ML20332A083
| ML20332A083 | |
| Person / Time | |
|---|---|
| Site: | Purdue University |
| Issue date: | 12/07/2020 |
| From: | Mohamed Shams NRC/NRR/DANU |
| To: | Bean R Purdue University, Indiana |
| Tate T | |
| References | |
| EA-20-144 IR 2020201 | |
| Download: ML20332A083 (19) | |
See also: IR 05000182/2020201
Text
December 7, 2020
Dr. Robert Bean, Director
Purdue University Radiation Laboratory
School of Nuclear Engineering
400 Central Drive
West Lafayette, IN 47904-2017
SUBJECT: PURDUE UNIVERSITY REACTOR - U.S. NUCLEAR REGULATORY
COMMISSION SPECIAL INSPECTION REPORT 05000182/2020-201
Dear Dr. Bean:
This letter refers to the U.S. Nuclear Regulatory Commission (NRC) special inspection
conducted during October 27 - November 6, 2020, at the Purdue University Reactor facility.
The special inspection was conducted pursuant to event notification (EN 54958) on
October 20, 2020, later supplemented on November 3, 2020, Agencywide Documents Access
and Management System (ADAMS) Accession No. ML20311A264, describing the causes of,
and corrective actions for, operating the Purdue research reactor at power levels in excess of
the licensed maximum power level. The NRC inspectors discussed the preliminary inspection
findings with you at the conclusion of the on-site portion of the special inspection on
October 29, 2020. A final exit briefing was conducted via teleconference with you on
November 6, 2020. The enclosed report presents the results of this special inspection.
Based on the results of this special inspection, two apparent violations and one Severity
Level IV violation were identified by the NRC inspectors. The apparent violations are being
considered for escalated enforcement actions in accordance with the NRC Enforcement Policy.
The current Enforcement Policy is included on the NRCs Web site at
https://www.nrc.gov/about-nrc/regulatory/enforcement/enforce-pol.html. The apparent violations
are related to the Purdue research reactor exceeding the maximum licensed power level
(License Condition 2.C.1) and operating the Purdue research reactor prior to completing the
applicable surveillance testing for replaced equipment (technical specification 4.2.g). The
Severity Level IV violation is related to Purdue inadequately posting a radiation area, as
required by Title 10 of the Code of Federal Regulations (10 CFR), Part 20, Standards for
Protection Against Radiation. Purdue identified the first apparent violation and notified the
NRC in EN 54958. NRC inspectors identified the second apparent violation and the Severity
Level IV violation during this special inspection. The apparent violations and the Severity Level
IV violation are discussed in the Summary of Findings, section of the enclosed report. The
circumstances surrounding these issues, the significance of the issues, and the need for lasting
and effective corrective action were discussed with members of your staff at the special
inspection exit meeting on November 6, 2020. As a result, it may not be necessary to conduct a
predecisional enforcement conference (PEC) in order to enable the NRC to make an
enforcement decision.
R. Bean -2-
In addition, since your facility has not been the subject of escalated enforcement actions within
the last 2 years and based on our understanding of your planned corrective actions, a civil
penalty may not be warranted in accordance with Section 2.3.4 of the Enforcement Policy. The
final decision will be based on you confirming on the license docket that the corrective actions
previously described to the NRC staff have been or are being taken.
Before the NRC makes its enforcement decision concerning the apparent violations, we are
providing you an opportunity to: (1) respond to the apparent violation(s) addressed in this
inspection report within 30 days of the date of this letter, or (2) request a PEC. If a PEC is held,
it will be open for public observation and the NRC will issue a press release to announce the
time and date of the conference. If you decide to participate in a PEC, please contact Mr. Travis
Tate at (301) 415-3901 within 10 days of the date of this letter. A PEC should be held within
30 days of the date of this letter.
If you choose to provide a written response for the apparent violations, it should be clearly
marked as a Response to Apparent Violations in NRC Special Inspection
Report 05000182/2020-201; EA-20-144 and should include for each apparent violation: (1) the
reason for the apparent violation or, if contested, the basis for disputing the apparent violation;
(2) the corrective steps that have been taken and the results achieved; (3) the corrective steps
that will be taken; and (4) the date when full compliance will be achieved. Your response may
reference or include previously docketed correspondence, if the correspondence adequately
addresses the required response. Additionally, your response should be sent to the NRCs
Document Control Center, with a copy mailed to Dr. Mohamed Shams, Director, Division of
Advanced Reactors and Non-Power Production and Utilization Facilities, Office of Nuclear
Reactor Regulation, 11555 Rockville Pike, Rockville, MD 20852-2738 within 30 days of the date
of this letter. If an adequate response is not received within the time specified or an extension
of time has not been granted by the NRC, the NRC will proceed with its enforcement decision or
schedule a PEC.
If you choose to request a PEC, the conference will afford you the opportunity to provide your
perspective on these matters and any other information that you believe the NRC should take
into consideration before making an enforcement decision. The decision to hold a PEC does
not mean that the NRC has determined that a violation has occurred or that enforcement action
will be taken. This conference would be conducted to obtain information to assist the NRC in
making an enforcement decision. The topics discussed during the conference may include
information to determine whether a violation occurred, information to determine the significance
of a violation, information related to the identification of a violation, and information related to
any corrective actions taken or planned.
In addition, please be advised that the number and characterization of apparent violations
described in the enclosed inspection report may change as a result of further NRC review. You
will be advised by separate correspondence of the results of our deliberations on this matter.
In accordance with 10 CFR Part 2, Agency Rules of Practice and Procedures, Section 2.390,
Public inspections, exemptions, requests for withholding, a copy of this letter, its enclosure(s),
and your response, if you choose to provide one, will be made available electronically for public
inspection in the NRC Public Document Room or from ADAMS, accessible from the NRC Web
site at http://www.nrc.gov/reading-rm/adams.html. To the extent possible, your response should
not include any personal privacy, proprietary, or safeguards information so that it can be made
available to the public without redaction.
R. Bean -3-
If you have any questions concerning this matter, please contact Mr. Travis Tate, Chief,
Non-Power Production and Utilization Facilities Oversight Branch at (301) 415-3901.
Sincerely,
/RA/
Mohamed K. Shams, Director
Division of Advanced Reactors and Non-Power
Production and Utilization Facilities
Office of Nuclear Reactor Regulation
Docket No. 50-182
License No. R-87
Enclosures:
As stated
cc: w/enclosures: See next page
Purdue University Docket No. 50-182
cc:
Mark Lundstrom, Dean of Engineering
Purdue University
School of Nuclear Engineering
400 Central Drive
West Lafayette, IN 47907
Mayor
City of West Lafayette
1200 N. Salisbury Street
West Lafayette, IN 47906
John H. Ruyack, Manager
Epidemiology Res Center/Indoor & Radiological Health
Indiana Department of Health
2525 N. Shadeland Avenue, Suite E3
Indianapolis, IN 46219
Howard W. Cundiff, P.E., Director
Consumer Protection
Indiana State Department of Health
2 North Meridian Street, Suite 5D
Indianapolis, IN 46204
Clive Townsend, Reactor Supervisor
Purdue University
School of Nuclear Engineering
400 Central Drive
West Lafayette, IN 47907
Test, Research and Training
Reactor Newsletter
Attention: Amber Johnson
Dept of Materials Science and Engineering
University of Maryland
4418 Stadium Dr.
College Park, MD 20742-2115
ML20332A083 *concurrence via e-mail NRC-002
OFFICE NRR/DANU/PM* RIII/DRP/B1* NRR/DANU/LA*
NAME POBryan JHavertape NParker
DATE 12/1/2020 12/1/2020 11/30/2020
OFFICE NRR/DANU/BC* NRR/DANU/D
NAME TTate MShams
DATE 12/2/2020 12/7/2020
NOTICE OF VIOLATION
Purdue University Docket No. 50-182
Purdue University Research Reactor License No. R-87
During a U.S. Nuclear Regulatory Commission (NRC) special inspection conducted during
October 27 - November 6, 2020, a violation of NRC requirements was identified. In accordance
with the NRC Enforcement Policy, the violation is listed below:
Title 10 of the Code of Federal Regulations (10 CFR) Section 20.1003 defines a
radiation area as an area, accessible to individuals, in which radiation levels could result
in an individual receiving a dose equivalent in excess of 0.005 rem (0.05 mSv) in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />
at 30 centimeters from the radiation source or from any surface that the radiation
penetrates.
Section 20.1902(a) of 10 CFR, Posting of radiation areas, states that, [t]he licensee
shall post each radiation area with a conspicuous sign or signs bearing the radiation
symbol and the words CAUTION, RADIATION AREA.
Contrary to the above, on several occasions between August 30, 2019, and
September 15, 2020, Purdue did not post the reactor pool top area, which was a
radiation area, with a conspicuous sign or signs bearing the radiation symbol and the
words CAUTION, RADIATION AREA. Specifically, the Purdue research reactor was
operated during this time at power levels resulting in radiation dose rates in excess of
0.005 rem per hour at 30 centimeters from the reactor pool top. The reactor pool top is
an area accessible to individuals and, despite indications that a radiation area existed at
the reactor pool top, the area was not posted as a radiation area.
This is a Severity Level IV violation (Section 6.7).
Pursuant to the provisions of 10 CFR Section 2.201, Notice of violation, the Purdue University
Reactor facility is hereby required to submit a written statement or explanation to the
U.S. Nuclear Regulatory Commission, ATTN: Document Control Desk, Washington,
DC 20555-0001, within 30 days of the date of the letter transmitting this Notice of Violation
(Notice). This reply should be clearly marked as a Reply to a Notice of Violation, and should
include: (1) the reason for the violation, or, if contested, the basis for disputing the violation or
severity level, (2) the corrective steps that have been taken and the results achieved, (3) the
corrective steps that will be taken, and (4) the date when full compliance will be achieved. Your
response may reference or include previous docketed correspondence, if the correspondence
adequately addresses the required response. If an adequate reply is not received within the
time specified in this Notice, an Order or a Demand for Information may be issued as to why the
license should not be modified, suspended, or revoked, or why such other action as may be
proper should not be taken. Where good cause is shown, consideration will be given to
extending the response time.
If you contest this enforcement action, you should also provide a copy of your response, with
the basis for your denial, to the Director, Office of Enforcement, United States Nuclear
Regulatory Commission, Washington, DC 20555-0001.
Enclosure 1
-2-
Because your response will be made available electronically for public inspection in the NRC
Public Document Room or from the NRCs document system (Agencywide Documents Access
and Management System), accessible from the NRC Web site at http://www.nrc.gov/reading-
rm/adams.html, to the extent possible, it should not include any personal privacy, proprietary, or
safeguards information so that it can be made available to the public without redaction. If
personal privacy or proprietary information is necessary to provide an acceptable response,
then please provide a bracketed copy of your response that identifies the information that
should be protected and a redacted copy of your response that deletes such information. If you
request withholding of such material, you must specifically identify the portions of your response
that you seek to have withheld and provide in detail the bases for your claim of withholding
(e.g., explain why the disclosure of information will create an unwarranted invasion of personal
privacy or provide the information required by 10 CFR 2.390(b) to support a request for
withholding confidential commercial or financial information). If safeguards information is
necessary to provide an acceptable response, please provide the level of protection described
in 10 CFR 73.21, Protection of Safeguards Information: Performance Requirements.
In accordance with 10 CFR 19.11, Posting of notices to workers, you may be required to post
this Notice within two working days of receipt.
Dated this 7th day of December 2020
U.S. NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
Docket No: 50-182
License No: R-87
Report No: 05000182/2020-201
Licensee: Purdue University
Facility: Purdue University Research Reactor
Location: West Lafayette, IN
Dates: October 27 - November 6, 2020
Inspectors: Phil OBryan
Joshua Havertape
Approved by: Travis Tate, Chief
Nonpower Production and Utilization
Facility Oversight Branch
Division of Advanced Reactors and Non-Power
Production and Utilization Facilities
Office of Nuclear Reactor Regulation
Enclosure 2
SUMMARY OF FINDINGS
Purdue University
Research Reactor Facility
Special Inspection Report No. 05000182/2020-201
The U.S. Nuclear Regulatory Commissions (NRCs) program for overseeing the safe operation
of research and test reactors is described in Manual Chapter 2545, Research and Test Reactor
Inspection Program. In response to event notification (EN 54958) by Purdue University, a
Special Inspection Team was established in accordance with NRC Management Directive 8.3,
NRC Incident Investigation Program. The special inspection team used inspection procedure
69001, Class II Research and Test Reactors, inspection procedure 93812, Special Inspection
Team, and a special inspection charter to conduct this special inspection.
NRC-Identified and Self-Revealing Findings
1. Apparent Violation: The Purdue University reactor facility (herein referred to as Purdue)
operating license, condition 2.C.1, states that the Purdue University is authorized to
operate the facility at steady state power levels not in excess of 12 kilowatts (thermal).
Contrary to this, on several occasions between October 31, 2019, and September 15,
2020, Purdue operated in excess of 12 kilowatts (thermal).
Purdue received a license amendment (Amendment No. 14, dated April 1, 2019) that
allowed Purdue to install a digital instrumentation and control (I&C) system at their
reactor facility. This installation included replacing the nuclear instrument (NI) system
and detectors. Purdue performed the initial reactor startup after the digital I&C
modification on August 27, 2019. After the reactor startup, Purdue performed several
gold foil irradiations in order to calibrate the NI detectors. However, Purdue used an
erroneous efficiency correction factor for the instrument used to count the gold foils.
This error resulted in less conservative calculated values for actual reactor power by a
factor of approximately three. Purdue then calibrated the NI detectors based on the
incorrect calculation and NI indicated power was less than actual power by a factor of
approximately three. Since Purdue operated the reactor several times between
October 31, 2019, and September 15, 2020, at indicated power of 5 kilowatts (kW), and
at a maximum indicated power of 7.4 kW on February 14, 2020, after accounting for the
300 percent error in indicated reactor power, the actual reactor power exceeded the
maximum licensed power of 12 kW. Purdue discovered this error and license condition
violation and notified the NRC on October 20, 2020.
This is an apparent violation (AV) pending significance determination.
2. Apparent Violation: Purdues technical specification (TS) 4.2.g states that, Appropriate
surveillance testing on any technical specification required system shall be conducted
after replacement, repair, or modification before the system is considered operable and
returned to service. Contrary to this, after replacement of the NI system and detectors,
Purdue considered the NI system operable and returned it to service between
August 27, 2019, and October 9, 2020, prior to completing the appropriate surveillance
testing.
2
On August 27, 2019, Purdue restarted the reactor after an extended shutdown. During
the extended shutdown, Purdue replaced the NI system, including the NI detectors. The
plan to calibrate the NI detectors was contained in the Purdue startup plan titled Purdue
University Reactor Number One: Digital I&C Startup Plan and Checklist. This startup
plan specified eight gold foil irradiations between initial criticality and 10 kW reactor
power to complete the calibration of the NI detectors. Purdue did not complete the eight
gold foil irradiations, however, due to unexpectedly high radiation levels at the top of the
reactor pool. Nevertheless, Purdue declared the NI system operable and operated the
reactor several times between August 27, 2019, and October 9, 2020, for reasons other
than NI calibration (i.e., student and operator training, and experiments). This is an
inspector identified issue.
3. Severity Level IV Violation: A radiation area is defined in 10 CFR 20.1003 as an area,
accessible to individuals, in which radiation levels could result in an individual receiving a
dose equivalent in excess of 0.005 rem (0.05 mSv) in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> at 30 centimeters from the
radiation source or from any surface that the radiation penetrates. Section 20.1902(a)
of 10 CFR, Posting of radiation areas, requires that [t]he licensee shall post each
radiation area with a conspicuous sign or signs bearing the radiation symbol and the
words CAUTION, RADIATION AREA. Contrary to this, the licensee did not post the
reactor pool top area, an accessible area with radiation dose rates in excess of 0.005
rem per hour, as a radiation area between August 30, 2019, and September 15, 2020.
After the digital I&C installation, Purdues reactor startup plan specified raising power
incrementally for NI system calibration. The startup plan also specified that radiation
dose rates were to be measured at various locations in and around the facility during
power ascension to ensure no abnormalities existed. The highest radiation levels
measured were at the reactor pool top, an area accessible to personnel. When
indicated reactor power reached approximately 1 kW, the reactor pool top radiation level
exceeded 0.005 rem per hour (5 mr/hr). Facility personnel were aware that the radiation
levels exceeded 5 mr/hr but did not recognize that this required the area to be posted as
a radiation area per 10 CFR 20.1902(a). The reactor was operated at or above 1 kW
indicated reactor power several times between August 30, 2019, and September 15,
2020. This is an inspector identified issue.
3
REPORT DETAILS
1. Introduction
a. Background
Purdue renewed their research reactor operating license in 2016. The license
renewal also increased the maximum allowed power level from 1 kW to 12 kW.
However, since Purdue was also pursuing a license amendment to upgrade the
I&C systems (License Amendment 14, dated April 1, 2019), they chose not to
operate the reactor until they installed the new I&C system. This I&C system
upgrade installed new digital I&C equipment, including a new NI system and NI
detectors.
The Purdue NI system consists of four channels. Channel 1 is the startup
channel and measures neutron flux level in counts per second (cps). This
channel does not require calibration. Channels 2, 3, and 4 read in percent
reactor power and they must be calibrated so that the measured neutron flux
level (actual reactor power) is equivalent to the reactor power indicated by the
instruments. All four NI channels, and their associated protective functions, are
required to be operable by TS 3.2 when operating the reactor. The reactor
limiting safety system setting, as defined by TS 2.2, is a reactor high power
scram setting of 12 kW. This reactor scram is initiated by the NI system.
The digital I&C system upgrade was completed in 2019. Since the NI system
instrumentation and detectors were new, Channels 2, 3, and 4 required
calibration. Purdue calibrates the NIs using gold foil irradiation. Gold foil
irradiation is performed by inserting a gold foil specimen into a tube in the vicinity
of the reactor and irradiating it for a short period of time at a constant reactor
power level. The radioactivity of the gold foil is then measured using a High
Purity Germanium (HPGe) detector, and a reactor neutron flux rate is calculated.
This calculated neutron flux rate is then used to determine a calibration factor for
each NI channel requiring calibration. Finally, the calibration factor for each NI
channel is used to adjust the NI channel and the channel is calibrated.
Purdue restarted the reactor on August 27, 2019, and used a startup plan titled
Purdue University Reactor Number One: Digital I&C Startup Plan and Checklist
as a procedure to perform various tests, including NI system calibration. This
startup plan specified using gold foil irradiation at eight different reactor power
levels from initial criticality to 10 kW reactor power.
b. Event Description
Purdue started the reactor on August 27, 2019, and, on August 29, 2019,
performed the initial gold foil calibrations of the NIs. Between August 29, 2019,
and February 14, 2020, NI detector calibrations were performed after initial
criticality, at 100 watts (W), 500 W, 1 kW, 2 kW, and 5 kW indicated reactor
power. However, while raising reactor power for the 7.5 kW indicated reactor
power level calibration on February 14, 2020, the reactor automatically
scrammed due to high radiation levels at the pool top area radiation monitor.
Calibration activities were then suspended pending resolution of the high pool top
4
radiation levels. Between initial startup and October 9, 2020, the reactor was
also operated for various other reasons such as academics, experiments, and
operator training.
On October 9, 2020, a gold foil was irradiated to validate neutron flux levels for
an experiment. The gold foil indicated that reactor power was higher than
anticipated and the cause was investigated. On October 19, 2020, Purdue staff
determined that an error occurred in calculating the HPGe detector efficiency
factor used to calculate gold foil radioactivity level for the NI calibrations
performed between August 29, 2019, and February 14, 2020. This error resulted
in NI Channels 2, 3, and 4 were calibrated so that indicated reactor power level
was less than actual power level by a factor of approximately three.
The HPGe detector efficiency determination is performed using a radioactive
check source of known radioactivity level. The radioactive check source is
counted in the HPGe detector and the measured radioactivity level is compared
to the actual source radioactivity level. An efficiency factor is then calculated
based on the difference between the measured and the actual radioactivity
levels. Gold foils must be counted in the same position and distance from the
HPGe detector for the efficiency factor to be valid for NI calibration calculations.
On October 19, 2020, the HPGe detector efficiency calculations from August
2019 and October 2020 were compared. Purdue noted that the calculated HPGe
detector efficiency factors differed by a factor of approximately three, and it was
determined that the gold foils used for NI calibration starting in August 2019 were
counted at a different HPGe shelf location (i.e. different distance) than the
radioactive check source used for the HPGe detector efficiency calculation.
The NI calibrations performed between August 29, 2019, and February 14, 2020,
were performed using the incorrect HPGe efficiency factor. Since the reactor
was operated several times between October 31, 2019, and September 15,
2020, above 4 kW indicated power, the actual reactor power exceeded 12 kW
during these operations. The highest actual reactor power reached was on
February 14, 2020, and was between 18 kW (Channel 3 indication) and 22.2 kW
(Channel 4 indication).
5
Sequence of Events
The inspectors interviewed licensee personnel, reviewed records, and observed
demonstrations conducted by the licensee to develop the sequence of events leading up
to and following the events described above.
4/1/2019 Digital I&C License Amendment approved.
Early 2019 (exact date unknown) the digital I&C system installation was completed.
08/27/2019 The reactor was started up for the first time after the extended
shutdown using an auxiliary nuclear instrument and NI Channel 1.
08/29/2019 The first three gold foil irradiations were performed at approximately
1 W, 10 W, and 100 W calculated reactor power. NI Channels 2 and 3
calibrations were adjusted using an incorrect HPGe detector efficiency
factor. The pool top radiation level for the calibrations was recorded as
less than 1 milliroentgen per hour (<1 mr/hr).
08/30/2019 The fourth gold foil irradiation was complete at a calculated reactor
power of approximately 500 W. NI Channels 2, 3, and 4 calibrations
were adjusted. Radiation surveys at the reactor pool top determined
that the radiation level was 3 mr/hr.
Later that day, the reactor was started again and indicated reactor
power was raised to approximately 1 kW. Pool top radiation surveys
were not recorded.
8/31/2019 - The reactor was not operated.
9/16/2019
9/20/2019 The fifth gold foil irradiation was performed at a calculated power of
approximately 1 kW. NI Channels 2, 3, and 4 calibrations were
adjusted. At 954 W, the pool top radiation level was measured to be
5 mr/hr.
Later that day, the reactor was started, and calculated reactor power
was raised to 2 kW for the first time. Pool top radiation levels were not
recorded.
10/09/2019 The sixth gold foil irradiation was complete at a calculated reactor
power of approximately 2 kW. No NI channel calibration adjustments
were made based on this irradiation. The pool top radiation level was
recorded as 13 mr/hr.
10/10/2019 Channel 2 calibration adjusted due to detector relocation. The reactor
was started and operated at an indicated reactor power of 600 W, then
shutdown.
Pool area radiation monitor setpoints were adjusted to an alert setpoint
of 30 mr/hr and scram setpoint of 50 mr/hr.
6
10/15/2019 - The reactor was operated three times. No calibration adjustments or
10/29/2019 gold foil irradiations were performed.
10/30/2019 The seventh gold foil was irradiated at a calculated reactor power of
approximately 2 kW. No radiation surveys were documented.
10/31/2019 Channels 2, 3, and 4 calibration adjustments were made based on the
irradiation performed on 10/30/2019.
The reactor was started for the next gold foil irradiation at 5 kW, but the
reactor scrammed before reaching 5 kW due to a high radiation scram
signal from the pool top radiation monitor. Purdue determined that the
scram signal was erroneously generated at 20 mr/hr. This was the first
time that the reactor was operated above 4 kW calculated reactor
power, which correlated to an actual reactor power of greater than
12 kW - Purdues maximum licensed power level.
11/1/2019 - The reactor was operated regularly for student and operator training.
12/11/2019
12/12/2019 The eighth gold foil was irradiated at a calculated reactor power of
approximately 5 kW. No radiation survey documented.
12/13/2019 Channels 2, 3, and 4 calibration adjustments were made based on the
gold foil irradiation performed on 12/12/2019. The reactor was started
and operated at 5 kW calculated reactor power.
12/14/2019 - The reactor was not operated.
1/28/2020
1/29/2020 - The reactor was operated several times for student and operator
2/12/2020 training.
2/14/2020 The reactor was started, and an attempt was made to raise reactor
power to 7.5 kW. However, the reactor experienced a high pool
radiation level scram prior to reaching 7.5 kW. Recorders indicated that
the pool top radiation level briefly reached the scram setpoint of
50 mr/hr. The highest indicated reactor power was 6 kW on NI
Channel 3 and 7.4 kW on NI Channel 4. The highest actual reactor
power reached was between 18 kW (Channel 3 indication) and 22.2 kW
(Channel 4 indication).
2/14/2020 - The reactor was operated four times for student and operator training.
3/12/2020
3/13/2020 - The reactor was not operated. A camera inspection of the reactor on
9/8/2020 8/11/2020 revealed no abnormalities.
09/09/2020 - The reactor was operated three times for student and operator training.
9/18/2020
7
10/9/2020 The ninth gold foil was irradiated at approximately 250 W indicated
reactor power to verify neutron flux levels for an experiment.
10/19/2020 Purdue determined that the HPGe detector efficiency factor
determination used for NI calibrations was incorrect by a factor of
approximately three in the nonconservative direction (i.e. indicated
power was lower than actual power by a factor of three).
2. Adequacy of Facility Procedures for Nuclear Instrument Calibration
The Purdue procedure for NI calibration is Standard Operating Procedure 4 (SOP-4),
Power Calibration by Gold Foil. While reviewing this event, Purdue found that SOP-4
was inadequate because it did not require an independent operator to verify key
parameters and calculations. SOP-4 also relied on skill of the craft, and did not include
detailed procedural steps for portions of the calibration process.
For example, one person determined HPGe detector efficiency and performed the
detector efficiency factor calculation. This person relied only on his knowledge of HPGe
detector operation and did not use a procedure. The calculated efficiency factor was
then recorded in a notebook. Although it was the habit of Purdue operators to have the
calculations second checked, this was not a requirement. The lack of a required
independent verification introduced opportunities for errors and inconsistencies in the
key parameters and calculations to not be captured. NRC inspectors agreed with
Purdues assessment of this procedure.
The Purdue start up plan, Purdue University Reactor Number One: Digital I&C Startup
Plan and Checklist, specified how the reactor would be started and tested after the
digital I&C modifications, including methodology for performing the gold foil NI
calibrations. NRC inspectors found that this procedure contained weaknesses including
1) lack of guidance on TS operability requirements after NI system replacement, 2) lack
of guidance for determining radiation levels inside the reactor bay when raising reactor
power beyond previous maximum power levels and ensuring all areas met posting
requirements of 10 CFR 20.1902, Posting Requirements, 3) lack of guidance for
required actions if procedural steps could not be completed, if other actions were taken
that could affect NI calibration, or if the procedure was suspended, and 4) lack of
guidance for the use of diverse reactor parameters, such as radiation levels, control rod
bank height, and gold foil activity levels from historical NI calibrations to verify indications
of reactor power.
3. Licensee Response to the Event
Maximum reactor power level was incrementally raised over several months after the
Purdue reactor restart. As the maximum power was raised, Purdue operators noticed
pool top radiation levels were higher than expected. In fact, Purdue realized that they
would not be able to complete high power NI calibrations without causing pool top
radiation monitor alarms and protective action (high radiation scram). On October 10,
2019, Purdue raised the pool top radiation alarm setpoint to 30 mr/hr and the pool top
high radiation scram setpoint to 50 mr/hr - the highest radiation scram setpoint allowed
by TS. Purdue could not definitively explain the high radiation levels. Potential reasons
discussed by the Purdue staff included having a new pool top radiation monitor which
8
was in a different location than the old radiation monitor, and irradiation ports streaming
radiation through the pool water.
On February 14, 2020, the reactor scrammed due to a high pool top radiation level while
attempting to raise reactor power to 7.5 kW indicated reactor power. Purdue responded
to the February 14, 2020, pool top high radiation reactor scram by suspending reactor
operations above 5 kW indicated reactor power, which they believed was the highest
reactor power for which a successful NI calibration was performed. They also relocated
irradiation ports away from the reactor to reduce streaming radiation. Purdue reported
that relocating irradiation ports reduced the pool top radiation level but did not record the
magnitude of the reduction. Reactor operations continued until October 9, 2020, when a
gold foil was irradiated and indicated that actual reactor power was significantly higher
than indicated reactor power.
NRC inspectors found that there were opportunities for Purdue to more comprehensively
investigate the cause of the high pool top radiation levels and failed to do so. NRC
inspectors determined that formal investigative techniques, such as a fault tree analysis,
were not used. NRC inspectors noted that Purdue was disadvantaged in their
investigation by not having comparable historical NI data because all components of the
NI system were newly installed.
4. Root Cause Determination and Contributing Causes
Purdue determined that the root cause of the event was an error in the calculation of the
HPGe efficiency factor. Purdue also identified the following contributing causes:
1) The HPGe detector efficiency factor determination was not independently verified,
2) The HPGe detector efficiency factor was determined without the use of a procedure,
and
3) The previous NI system calibration settings were not relevant to the new NI system
calibration settings, and therefore, no historical information was available to
determine if settings were reasonable.
Purdue also determined that the cause of the failure to post the reactor bay as a
Radiation Area was caused by a lack of procedures to determine radiation levels in the
reactor bay after power uprate.
NRC inspectors agree with the causes listed above and identified the following additional
contributing causes of the event:
1) Skill of the craft in lieu of procedural use is common at Purdue,
2) Radiation surveys were informally performed in the reactor bay and operators failed
to record radiations levels on several occasions during power ascension,
3) Purdue reactor management considered the NI system to be operable before the NI
system was calibrated at reactor power levels above 5 kW, and
4) The Reactor Safety Committee did not formally review each startup plan delay and
procedural deviation.
9
5. Corrective Actions
Purdue implemented, or plans to implement, the following corrective actions:
1) SOP-4 was revised to require two independent determinations of the HPGe detector
efficiency factor, two independent measurements of gold foil radioactivity level, and
two independent calculations of reactor power for NI calibrations,
2) The startup plan was revised to include:
a. requirements for measuring radiation levels during power ascension and
verifying postings in the reactor bay and in adjacent areas of the facility,
b. steps to conservatively increase the initial NI calibration factors by a factor of
10 and reperforming all gold foil calibrations,
c. directions to not allow reactor operations for anything other than NI
calibration,
d. directions for using NI channel data from previous reactor operations as a
cross check of reactor power, and
e. a requirement that members of the Reactor Safety Committee review and
approve deviations from the startup plan.
3) Other reactor procedures will be reviewed to identify when the procedure relies
excessively on skill of the craft assumptions,
4) Radiation survey requirements will be specified in facility procedures and reactor
operators in training will be qualified as radiation workers.
5) Purdue TSs will be amended prior to startup to clarify allowances for reactor
operation in order to calibrate repaired, replaced, or modified NI channels.
NRC inspectors found that these corrective actions are adequate to prevent recurrence
of the event.
6. Related Actions that Contributed to the Event
As discussed in Section 5 of this report, there were several factors that contributed to the
event. Additionally, NRC inspectors noted that Purdues actions were often not
consistent with the NRCs policy statement on nuclear safety culture. The NRC defines
nuclear safety culture as: the core values and behaviors resulting from a collective
commitment by leaders and individuals to emphasize safety over competing goals to
ensure protection of people and the environment.
With regards to identifying NI calibration errors, NRC inspectors found that
Purdue demonstrated weaknesses with the following nuclear safety traits:
1) Problem Identification and Resolution, defined as Issues potentially
impacting safety are promptly identified, fully evaluated, and promptly
addressed and corrected commensurate with their significance, and
2) Questioning Attitude, defined as Individuals avoid complacency and
continually challenge existing conditions and activities in order to identify
discrepancies that might result in error or inappropriate action.
With regards to excessive skill of the craft use and procedural deviations,
NRC inspectors found that Purdue demonstrated weaknesses in the nuclear
safety trait of Work Processes, defined as The process of planning and
controlling work activities is implemented so that safety is maintained.
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7. Consequences of the Event
The NRC inspectors determined that there were no actual nuclear safety consequences
as a result of this event. The NRC inspectors found the Purdue reactor safety analysis
demonstrates that the reactor fuel will not exceed its temperature safety limit of 530
degrees centigrade at a reactor power of 98.6 kW. Since the highest actual reactor
power reached during the event was approximately 22.2 kW, no fuel damage is
expected. The NRC inspectors found that a fuel inspection performed by Purdue in
August 2020, reactor pool water chemistry analyses, and facility radiation surveys
confirm that no fuel damage occurred. NRC inspectors determined that there are no
other reactor components susceptible to damage at a reactor power level of 22.2 kW.
Since the NI system would have initiated a reactor scram during an over-power scenario
at 36 kW actual reactor power (three times an indicated reactor power setpoint of
12 kW), the reactor fuel would also be undamaged during this type of accident.
The NRC inspectors determined that radiation levels in the reactor bay during the event
contributed to slightly higher dose rates for personnel in the reactor bay during reactor
plant operations, but these doses were within regulatory limits established in 10 CFR
Part 20, Standards for Protection Against Radiation, as measured by personnel
dosimetry. The highest dose rate at the reactor console occurred when the reactor
operated at 22.2 kW actual reactor power on February 14, 2020. The area radiation
monitor in the vicinity of the console recorded the dose rate as 0.13 mr/hr above
background level during this time period. This dose rate, and the dose rates at lower
reactor power levels, would contribute only a small amount to operators doses for the
relatively short time that the operators were at the console (typically 1 to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />).
The NRC inspectors determined that area radiation monitors located on the walls of the
reactor bay read <0.1 mr/hr throughout the event. Therefore, dose rates in uncontrolled
areas did not exceed the regulatory dose rate limit of 2 mr/hr. NRC inspectors found
dosimeters located in adjacent spaces also showed that the maximum dose in any
uncontrolled area, assuming constant occupancy, did not exceed the regulatory limit of
100 millirem. Actual occupancy in adjacent, uncontrolled spaces was much less than
this. Therefore, inspectors found that radiation dose consequences of this event were
insignificant.
8. Exit Interview
The NRC inspectors conducted an inspection debrief with Purdue reactor management
at the conclusion of the onsite portion of the special inspection on October 29, 2020.
NRC inspectors discussed the inspection results in an inspection exit meeting at the
conclusion of the special inspection with Dr. Bean, Facility Director and members of his
staff on November 6, 2020.
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PARTIAL LIST OF PERSONS CONTACTED
Licensee Personnel
R. Bean Facility Director
C. Townsend Reactor Supervisor
D. Storz Reactor Instrumentation Specialist
Other Personnel
M. Tang Interim Radiation Safety Officer
INSPECTION PROCEDURES USED
IP 69001 Class 2 Research and Test Reactors
IP 93812 Special Inspection
ITEMS OPENED, CLOSED, AND DISCUSSED
OPENED
50-182/2020-201-01 AV Exceeding Maximum Licensed Power Level
(License Condition 2.C.1)
50-182/2020-201-02 AV Operating with Inoperable Nuclear Instrumentation
(TS 4.2.g).
50-182/2020-201-03 VIO Failure to Post a Radiation Area
Licensee Documents Reviewed
- Purdue University Reactor Number One: Digital I&C Startup Plan and Checklist,
Revision 0
- Purdue University Reactor Number One: Operating Principles and Core Characteristics
Manual, Revision 0
- Purdue University Reactor Number One, Standard Operating Procedure 4, SOP-4,
Power Calibration by Gold Foil, Revision 1
- Reactor Console Logbook from August 22, 2019, to October 23, 2020
- Report on Reactor Operations for January 1, 2019, to December 31, 2019
- Purdue University Reactor Water Analysis Report, dated October 12, 2020
Attachment