ML061090188
| ML061090188 | |
| Person / Time | |
|---|---|
| Site: | 05000128 |
| Issue date: | 05/11/2006 |
| From: | Charemagne Grimes NRC/NRR/ADRA/DPR |
| To: | Maldanado T Texas A&M Univ |
| Mendonca M, NRC/NRR/DPR/PRT, 415-1128 | |
| References | |
| EA-06-113 IR-06-203 | |
| Download: ML061090188 (35) | |
See also: IR 05000128/2006203
Text
May 11, 2006
Dr. Theresa A. Maldonado, Deputy Director
Texas Engineering Experiment Station
Texas A&M University
1095 Nuclear Science Road
College Station, TX 77843-3575
SUBJECT: NRC SPECIAL INSPECTION REPORT NO. 50-128/2006-203 AND NOTICE OF
VIOLATION
Dear Dr. Maldonado:
On March 29, 2006, the Nuclear Regulatory Commission (NRC) completed a Special Inspection
at your Texas Engineering Experiment Station, Nuclear Science Center Research Reactor
Facility. The special inspection included an examination of activities conducted under your
license as they relate to safety and compliance with the Commissions rules and regulations
and with the conditions of your license. Within these areas, the inspection included selected
examination of procedures and representative records, observations of activities, and interviews
with personnel. The enclosed report documents the inspection findings, which were discussed
with you, Dr. W. D. Reece, the Facility Director, and Dr. Latha Vasudevan, the facility Radiation
Safety Officer, on March 29, 2006.
The event that led to the conduct of the Special Inspection can be summarized as follows:
During work involving radioactive material, licensee employees of the Texas Engineering
Experiment Station, Nuclear Science Center (NSC) are required to wear an Optically Stimulated
Luminescent dosimeter for whole body monitoring and a finger ring containing a
thermoluminescent dosimeter chip for extremity monitoring. At the end of January 2006, the
NSC Radiation Safety Officer (RSO) gathered all the dosimeters used during the month by
facility personnel and sent them to the dosimetry vendor for processing. The RSO did not
receive the dosimetry results report until February 24, 2006. The report indicated that a worker,
who had been conducting neutron activation analysis (NAA) using the pneumatic transfer
system during January, had received a potential extremity overexposure. The NSC Facility
Director and RSO immediately noted the results, restricted the worker from further work with
radioactive material that would contribute to an extremity dose, and began a review of the
situation. After consideration of various factors, the Director and RSO determined that the
extremity dose was an apparent anomalous result. The person involved was placed on
restricted duty and allowed to continue work, although all the sample processing work for
February had been completed at that point.
At the end of February, personnel dosimeters were again gathered and sent to the vendor for
processing. Those dosimetry results, which were received on March 15, 2006, indicated that
the worker conducting NAA using the pneumatic system had received a much higher than
normal extremity dose during February. The licensee notified the NRC of the event on
March 15, 2006. Subsequently, by written report dated April 14, 2006, you concluded that there
was no overexposure of that individual or any individual at your facility. Additionally in your
2
written report you indicated that you have taken or plan to take various steps to prevent
overexposure of individuals conducting NAA at your facility. These steps include that
manufacturing holders and manipulators to minimize extremity doses from NAA work,
conducting additional training on NAA and general handling of radioactive materials for
employees, establishing a contractual agreement with your dosimetry provider to ensure that
you receive immediate notification of doses greater than the annual regulatory limits, mounting
a permanent radiation detector in NAA work area, developing specific written procedures on
NAA work, and providing additional dosimetry for those involved in NAA work over the next
several months.
Due to the significance of the potential overexposure event, an NRC inspector was dispatched
to the site and arrived on March 20, 2006. Because of the complicated nature of personnel
monitoring, dosimetry processing, and the apparent incongruent dosimetry results, a Special
Inspection Team was assigned to review the event. The Special Inspection Team began their
review on March 27, 2006.
Based on the results of this inspection, the NRC has determined that a Severity Level IV
violation of NRC requirements occurred. The violation was evaluated in accordance with the
NRC Enforcement Policy. The current Enforcement Policy is included on the NRCs Web site
at www.nrc.gov; select What We Do, Enforcement, then Enforcement Policy. The violation is
cited in the enclosed Notice of Violation (Notice) and the circumstances surrounding it are
described in detail in the subject inspection report. The violation is being cited in the Notice
because the facilitys staff had prior opportunity to identify the problem (on noting the higher
extremity dose to a worker in October 2005), but failed to take action to prevent the event.
Further, the facilitys staff did not thoroughly assess the February 24, 2006, exposure report of
a potential overexposure to identify the root causes of the problem and was too quick to dismiss
it as being anomalous. The violation relates to the failure to provide radiological surveys that
are reasonable under the circumstances to evaluate the magnitude and extent of radiation
levels and the potential radiological hazards.
You are required to respond to this letter and should follow the instructions specified in the
enclosed Notice when preparing your response. The NRC will use your response in
accordance with its policies to determine whether further enforcement action is necessary to
ensure compliance with regulatory requirements.
In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter and its
enclosure will be available electronically for public inspection in the NRC Public Document
Room or from the Publicly Available Records (PARS) component of NRCs document system
(ADAMS). ADAMS is accessible from the NRC Web site at (the Public Electronic Reading
Room) http://www.nrc.gov/reading-rm/adams.html.
3
Should you have any questions regarding this inspection, please contact Brian Thomas, Chief,
Research and Test Reactors Branch at 301-415-2170.
Sincerely,
/RA/
Christopher Grimes, Director
Division of Policy and Rulemaking
Office of Nuclear Reactor Regulation
Docket No. 50-128
License No. R-83
Enclosures: 1. Notice of Violation
2. NRC Special Inspection Report No. 50-128/2006-203
cc w/encl.: Please see next page
Texas A&M University System Docket No. 50-128
cc w/encl:
Mayor, City of College Station
P.O. Box Drawer 9960
College Station, TX 77840-3575
Governors Budget and
Planning Office
P.O. Box 13561
Austin, TX 78711
Texas A&M University System
ATTN: Dr. Warren D. Reece, Director
Nuclear Science Center
Texas Engineering Experiment Station
F. E. Box 89, M/S 3575
College Station, Texas 77843
Texas State Department of Health
Radiation Control Program Director
Bureau of Radiation Control
Dept. of Health
1100 West 49th Street
Test, Research and Training
Reactor Newsletter
202 Nuclear Sciences Center
University of Florida
Gainesville, FL 32611
Should you have any questions regarding this inspection, please contact Brian Thomas, Chief,
Research and Test Reactors Branch at 301-415-2170.
Sincerely,
/RA/
Christopher Grimes, Director
Division of Policy and Rulemaking
Office of Nuclear Reactor Regulation
Docket No. 50-128
License No. R-83
Enclosures: 1. Notice of Violation
2. NRC Special Inspection Report No. 50-128/2006-203
cc w/encl.: Please see next page
DISTRIBUTION:
PUBLIC PRTA r/f AAdams CBassett
PDoyle TDragoun WEresian DHarrison
DHughes EHylton PIsaac DStarkey
MMendonca JQuichocho WSchuster BThomas
MVoth KWitt PYoung DBarss (MS O6-H2)
BDavis (Ltr only O5-A4) NRR enforcement coordinator (Only for IRs with NOVs, O10-H14)
ACCESSION NO.: ML061090188 TEMPLATE #: NRR-
OFFICE PRT:RI PRT:LA PRT:BC DPR:DIR
NAME CBassett:tls* EHylton* BThomas* CGrimes:tls*
DATE 4/25/06 5/9/06 5/10/06 5/11/06
OFFICIAL RECORD COPY
NOTICE OF VIOLATION
Texas A&M University Docket No.: 50-128
Texas A&M University Nuclear Science Center License No.: R-83
During an NRC inspection conducted on March 27-29, 2006, a violation of NRC requirements
was identified. In accordance with the NRC Enforcement Policy, the violation is listed below:
10 CFR 20.1501(a) requires that each licensee shall make or cause to be made, surveys that:
1) may be necessary for the licensee to comply with the regulations, and 2) are reasonable
under the circumstances to evaluate the magnitude and extent of radiation levels; and
concentrations or quantities of radioactive material; and the potential radiological hazards.
Contrary to the above, the licensee failed to make reasonable surveys to evaluate the
magnitude and extent of shallow dose equivalent radiation levels following the initial trial runs of
vials containing plastic disks and following the first indication of a possible overexposure on
February 24, 2006.
This is a Severity Level IV violation (Supplement IV).
Pursuant to the provisions of 10 CFR 2.201, Texas A&M University is hereby required to
submit a written statement or explanation to the U.S. Nuclear Regulatory Commission, ATTN:
Document Control Desk, Washington, D.C. 20555-0001 with a copy to the responsible
inspector, 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; EA-06-113," and
should include for each violation: (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 to avoid further violations, 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 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, D.C. 20555-0001.
Because your response will be made available electronically for public inspection in the NRC
Public Document Room or from the Publicly Available Records (PARS) component of the
NRCs document system (ADAMS), 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. ADAMS is accessible from the NRC Web site at (the Public Electronic
Reading Room) http://www.nrc.gov/reading-rm/adams.html. 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
Enclosure 1
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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.
In accordance with 10 CFR 19.11, you may be required to post this Notice within two working
days.
Dated at Rockville, Maryland
this day of May 2006
U. S. NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
Docket No: 50-128
License No: R-83
Report No: 50-128/2006-203
Licensee: Texas A&M University
Facility: Texas Engineering Experiment Station
Nuclear Science Center
Location: College Station, TX
Dates: March 27-29, 2006
Inspectors: Craig Bassett
Sami Sherbini
Approved by: Brian Thomas, Chief
Research and Test Reactors Branch
Division of Policy and Rulemaking
Office of Nuclear Reactor Regulation
SUMMARY OF FINDINGS
Texas A&M University
Texas Engineering Experiment Station
Inspection Report No. 50-128/2006-203
The report covered a period of three days of inspection by two inspectors. The NRCs program
for overseeing the safe operation of research and test reactors is described in Manual Chapter
2545, Research and Test Reactor Inspection Program. A Special Inspection was established
in accordance with NRC Management Directive 8.3, NRC Incident Investigation Program.
The Special Inspection Team charter did not require the team to address compliance or assess
significance of findings and observations. Another inspection will be scheduled to address the
follow-up items identified by the team.
NRC-identified and Self-Revealing Findings
During work involving radioactive material, licensee employees of the Texas Engineering
Experiment Station, Nuclear Science Center (NSC) are required to wear an Optically Stimulated
Luminescent dosimeter for whole body monitoring and a finger ring containing a
thermoluminescent dosimeter chip for extremity monitoring. At the end of January 2006, the
NSC Radiation Safety Officer (RSO) sent the dosimeters used by facility staff personnel to the
dosimetry vendor for processing. The RSO did not receive the dosimetry results report until
February 24, 2006. The report indicated that a worker, who had been conducting neutron
activation analysis (NAA) using the pneumatic transfer system during January, had received a
whole body dose of 0.033 rem and an extremity dose to the hand of 75.8 rem. The NSC
Facility Director and RSO immediately noted the results, restricted the worker from further work
with radioactive material that would contribute to an extremity dose, and began a review of the
situation. After careful consideration of various factors involved, the Director and RSO
determined that this was an anomalous reading and allowed the person to continue restricted
activities, although all the sample processing work for February had been completed at that
point. At the end of February, personnel dosimeters were again gathered and sent to the
vendor for processing. Those dosimetry results, which were received on March 15, 2006,
indicated that the worker conducting NAA using the pneumatic system had received a whole
body dose of 0.006 rem and an extremity dose of 37.54 rem during February. The licensee
notified the NRC of the event on March 15, 2006.
An NRC inspector was dispatched to the site and arrived on March 20, 2006. Because of the
complicated nature of personnel monitoring, dosimetry processing, and the apparent
incongruent dosimetry results, a Special Inspection Team was assigned to review the event.
The Special Inspection Team began their review on March 27, 2006. The team found that the
licensees initial response to the event was less than acceptable. The licensee did not
thoroughly assess the first report of a potential overexposure and was too quick to dismiss it as
being erroneous. Also, there was confusion on the need to report such an event. However, the
team also reviewed the licensees immediate corrective actions, including the dose calculations,
and found those actions to be generally acceptable.
Nevertheless, based on the results of this inspection, the team found that the licensee failed to
conduct acceptable surveys of the sample vials of irradiated material when a NAA experiment
involving the pneumatic system was first initiated, failed to train and monitor a worker on
handling sample vials with his hands/fingers, and failed to conduct surveys of the sample vials
of irradiated material following the first indication of a possible overexposure on February 24,
2006, to determine the cause of the problem which together lead to a substantial increase in
the extremity exposure of one worker at the facility.
Enclosure 2
REPORT DETAILS
1. Introduction
a. Event Description
The licensees research and test reactor (RTR) is operated under the authority and
administration of the Deputy Director of the Texas Engineering and Experiment
Station (TEES). The RTR is located in the Nuclear Science Center (NSC) and is
managed by the Director of the NSC and his staff. Daily operations activities are
conducted under the supervision of the Associate Director, while the support activities,
including radiation protection, are overseen by the Radiation Safety Officer (RSO).
One of the projects in progress during January was neutron activation analysis (NAA)
of small plastic disks using the facility pneumatic transfer system. During this work
involving radioactive material, licensee employees are required to wear an Optically
Stimulated Luminescent (OSL) dosimeter for whole body monitoring and a finger ring
containing a thermoluminescent dosimeter (TLD) chip for extremity monitoring.
At the end of January, the licensee sent the dosimeters used by all employees who
worked at the NSC during the month to the dosimetry vendor for processing. The
licensee did not receive those dosimetry results until February 24, 2006. The results
indicated that one employee, who will be referred to in this report as Worker A, had
received a whole body dose (or deep dose equivalent (DDE)) of 0.033 rem and an
extremity dose (or shallow dose equivalent (SDE)) of 75.8 rem. The individual, who
had been conducting NAA work using the pneumatic transfer system, was immediately
prohibited from any work which could cause an increase dose to the extremities.
Upon receiving the dosimetry report, the RSO began a review of the situation. The
licensee determined that processing these NAA samples was a standard procedure
that had been conducted numerous times over the past year and nothing in the
process had changed. While Worker A had not been the primary person responsible
for NAA processing in the past, he had assisted in the procedure many times during
the previous six months and was trained on, and familiar with, the operation. The
licensee also noted that the dosimetry processor had, on occasion in the past,
supplied erroneous dosimetry reports to the facility, including a high reading for an
individual who had not used his dosimeter for several months. After consideration of
the circumstances fo the event, the licensee concluded that this was an anomalous
reading and prepared a dose assessment report based on the average extremity dose
of the individual from the past three months. Worker A was placed on restricted duty
and allowed to return to work although all the NAA samples for the testing period had
already been processed.
At the end of February, the dosimeters were again gathered and sent to the vendor for
processing. The licensee received those dosimetry results on March 15, 2006, which
indicated that Worker A had received a DDE of 0.006 rem and a SDE of 37.54 rem.
The licensee notified the NRC of the event on March 15, 2006. However, because the
next two days and the following weekend were scheduled as Spring Break for the
University, no one was available at the facility during Thursday or Friday. An NRC
inspector was dispatched to the site and arrived the morning of Monday, March 20,
2006. Because of the numerous questions involved with the dosimetry aspects of the
event, a Special Inspection Team was subsequently formed and began their review of
the potential overexposure on March 27, 2006.
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b. Background and Chronology of Work Activities
As noted above, the licensee had been processing these NAA samples using the
pneumatic transfer system at the facility for approximately one year. Another person,
Worker C, had been the primary person who had handled the samples during 2005. A
third person, Worker B, also performed the work of handling the samples on occasion.
Worker A had been assisting as needed with this work for about six months. During
2005, neither Worker B nor Worker C had received extremity doses of the magnitude
received by Worker A in January and February 2006. The highest extremity dose
during 2005 was 1.58 rem and was received by Worker C. The most recent numbers
of samples, the period of time worked, and the finger ring TLD readings are shown
below in Table 1.
Table 1
Employee Number of Samples and Period of Time TLD Results,
Types of Material rem
Worker C 226 (silicon (Si)) October 2005 1.58
Worker C 240 (Si and silver (Ag)) November 2005 0.88
Worker B 88 (NIST Ag) December 2005 0.08
Worker B 195 (Ag and iodine (I)) January 10-27, 2006 0.18
Worker A 140 (Ag) January 17-30, 2006 75.8
Worker A 141 (Si, Ag, and I) February 6-22, 2006 37.54
Worker A 0 March 1-23, 2006 0.04
As will be detailed below, during January and February 2006, Worker A also helped
complete one radioactive material shipment, conducted various routine surveys, and
performed routine calibrations of counting instruments. Again, other licensee
employees also helped with and/or completed the same or similar tasks during this
same time period.
2. Event Follow-up - Sequence of Events
a. Inspection Scope
The inspectors interviewed licensee personnel, observed tests conducted by the
licensee, and reviewed various logs, dose calculations, and other documentation to
develop the following sequence of events leading up to and following the potential
b. Observations and Findings
Date Event Description
01/01-16/2006 Worker A was out of the country on vacation.
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01/17-30/2006 Worker B processed 195 Ag- and I-samples using the pneumatic
transfer system.
01/17/2006 Worker A processed 21 Ag-samples using the pneumatic system.
01/23/2006 Worker A processed 34 Ag-samples using the pneumatic system.
01/24/2006 Worker A completed the shipping surveys and the associated
paperwork for a radioactive material shipment consisting of shielded
containers of Argon-41 (Ar-41).
01/25/2006 Worker A processed 41 Ag-samples using the pneumatic system.
01/30/2006 Worker A processed 44 I-samples using the pneumatic system.
01/31/2006 Worker A and Worker B completed the monthly Facility Air Monitoring
(FAM) test using a source containing 4.68 nanocuries (nCi) of
Technetium-99 (Tc-99) and a source containing ~22.5 millicuries
02/01-02/2006 The licensee collected facility personnel dosimeters used during
January and mailed them to the dosimetry processor for processing.
02/06/2006 Worker A processed 51 I-samples using the pneumatic system.
02/07/2006 Worker A processed 15 I-samples using the pneumatic system.
02/13/2006 Worker A assisted two other individuals in completing the Channel 6
Building Gas Monitor calibration which involved setting up tubing
which passed Ar-41 gas through the gas monitor detector.
02/15/2006 Worker A processed 27 Si-samples using the pneumatic system.
Worker A completed calibration of the sample counters using the
source containing 4.68 nCi of Tc-99 and completed the calibration of
the alarming rate meters using an electronic pulser and a small check
source (containing <10 microcuries of Cesium-137 (Cs-137)).
02/21/2006 Worker A processed 24 I-samples using the pneumatic system.
02/22/2006 Worker A processed 24 I-samples using the pneumatic system.
02/24/2006 The licensee received the results from the dosimetry processor which
indicated that Worker A had received a dose to the extremities of
75.8 rem.
The worker was suspended from working with pneumatic samples
and an investigation was begun immediately.
-4-
02/27/2006 Worker A and Worker B completed the monthly FAM test using a
source containing 4.68 nCi of Tc-99 and a source containing ~22.5
mCi of Co-60.
The licensee contacted the dosimetry vendor to confirm that the
finger ring dosimeter results were accurate.
02/28/2006 Worker A completed a radiation and contamination survey of the
Material Handling Area and calibrated the instrument to be used to
count the swipes using a check source containing 4.68 nCi of Tc-99.
03/01-02/2006 The licensee collected facility personnel dosimeters used during
February and mailed them to the dosimetry processor for processing.
03/06/2006 Worker A processed 7 background samples using the pneumatic
system. Worker A also helped process 8 nautical archeology
samples for a student lab.
03/07/2006 Worker A helped process 14 nautical archeology samples for a
student lab.
03/09/2006 Worker A helped process 13 gold (Au) foil samples for a student lab.
03/15/2006 The licensee received the results from the dosimetry processor which
indicated that Worker A had received a dose to the extremities of
37.54 rem.
The NRC was notified immediately and an investigation of the event
begun.
03/16-19/2006 Texas A&M University spring break.
03/20/2006 An NRC inspector arrived on site to conduct a preliminary review of
the potential overexposure and conduct a routine inspection.
The inspector observed a time-motion study of pneumatic sample
handling performed by Worker A to determine the length of time his
hands were in contact with each sample. The time was measured as
15 seconds per sample.
03/21/2006 The licensee initiated extremity dose calculations using the computer
code VARSKIN - Mod2 and also using a separate computer code
MCNP model.
The licensee again contacted the dosimetry vendor to confirm that the
finger ring dosimeter results were accurate.
03/22/2006 The inspector observed as Worker D processed two Ag-samples
using the pneumatic transfer system and measured the dose rates
from the various components with an open-window ion chamber. The
results were as follows in Table 2:
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Table 2
Items Contact Reading
Outer vial (with foam and inner vial) 2.6 Roentgen per hour (R/hr)
Foam cushioning material separately 470 mR/hr
Outer vial separately 26 mR/hr
Inner vial (with plastic disk sample) 2.4 R/hr
From these measurements and using a volume correction factor of
10, the licensee calculated a dose to the extremities from processing
140 pneumatic samples of 20.22 rem.
03/23/2006 Initial licensee dose estimates using VARSKIN - Mod2 indicated a
worst case beta dose to the extremities from processing 140
pneumatic samples of 17.46 rem.
03/24/2006 Initial dose modeling using MCNP resulted in a dose estimate to the
extremities from processing 140 pneumatic samples of 9.94 rem.
03/25/2006 The inspector observed the calibration of 15 TLD chips using a known
source of radiation against a NIST traceable Farmers ion chamber.
03/26/2006 The inspector observed as the 15 TLD chips were processed to
determine the dose received. The TLD chips were then annealed in
anticipation of using them in another test on Monday.
03/27/2006 A Special Inspection Team arrived on site to conduct a review of the
potential overexposure and the licensees response.
The licensee received the results from the dosimetry processor
indicating that the extremity exposure received by Worker D during
the re-enactment of sample handling was not measurable.
The team observed a test conducted by the licensee to expose (for
one minute) a set of 6 TLDs to an irradiated sample vial processed in
a similar manner as those that had been processed during January
and February. Two TLD chips were placed so as to be in contact with
the source at the side of the sample vial. This test was conducted
twice with two different sets of TLDs. Two vendor finger rings were
also exposed to the sample sources (placed in contact with the vials
for one minute) and subsequently sent to the vendor for processing.
-6-
The NRC began calculating a potential extremity dose using
VARSKIN to estimate a worst case beta dose from processing 140
pneumatic samples.
03/28/2006 The inspectors observed as the TLD chips, which had been exposed
to the sample vials on March 27, were processed to determine the
dose received.
Dose estimates using the dose numbers derived from the exposure of
the TLD chips indicated a dose to the extremities from processing
140 pneumatic samples of approximately 24.7 rem.
The licensee again contacted the dosimetry vendor to discuss the
finger ring dosimeter results and to obtain information on the vendors
processing procedures and techniques.
The NRC began modeling the event scenario using MCNP to obtain a
second estimate of the worst case extremity dose from processing
140 pneumatic samples.
03/29/2006 The dosimetry processor provided results for the two finger rings that
were sent indicating a dose of 0.39 rem for one minute exposure on
one ring and 0.46 rem for one minute exposure on the other. This
would result in a worst case extremity exposure of 16.1 rem from
processing 140 samples.
The inspectors observed a re-enactment by Worker A of the sample
handling technique concentrating on the time required to transport the
sample from the pneumatic transfer area to the counting area. The
average time was 12 seconds.
03/30/2006 Worker A was sent for a medical examination. The doctor found no
problems or abnormalities. Consultation with another specialist was
scheduled by the first doctor. A follow-up exam was scheduled for
April 27, 2006.
c. Conclusions
Based on the records reviewed, following notification of a potential overexposure, the
licensee restricted the individual with the potential extremity overexposure from
handling NAA pneumatic samples. However, the sample handling work for the period
had been completed at that point.
3. Procedures and Training
a. Inspection Scope (IP 69001)
The inspectors reviewed selected aspects of the following to verify compliance with TS Section 6.3 concerning facility procedures:
-7-
- Pneumatic System Training Module
- Facility records for pneumatic system and radiation worker training
- Reactor Safety Board (RSB) meeting minutes from 2004 through the present
Rev. 3, dated February 25, 2002
February 25, 2002
July 31, 1986
- NSC SOP,Section IV, Procedure C, Pneumatic System Operation, Rev. 0,
dated February 8, 1991
dated December 19, 1997
Procedures), Revision 3, dated August 19, 2003
2002
Revision 2, dated December 19, 1997
January 31, 2005
- NSC Form 844, Radiation Work Permit, Number (No.) 005, Revision (Rev.)
No. 05-0, dated November 15, 2005
- Texas A&M University, Nuclear Science Center, Pneumatic System Training
Module, Rev. dated January 10, 2001
- Texas A&M University, Nuclear Science Center, Radiation Worker Training
Module, no revision date
b. Observations and Findings
The inspectors reviewed various NSC SOP Sections and selected procedures. These
SOP Sections and procedures provided guidance for the administrative, operations,
and health physics functions of the facility. The inspectors confirmed that written
procedures were available for those tasks and items required by TS Section 6.3. The
licensee controlled changes to procedures and the RSB conducted the review and
approval process as required.
The inspectors also reviewed the procedures, Radiation Work Permit (RWP), and
training modules that were related to the potential overexposure event. It was noted
that, although the procedures and training modules gave guidance and instruction on
the general use and handling of radioactive material, very little specific information
was included on use of survey meters during processing samples and on remote
handling of radioactive material and the use of tongs or other tools to provide distance
and/or shielding from a potential source of radiation. Licensee personnel indicated
that such issues were generally taught and discussed in class. It was also noted that
facility staff members were not forbidden from using their hands for a brief period to
perform some functions such as removing the inner sample vial from the outer vial if
the dose rates allowed. The licensee was informed that the issue of ensuring that
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sufficient guidance and instruction on the proper handling of radioactive material was
an area for improvement and would be followed by the NRC as an Inspector Follow-up
Item (IFI) (IFI 50-128/2006-203-01).
(The issue of proper handling of radioactive material will be addressed in more detail
in Section 5 of this report.)
The inspectors also reviewed the 2005 training records and interviewed NSC staff
members concerning the training received at the facility. The inspectors determined
that the training of personnel on procedures and general Radiation Worker and
ALARA training was acceptable, although as discussed above that specific guidance
and instructions will be the subject of future inspector follow-up actions.
c. Conclusions
Based on the procedures and records reviewed and observations of NSC staff during
the inspection, the inspectors determined that the procedural control and
implementation program was acceptably maintained. Procedures, RWPs, and the
training program could be improved with respect to radioactive material handling and
the use of tools and shielding devices.
4. Licensee Investigation of and Response to the Event
a. Inspection Scope
The inspectors reviewed the following concerning the licensees response to the event
to ascertain compliance with 10 CFR 20.2202(b)(1)(iii):
- Pneumatic System Training Module
C various licensee records and E-mails
- RSB meeting minutes from 2004 through the present
- Personnel dosimetry records for 2005 through the present
- RSB completed audits and reviews from 2004 through the present
- Facility records for pneumatic system and radiation worker training
- Annual Report for the Texas A&M University Nuclear Science Center for 2004
- various forms associated with the procedures mentioned below for 2005
C NSC Safety Evaluation for the Use of Pneumatic Transfer Systems, undated
C NSC Form 111, Experiment Authorization, Pneumatics Transfer System
Irradiations, dated January 1, 1989
dated December 4, 1997
December 19, 1999
October 15, 1999 and Procedure Change Notice (PCN) dated August 28, 2002
dated December 19, 1997
-9-
October 3, 1990
1995
b. Observations and Findings
(1) Initial Notification of Potential Overexposure
10 CFR 20.2202(b) states, in part, that: Each licensee shall, within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of
discovery of the event, report any event involving loss of control of licensed
material possessed by the licensee that may have caused, or threatens to cause,
any of the following conditions: (1) An individual to receive, in a period of 24
hours [empahsis added]-. . . .(iii) A shallow-dose equivalent to the skin or
extremities exceeding 50 rems (0.5 Sv) . . . .
The licensees response upon receiving the first dosimetry report, for the January
2006 period, was to restrict Worker A from work that would result in extremity
exposure. At the time this action was taken Worker A had already worked most
of the following period, February 2006, because the report for January was
received toward the end of February. The licensee also initiated an investigation
of the work performed by Worker A to determine if there was anything unusual
that may have contributed to the high dose, but none was found. The licensee
stated that in the past, dosimetry reports have occasionally shown high readings
that were later proven to be false and, because their investigation did not, at first,
reveal anything unusual in this case, they believed the reading to be false, and
did not report the initial dosimetry results to the NRC.
The licensee immediately notified the NRC upon receipt of the second report
containing an unusually high reading for the same worker. Although these
responses by the licensee are generally acceptable, the NRC must be notified of
any conditions that conform to the notification and reporting requirements in Part
20, even in the face of great uncertainty regarding the validity of the data, as was
the case in this event. The licensee did not notify the NRC after receiving the first
high dosimetry report even though the dose reported was substantially above the
limit. As noted above, they evaluated the problem and reached the conclusion
that the 75.8 rem dose was erroneous. Although the dose was not likely to have
been received in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the conservative action would have been to report.
Because the licensee did not report the potential overexposure as required by the
regulations, the licensee indicated that Event Notification to the NRC will be
carefully evaluated for the future so that proper notifications are made in a timely
manner. The licensee was informed that review of the Event Notification
procedure would be followed by the NRC as an IFI and would be reviewed by the
NRC during a future inspection (IFI 50-128/2006-203-02).
It was noted that, following the receipt of the dosimetry report on February 24,
2006, the licensee did not conduct any type of surveys of sample vials containing
irradiated material to determine the potential dose that could be received by a
-10-
person handling the material. Based on their review of the employees work
duties and assignments, his previous dose history, and the extremity dose to the
hands that had been received by another worker, who had handled samples in
January, the licensee decided that a calculated dose assessment was needed for
the employee. This NRC determined that the licensee did not do as thorough a
job as they could have in investigating the first reported high dosimeter reading
(for January). The issue of not conducting a proper evaluation of the event was
noted as a problem by the NRC and will be discussed further later in the report.
(2) Second Notification of Potentially High Dose to the Extremities
On March 15, 2006, the licensee received the results from the dosimetry
processor which indicated that Worker A had received a dose to the extremities of
37.54 rem during February. The Facility Director and RSO reviewed the results
and the NRC was notified immediately.
After licensee personnel returned to work on Monday, March 20, they began an
intensive investigation into the cause of the apparent extremity overexposure.
The Facility Director and the Radiation Safety Officer (RSO) investigated several
possibilities. These included the following:
- Reiterated the restriction that Worker A was not to be involved in handling
any radioactive samples or any work that would cause further dose to the
extremities.
- Reviewed the dosimetry records of everyone who had been involved in the
NAA project for the past 12 months.
- Conducted various interviews with the individual involved in the apparent
overexposure to determine exactly what the individual had done for the
months of January and February of 2006. (These activities are summarized
in Paragraph 2 - Sequence of Events above.)
- Determined the number of samples processed by the individual during those
months. During January, the individual processed 140 samples and during
February, 141 samples.
- Conducted time-motion studies on the pneumatic sample processing. The
licensee concluded that each sample was handled for approximately 15
seconds.
- Completed various test runs of samples to verify the beta and gamma dose
rates on the vials and foam after the end of irradiation (EOI) and about five
seconds after the sample was returned to the lab. Separate radiation
readings were taken of the outer vial containing all the enclosed components,
the outer vial by itself, the foam packing used to cushion the inner vial, and
the inner vial containing the small plastic disk sample. (The readings noted
are given in Paragraph 2 - Sequence of Events above.)
- Calculated doses to the extremities based on the time-motion studies and the
dose rates noted from the various tests that they conducted. (The initial
estimates are given in Paragraph 2 - Sequence of Events above and are
summarized in a table in Paragraph 6.b.(4) below.)
-11-
- Contacted the customer to ascertain whether or not the composition of the
samples had changed. The licensee was informed that the composition of
the plastic disks being tested had not changed.
- Reviewed the analyses of the samples run during January and February to
determine whether or not the relative quantities of the various isotopes noted
in the samples had changed. No changes were noted and all samples
contained relatively the same quantities of isotopes. Typical quantities
included 90 microcuries (FCi) of Ag-108 and 15 FCi of I-128.
- Reviewed the location where all employees dosimeters are stored. The
individual involved indicated that he always placed his dosimeter and finger
ring in the storage rack, as did all other employees. No problems were
noted.
- Reviewed the use and storage of the various sources that are maintained at
the facility. No anomalies were noted.
- Contacted the dosimeter vendor to request that the doses for January and
February be checked and reevaluated. The vendor indicated that the
processing and calculations were correct and forwarded the resulting glow
curves to the licensee.
- The licensee reviewed the dosimeter results of others who had handled the
samples and noted that another person, Worker B, had also used the
pneumatic transfer system during January but had received an extremity
dose of 0.18 rem and had handled more samples than Worker A.
- Sent Worker As finger ring used during March to the dosimetry process for
emergency processing. The results indicated an exposure of 0.040 rem for
March.
- Using MICROSHIELD, calculated the gamma dose rates that Worker A
received to the extremities during January and February. The results would
not significantly increase the persons dose.
(3) Corrective Actions Taken or Planned
The licensee has taken various actions to improve their radiation protection
program. One of these actions, which was in fact initiated before this incident,
was to develop a plastic jig that is to be used to hold the sample vial while the
workers cuts off the top. This will prevent any direct handling of the vials by the
workers hands. A tool will also be used to permit quicker cutting than is
achievable using a razor blade. The jig was ready for use at the time of this
inspection, but had not yet been adopted for routine use. The licensee also
stated that they will be holding training sessions for all of their workers to describe
this incident and to instruct them on the proper handling of the samples and the
use of the jig. The radiation safety program at the facility, including sample
monitoring and contamination control practices, were otherwise found to be
acceptable for the type of radiation work conducted at the facility.
In addition, the licensee has also taken or plans to take the following actions as a
result of the exposure event:
-12-
Corrective Action Completed
- Restricted the individual from working with any pneumatic system samples or
doing work that would cause an extremity dose.
- Conducted a separate study of the pneumatic system sample handling
process using another individual and had that persons finger ring analyzed
after two sets of samples were processed. Those results indicated a
minimum dose.
- Held a meeting on Thursday, March 30, for the NAA pneumatics-trained
personnel to review the event and review the subjects of ALARA, radioactive
material handling, and the use of the newly developed tools and beta shields.
- Worker A was sent for a medical examination on Thursday, March 30. The
doctor found no problems or abnormalities. A follow-up exam was scheduled
for April 27, 2006.
- An RSB meeting was held on April 13, 2006, to review the event.
- Worker As was reclassified as a Non-Rad Worker and will no longer be
issued dosimetry (at least for the remainder of this year).
Corrective Action Planned
- Hold a meeting for all NSC personnel to review the event and review the
subjects of ALARA, radioactive material handling, and the use of tools, tongs,
and beta shields.
- Plan to issue two finger ring badges to each NAA worker and send the finger
rings to the vendor for processing every two weeks, instead of every month,
for the next three months.
- Lock the storage cabinets containing the sources at the facility.
- Revise the training program on radioactive materials handling.
- Initiate a program for the NSC Director and/or the RSO to observe work
practices on a regular basis to note good and bad practices and correct any
problems noted.
- Review the SOP for radioactive material handling and consider special
handling procedures in the laboratories.
- Event Notification to the NRC will be carefully evaluated for the future so that
proper notifications are made in a timely manner.
- Reassess the dosimetry vendors response and licensee needs for reliable
and rapid information on potential overexposures.
- Work with the dosimetry vendor to ensure that E-mail can and will be sent
following any indication of an overexposure after the vendor processes the
- Plan to permanently install a radiation detector inside the Fume Hood near
the point where the pneumatic transfer system tube ends.
The licensee was informed that the corrective actions taken will be followed by
the NRC as an IFI and will be reviewed during a future inspection (IFI 50-
128/2006-203-03).
-13-
c. Conclusions
Even though the licensee concluded that it was not valid, they did not take the
conservative action to notify the NRC within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of receiving notification of a
possible extremity overexposure. The licensee did not do as thorough a job as they
could have in investigating the first reported high dosimeter reading (for January).
The licensees subsequent corrective actions, including the dose calculations, were
found to be acceptable.
5. Root Cause Determination and Related Contributing Actions
a. Inspection Scope (IP 69001)
The inspectors reviewed selected aspects of the following to verify compliance with
10 CFR Parts 19 and 20 and TS Sections 3.5, 4.5, 5.4, and 6.6 requirements:
- Licensee records and E-mails
- Licensee dose calculations and test data
- RSB meeting minutes from 2004 through the present
- Personnel dosimetry records for 2005 through the present
- RSB completed audits and reviews from 2004 through the present
- Facility records for pneumatic system and radiation worker training
- Personnel dosimetry records for facility personnel for 2005 to date
- Annual Report for the Texas A&M University Nuclear Science Center for 2004
- various forms associated with the procedures mentioned below for 2005
C NSC Safety Evaluation for the Use of Pneumatic Transfer Systems, undated
C Experiment Authorization No. E-2-1, Pneumatics Transfer System Irradiations,
dated January 1, 1989
- NSC SOP,Section IV, Procedure C, Pneumatic System Operation, Rev. 0,
dated February 8, 1991
dated December 19, 1997
2002
Revision 2, dated December 19, 1997
- NSC Form 844, Radiation Work Permit, Number (No.) 005, Revision (Rev.)
No. 05-0, dated November 15, 2005
- Texas A&M University, Nuclear Science Center, Pneumatic System Training
Module, Rev. dated January 10, 2001
- Texas A&M University, Nuclear Science Center, Radiation Worker Training
Module, no revision date
b. Observations and Findings
(1) Licensee Root Cause Determination
The licensee initially concluded that, based on the calculations and
measurements made, even in full contact with the NAA sample vial (the source),
-14-
doses reported by the dosimetry processor could not be reached. The licensee
indicated that the original dosimetry results were most likely overly conservative.
Considering the sources available at the NSC, it was not known how such high
extremity doses could be received in a one month period. However, after more
consideration, the licensee determined that the root cause of the event was failure
to follow procedure in that Worker A apparently handled the sample vials in a
different manner than any of the other workers had and held the sample vial in his
hands as opposed to touching it briefly while cutting the end off.
The licensee also noted that no other employee had ever received hand doses
unexpectedly, especially at the levels reported in this event. No other work had
ever produced such hand doses, nor should it be possible if procedures are
followed. The licensee conjectured that the possibility remained that the rings
were removed and placed next to a source for an extended period of time.
However, Worker A did not recall any such circumstance.
(2) NRC Root Cause Investigation
10 CFR 20.1501(a) requires that each licensee shall make or cause to be made,
surveys that: 1) may be necessary for the licensee to comply with the
regulations, and 2) are reasonable under the circumstances to evaluate the
magnitude and extent of radiation levels; and concentrations or quantities of
radioactive material; and the potential radiological hazards.
The inspectors reviewed the licensees review and associated actions following
the initial proposal to conduct the NAA experiments on the clients plastic disks. It
was noted that this experiment was conducted under Experiment Authorization
(EA) No. E-2-1, Pneumatic Transfer System Irradiations, dated January 1, 1989.
The EA, the associated Safety Evaluation, SOP IV-C, Pneumatic System
Operation, and the Pneumatic System Training Module, provided general
guidance on using the system and how to handle a sample once it returns from
being irradiated in the reactor. Those instructions included checking the sample
with an ionization chamber before removing it from the pneumatic system and
handling the sample carefully because of external contamination concerns. None
of the aforementioned documents required that the initial samples run under a
new experiment be surveyed in detail to determine the extent of radiation hazards
that might be present. The licensee indicated that surveys were taken and that
the radiation levels were known but that no survey documentation was made, i.e.,
no survey results were available to document surveys that were reportedly
conducted during the initial trial runs of the sample vials containing plastic disks
after irradiation. It was noted that no procedural steps were written and no
engineering controls were implemented to ensure that occupational doses would
not be adversely affected. The failure to make adequate surveys to fully establish
the radiological hazards that were present following the initial trial runs of vials
containing plastic disks was determined to be a root cause of the problem.
Contributing factors were considered as well. The most apparent factor was the
improper handling of the sample vials in that Worker A handled the sample vials
with his hands. Tongs were provided for use in handling the vials but their use
-15-
was not mandatory. Although the practice of using ones hand/fingers to handle
the sample vials was not prohibited by facility procedure, and indeed allowable as
taught during pneumatics system training, the handling was only supposed to be
for a brief period and at the opposite end of the vial from where the sample was
located. During a demonstration, Worker A held the sample vials in a different
manner than taught or intended by management and apparently in a different
manner than other workers. Typically, workers held the vial close to the top,
away from the source, with the finger tips, while handling. Worker A, however, at
least during the demonstration, grasped the vial with his fingers folded around it,
with the vial resting against his palm, while handling and cutting off the end cap.
The training and monitoring of these activities did not prevent or identify in a
timely manner this improper handling of the sample by Worker A and resulted in a
significantly increased dose to the extremities.
An additional contributing factor was failure to follow procedure. The procedure
requires that the person processing the samples measure the samples with a
portable radiation survey instrument after the samples return from being irradiated
in the reactor core. During an interview with Worker A, the individual admitted
that he did not monitor each sample upon its return. His practice was to look at
the survey meter that was placed just outside the Fume Hood and adjacent to
some shielding that was near the pneumatic transfer system return tube. When
the sample vials arrived back in the Fume Hood return tube, the worker would
glance at the meter and, if there were no high readings, he would pick up the
sample vial for further processing. This practice may have resulted in the worker
picking up the vials too soon after they returned from being irradiated in the
reactor core.
The NRC concluded that: failure to make adequate surveys to fully establish the
radiological hazards that were present following the initial trial runs of vials
containing plastic disks and failure to conduct surveys of the sample vials of
irradiated material following the first indication of a possible overexposure on
February 24, 2006, to determine the cause of the problem lead to failure to
acceptably train and monitor workers regarding the handling of sample vials with
their hands/fingers (VIO 50-128/2006-201-04).
c. Conclusions
The licensee determined that the root cause for this event was failure to follow
procedure. The NRC determined that failure to conduct an acceptable survey of the
sample material when the experiment was first initiated was the root cause of the
problem that lead to a potential overexposure. The lack of initial surveys, as well as,
allowing workers to handle sample vials which lead to improper sample handling by
Worker A and failure to follow procedure were contributors to a violation of the
regulations.
6. Dose Assessment
a. Inspection Scope (IP 69001)
The inspectors reviewed selected aspects of the following to verify compliance with
10 CFR Parts 19 and 20 and TS Sections 3.5, 4.5, 5.4, and 6.6 requirements:
-16-
- various licensee records and E-mails
- licensee dose calculations and test data
- personnel dosimetry records for facility personnel for 2005 to date
b. Observations and Findings
The routine personnel dosimetry used at this facility for workers handling irradiated
samples consists of one whole body dosimeter to monitor whole body and eye doses,
and one finger ring dosimeter to monitor hand exposures. The whole body dosimeter
is an OSL dosimeter, and the finger ring dosimeter consists of a standard TLD chip,
suitably encapsulated and encased in a plastic ring that can be worn on one of the
workers fingers. Workers are instructed to wear the finger ring dosimeter facing the
radiation source and on the finger likely to receive the highest dose. The dosimetry
change period at the facility is monthly. The licensee received the first unusual
dosimetry report from the dosimetry processor on February 24, 2006, and the report
was for the period January 1, 2006 to January 31, 2006. All of the results in the report
were within the expected range except for the affected worker, referred to in this
report as Worker A. This workers whole body dosimeter showed a DDE of 0.034 rem,
which is within the expected range for the type of work he performed, but the SDE was
reported to be 75.8 rem. This result was well outside the normal range, the history of
the facility indicating that SDE have not previously exceeded about 1.5 rem for a
badging period. The licensee restricted Worker A from further radiation work,
conducted a review of the workers activities, and performed bounding calculations.
The calculations indicated that the activities in which Worker A had engaged in during
the month could not have delivered that high a dose. Having previously encountered
erroneous dosimetry reports from the vendor, including a high reading for a dosimeter
used to monitor background in a reception area, the licensee concluded that the high
reading was erroneous, and was preparing to contact the dosimetry processor to
discuss the case. Before that was done, however, the dosimetry report for the period
February 1, 2006 to February 28, 2006.
As in the previous months report, the DDE for Worker A, 0.006 rem, was low, as
expected, but the SDE was 37.54 rem, again far higher than expected. The licensee
immediately notified the NRC of a potential exposure above the applicable regulatory
limit and initiated a more thorough investigation of both the January and February high
readings. The dosimetry processor did not immediately report either of the high
readings to the licensee, as is usual good practice when an unusual dosimetry result is
obtained during processing.
(1) Re-enactments
Following initiation of an NRC inspection, and before the start of the NRC special
inspection, an NRC inspector observed Worker A re-enacting the type of radiation
work he had been performing during the months of January and February. The
work consisted the following steps:
1. Retrieve the plastic vial containing the irradiated sample from the reactors
pneumatic system.
2. Survey the sample for radiation levels.
-17-
3. Cut of the top of the plastic vial, which had been heat-sealed, using a razor
blade.
4. Retrieve the inner plastic vial that contains the irradiated sample.
5. Place the inner vial containing the sample in a small glass vial and count on a
high-resolution gamma spectroscopy system to identify the activated
radionuclides in the sample and quantify their activities.
These steps were the usual steps followed by all the workers engaged in this type
of work. However, one unusual feature was noted in the manner in which Worker
A cut the tops off of the vials with the razor blade. Normally, the worker would
hold the vial close to the top, away from the source, with the finger tips, while
cutting. Worker A, however, grasped the vial with his fingers folded around it,
with the vial resting against his palm, while cutting. He is left handed, and the vial
was grasped with the right hand. The finger ring was also worn on the right hand,
with the sensitive element facing the palm side of the hand, almost directly
opposite the activated sample. This manner of wearing the finger ring dosimeter
conforms to recommended monitoring practices for the facility. During the re-
enactments, it was found that he held the vial in this position for an average of 15
seconds per sample. Records indicated that he had handled 140 samples during
each of the two months in question.
(2) Experimental Dose Estimates
Order of magnitude calculations performed by the licensee as well as by NRC of
the doses that may arise from the samples showed that the reported SDEs of
75.8 and 37.54 rem could not have been due to photon emissions from the
samples. The activities in the samples were of the order of 100 µCi for one of the
activated radionuclides, and far less for the other activated components. The
estimated doses resulting from the photon emissions from such activity levels
were several orders of magnitude lower than the values that could account for the
high SDE dosimeter readings. It was therefore tentatively concluded that, if the
dosimeter readings were not erroneous, they were probably caused by beta
emissions from the samples. The total thickness of the two plastic vial walls plus
a surgical glove worn by the worker is about 0.25 cm, and beta radiation with
energies above about 0.6 MeV will penetrate this thickness of plastic material.
The beta emissions from nearly all of the activation products in the samples were
sufficiently energetic that significant fractions of their energy spectra fell above
0.6 MeV.
In an attempt to quantify the dose rates from the vials, several samples identical
to the ones handled by Worker A were irradiated in the reactor during the NRC
inspection, for the same length of time, namely four minutes, as that used during
routine irradiations. Upon removal from the pneumatic system, each sample vial
was placed on a bench and a set of TLD chips were held against the wall of the
vial for a period of approximately one minute. Six chips were used in each test,
distributed along the length of the vial to obtain an axial dose distribution. Two of
these chips were placed opposite the irradiated sample, which is the location
expected to yield the highest dose rate. In addition, a finger ring dosimeter was
also placed against the vial wall opposite the activated sample. The TLD chips
-18-
were stored overnight to permit unwanted parts of the glow curves to decay away
(standard procedure), and were read by the licensee the following morning. The
finger ring dosimeters were sent to the dosimetry processor for emergency
processing. The licensee operates a TLD chip reader system calibrated using
radiation measuring detectors traceable to the National Institute of Standards and
Technology (NIST). The dose rates obtained from these experimental
measurements are shown in Table 3 below.
Table 3
Location of Chip Dose Rate - mrad/min Location of Chip Dose Rate - mrad/min
1 38.2 7 42.6
2 81.4 8 104.3
3 419.9 9 681.0
4 1115.4 10 622.0
5 180.4 11 187.4
6 23.2 12 18.2
The readings are all corrected for background. Chips #1 and #7 were close to the
top of the vial, Chips #2 and #8 were about halfway along the length of the vial,
chips #3, #4, #9, and #10 were opposite the irradiated sample, and chips #5, #6,
- 11, and #12 were below the bottom of the vial.
If the reading of the four chips opposite the sample are averaged, the result is
710 rad/min. Using an estimated 15 seconds contact time per sample, based on
re-enactments, and 140 samples handled per month, the total contact time is
estimated to be 35 minutes, and the dose would in this case be 24.8 rads. Using
the highest chip reading of 1115.4 rad/min, the total dose resulting from a contact
time of 35 minutes would be 39.0 rads, whereas using the smallest of the four
center chip readings gives a total dose of 14.7 rads. The results of the two finger
ring irradiations were reported by the processor before the end of this inspection
as 460 and 390 mrad/min. Using the exposure duration of 35 minutes, these
dose rates give a total dose for the month of 16.1 and 13.7 rad, respectively.
(3) Dose Calculations
As a second approach in attempting to assess the doses received by Worker A,
and to provide supporting data for the experimental measurements, both the
licensee and the NRC calculated the doses that would result from handling the
irradiated samples. The licensee attempted to use the computer codes VARSKIN
to calculate doses resulting from beta radiation, and MICROSHIELD to calculate
the doses arising from photons. However, neither code is capable of
representing the exposure geometry in this case with sufficient accuracy, and
-19-
both the licensee and NRC also used the Monte Carlo transport code MCNP to
supplement the VARSKIN calculations. MCNP can be used to model the
exposure geometry with any desired degree of accuracy, and can calculate doses
resulting from both photons and electrons. The dimensions used for the vials
were 7.5 cm length and 1.7 cm outer diameter for the larger outer vial, and 1.0 cm
length and 1.2 cm outer diameter for the inner vial. Each of the vials has a wall
thickness of 0.1 cm, and the vials are made of polyethylene. The calculations
were based on sample activities obtained by reviewing the records of the isotopic
gamma analyses and also by irradiating several samples during the inspection
under the same conditions used by Worker A. The isotopic composition used in
the calculations is shown in Table 4 below.
Table 4
Radionuclide Activity, µCi
Ag-108 90.0
Al-28 2.48
Cl-38 0.19
I-128 15.9
Na-24 0.54
The silver and iodine activities arise from the silver iodide contained in the
irradiated samples, and the aluminum, sodium, and chlorine most likely arise from
irradiation of trace constituents in the vial material.
The dose arising from photon irradiation was calculated by NRC to be about
0.03 rem for the badging period, and is therefore a negligible contributor to the
total SDE. The dose arising from beta radiation was estimated using MCNP to be
about 21 rads for a badging period of one month, using a total exposure duration
of 35 minutes. The licensees result from their MCNP calculations were 12.3 rads
without surgical gloves and 5.0 rads with the gloves. NRC also used VARSKIN to
calculate the beta dose. Although this code cannot accurately model the actual
exposure geometry, an approximation to that geometry was used, and the dose
calculated for the monitoring period of one month was 22 rads. The licensees
estimate using VARSKIN was 17.5 rads.
(4) Summary of Measurement and Calculation Results
Table 5 below summarizes the results of the TLD and ring badge measurements
and the calculations performed by NRC and the licensee. All the doses shown
are based on estimating the dose rate per minute and multiplying by an exposure
duration of 35 minutes to obtain the dose for the month.
-20-
-21-
Table 5
Type of Dose Estimate Dose During the Month, rad
Mean of TLDs chip readings 24.8
Maximum TLD chip reading 39.0
Minimum TLD chip reading 14.7
Finger ring reading 16.1
Finger ring reading 13.7
MCNP calculation with gloves (NRC) 21.0
MCNP calculation with gloves (licensee) 5.0
MCNP calculation w/o gloves (licensee) 12.3
VARSKIN calculation (NRC) 22.0
VARSKIN calculation (licensee) 17.5
The results shown in the table show reasonable agreement considering the
various methods of calculation and measurement used to obtain these estimates.
They span a range of about 5 - 40 rads if the high TLD chip reading is included,
but span a much narrower range of 14 - 25 rads if the high reading is excluded,
as well as the licensees MCNP calculation with gloves. It therefore appears that
much of the data support the conclusion that the dose to Worker A was of the
order of probably not more than 25 rad, assuming the exposure duration of 35
minutes per month is correct. This is a factor of about 3 lower than the dose of
75.8 rad reported for the January period, and still significantly lower, by a factor of
about1.5 for the February period. The dose rates on which the tabulated doses
are based are probably reliable, especially since the calculations and
measurements are in agreement. The exposure duration was obtained by
multiplying the estimated contact time per sample, namely 15 seconds, by the
number of samples handled during the month. The number of samples handled
is a matter of record, and the exposure duration per sample is based on timing
the re-enactments observed by the NRC inspector.
It is possible that during the actual handling of samples, Worker A took much
longer to perform the required sample handling than was demonstrated during the
re-enactments, especially if one makes the reasonable assumption that this
worker gained increasing skill in handling the samples during this period. The
SDE pattern reported by the processor, namely 75.8 and 37.5 rads, is consistent
with this possibility. The time available to handle a sample, however, is not
unlimited, but is constrained by the nature of the process of sample irradiation
-22-
and analysis. Most of the radioactive materials produced by sample irradiation
have half-lives of the order of a few minutes, and the sample must therefore be
quickly transferred from the pneumatic system to the counting detector before the
activity decays away, thereby precluding the possibility of accurate isotopic
analysis. Re-enactments and interviews with Worker A and others have shown
that the total time taken from removal of the sample from the reactor pneumatic
system to the start of counting on the gamma spectrometer is very close to one
minute. Of this, 5 seconds are used to remove the sample from the pneumatic
system, and 10 seconds to set up the counting system in preparation for
counting. This leaves a maximum of about 45 seconds to handle the sample. If
the assumption is made that all of this time is taken up in sample handling, the
doses for the month based on a 15-second handling time are increased by a
factor of three. For example, a dose of 25 rads for the month estimated on the
basis of the mean TLD chip results becomes a dose of 75 rad, which is the SDE
dose reported for January. Improved handling skills would lead to reduced
handling time, and therefore a reduced dose for the month of February.
It should be noted that the above is highly speculative, and requires making some
unlikely assumptions, such as that the worker took 45 seconds to handle each of
the 140 samples during January, and that during each of these, the workers
fingers were placed around the sample such that the dosimeter chip was always
opposite the irradiated sample. Although not impossible, these coupled
conditions are highly unlikely. A more convincing conclusion is that the dose
received for January was of the same order of magnitude as that received during
February, and that the dosimeter used during the January badging period read on
the high side, an occurrence that is not infrequent.
(5) Dose Assignment
NRCs 10 CFR Part 20 defines the SDE as the dose at a depth of 0.007 cm in
skin averaged over the 10 cm2 area of skin that receives the highest dose from
the source of exposure. NRC performed calculations using MCNP to determine
the ratio of the dose registered by the finger ring dosimeter to the dose averaged
over the highest exposed 10 cm2 area of the skin of the workers hand. The result
showed the ratio to be 2.9. This means that the doses registered by the
dosimeter should be divided by 2.9 to determine the dose to be used to show
compliance. If the reported SDE for January and February, namely 75.8 and
37.54 rads, respectively, are considered valid and used to show compliance, the
total reported dose for January and February would be 113.3 rads, and the dose
to be assigned to Worker A would be 39.1 rads for the period starting January 1st
through the end of February. If the dose estimated on the basis of measured and
calculated dose rates and a 15-second handling period per sample, namely about
25 rads, is used for each of the 2 months, the total dose would be 50 rads, and
the assigned total dose would be 17 rads. In either case, the assigned dose is
significantly lower than the regulatory dose limit on SDE, which is 50 rem for the
year.
-23-
c. Conclusions
The inspectors concluded that, by using dose averaging to determine the SDE as
prescribed by the regulations, the assigned dose for the individual involved in the
event would be lower than the annual dose limit to the extremities for the year.
7. Licensee Actions to Ensure Regulatory Requirements Are Met
a. Inspection Scope (IP 69001)
The inspectors reviewed selected aspects of the following to verify compliance with
10 CFR Parts 19 and 20:
- Licensee records and E-mails
- Licensee dose calculations and test data
- Personnel dosimetry records for facility personnel for 2005 to date
dated December 19, 1997
2002
Revision 2, dated December 19, 1997
- NSC Form 844, Radiation Work Permit, Number (No.) 005, Revision (Rev.)
No. 05-0, dated November 15, 2005
- Texas A&M University, Nuclear Science Center, Pneumatic System Training
Module, Rev. dated January 10, 2001
- Texas A&M University, Nuclear Science Center, Radiation Worker Training
Module, no revision date
b. Observations and Findings
As noted above, once the licensee was aware of the dosimetry results for January,
Worker A was restricted from handling any radioactive samples and a review of the
situation was initiated. After consideration of the sample handling process and other
factors involved, the licensee concluded that this was an anomalous reading and a
dose estimate, based on past extremity doses, was prepared. Worker A was then
allowed to resume restricted or limited duty. Worker A did some tasks around the
facility but did not process any additional NAA sample vials because all the samples
for the period had already been processed.
On March 15, 2006, the licensee received the results from the dosimetry processor
which indicated that Worker A had received a dose to the extremities of 37.54 rem
during February. The Facility Director and RSO reviewed the results and the NRC
was notified immediately. It was reiterated that Worker A was only to be involved in
limited duty which did not involve dose to the extremities. As noted above, the
licensee then conducted re-enactments of the sample handling process, completed
careful measurements of the dose rates of the irradiated sample vials, and initiated
dose calculations using the dose measurements and various computer programs and
models including VARSKIN and MCNP. All NSC staff members were made aware of
-24-
the event and the fact that Worker A was not allowed to perform work involving
radioactive material that would result in a dose to the extremities. Worker A was also
sent for a medical examination on Thursday, March 30. The doctor found no
problems and no abnormalities. A follow-up exam was scheduled for April 27, 2006.
c. Conclusions
The inspectors determined Worker A had been restricted from working with or
handling radioactive material that would result in any additional dose to the
extremities.
8. Timely Reporting in the Future
a. Inspection Scope (IP 69001)
The inspectors reviewed selected aspects of the following to verify compliance with
10 CFR Parts 19 and 20:
dated December 19, 1997
2002
Revision 2, dated December 19, 1997
- NSC Form 844, Radiation Work Permit, Number (No.) 005, Revision (Rev.)
No. 05-0, dated November 15, 2005
- Texas A&M University, Nuclear Science Center, Pneumatic System Training
Module, Rev. dated January 10, 2001
- Texas A&M University, Nuclear Science Center, Radiation Worker Training
Module, no revision date
b. Observations and Findings
As noted above, on February 24, 2006, the licensee received the results from the
dosimetry processor which indicated that Worker A had received a dose to the
extremities of 75.8 rem. Following receipt of this report, the Facility Director and the
Radiation Safety Officer informed the person of the extremity dose and prohibited the
individual from any duties that would add to his extremity dose. They subsequently
initiated an investigation. Worker A was questioned about his activities including:
1) where he typically stored his dosimetry when it was not in use, 2) whether or not he
had had any medical procedures involving radioactive materials, 3) whether he had
handled any radioactive material which was unknown to the NSC staff, or 4) whether
he was aware of any thing that would cause a high extremity dose. The individual had
no recollection of anything that would result in a high exposure to the hands other than
the high volume of pneumatic samples that were being processed during January and
February. The employee had handled 140 silver samples in January 2006.
In reviewing the apparent overexposure, the licensee reviewed various circumstances:
1) The process had been ongoing for over a year and no one had ever received doses
-25-
that exceeded 1.58 rem while performing this task. 2) Even during January 2006,
another employee had handled 195 samples and had received only 0.18 rem extremity
exposure. 3) Nothing in the process had changed and the composition of the samples
had not changed. 4) The dosimetry vendor had, in the past, contacted the licensee to
notify them of a potential problem with high doses. This was not done in this case for
some reason. 5) The dosimetry vendor also had sent the licensee anomalous
readings in the past and the current potential overexposure of the employees hands
was determined to be such based on past experience with handling this type of
sample. Based on the above and the employees work duties and assignments, his
previous dose history, and the extremity dose to the hands that had been received by
another worker, who had handled samples in January, the licensee decided that a
calculated dose assessment was needed for the employee.
On March 15, 2006, the licensee received the results from the dosimetry processor
which indicated that Worker A had received a dose to the extremities of 37.54 rem
during February. The Facility Director and RSO reviewed the results and the NRC
was notified immediately and it was reiterated that Worker A was restricted from any
handling of radioactive material that would produce an extremity dose. As noted
above, the licensee then conducted re-enactments of the sample handling process,
completed careful measurements of the dose rates of the irradiated sample vials, and
initiated dose calculations using the dose measurements and various other computer
models. All NSC staff members were made aware of the event and the fact that
Worker A was not allowed to perform work involving radioactive material that would
result in a dose to the extremities.
As a result of the event and the subsequent investigation of the possible cause(s) of
the reported overexposure, licensee management and staff were forcefully reminded
of the requirements in the regulations and their own procedures for reporting such
events in a timely manner. The corrective action for this problem, as indicated by the
licensee, was simply to report any such instances in the future. The licensee
determined that it would be much more prudent to report such an event, even if there
are questions about the veracity of the data, than to not report it. Also, if the data
show that the report was made in error, the report could be retracted.
c. Conclusions
The inspectors determined that the licensee will report any such event in the future.
9. Exit Interview
The inspection scope and results were summarized on March 29, 2006, with licensee
representatives. The inspectors discussed the findings for each area reviewed. The
licensee acknowledged the findings presented and did not identify as proprietary any of the
material provided to or reviewed by the inspectors during the inspection.
PARTIAL LIST OF PERSONS CONTACTED
Licensee
T. Fisher Supervisor, Reactor Maintenance
T. Maldonado Deputy Director, Texas Engineering Experiment Station
B. Pack Health Physics Technician
D. Reece Director, Nuclear Science Center
J. Remlinger Manager, Reactor Operations
L. Vasudevan Radiation Safety Officer
INSPECTION PROCEDURE USED
IP 69001 Class II Research and Test Reactors
ITEMS OPENED, CLOSED, AND DISCUSSED
Opened
50-128/2006-203-01 IFI Follow-up on the issue of ensuring that sufficient guidance and
instruction on the proper handling of radioactive material was
included in procedures, RWPs, and in the training program
(Paragraph 3.b.).
50-128/2006-203-02 IFI Follow-up on the licensees review of their Event Notification
procedure (Paragraph 4.b.(1)).
50-128/2006-203-03 IFI Follow-up on the licensees corrective actions taken in response
to the exposure event (Paragraph 4.b.(3)).
50-128/2006-201-04 VIO Failure to make adequate surveys to fully establish the
radiological hazards that were present following the initial trial
runs of vials containing plastic disks and failure to conduct
surveys of the sample vials of irradiated material following the
first indication of a possible overexposure on February 24, 2006,
to determine the cause of the problem which lead to a failure to
acceptably train and monitor workers regarding the handling of
sample vials with their hands/fingers (Paragraph 5.b(2)).
Closed
None
LIST OF ACRONYMS USED
Ag Atomic symbol for silver
ALARA As low as reasonably achievable
Ar Atomic symbol for argon
CFR Code of Federal Regulations
cm2 centimeters squared
Co Atomic symbol for cobalt
HP Health Physics
I Atomic symbol for iodine
IFI Inspector Follow-up Item
IP Inspection Procedure
FCi microcurie
mCi millicurie
MeV million electron volts
mrad milliRAD
mrem millirem
nCi nanocurie
NAA Neutron activation analysis
NIST National Institute of Standards and Technology
NSC Nuclear Science Center
NRC Nuclear Regulatory Commission
OSL Optically stimulated luminescent
RAD Radiation Absorbed Dose
RSO Radiation Safety Officer
RSB Reactor Safety Board
RWP Radiation Work Permit
SDE Shallow dose equivalent
Si Atomic symbol for silicon
SOP Standard Operating Procedure
Tc Atomic symbol for technetium
TLD Thermoluminescent dosimeter
TS Technical Specifications
TEES Texas Engineering Experiment Station
VIO Violation