Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
WASHINGTON, D.C. 20555
September 24, 1991
NRC INFORMATION NOTICE 91-60: FALSE ALARMS OF ALARM RATEMETERS
BECAUSE OF RADIOFREQUENCY INTERFERENCE
Addressees
All Nuclear Regulatory Commission (NRC) licensees authorized to use sealed
sources for industrial radiography.
Purpose
This information notice is being issued to alert licensees to recently
reported false alarms of alarm ratemeters. These false alarms reportedly
occurred when the alarm ratemeters were exposed to radiofrequency
interference (RFI) originating from different sources, including a variety
of radar, welding machines, and hand-held radios. Except for permanent
radiography facilities where other appropriate alarming or warning devices
are in routine use, radiography personnel are required, by 10 CFR 34.33, to
wear an alarm ratemeter when performing radiographic operations. It is
expected that licensees will review this notice, distribute it to
responsible staff, and consider actions, as appropriate, to avoid similar
problems. However, suggestions contained in this information notice do not
constitute any new NRC requirements, and no written response is required.
Description of Circumstances
An NRC licensee recently advised NRC of incidents in which alarm ratemeters
alarmed because of apparent RFI, not because of ionizing radiation levels
exceeding background. In one instance, alarm ratemeters worn by radiography
personnel began to continuously alarm as the individuals climbed onto an
open deck of a ship on their way to a work site. No radiographic
operations were being conducted in the area. The individuals immediately
surveyed their radiography equipment with their radiation survey instruments
and did not detect high radiation levels.
The individuals' self-reading dosimeters also showed no apparent radiation
exposure. Licensee investigation determined that the likely source was
either shipboard radar or other RFI emitters. The licensee also reported
that there had been several other instances of false alarms that occurred
when alarm ratemeters were located: (1) within 20 feet of hand-held two-way
radios operating at frequencies around 800 megahertz (MHz); (2) within 1
foot of portable radios operating on frequencies ranging upward from about
130 MHz; (3) near welding machines; (4) in the vicinity of various radar
systems; and (5) near various pieces of electronic office equipment.
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IN 91-60
September 24, 1991
Page 2 of 3
One alarm ratemeter manufacturer indicated to NRC that other users have also
reported RFI induced false alarms. These reports all appear to involve the
same ratemeter model. This manufacturer also reported that several returned
alarm ratemeters appeared to have been purposely damaged by users in an
effort to defeat the devices.
Several manufacturers are already aware of the effects of RFI on alarm
ratemeters and are in the process of correcting the problem. Licensees who
have questions concerning their alarm ratemeter's susceptibility to RFI
should contact the manufacturer directly.
Discussion
Licensee personnel should be instructed to be aware of the possible presence
of RFI sources, such as two-way radios, that may interfere with radiation
detection and measurement equipment, including alarm ratemeters. Such RFI
sources may be found at temporary job sites such as construction sites,
shipyards, and aviation facilities.
Licensees should also familiarize themselves and their radiography personnel
with other operating aspects of their alarm ratemeters so that they may
recognize false alarms that could result from depleted batteries, a device
malfunction, or other conditions.
Radiography personnel should be provided with guidance to be followed in
case an alarm ratemeter alarms. It is essential that radiography personnel
avoid complacency about false alarms, regard all alarms as the result of
elevated radiation exposure levels, and act accordingly until they are able
to assure themselves, through radiation surveys and examination of
self-reading dosimeters, that the alarm is not caused by ionizing radiation.
The manufacturer's report of possible intentional damage to alarm ratemeters
is of concern to NRC. Intentionally damaging and then using the damaged
device when performing radiographic operations will be viewed as a willful
violation of NRC regulations and considered for appropriate enforcement
action, including civil penalties; license modification, suspension, or
revocation; or orders to remove individuals from licensed operations.
Licensees are reminded that the recent amendment to 10 CFR 34.33 (effective
January 10, 1991) requires that radiography personnel use alarm ratemeters
that alarm at a preset dose rate of 500 mR/hr. This amendment also
specifies that ratemeters must be checked before use, to ensure that the
alarm properly functions (sounds).
Although the use of alarm ratemeters will help to alert personnel to
possible hazardous radiation levels, it is important that licensees
emphasize to radiography personnel that alarm ratemeters are NOT intended to
replace the use of survey meters or the performance of thorough radiation
surveys during industrial radiography operations. As was recently discussed
in Information Notice No. 91-23, significant consequences, including
serious bodily injuries or death, may result from the failure to perform
adequate radiation surveys and properly handle industrial radiography
equipment. Licensees are also reminded
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IN 91-60
September 24, 1991
Page 3 of 3
that failure to have present, or to use, radiographic equipment, radiation
survey instruments, and/or personnel monitoring devices, as required by 10
CFR Part 34, will be cited as Severity Level III violations and may lead to
civil penalties. NRC's enforcement policy in this area is further discussed
in NRC Information Notice 91-49, "Enforcement of Safety Requirements for
Radiographers."
No written response is required by this information notice. If you have any
questions about this matter, please contact the appropriate Regional Office
or this Office.
Richard E. Cunningham, Director
Division of Industrial and
Medical Nuclear Safety
Office of Nuclear Material Safety
and Safeguards
Technical contacts: Torre Taylor, NMSS
301-492-0611
John M. Pelchat, Region II
404-331-5083
Attachments:
1. List of Recent NMSS Information Notices
2. List of Recent NRC Information Notices
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