EML-624 A FIRST RESPONDERS GUIDE TO PURCHASING RADIATION PAGERS FOR HOMELAND SECURITY PURPOSES Paul Bailey Environmental Measurements Laboratory U.S. Department of Homeland Security 201 Varick Street, 5 th Floor New York, NY 10014-7447 August 2004 DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability nor responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. This report has been reproduced directly from the best available copy. Available to the public from the U.S. Department of Commerce, Technology Administration, National Technical Information Service, 5285 Port Royal Road, Springfield, Virginia 22161, (703) 487-4650.
August 2004 A First Responders Guide to Radiation Pagers Page 2 of 11 TABLE OF CONTENTS 1. Introduction and Scope...3 2. Overview of Radiation Pagers and Their Role in a Conduct of Operations...3 2.1 What a Radiation Pager Is...3 2.2 What a Radiation Pager Is Not...4 2.3 When a Radiation Pager Alarms...4 3. How the Radiation Pager Is Designed to Alarm...6 4. Detailed Examples of Using a Radiation Pager...6 4.1 Locating Increased Levels of Radiation...6 4.2 Localizing a Radiation Source...7 4.3 Primitive Radiation Protection...7 5. Physical Factors...7 5.1 General Physical Factors...7 5.2 Required Maintenance and Calibration...9 5.3 Decontamination...9 6. Special Considerations Specific to Radiation Pagers...10 6.1 Dose and Energy Compensation...10 6.2 Range of Dose Rate Reading and Measurement...10 6.3 Neutron Detection...11 6.4 Computer Interface (Getting the Readings on a PC)...11 7. Training...11 8. References...11
August 2004 A First Responders Guide to Radiation Pagers Page 3 of 11 1. INTRODUCTION AND SCOPE Most of the hard work of finding a good radiation pager has already been done. The United States Department of Homeland Security (DHS) Science and Technology Directorate led an effort to develop a consensus standard for radiation pagers. The result was ANSI N42.32-2003 (or just N42.32). This standard is intended to provide a means for verifying the capability of these instruments to reliably detect significant changes above background levels of radiation and alert the user to these changes. This standard (N42.32) is a performance standard. Organizations that use radiation pagers need not read or understand N42.32 DHS will identify those radiation pagers that meet the requirements of N42.32. However, N42.32 specifies a minimum performance requirement in only a limited number of areas. Other considerations are left up to the consumer that are specific to specific missions the pagers are intended to aid. This document describes additional considerations for the purchase of radiation pagers that are not covered in ANSI N42.32. Also described are the sorts of missions a radiation pager can aid; how-to sections on using radiation pagers are also included. 2. OVERVIEW OF RADIATION PAGERS AND THEIR ROLE IN A CONDUCT OF OPERATIONS 2.1 WHAT A RADIATION PAGER IS A radiation pager can detect, and alert a minimally trained wearer to the presence of, small increases in the levels of ionizing radiation. The wearer should be able to use the radiation pager effectively while performing other tasks; that is, the pager should not require the attention of the wearer until it alarms. As secondary tasks, a radiation pager may be useful for locating a radiation source and providing crude radiation safety information (radiation dose rate information). These uses are detailed in section 4 of this document.
August 2004 A First Responders Guide to Radiation Pagers Page 4 of 11 2.2 WHAT A RADIATION PAGER IS NOT A radiation pager is not an accurate radiation dosimeter. 1 A radiation pager is not a radionuclide identifier. For example, it will not be able to differentiate the commonly used medical radionuclide technicium-99 ( 99 Tc) from the potential dirty bomb radionuclide cobolt-60 ( 60 Co). Finally, a radiation pager s size and weight constraints render it incapable of achieving the sensitivity of most larger detectors. 2.3 When a Radiation Pager Alarms Radiation pagers do not always alarm when in the presence of radioactive materials. This can happen for any of the following reasons: A detector malfunction. The radiation source is well shielded. This usually involves a large mass of dense metal such as lead. The source is not emitting a sufficient number of gamma rays or neutrons some materials emit almost entirely nonpenetrating radiation. The source is too far from the detector. The source is of insignificant size. 1 Most radiation pagers on the market use the units of radiation dosimetry and appear to be calibrated in these units. However, none meets the widely accepted standard for radiation dosimetry (ANSI N13.11) and few of the available units even record the wearer s radiation dose. This is because measuring radiation dose accurately almost always involves decreasing the sensitivity of the radiation detector, which is contradictory to the goal of a radiation pager. There are electronic personal dosimeters, designed for radiation safety, that can be relied upon to alarm when there is even the slightest health threat, with near zero possibility of false alarm. None of these operate at radiation levels that are low enough to meet N42.32 s stringent response requirements.
August 2004 A First Responders Guide to Radiation Pagers Page 5 of 11 If a radiation pager is alarming because of gamma-ray radiation, it can be assumed that there is a radiation source in the vicinity. The cause off the alarm can be categorized as follows: A detector malfunction. Response to electromagnetic or other interference. A random false alarm. 2 An innocent alarm. This implies that the gamma-ray radiation rate increased, but the source is benign. Possible sources of innocent alarms include: o Medical patients who recently received radiological treatments o Changes in the natural radiation environment, such as the slight increase during a rainstorm or changes in surrounding construction materials. o Licensed radioactive material. Illicit radioactive material. If a radiation pager has a separate neutron counter and is alarming because of neutron radiation, the alarm is much more likely to be significant. Possible reasons for the alarm can be categorized as follows: A detector malfunction. A nearby very large mass of metal (for example, a measurements taken on a ship). An innocent alarm. o A well logger. o A moisture density gauge. Illicit radioactive material such as fissile material. 2 False alarms are usually distinguishable from true alarms after some experience with a radiation pager. A false alarm usually involves only one pulse or beep while real alarms are sustained.
August 2004 A First Responders Guide to Radiation Pagers Page 6 of 11 3. HOW THE RADIATION PAGER IS DESIGNED TO ALARM The radiation pagers presently on the market are not all designed to alarm the same way. There are two general concepts of operation for radiation pagers that span today s market of radiation pagers. The most basic mode of operation is for the radiation pager to alarm when the measured radiation field is more intense than a preset alarm level. A second concept of alarm operation starts with the radiation pager measuring a background value and then alarming based on the measured radiation field using a statistical test. 3 There are advantages and disadvantages to the two applicable alarm modes of operation. Radiation pagers that alarm based on a statistical test are more adaptable and more sensitive; however, they may require more attention on the part of a wearer. This is because certain areas or buildings have increased natural radiation and when a wearer enters such an area the alarm may go off. Radiation pagers that alarm based on an absolute alarm set point can be programmed to avoid false alarms almost completely, even when the wearer is in changing natural background environments, by using an elevated set point; however, this comes at the price of not detecting real alarms at low levels. 4. DETAILED EXAMPLES OF USING A RADIATION PAGER 4.1 LOCATING INCREASED LEVELS OF RADIATION When locating increased levels of radiation, the wearer will usually have his attention focused on another task. The radiation pager will be attached to the wearer and the wearer will walk past a radiation source or a radiation source will pass the wearer. The alarm should be triggered and attract the user s attention immediately. If the wearer is alerted to the radiation source only after moving well past the source, the radiation pager may not be of much value. 3 This method is simplified here for clarity.
August 2004 A First Responders Guide to Radiation Pagers Page 7 of 11 4.2 LOCALIZING A RADIATION SOURCE To effectively localize a radiation source, the wearer must focus attention on the radiation pager, perhaps holding it in hand. 4 Observing the reading or alarm intensity, the wearer should try to find where intensity is highest by moving the radiation pager around and closing in on the higher readings. The source has been localized when the radiation pager s reading cannot be increased by moving it to a new location. 4.3 PRIMITIVE RADIATION PROTECTION If the radiation pager reads out in the units of dose or has a scale indication that can be correlated to the units of dose, the device can be used for crude radiation protection. The wearer can simply move around with the radiation pager in hand until the reading is less than a predetermined level. Keeping the pager at or below this level, the wearer can even trace out an area of concern and use this information to restrict access to that area. As a cautionary note: some pagers may not be well suited to this task because of a design flaw that causes them to read very low numbers when the radiation intensity gets extremely high. See section 6.2 or ask the manufacturer for more details about the detector s response at high dose rates. What dose rate is appropriate is outside the scope of this document. However, guidance on this topic is being developed. 5. PHYSICAL FACTORS 5.1 GENERAL PHYSICAL FACTORS While ANSI N42.32 does include suggested physical characteristics of a radiation pager, each organization has its own set of needs and perhaps some extreme conditions. Common considerations include expected temperature range of use, alarm modes needed, size and weight, attachment mechanism, battery life, and the likelihood of radio interference. 4 This can be helpful because the wearer s own body can block the radiation from reaching the detector.
August 2004 A First Responders Guide to Radiation Pagers Page 8 of 11 Expected temperature range Temperature extremes can render a radiation pager useless temporarily or even permanently. In general, most liquid crystal displays (LCDs) will fail at low temperatures, but alarms may continue to work. At high temperatures, the device may become less sensitive and it may display values that are too high or too low. N42.32 requires that the pager function from 4 F to 122 F. Alarm modes Most pagers can beep as an alarm. Some have the option of a silent (vibratory) alarm; others have blinking lights. In general N42.32 only requires that the alarm be capable of getting the wearer s attention, so each organization must decide on its own alarm mode needs. Size and weight The device s size and weight is often an issue for first responders. N42.32 only suggests a weight of less than 1 pound; most organization will have more strict requirements. Attachment mechanism The radiation pager should have a method of attachment to the wearer that is acceptable for the intended use. N42.32 only requires that some attachment mechanism exists, leaving it up to the organization to determine what attachment mechanisms are appropriate. Battery life The battery life and replacement or recharge schedule can be important, and N42.32 is very liberal. The standard only requires that replaceable batteries be commercially available and field replaceable, and that a low-battery warning light come on 4 hours before the unit fails.
August 2004 A First Responders Guide to Radiation Pagers Page 9 of 11 Radio interference Because radio communications are a rapidly changing area and close-range radio interference can be difficult to measure and to simulate in a laboratory setting, an instrument meeting ANSI N42.32 may or may not function in close proximity to a twoway radio, anti-shoplifting portals, power stations, or transformers. Radiation detection equipment is especially unlikely to function properly near a radio repeater. The most likely indication of failure due to radio interference is spurious high measurements and spurious alarms. Organizations may want to test the radiation pager with their radio equipment or notify users of the possibility of this type of false alarm. 5.2 REQUIRED MAINTENANCE AND CALIBRATION Most pagers require little more than battery changes and occasional calibration. In addition, organizations may want to implement a functional check. A functional check makes sure that the device is still functioning. An example of a functional check is keying up a two way radio a few times at the start of a shift to make sure that it is on and working. Some manuals include a procedure for a functional check, but others do not. While the manufacturer may be one possible source of a daily functional check, the possibility of setting up your own should be considered. A local hospital or other contacts who routinely handle radioactive materials may be able to help develop appropriate procedures. Naturally occurring radioactive materials can also be used to verify that the pager can still alarm. A granite building face or bags of deicing or water softening salt that contains potassium (K) are good examples of readily available materials. 5.3 DECONTAMINATION During the course of a nuclear weapons event or a radiological dispersal event, a radiation pager may become contaminated. A radiation pager is contaminated when
August 2004 A First Responders Guide to Radiation Pagers Page 10 of 11 radioactive material is on or in the pager. A radiation pager that is severely contaminated with a gamma-ray emitting radionuclide will be of little use, since it will largely read radiation from itself. A contaminated radiation pager may be decontaminated, or it may have to be disposed of as a contaminated material. Before purchasing a pager, it may be useful to discuss a decontamination procedure with the manufacturer. 6. SPECIAL CONSIDERATIONS SPECIFIC TO RADIATION PAGERS 6.1 DOSE AND ENERGY COMPENSATION Energy compensation is the act of changing a radiation detector so that its reading is proportional to the health hazard of the radiation on humans. This compensation is generally accomplished at the cost of sensitivity and is therefore often undesirable for a radiation pager, whose primary function requires that it be sensitive to small changes in the radiation field. 6.2 RANGE OF DOSE RATE READING AND MEASUREMENT When dealing with intense sources, the pager needs to have a high range in order to be able to locate the source. If the radiation pager reaches its maximum too soon it will simply be off-scale when the wearer gets close to the hot radiation source. Radiation pagers that read high dose rates will be more useful for locating a more radioactive source. In addition, when the radiation level gets very high, some radiation pagers readings may begin to decrease. This can be very dangerous if the wearer is attempting to use the radiation pager for radiation protection. N42.32 requires that this not happen until twice the radiation pager s off-scale reading is reached, but this is not a very stringent requirement and severely limits the wearer s ability to use radiation pagers for radiation protection. Manufacturers should know when their pager s reading begins to decrease due to elevated radiation.
August 2004 A First Responders Guide to Radiation Pagers Page 11 of 11 6.3 NEUTRON DETECTION Some radiation pagers have been designed to detect neutrons distinct from gamma rays. Detection of neutrons is valuable because they are the most penetrating radiation type that can be detected by homeland security instrumentation. There are also very few legal neutron sources, so the presence of neutrons makes it more likely that the radioactive material is associated with an illicit activity. However, the limiting factor in the pager s capability to detect neutrons is its physical size. Even a perfectly designed radiation pager is unlikely to be able to detect even a minimally shielded neutron source of interest from more than 6 feet away. 6.4 COMPUTER INTERFACE (GETTING THE READINGS ON A PC) Many radiation pagers on the market can store readings and later download them onto a computer. The exact details of what is stored and how it is read is not at all consistent or standardized in N42.32. Because of this, any organization that requires data storage of pager operation should carefully specify the needs for computer interface and identify what data is required before make a purchasing decision. 7. TRAINING Currently there are no national training centers for using radiation pagers, however, since the only necessary function of a radiation pager is to alarm, most of the training can focus on your organizations conduct of operations. In addition, DHS is presently developing a training standard that will encompass radiation pagers. 8. REFERENCES ANSI N42.32-2003, Performance Criteria for Alarming Personal Radiation Detectors. ANSI N42.32-2003 is referred to in this document simply as N42.32.