Information Notice 1997-36, Unplanned Intakes by Worker of Transuranic Airborne Radioactive Materials and External Exposure Due to Inadequate Control of Work
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UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
June 20, 1997
UNPLANNED INTAKES BY WORKER OF
TRANSURANIC AIRBORNE RADIOACTIVE
MATERIALS AND EXTERNAL EXPOSURE DUE TO
INADEQUATE CONTROL OF WORK
Addressees
All holders of operating licenses and construction permits. All licensees of nuclear power
reactors in the decommissioning stage and fuel cycle licensees.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert
licensees to inadequate radiological work controls in highly contaminated areas. These
inadequate controls created a substantial potential for personnel radiation exposures in
excess of NRC limits and resulted in unplanned intakes by workers of airborne radioactive
materials, including transuranics (alpha emitters). It is expected that recipients will review the
information in this notice for applicability to their facilities and consider actions, as
appropriate, to avoid similar problems. However, suggestions contained in this information
notice are not NRC requirements; therefore, no specific action or written response is
required.
Description of Circumstances
On November 2, 1996, the Haddam Neck plant was in a refueling and maintenance outage.
Before flooding the reactor cavity, the fuel transfer canal (FTC), the fuel transfer cart and
tracks, and the upender needed to be inspected and debris removed to ensure cleanliness.
In preparation for the inspection and entry to the FTC, two workers (a maintenance
supervisor and a reactor vendor representative) met with health physics (HP) supervisors and
HP technicians (HPTs) to discuss the entry. As this work was not on the master outage
schedule, this was the first notice to HPTs of the work. The governing work procedure
provided no work scope detail. The meeting was not effective; there was no common
understanding between the workers and the HPTs as to what work was to be done and the
radiological conditions in the work area. The HPTs mistakenly believed that the workers
would principally walk along the FTC tracks but could periodically leave the tracks to pick up
debris (e.g., tie wraps) that had fallen down from the charging floor. The HPTs did not know
that the workers would collect, by hand, paint chips, metal rust, and dried, dirtlike materials
from the floors and walls.
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IN 97-36 June 20, 1997 Just before the entry, the HPTs briefed the workers on the radiological conditions. Since the
FTC was decontaminated in August 1996, the workers were led to believe that the canal was
generally "clean." The licensee had not performed any prework contamination or radiation
surveys to support the job. Surveys later found that the FTC contained removable
contamination of up to 800 microgrey/h [80 milliradlhr] (beta/gamma) and 500 Bq [30,000
disintegrations per minute) per 100 square centimeters (dpml100 cm2) alpha contamination.
In addition, a local hot spot on the canal floor, readily accessible to the workers, exhibited
external radiation levels of 250 mSv/h [about 25 R/h] on contact and 80 mSvlh [about 8 R/h]
at waist level. The prework briefing of the workers was inadequate, and the workers were
not informed of the actual radiological conditions. Additionally, the work was allowed to
commence under an invalid (because it did not allow FTC entry) radiation work permit
(RWP), rather than a specific RWP for the FTC. As a result, no comprehensive, prework
radiation or contamination surveys were performed. The decision not to issue respiratory
protection was based on previous air sample results (after the August 1996 reactor cavity
decontamination to support worker tours of the area). However, this dated sampling was not
representative of the extensive debris cleanup activity on November 2, 1996.
While in the FTC, the workers scraped up debris from the FTC and placed it in a plastic bag.
Unknown to the workers, this activity generated significant airborne radioactive materials and
created a high-intensity external radiation source.
After completion of the work, one workers dosimeter alarmed upon exiting the reactor cavity.
The plastic bag of debris was surveyed for the first time and read 200 mSv/h [about 20 R/h]
on contact (it was placed in shielded storage). A later survey of the bag indicated 600 mSv/h
[about 60 R/h] on contact and about 40 mSv/h [about 4 R/h] about 30 centimeters away. The
workers wore no additional dosimetry other than their electronic alarming and standard chest
thermoluminescence dosimeters (TLDs). The workers found significant contamination, while
whole-body frisking. Nasal smears of the workers indicated 3333 Bq 1200,000 dpmJ
(beta/gamma) shortly after exiting the cavity. Subsequent to the event, the licensee
determined (by analysis and reconstruction) the workers' deep-dose equivalent (DDE), the
shallow-dose equivalent (SDE, whole body), the maximum doses to the extremities, and the
lens dose equivalent (LDE) from the collection and handling of the debris. None of the
worker's external doses were in excess of the limits, with the maximum assigned doses
(mSv) of 4.73 [473 mrem], DDE; 4.73 [473 millirem], SDE; 11.6 [1164 mreml, extremity; and
3.97 [397 mrem], LDE.
With the workers out of the cavity, an HPT checked the FTC air sample using a hand-held
frisker and found that the sample exhibited an elevated count rate, indicating the presence of
potential airborne radioactive material. This air sample later indicated about 0.8 derived air
concentration (DAC) beta and 24 DAC alpha. The general area air sample was not
representative (not in the breathing zone of the workers) of the concentrations encountered
by the workers during the debris cleanup.
A backup air sample of the reactor cavity was started, well away (non-representative) from
the FTC. The sample was also checked in the field with a different (but defective) hand-held
IN 97-36 June 20, 1997 frisker, which erroneously indicated no airborne radioactive materials were present. Other
HPTs in the area were then notified (misinformed) that the air within the reactor cavity was
clean. The inspector later found that the licensee had failed to establish and implement an
effective program to adequately check for proper operability of the frisker in containment.
On the basis of the erroneous negative air sample result, HPTs authorized two other workers
to enter the reactor cavity and clean the reactor vessel stud holes. These workers
unknowingly spent about 15 minutes in an area with elevated airborne radioactive material
levels and subsequently exited the reactor cavity. Their subsequent whole-body counts
showed no significant intakes.
The licensee's subsequent counting of the backup air sample prompted identification of the
inoperable frisker and subsequent evacuation of the reactor cavity and initiation of an
investigation. The backup air sample was found to indicate airborne radioactivity
concentrations of 3.5 DAC beta and 108 DAC alpha. The air sample collected near where
the two workers were working on the reactor vessel studs was later found to indicate
1.5 DAC beta and 53 DAC alpha. In spite of these air sample results (high alpha DACs),
their non-representative nature (not near the FTC), and the stay-times of the workers and
their work practices in the FTC (handling contaminated debris), the licensee did not recognize
the potential for excessive personnel exposure until about a week after the event.
Discussion
In the Haddam Neck event, inadequate radiological evaluations and controls led to unplanned
internal exposures with a substantial potential for worker overexposures. Of more concern
was that until identified by an NRC inspector five days after the event, the licensee failed to
recognize the potential for significant internal doses from transuranic radionuclides known to
be present in the FTC. The presence of these alpha-emitting nuclides was evident from
loose surface contamination sampling (smears) and air samples. This failure led to untimely
initiation of in-vitro bioassays (fecal sampling) for the transuranic material intake to assess
personnel exposures. While the whole-body counting (WBC) indicated a relatively low
intake/dose from cobalt-60, the licensee failed to use the high alpha-to-beta gamma ratios
(from the air and smear samples) to identify the potential for significant internal doses to
workers from the transuranic component. When the NRC inspector noted the WBC result for
the gamma emitters (power plant WBC's do not detect alpha radiation) and took into account
the relative workplace abundance and typical DAC alpha-to-beta gamma nuclide ratios, he
informed the licensee of the transuranic concern.
The licensee then initiated fecal sampling to account for doses from all nuclides (including
alpha emitters). The licensee contracted outside consultants to perform a detailed analysis of
the event and calculate the workers' internal dose. On the basis of this effort, the licensee
reported a maximum 9.13 mSv [913 mrem] committed effective dose equivalent (CEDE) and
58.7 mSv 15873 mrem] total organ dose equivalent (TODE) to the bone surface. None of the
reported doses are In excess of regulatory limits. However, the NRC staff is still reviewing
the licensee's methods, assumptions and models for the internal dose assessment.
IN 97-36 June 20, 1997 For reactor facilities that have experienced fuel defects, experience has shown that long after
the defective fuel has been removed, significant alpha contamination may remain in generally
inaccessible locations, such as the FTC equipment drains and sumps, and other refueling
areas. Even minor disturbance of the contaminated surfaces can result in the release of
alpha-emitting radionuclides, whose DACs are orders of magnitude more restrictive and
limiting (at much lower concentrations) compared with the normal beta-emitting and gamma- emitting isotopes usually encountered in reactor plant environments (fission, corrosion, and
wear products). Additionally, alpha contamination may be incorporated into a
contamination/corrosion layer on the interior surfaces of system components that carry
primary fluids or steam. Surveys for loose surface contamination may not identify the fixed
alpha contamination, but abrasive work (e.g., grinding or welding) may result in alpha- emitting airborne radioactive materials. This latter characteristic may be particularly important
at reactor facilities undergoing decommissioning.
As a result of this event, the licensee performed root cause analyses. On the basis of these
analyses and the findings of an independent review team, the licensee has initiated certain
corrective actions, which include the following:
1.
All work presenting a significant radiological challenge (within designated high-risk
areas) was suspended until a work approval program was instituted. This program
now requires review of all RWPs by the plant Radiation Protection Manager (RPM)
and the Work Services Director, and RWP approval by the RPM or the Radiological
Protection Supervisor.
2.
The work control program now includes an RWP procedure requiring clear
descriptions of authorized work and controls, improved procedures for high-risk
evolutions, and representative prework surveys.
3.
The license stopped the use of in-field counting and checks for air samples as a basis
for reducing or relaxing radiological work controls.
4.
All work in high alpha-intake risk areas requires the use of respirators until
representative air sampling justifies work without respiratory protection.
Events involving unplanned intakes of airborne radioactivity at nuclear power plants occur
generally during maintenance and refueling outages, are infrequent, and typically result in
intakes by workers of radioactive material that are well within the limits of 10 CFR Part 20.
However, as indicated in the event describe in this notice, the potential for significant
unplanned personnel exposures does exist at nuclear power plants (see related
correspondence).
Related Communications and Correspondence
The following related communications and correspondence are noted:
NRC Inspection Report No. 50-219/96-12, dated December 19, 1996.
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IN 97-36 June 20, 1997 *
NRC Information Notice 90-47, "Unplanned Radiation Exposures to Personnel
Extremities Due to Improper Handling of Potential Highly Radioactive Sources," dated
July 27, 1990.
NRC Information Notice 92-75, "Unplanned Intakes of Airborne Radioactive Material
by Individuals at Nuclear Power Plants," dated November 12, 1992.
This information notice does not require any specific action or written response. If you have
any questions about the information in this notice, please contact one of the technical
contacts listed below.
Marylee M. Slosson, Acting Direct r
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Ronald L. Nimitz, RI
(610) 337-5267 E-mail: rln@nrc.gov
William J. Raymond, RI
(860) 267-2571 E-mail: wjr@nrc.gov
James E. Wigginton, NRR
301-415-1059 E-mail: jew2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
I/d P'
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t
Attachment
June 20, 1997 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
97-35
97-34
97-33
Retrofit to Industrial
Nuclear Company (INC)
IR100 Radiography Camera
to Correct Inconsistency
Compatibility
Deficiencies in Licensee
Submittals Regarding
Terminology for Radio- logical Emergency Action
Levels in Accordance
With the New Part 20
Unanticipated Effect
of Ventilation System
on Tank Level Indica- tions and Engineering
Safety Features Actua- tion System Setpoint
Potential Problems
with Post-Fire Emer- gency Lighting
Defective Worm Shaft
Clutch Gears in
Limitorque Motor-
Operated Valve
Actuators
Failures of Reactor
Coolant Pump Thermal
Barriers and Check
Valves in Foreign
Plants
06/18/97
06/12/97
06/11/97
06/10/97
06/10/97
06/03/97
All industrial radiography
licensees
All holders of OLs or CPs
for test and research
reactors
All holders of OLs or CPs
for nuclear power reactors
All holders of OLs or CPs
for nuclear power reactors
All holders of OLs or CPs
for nuclear power reactors
All holders of OLs or CPs
for pressurized-water
reactor plants
95-36, Supp. 1
97-32
97-31 OL = Operating License
CP = Construction Permit
IN 97-37 June 20, 1997 the fire to spread to that room and could have resulted in the loss of the A switchgear as
well.
The Pilgrim licensee enhanced the fire protection design in the turbine building by installing
containment curbs at the fire doors leading to the A essential switchgear room and the
stairway leading to the radwaste holding tanks, and modified the iso-phase bus duct by
installing an 8-inch diameter downcomer drain line on each of the three phases. Each drain
line is routed to drain into the oil leak retention pit, and will be equipped with a rupture disc
designed to open under 2 psig of static oil pressure in the drain line down-comer.
This information notice requires no specific action or written response. If you have any
questions about the Information in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
original signed by S.H. Weiss for
Marylee M. Slosson, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Patrick Madden, NRR
301-415-2854 E-mail: pmm@nrc.gov
David Skeen, NRR
301-415-1174 E-mail: dls2nrc.gov
Attachment: List of Recently Issued NRC Information Notices
Tech Editor has reviewed and concurred on 5/19197 DOCUMENT
NAME: G:XDLSUN97-XX.PLG
- SEE PREVIOUS CONCURRENCES
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05/27/97
06/13/97
//797
/
05/27/97
IN 97-XX
June XX, 1997 the fire to spread to that room and could have resulted In the loss of the A switchgear as
well.
The Pilgrim licensee enhanced the fire protection design In the turbine building by installing
containment curbs at the fire doors leading to the A essential switchgear room and the
stairway leading to the radwaste holding tanks, and modified the Iso-phase bus duct by
installing an 8-inch diameter downcomer drain line on each of the three phases. .Each drain
line is routed to drain into the oil leak retention pit, and will be equipped with a rupture disc
designed to open under 2 psig of static oil pressure in the drain line down-comer.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Marylee M. Slosson, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Patrick Madden, NRR
301-415-2854 E-mail: pmm@nrc.gov
David Skeen, NRR
301-415-1174 E-mail: dls@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:XDLSklN97-XX.PLG
- SEE PREVIOUS CONCURRENCES
OFC
TECH
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NAME
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DATE
06102197
05/27/97 A 97
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IN 97-XX
June XX, 1997 the fire to spread to that room and could have resulted in the loss of the A switchgear as
well.
The Pilgrim licensee enhanced the fire protection design in the turbine building by installing
containment curbs at the fire doors leading to the A essential switchgear room and the
stairway leading to the radwaste holding tanks, and modified the iso-phase bus duct by
installing an 8-inch diameter downcomer drain line on each of the three phases. Each drain
line is routed to drain into the oil leak retention pit, and will be equipped with a rupture disc
designed to open under 2 psig of static oil pressure in the drain line down-comer.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Marylee M. Slosson, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Patrick Madden, NRR
(301) 415-2854 E-mail: pmmenrc.gov
David Skeen, NRR
(301) 415-1174 E-mail: dlsenrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\\DLS\\lN97-XX.PLG
OFC
TECH
C:SPLB
C:PECB
D:(A)DRPM
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NAME
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DATE
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/97 OFFICIAL RECORD COPY]
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IN 97-XX
Month XX, 1997 The Pilgrim licensee enhanced the fire protection design in the turbine building by installing
containment curbs at the fire doors leading to the A essential switchgear room and the
stairway leading to the radwaste holding tanks, and modified the iso-phase bus duct by
installing an 8-inch diameter downcomer drain line on each of the three phases. Each drain
line is routed to drain into the oil leak retention pit, and will be equipped with a rupture disc
designed to open under 2 psig of static oil pressure in the drain line down-comer.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Marylee M. Slosson, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: Patrick Madden, NRR
(301) 415-2854 E-mail: pmm@nrc.gov
David Skeen, NRR
(301) 415-1174 E-mail: dls@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:IDLSUIN97-XX.PLG
OFC
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D:(A)DRPM
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