EMERGENCY WORKER RADIATION EXPOSURE MONITORING SYSTEM

5EMERGENCY WORKER RADIATION EXPOSURE MONITORING SYSTEM

Emergency workers include the following: radiation monitoring team personnel; transportation services (evacuation vehicle/bus drivers); law enforcement, fire fighting, and rescue personnel, including ambulance crews; personnel carrying out backup route alerting procedures; traffic control personnel; emergency operating center personnel; same personnel at institutional, health service, or industrial facilities, and some essential services or utility personnel (electric, gas, water, water treatment, telephone, etc.). These personnel are considered emergency workers only when their services are required to protect the health and safety of the general public during the emergency phase of an accident.

Emergency workers, such as radiation monitors, police, firemen, rescue personnel, ambulance crews, evacuation vehicle/bus drivers, and personnel carrying out backup route alerting or traffic control functions may be exposed to the airborne release while carrying out their missions.

Consequently, the means for measuring the radiation exposure of these personnel must be available at the beginning of the nuclear accident.

The objective of the emergency worker radiation exposure monitoring system is to minimize the exposure of emergency workers to radiation from the accident and to measure their accrued exposure. Three categories of data are needed for emergency worker exposure mission planning.

These categories are:

1. 
   Projected exposure rate patterns for planning purposes,
   
2. 
   Survey measurements to estimate radiation exposure at specific assigned emergency worker locations within the plume EPZ, and
   
3. 
   Personal dosimetry to measure accrued radiation exposure.
   

The primary radiation exposures of concern to emergency workers are: 1) whole body external exposure to gamma radiation from airborne particulates, gases, and particulate radioactivity deposited on or near the ground and 2) internal exposure to the thyroid from the inhalation of radioiodines. Consequently, dosimetry for external beta radiation is not required.

The PAGs^lviii for emergency workers are:

Category Whole Body Exposure Thyroid Exposure
Emergency Workers 25 rem 125 rem

Lifesaving Missions 75 rem No limit

5.1Projected Exposure Rate Patterns for Planning Purposes

Whenever emergency personnel are planning to undertake an operation, it is essential that the best estimate of the situation be known by the personnel directly involved. All sources of information, including projected exposure rate patterns, should be considered and a best estimate made of the exposure likely to be received during a specific mission. The mission must be planned by taking into consideration the most likely situation as well as the most potentially hazardous situation. Items to be considered include alternative entry and exit routes, potential changes in meteorological conditions, areas or roads to be avoided, equipment: and vehicle failure, and other relevant items.

5.2Exposure Rate Survey Measurements at Specific Emergency Locations

Radiation surveys of the exposure rates at all emergency locations where operations will be conducted are necessary in order to determine the amount of time available to workers for carrying out their emergency assignments.

Two types of measurements are required:

1. 
   Gamma radiation exposure rate measurements.
   

Low-range and high-range survey meters are required that can measure the gamma exposure rate from 0.1 mR/h to 100 K/h, as discussed in Section 4 for plume exposure rate verification.

2. 
   Radioiodine concentration measurements.
   

The airborne radioiodine concentration should be measured to estimate the thyroid dose commitment. This measurement requires an air sampler with an iodine absorber cartridge and a detection instrument. The equipment needed and a method for making this measurement are described in Appendix D.

Emergency workers on the monitoring teams involved in the plume exposure rate verification mast have the necessary equipment and instrumentation to conduct the measurements described in both Items 1 and 2 on the preceding page. Emergency workers assigned to non-plume exposure rate verification activities, such as route alerting or driving evacuation buses, should rely on their direct reading dosimeters as a means of monitoring their exposure. However, it would be desirable for those individuals assigned to access control points, e.g., special traffic control points established to prevent unauthorized access to evacuated areas, and fire and rescue personnel, including ambulance crews, to be equipped with one of the survey meters indicated in Item 1 on the preceding page.

5.3Measurement of External Gamma Radiation Exposure

Personal dosimetry should be provided to all personnel involved in emergency operations in any area where significant radiation exposures may be possible. Such dosimetry will provide data to the individual to control his/her exposure to gamma radiation while completing the mission assignment and to the organization's administrative records department to quickly document any significant radiation exposure to the worker. The major dosimetry systems^lix that should be considered as alternatives are:

1. 
   Direct or self-reading ionization chamber (pocket) dosimeters,
   
2. 
   Indirect or non self-reading ionization chamber (pocket) dosimeters,
   
3. 
   Thermoluminescent dosimetry (TLD) systems,
   
4. 
   Film badge systems, and
   
5. 
   Combinations of systems, e.g., TLD plus direct reading dosimeters.
   

From the radiological emergency standpoint, direct reading ionization chamber dosimeters are clearly the best system for measuring whole body gamma exposure for personnel and providing a continuous indication of the amount of the radiation exposure. The reasons for the recommendation of these devices include the following:

1. 
   A cumulative exposure for each individual can be read at any time or location without the need for ancillary equipment,
   
2. 
   They can be used repeatedly by simply recharging,
   
3. 
   They have a long shelf life with little to no maintenance requirements,
   
4. 
   The individual can directly read his/her exposure,
   
5. 
   They measure gamma exposure accurately and are reasonably energy independent from 70 keV to 2 MeV, and
   
6. 
   They are hermetically sealed at the time of manufacture and are relatively insensitive to environmental conditions.
   

The disadvantages to the use of the direct reading ion chamber dosimeter include the following:

1. 
   No permanent record of the exposure is possible except by manually recording the exposure readings,
   
2. 
   The exposure readings on the devices may be sensitive to a significant mechanical shock, e.g., if dropped more than a few feet to a concrete surface, and
   
3. 
   The initial cost is high.
   

Direct reading ionization chamber dosimeters are clearly the most desirable option, because the primary requirement for personal dosimetry for emergency workers is that an individual be able to read his/her exposure at any time to prevent the accumulation of excessive dose. Large quantities of dosimeters of this type have been used satisfactorily for years by industrial workers, civil defense personnel, and the military. However, the users of the direct reading dosimeters must have assurance that the dosimeters are capable of meeting the criteria of Standard N322-1977 of the American National Standards Institute.

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