPORT REPORT NO.:

50-326/OL 26-01 FACILITY DOCKET NO.:

50-326 FACILITY LICENSE NO.:

R-116 FACILITY:

University of California-Irvine EXAMINATION DATES:

Week of January 5, 2026 SUBMITTED BY:

SUMMARY

During the week of 1/5/2026, a Category A written operator licensing examination was administered to one Reactor Operator (RO) retake candidate. The candidate passed all applicable portions of the examination.

REPORT DETAILS 1.

Examiner:

Amy E. Beasten, PhD, Chief Examiner, NRC 2.

Results:

RO PASS/FAIL SRO PASS/FAIL TOTAL PASS/FAIL Written 1/0 0/0 1/0 Operating Tests 0/0 0/0 0/0 Overall 1/0 0/0 1/0 3.

Exit Meeting:

Amy E. Beasten, PhD, Chief Examiner, NRC John Keffer, Reactor Supervisor and Facility Manager, University of California--Irvine Prior to administration of the written exam, based on facility comments, adjustments were accepted. Comments provided corrections and additional clarity to questions/answers and identified where changes were appropriate based on current facility conditions. Upon completion of all operator licensing examinations, the NRC examiners met with facility staff representatives to discuss the results and observations. At the conclusion of the meeting, the NRC examiners thanked the facility for their support in the administration of the examination.

1/16/2025 Amy E. Beasten, Chief Examiner Date University of California-Irvine Operator Licensing Examination Week of January 5, 2026

U. S. NUCLEAR REGULATORY COMMISSION NON-POWER REACTOR LICENSE EXAMINATION FACILITY:

University of California-Irvine REACTOR TYPE:

TRIGA DATE ADMINISTERED:

January 7, 2026 CANDIDATE:

INSTRUCTIONS TO CANDIDATE:

Answers are to be written on the Answer sheet provided. Attach all Answer sheets to the examination. Point values are indicated in parentheses for each question. A 70% in each category and a 70% overall are required to pass the examination. Examinations will be picked up three (3) hours after the examination starts.

CATEGORY VALUE

% OF TOTAL CANDIDATE'S SCORE

% OF CATEGORY VALUE CATEGORY 20.00 33.0 A. REACTOR THEORY, THERMODYNAMICS, AND FACILITY OPERATING CHARACTERISTICS 20.00 33.0 B. NORMAL AND EMERGENCY OPERATING PROCEDURES AND RADIOLOGICAL CONTROLS 20.00 33.0 C. FACILITY AND RADIATION MONITORING SYSTEMS 20.00 TOTALS FINAL GRADE All work done on this examination is my own. I have neither given nor received aid.

Candidate's Signature

NRC RULES AND GUIDELINES FOR LICENSE EXAMINATIONS During the administration of this examination the following rules apply:

1.

Cheating on the examination means an automatic denial of your application and could result in more severe penalties.

2.

After the examination has been completed, you must sign the statement on the cover sheet indicating that the work is your own and you have neither received nor given assistance in completing the examination. This must be done after you complete the examination.

3.

Restroom trips are to be limited and only one candidate at a time may leave. You must avoid all contacts with anyone outside the examination room to avoid even the appearance or possibility of cheating.

4.

Use black ink or dark pencil only to facilitate legible reproductions.

5.

Print your name in the blank provided in the upper right-hand corner of the examination cover sheet and each Answer sheet.

6.

Mark your Answers on the Answer sheet provided. USE ONLY THE PAPER PROVIDED AND DO NOT WRITE ON THE BACK SIDE OF THE PAGE.

7.

The point value for each question is indicated in [brackets] after the question.

8.

If the intent of a question is unclear, ask questions of the examiner only.

9.

When turning in your examination, assemble the completed examination with examination questions, examination aids and Answer sheets. In addition turn in all scrap paper.

10.

Ensure all information you wish to have evaluated as part of your Answer is on your Answer sheet. Scrap paper will be disposed of immediately following the examination.

11.

To pass the examination you must achieve a grade of 70 percent or greater in each category and a 70 percent overall.

12.

There is a time limit of three (3) hours for completion of the examination.

Candidate Name:

Category A: Reactor Theory, Thermodynamics, & Facility Operating Characteristics A N S W E R S H E E T Multiple Choice (Circle your choice, or write on the line)

If you change your answer, write your selection in the line. Answers written on the line will be taken as the final answer.

A01 a b c d ___

A02 a b c d ___

A03 a b c d ___

A04 a b c d ___

A05 a b c d ___

A06 a________ b________ c________ d ________ (0.25 each)

A07 a b c d ___

A08 a b c d ___

A09 a b c d ___

A10 a b c d ___

A11 a b c d ___

A12 a b c d ___

A13 a b c d ___

A14 a b c d ___

A15 a b c d ___

A16 a b c d ___

A17 a b c d ___

A18 a b c d ___

A19 a b c d ___

A20 a b c d ___

(***** END OF CATEGORY A *****)

EQUATION SHEET

=

+

DR - Rem, Ci - curies, E - Mev, R - feet 1 Curie = 3.7 x 1010 dis/sec 1 kg = 2.21 lb 1 Horsepower = 2.54 x 103 BTU/hr 1 Mw = 3.41 x 106 BTU/hr 1 BTU = 778 ft-lb

°F = 9/5 °C + 32 1 gal (H2O) 8 lb

°C = 5/9 (°F - 32) cP = 1.0 BTU/hr/lb/°F cp = 1 cal/sec/gm/°C

2 2

max

P 1

sec 1.0

eff

T UA H

m T

c m

Q P

sec 10 1

4

2 1

1 1

2 1

eff eff K

CR K

CR

eff SUR 06 26

te P

P 0

eff K

S S

SCR

1

2 2

1 1

CR CR

0 1

P P

1 2

1 1

CR CR K

M eff

)

(

0 10 t

SUR P

P 2

1 1

1 eff eff K

K M

eff eff K

K SDM

1 2

1 1

2 eff eff eff eff K

K K

K

693

.0 2

1 T

eff eff K

K 1

2 2

2 2

1 1

d DR d

DR

t e

DR DR

0

1 2

1 2

2 2

Peak Peak

2 6

R n

E Ci DR

Category A: Reactor Theory, Thermodynamics, and Facility Operating Characteristics QUESTION A.01

[1.0 point]

Which ONE of the following statements best describes the resonance escape probability (p)?

a. The probability that a neutron will cause fission before slowing down.

b. The probability that a neutron will not cause fission before slowing down.

c.

The probability that a neutron will not be absorbed while slowing down through the resonance energy range.

d. The probability that a neutron will not be captured while slowing down through the resonance energy range.

QUESTION A.02

[1.0 point]

Which ONE of the following statements best describes the reason why reactors are under-moderated?

a. It increases the thermal utilization factor.

b. It ensures that an increase in fuel temperature adds negative reactivity by increasing the moderator-to-fuel ratio.

c.

It enhances neutron leakage as moderator temperature increases to maintain a controllable neutron flux.

d. It ensures that an increase in moderator temperature adds negative reactivity by decreasing the moderator-to-fuel ratio.

QUESTION A.03

[1.0 point]

Following a reactor scram from 50 kW, the reactor period has stabilized and power level is decreasing at a constant rate. What is the reactor power ten minutes following the scram?

a. 1.94 W b.

19.4 W c.

194 W d.

1.94 kW

Category A: Reactor Theory, Thermodynamics, and Facility Operating Characteristics QUESTION A.04

[1.0 point]

As the multiplication factor K increases in a subcritical reactor, what happens to the time required to reach a NEW steady state count rate?

a.

It increases.

b.

It decreases.

c.

It remains the same.

d.

It becomes infinite.

QUESTION A.05

[1.0 point]

Which ONE of the following statements best describes why U-235 is considered FISSILE?

a.

U-235 can fission only with fast neutrons.

b.

U-235 can fission with fast and thermal neutrons.

c.

U-235 has a binding energy lower than the critical energy for fission.

d.

U-235 can fission with thermal neutrons.

QUESTION A.06

[1.0 point, 0.25 each]

Match the reaction type (symbol) in Column A with the neutron interaction in Column B.

Options in Column B may be used once, more than once, or not at all.

Column A a.

(n, p) b.

(n, n) c.

(n, n) d.

(n, )

Column B 1.

Inelastic scattering 2.

Charged particle reaction 3.

Radiative Capture 4.

Elastic scattering

Category A: Reactor Theory, Thermodynamics, and Facility Operating Characteristics QUESTION A.07

[1.0 point]

The moderator temperature coefficient for a reactor is -0.00092 k/k/°F. What is the total reactivity change caused by a temperature decrease of 25°F?

a.

0.0980 b.

0.0690 c.

0.0178 d.

0.0230 QUESTION A.08

[1.0 point]

Which ONE of the following terms in the six-factor formula is MOST affected by control rod movement?

a.

Fast fission factor ()

b.

Thermal non-leakage probability (LT) c.

Thermal utilization factor (f) d.

Reproduction factor ()

QUESTION A.09

[1.0 point]

Which ONE of the following statements best describes the differential control rod worth?

a.

It is the total reactivity inserted by a control rod at a given position.

b.

It is the rate of change of reactivity per unit movement of a control rod.

c.

It is the reactivity worth of a fully inserted control rod.

d.

It is the average reactivity change over the entire distance of rod travel.

QUESTION A.10

[1.0 point]

Which ONE of the following statements is defined as the balance between production of neutrons and their absorption and leakage in the core?

a.

Utilization Factor b.

Reproduction Factor c.

Infinite Multiplication Factor d.

Effective Multiplication Factor

Category A: Reactor Theory, Thermodynamics, and Facility Operating Characteristics QUESTION A.11

[1.0 point]

Which ONE of the following statements regarding fission product poisoning is true?

a.

Following a reactor shutdown, the concentration of Sm-149 reaches a peak because some fission is still occurring in the core.

b.

During normal reactor operation, Sm-149 is removed from the core by both radioactive decay and neutron absorption.

c.

Following a reactor shutdown, the concentration of Xe-135 reaches a peak based on the decay of I-135 in the core.

d.

During normal reactor operation, Xe-135 is removed from the core only by radioactive decay.

QUESTION A.12

[1.0 point]

An experimenter inserts an experiment into the core, and the count rate decreases from 180 cps to 75 cps. Given the initial Keff of the reactor was 0.96, what is the worth of the experiment?

a. = + 0.06

b. = - 0.06

c. = + 0.04

d. = - 0.04 QUESTION A.13

[1.0 point]

Which ONE of the following statements best describes the difference between moderators and reflectors?

a.

Moderators scatter neutrons to decrease leakage from the core and reflectors thermalize neutrons.

b.

Moderators thermalize neutrons and reflectors scatter neutrons to decrease leakage from the core.

c.

Moderators absorb thermal neutrons and reflectors scatter fast neutrons.

d.

Moderators scatter fast neutrons and reflectors scatter thermal neutrons.

Category A: Reactor Theory, Thermodynamics, and Facility Operating Characteristics QUESTION A.14

[1.0 point]

Which ONE of the following statements best describes the importance of a negative temperature coefficient of reactivity?

a.

As fuel temperature increases, U-235 in the fuel is consumed, causing Pu-239 to form which becomes additional sources of fission causing control rods to be withdrawn farther, adding negative reactivity.

b.

As fuel temperature increases, the concentration of fission product poisons in the fuel matrix increases, adding negative reactivity through increased neutron absorption.

c.

An increase in reactor power causes an increase in fuel temperature which results in a negative reactivity addition, causing the power increase to slow or stop.

d.

As fuel temperature increases, moderator temperature increases rapidly through conduction heat transfer, adding negative reactivity.

QUESTION A.15

[1.0 point]

Which ONE of the following statements best describes the principal source of heat in the reactor after a shutdown from extended operation at full power?

a.

Subcritical reaction of photoneutrons.

b.

Spontaneous fission of Uranium-238.

c.

Production of delayed neutrons.

d.

Decay of fission fragments.

QUESTION A.16

[1.0 point]

During the initial rise to power, the nuclear instruments show that when Keff is 0.83, the count rate is 1175 cps. Once reactivity has been added, what count rate would correspond with a Keff of 0.97?

a.

207 cps b.

6658 cps c.

8324 cps d.

11270 cps

Category A: Reactor Theory, Thermodynamics, and Facility Operating Characteristics QUESTION A.17

[1.0 point]

During a reactor startup, criticality occurred at a higher rod height than the previous startup.

Which ONE of the following explanations could be the reason for the change?

a.

Nuclear Instrumentation drift.

b.

Moderator temperature was lower.

c.

An experiment with negative reactivity was added.

d.

The startup source was inserted into the core.

QUESTION A.18

[1.0 point]

Which ONE of the following conditions will decrease the shutdown margin of a reactor?

a.

Higher moderator temperature (assuming a negative temperature coefficient).

b.

Insertion of a negative reactivity worth experiment.

c.

Burnout of a burnable poison.

d.

Fuel depletion.

QUESTION A.19

[1.0 point]

Which ONE of the following parameters is the MOST significant in determining the differential rod worth of a control rod?

a.

Fuel temperature b.

Reactor power c.

Flux shape d.

Rod speed QUESTION A.20

[1.0 point]

What is the effective multiplication factor, given the source strength is 12,000 neutrons per second (N/sec) and it produces a stable neutron count rate of 65,000 N/sec?

a.

0.68 b.

0.73 c.

0.78 d.

0.82

(***** END OF CATEGORY A *****)

(********** END OF EXAMINATION **********)

Category A: Reactor Theory, Thermodynamics, and Facility Operating Characteristics A.01 Answer:

c. or d.

==Reference:

==

DOE Fundamentals Handbook, Volume 2, Module 3, p. 3 A.02 Answer:

d.

==Reference:

==

DOE Fundamentals Handbook, Volume 2, Module 3, p. 25 A.03 Answer:

a.

==Reference:

==

P = P0 e-t/T P = 50*0.07 (prompt drop) kW

• e(600s/-80s)

P = 3.5 kW

• e(-7.5)

P = 1.94 W Burn, Introduction to Nuclear Reactor Operations, Volume 2, p. 4-13 A.04 Answer:

a.

==Reference:

==

Burn, Introduction to Nuclear Reactor Operations, Volume 5, p. 5-7 A.05 Answer:

d.

==Reference:

==

DOE Fundamentals Handbook, Volume 1, Module 1, p. 50-51 A.06 Answer:

a. 2; b. 4; c. 1; d. 3

==Reference:

==

Burn, Introduction to Nuclear Reactor Operations, Volume 1, p. 2-28 A.07 Answer:

d.

==Reference:

==

DOE Fundamentals Handbook, Volume 2, Module 3, p. 21,

= T*T

= (-0.00092 k/k /°F) * (-25°F)

= 0.023 k/k A.08 Answer:

c.

==Reference:

==

Burn, Introduction to Nuclear Reactor Operations, Volume 3, p. 3-19 A.09 Answer:

b.

==Reference:

==

DOE Fundamentals Handbook, Volume 2, Module 3, p. 52 A.10 Answer:

d.

==Reference:

==

DOE Fundamentals Handbook, Volume 2, Module 3, p. 15 A.11 Answer:

c.

==Reference:

==

DOE Fundamentals Handbook, Volume 2, Module 3, p. 30-47

Category A: Reactor Theory, Thermodynamics, and Facility Operating Characteristics A.12 Answer:

b.

==Reference:

==

CR1 / CR2 = (1 - Keff2) / (1 - Keff1) 180 / 75 = (1 - Keff2) / (1 - 0.96) 2.4 = (1 - Keff2) / 0.04 0.096 = (1 - Keff2)

Therefore Keff2 = 0.904

= (Keff2 - Keff1) / (Keff2

• Keff1)

= (0.904 - 0.96) / (0.904

• 0.96)

= - 0.06 A.13 Answer:

b.

==Reference:

==

Burn, Introduction to Nuclear Reactor Operations, Section 2.7, 2-63 A.14 Answer:

c.

==Reference:

==

DOE Fundamentals Handbook, Volume 2, Module 3, p. 28 A.15 Answer:

d.

==Reference:

==

DOE Fundamentals Handbook, Volume 1, Module 1, p. 61 A.16 Answer:

b.

==Reference:

==

CR1 * (1 - Keff1) = CR2 * (1 - Keff2) 1175 * (1 - 0.83) = CR2 * (1 - 0.97) 199.75 = CR2

• 0.03 CR2 = 6658 A.17 Answer:

c.

==Reference:

==

Standard NRC Question A.18 Answer:

c.

==Reference:

==

Standard NRC Question A.19 Answer:

c.

==Reference:

==

Burn, Introduction to Nuclear Reactor Operations, Section 7, page 7-4 A.20 Answer:

d.

==Reference:

==

CR = S/(1-K) 65000 = 12000/(1 - K) 1 -K = 12000/65000 K = 0.82

(***** END OF CATEGORY A *****)

(********** END OF EXAMINATION **********)