Home > NRC Library > Document Collections > Generic Communications > Information Notices > 1991 > IN 91-60
Information Notice No. 91-60: False Alarms of Alarm Ratemeters Because of Radiofrequency Interference
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. . 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 . 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 .
Page Last Reviewed/Updated Tuesday, November 12, 2013