Proper Operation and Use of Alarm Dosimeters at Nuclear Power Plants
See the memorandum with enclosure from L. J. Cunningham to J. H. Joyner (and others) dated November 15, 1993.
This NRR memo was written by the Radiation Protection Branch in response to numerous inspection report findings and regional requests for guidance on the proper use and operation of alarm dosimeters. NMSS, RES, and Regional comments were considered in the development of this health physics position.
IMPROPER USE AND OPERATION OF ALARM DOSIMETERS: The following examples illustrate the types of problems occurring with alarm dosimeters (ADs) at nuclear power plants:
ADs not operated in the proper mode for their intended use [e.g., ADs used in the accumulated dose (integrating) mode when the licensee procedure or RWP requires use in the dose-rate mode].
Personnel continuing to work in high radiation areas rather than leaving when their AD alarms in the integrating mode.
HP personnel issuing ADs to individuals without telling them the proper mode of operation or the alarm setpoints.
Contract HP technicians not receiving training on the AD in use at the current facility (different facilities use different ADs).
ADs routinely being placed in plastic bags or inside the pockets of PCs to prevent contamination. These actions decrease the ability of the wearer to hear the AD alarms, particularly in high noise areas requiring hearing protection.
CALIBRATION OF ALARM DOSIMETERS: Regulatory Guide 8.28, "Audible-Alarm Dosimeters," states that audible-alarm dosimeters are not generally substituted for conventional survey meters. While this is technically correct and consistent with good HP practice, TS 6.12.1 allows an audible-alarm dosimeter to be used instead of a survey meter or HPT accompaniment after the dose rates in the area have been measured with a survey meter and the workers in the area have been informed of the measured dose rates.
10 CFR 20.1501 (b) states: "the licensee shall ensure that instruments and equipment used for quantitative radiation measurements (e.g., dose rate and effluent monitoring) are calibrated periodically for the radiation measured." Using an ADs cumulative alarm setpoint to initiate worker actions in HRAs (i.e., exit an area when the alarm sounds) meets the intent of the above regulation. Based on the above requirements, ADs should be part of a routine instrument calibration program if they are used to satisfy the requirements under 10 CFR 20.1501 (b) or if used under 10 CFR 20.1601 (c) "alternative methods" as specified in TS 6.12.1 as a condition for entry into high radiation areas.
TRAINING IN PROPER USE OF ALARM DOSIMETERS: In 10 CFR 19.12, "Instructions to Workers", it is stated: "all individuals working in or frequenting any portion of a restricted area shall be kept informed of the storage, transfer, or use of radioactive materials or of radiation in such portions of the restricted area; . . . shall be instructed in the purposes and functions of protective devices employed, . . . and instructed in the appropriate response to warnings made in the event of any unusual occurrence or malfunction that may involve exposure to radiation or radioactive material." To meet these 10 CFR Part 19 requirements, a licensee needs to train personnel in the proper operation of ADs. This training should minimally include: (1) different modes of operation, integrated dose and dose-rate; (2) the different types of alarms, including the different sounds of each alarm; (3) actions to be taken when receiving an alarm, leave the area and contact health physics or move to a lower dose-rate area; and (4) guidance for proper use of the ADs. The guidance for proper use as adapted from RG 8.28 is as follows:
An AD should not routinely be used as a survey meter (removed from the body and used to check dose rates in the area).
Care should be taken to avoid dropping ADs, but if dropped, the ADs proper operation should be verified.
ADs should normally not be used in high noise areas, when a user has a pronounced hearing loss, or when the AD would be muffled by heavy clothing (e.g., PCs). When ADs are used in high noise areas, workers should be instructed to frequently check their ADs visually (similar to reading a pocket ion chamber) or be equipped with a warning device (e.g., remote ear-piece or visual flashing light).
Source and battery checks should be done daily when the ADs are in use and before the first use.
Regulatory references: 10 CFR 19.12, 10 CFR 20.1501, 10 CFR 20.1601, ANSI N13.27-1981, Regulatory Guide 8.28, Technical Specifications
Subject codes: 1.2, 6.1, 6.4, 7.1, 8.1