United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 83-83: Use of Portable Radio Transmitters Inside Nuclear Power Plants

                                                            SSINS No.: 6835 
                                                            IN 83-83       

                                UNITED STATES
                        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 

Addressees: 

All nuclear power reactor facilities holding an operating license (OL) or 1 
construction permit (CP). 

Purpose: 

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. 

8311010034 
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                                                          Page 2 of 3      

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. 

Discussion: 

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 
part, nuclear 
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                                                          IN 83-83         
                                                          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
                    (301) 492-4973

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