Information Notice No. 83-83: Use of Portable Radio Transmitters Inside Nuclear Power Plants
SSINS No.: 6835
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
December 19, 1983
Information Notice No. 83-83: USE OF PORTABLE RADIO TRANSMITTERS INSIDE
NUCLEAR POWER PLANTS
All nuclear power reactor facilities holding an operating license (OL) or 1
construction permit (CP).
This information notice is to apprise you of reported instances in which
portable radio transmitters caused system malfunctions and spurious
actuations in nuclear power plants. No specific action is required in
response to this information notice, but it is expected that recipients will
review the information for applicability to their facilities.
Description of Circumstances:
Events over the past few years have caused concern in the NRC staff
regarding the potential of portable radio transmitters (commonly referred to
as walkie-talkies) to cause system malfunctions and spurious actuations. The
following four examples describe two events in which a safety-related system
was affected and two in which a non-safety-related system was affected.
The first example occurred at Grand Gulf on July 25, 1983, in which shutdown
cooling loop B was lost for 30 minutes because of a spurious isolation trip.
The isolation was initiated by an RHR equipment area high temperature trip
which immediately cleared. Rather than restart the loop immediately, the
operators first verified that no leak was present and thus the area high
temperature indication was false. Since shutdown cooling loop A was
inoperable at the time the reactor water clean up system was used as the
alternate heat removal system.
The licensee conducted an investigation, including an after-the-fact
interview with personnel who were in the vicinity of the trip circuitry. The
licensee concluded that the most plausible cause was an accidental keying of
a two-way FM radio near the trip unit. The licensee has and continues to
forbid the use of the radios for transmission in the vicinity of the control
room or near panels.
The walkie-talkie that was used has a power output of approximately 4 watts
in the frequency range of 451-456 MHz. The walkie-talkie was accidently
keyed in the upper cable spreading room which is the location of the RHR
equipment area high temperature trip unit (a Riley temperature switch model
PTGF-EG.) This temperature switch is a solid state device that is connected
by 16 AWG copper shielded cable to a thermocouple.
December 19, 1983
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The second example of a spurious actuation caused by a walkie-talkie
occurred at Sequoyah 1 on May 31, 1979. A health physics technician who was
in the in-core instrument room was attempting to communicate with the
control room when he keyed his walkie-talkie resulting in a spurious signal
to all four channels of pressurizer pressure initiating a safety injection.
The incore instrument room is located inside containment. The event was
duplicated intentionally with the same results.
The third example occurred at Three Mile Island on February 19, 1982.
Workers were preparing to enter the containment for some cleanup work when
combustible gas monitors they were carrying indicated the presence of
hydrogen and low levels of oxygen. The workers became suspicious when the
readings varied with the use of their face mask radios. Later gas sampling
outside of containment verified that the face mask radios caused false
readings on the combustible gas monitors.
The fourth example occurred at Farley in 1975. During initial energization
of a 600-V load center, a false operation of the transformer differential
relay was observed. The licensee determined that the Differential Relay Type
12 STD 15B5A is radio frequency sensitive and trips with an activated
transceiver located within approximately five feet of the relay. A test
revealed that the activated transceivers, having frequencies between 150 MHz
and 470 MHz with power ratings of 5-watt input to the final radio frequency
amplifier and placed within a radius of approximately 5 feet of the relay,
caused the differential relay operation. As a further test, the relay was
subjected to test currents of 0.5 amp and 5 amp applied to the restraint
windings to determine if the relay was less sensitive to radio frequencies
under simulated operating conditions. This test again resulted in a false
operation of the relay.
This GE Type STD differential relay is a solid state device with certain
parts mounted on a printed circuit board which apparently pick up a signal
from a transceiver and feed it into the relay amplifier. This would result
in the amplified signal passing into the operate section of the relay which
causes the false operation.
To date, solid state devices installed in nuclear power plants have been
responsible for all of the known cases of radio frequency interference (RFI)
generated by portable radio transmitters. Three of the four examples cited
in this information notice occurred during preoperational testing or early
in plant operation.
Many of the older nuclear power plants have so few solid state devices that
this explains their apparent invulnerability to RFI generated by portable
radio transmitters. As newer plants are built that use more solid state
equipment and as older plants retrofit solid state equipment, more cases of
RFI by portable radio transmitters are likely to result.
The use of portable radio transmitters, e.g., walkie-talkies, has been
common practice at many operating nuclear power plants, and for the most
December 19, 1983
Page 3 of 3
power plants have shown themselves to be largely, although not entirely,
invulnerable to the RFI that such radios generate. When such RFI has been
demonstrated to be a problem, nuclear power plants have successfully dealt
with the problem by prohibiting the use of portable radio transmitters in
certain areas. Nevertheless, the vulnerability of safety systems and
nonsafety systems to inadvertent actuation or malfunction poses a
significant threat to safe operation of the plant if the measures to prevent
use of radio transmitters fail under emergency situations.
Emergency situations in which posted restrictions on the use of portable
radio transmitters are likely to break down include those instances in which
individuals other than plant operating personnel may be present in the plant
or in which operating personnel are performing non-routine functions. Such
situations include but are not limited to firefighting, bomb searches, and
local operation of equipment normally performed from the control room.
Plans for dealing with such emergency situations require consideration of
the possibility for RFI if the nuclear power plant has a demonstrated or
implied vulnerability. When solid state equipment is retrofitted into an
existing plant, the potential for RFI vulnerability suggests that the
licensee should evaluate the impact on plant operation and safety.
The use of the increasingly popular cordless telephones presents another
possible source of RFI.
If plant operations make the use of portable radio transmitters near RFI-
sensitive equipment either necessary or likely in an emergency, then
administrative prohibitions are not adequate and the licensee should
consider hardware fixes. Typically such fixes include use of filters,
shielded cables, and modification of the affected equipment. Although there
are many industrial standards regarding RFI protection techniques, the NRC
has not formally adopted or endorsed any, nor are there any nuclear
standards that specifically address RFI protection.
As part of a wider program, the NRC is conducting research in the area of
electromagnetic interference (EMI), including RFI as one of its aspects.
Edward L. Jordan Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contact: Eric Weiss, IE
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