Information Notice No. 92-75: Unplanned Intakes of Airborne Radioactive Material by Individuals at Nuclear Power Plants
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
November 12, 1992
NRC INFORMATION NOTICE 92-75: UNPLANNED INTAKES OF AIRBORNE RADIOACTIVE
MATERIAL BY INDIVIDUALS AT NUCLEAR POWER PLANTS
All holders of operating licenses or construction permits for nuclear power
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert licensees to unplanned personnel intakes of radioactive
materials because of inadequate radiological, engineering, and procedural
controls regarding radiologically contaminated materials. It is expected that
recipients will review the information 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
During two events in 1991 at nuclear reactor facilities, licensee employees
received unplanned intakes of radioactive material while performing work in
radiologically controlled areas. The following discussions of these events
suggest inadequate licensee control in certain areas.
On May 23, 1991, four workers signed a radiation work permit (RWP) to enter
the torus room to remove insulation from a section of pipe. One was a health
physics technician (HPT) who was to provide continuous job coverage. All were
dressed in accordance with the RWP requirements, which included double
protective clothing (PC) and a negative pressure (particulate) respirator.
The HPT took an air sample just before removing the outer metal casing around
the insulation. When the casing was removed, parts of the insulation crumbled
into powder and formed a "cloud" of radioactive material in the air. The HPT
then surveyed the insulation and obtained a survey meter reading that was much
higher than expected, greater than 10 mSv/h (in the R/h range). The HPT
promptly ordered the workers to stop work and leave the area. All four of the
workers were contaminated, some in the chest area and some on the face. They
all had inhaled small amounts of radioactive material. The licensee estimated
that the intakes ranged between two and four maximum permissible
November 12, 1992
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concentration-hours (MPC-hrs). An air sample taken in the worker's breathing
zone in the torus room while the insulation was being removed showed airborne
radioactive concentrations of approximately 97 times MPC.
About 10 minutes after the four workers entered the torus room, two other
workers signed the same RWP to erect scaffolding in a room adjoining the torus
room. These workers did not wear respirators since the RWP did not require
respirators for use in the adjoining room. Consequently, after exiting the
area upon completing their work, both workers were found to be contaminated.
One was contaminated on the face and the other on the chest. The workers were
then decontaminated and sent to obtain a whole body count (WBC). The WBC
results for these two workers indicated much higher intakes than any of the
members of the first group (approximately 27 MPC-hrs). The airborne
radioactive material from the torus room was the source of their intakes; this
material entered the room through a gap in a sleeve around a pipe passing
between the two rooms. Natural convection between these two areas caused the
contaminated air to flow rapidly into the room where the two workers were
During the as low as is reasonably achievable (ALARA) pre-job review meeting
that was conducted to discuss the torus room scope of work, the licensee`s
ALARA group recommended using a high efficiency particulate air (HEPA)
filtration system while removing insulation. However, the licensee did not
use a HEPA filter system. Use of the HEPA system would have required removing
a heavy concrete floor plug to gain access to the torus room. To remove the
plug, the licensee needed to use a crane; maintenance personnel were requested
to remove the plug, but could not support the job in a timely manner.
Therefore, faced with a delay of several hours, the chief HPT and the
radiological supervisor (RS) decided to disregard the recommendation from the
ALARA group and deleted the HEPA system requirement from the RWP. However,
the chief HPT and the RS had not attended the pre-job ALARA briefing, where
workers stated that more insulation would need to be removed than originally
indicated and that health physics (HP) personnel had not surveyed this
additional larger area of insulation. As a result of missing the ALARA
briefing, the chief HPT and RS used incomplete information and inadequate pre-
job surveys in their decision to delete the HEPA system recommendation.
The decision to remove the insulation without using the HEPA system did not
prompt the licensee to reevaluate the adequacy of the respiratory protection
required by the RWP. For example, a negative pressure respirator has a
maximum protection factor of 50, while a positive pressure (continuous flow)
respirator has a maximum protection factor of 2000. Therefore, a positive
pressure respirator would have better protected the workers.
The licensee evaluated this event and found inadequate communication between
the insulation removers, the ALARA group, and HP personnel, and reached the
following conclusions. The scope of work was not communicated adequately to
radiation protection personnel. Also, the ALARA group did not adequately
consider the information presented by insulation removers regarding the
condition of the insulation and the amount of insulation to be removed. .
November 12, 1992
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Further, the change in job scope did not prompt the licensee to reevaluate the
adequacy of the initial planning and job requirements.
On March 25, 1991, a group of maintenance workers entered the reactor cavity
to perform general inspections and housekeeping activities in preparation for
flooding of the cavity. Access to the transfer canal was roped off and posted
with a sign stating "Caution: Do Not Enter." [The transfer canal is a narrow
passageway that connects the reactor cavity to the spent fuel pool (SFP) and
is used to transfer fuel between the two areas.] The RWP specified "Entry
Into The Transfer Canal Prohibited Under This RWP." The reactor cavity had
been decontaminated, but the transfer canal had not; personnel conducting the
last transfer canal survey had found loose contamination levels of 0.24 mGy/h
(24 mrad/h), smearable.
The licensee job leader (JL) and his crew entered the cavity after signing the
RWP. They inspected the reactor vessel flange and started general
housekeeping activities, including vacuum cleaning of the cavity area. During
these activities, the crew found indications of a surface defect in the vessel
flange. As a result, the JL summoned assistance from Reactor Services Section
(RSS) personnel. The RSS superintendent and another RSS engineer entered the
cavity to inspect the flange. After the engineers inspected the flange, the
crew removed the service platform and completed its housekeeping. The JL then
removed the rope and the "Caution: Do Not Enter" sign at the entrance to the
transfer canal. The work crew then removed a "stop log gate," (a large gate
installed between the transfer canal and the SFP), at the end of the transfer
canal near the SFP. While the gate was being lifted, the JL noted that some
sealant material had broken off and fallen on the floor of the transfer canal.
Since the vacuum cleaner had been removed from the cavity, the JL asked that a
brush and dustpan be sent down.
The JL then entered the transfer canal. Even though he had just removed the
rope barrier and sign, the RWP prohibiting such entry was still in effect.
Therefore, he was in violation of the RWP. While cleaning the transfer canal,
he noticed some damage to the stop log gate guides, and exited the canal to
summon the RSS engineers to inspect the guides. The JL then escorted the two
engineers into the transfer canal to perform the inspection, again in
violation of the RWP.
On leaving the cavity, the JL removed his protective clothing and went to the
whole body contamination monitor on the refueling floor to check for
contamination. The monitor alarmed, and a later survey indicated
contamination around his neck and upper torso. HP personnel escorted the JL
to a decontamination facility where extensive decontamination efforts were
performed. However, no change in count rate was noted, indicating a possible
intake of radioactive material. The licensee final estimate of the intake was
less than 50 MPC-hr.
November 12, 1992
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The region held an enforcement conference with the licensee to discuss NRC
staff concerns with programmatic weaknesses, including procedure violations,
inadequate HP controls, poor communication between the JL and HP, and an
inadequate understanding of the hazards that can result from using a dustpan
and brush in a highly contaminated area.
Section 20.103(b) of Title 10 of the Code of Federal Regulations
(10 CFR 20.103), "Exposure of individuals to concentrations of radioactive
materials in air in restricted areas," requires the use of process or other
engineering controls, to the extent practicable, to limit concentrations of
airborne radioactive material. In the Fitzpatrick case, the HEPA filtration
system was an available engineering control. When the use of these controls
is not practicable, the licensee is required to use other precautionary
procedures, such as increased surveillance, limitation of working times, or
provision of respiratory protective equipment to limit personnel intakes of
radioactive material to as low as is reasonably achievable.
Worker intakes of radioactive material at nuclear power plants are generally
far below the limits of 10 CFR Part 20. During normal plant operation,
airborne radioactive material is of little concern. However, the events
discussed herein demonstrate the need for vigilance in conducting maintenance
activities that could significantly increase airborne radioactive material.
These examples indicate that some licensees have not adequately implemented
certain radiological control requirements. In both of these events, process
or other engineering controls, (e.g., HEPA filtration systems, roped-off areas
and pre-work ALARA briefings) were available to help control the intake of
airborne radioactive material, but were not effectively used.
This information notice requires no specific action or written response. If
you have any questions about this matter, please call the technical contact
listed below or the appropriate Nuclear Reactor Regulation (NRR) project
ORIGINAL SIGNED BY
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Jack M. Bell, NRR
Daniel R. Carter, NRR
Ronald L. Nimitz, RI
Attachment: List of Recently Issued NRC Information Notices
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