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Action 5: Build a Fallout Mapping System

Download full checklist (PDF) • See phased implementation plan

Establish a rapid system for mapping and monitoring the dangerous fallout zone to specify which residents need to take what protective action.

Rapidly determining the DFZ (an immediate health threat) and the wider area of contamination will be critical to guiding the public and responders on protective actions. Larger radioactive particles will settle out within 1-2 hours of the nuclear detonation, creating the DFZ footprint.5 Identification of the DFZ perimeter should occur within the first hours of the detonation to guide response planning and strategies for an informed, delayed evacuation.22 On-the-ground federal support may not be available for 24 to 72 hours or longer, so local jurisdictions should plan in advance to characterize fallout deposition and radiation levels on their own at the outset.5 Until detailed measurements are obtained, the DFZ can be conservatively defined as extending 20 miles downwind in a keyhole pattern6 (see Figure 1). This rough sketch can be refined once modeling of the fallout plume becomes available and actual dose readings from the ground are taken. (Some jurisdictions are prepared to do this on their own, while others will rely on a federal agency like the Department of Energy [DOE]) Knowing the actual fallout footprint and radiation dose levels can vastly improve guidance about where to locate response staging areas, which residents need to evacuate, how soon, which routes present the lowest possible dose, and when and where residents may eventually return.


Task 5.1—Develop relationships in advance with federal partners; plan to integrate their contributions to fallout mapping and radiation measurements.

Before an incident occurs, local jurisdictions should contact federal partners with radiological assets and solicit their help in developing nuclear response plans. (See NCRP Report #16522 for a list of federal resources and activation times.) Ideally, jurisdictions (or their states) already have good working relationships with regional all-hazard federal partners such as FEMA Regional Administrators (RAs), DHHS/Assistant Secretary for Preparedness and Response (ASPR) Regional Emergency Coordinators (RECs), and DOD Defense Coordinating Officer & Elements (DCO/E); such partners may be helpful in directing jurisdictions to relevant resources. Jurisdictions located in states with nuclear power plants can also reach out to state agencies that already partner with many of the key federal agencies involved in radiation events.

Nuclear response plans should include procedures for integrating federal resources and establishing a bidirectional flow of mapping and monitoring information. Fifteen minutes to an hour after a nuclear detonation, for instance, the Interagency Modeling and Atmospheric Assessment Center (IMAAC)—led by DHS and supported by DOE—will start to provide plume and fallout projections to federal, state, and local authorities, thus helping to guide radiation monitoring and to identify at-risk populations.5 IMAAC maps and predictions will be refined as local field data become available over time. Additional DOE assets—Radiological Assistance Program (RAP) teams and Federal Radiological Monitoring and Assessment Center (FRMAC) resources—will also start to arrive 24 to 72 hours after the blast and provide assistance with actual radiation measurements.

Task 5.2—Conduct a regional inventory of monitoring staff, equipment, dosimeters, and personal protective equipment; plan for a surge in demand.

Following a nuclear detonation, radiation detection equipment and trained personnel will be in high demand over a broad geographic area. Thus, prior to an incident, jurisdictions throughout the region should assess numbers of trained staff, dosimeters, and radiation detection and monitoring equipment; coordinate the purchase of additional equipment (when feasible); standardize staff training programs; and standardize radiation exposure policies across the region.22 At-risk regions should be prepared to use radiation detectors with high-dose rate capabilities. (For additional technical guidance on detection systems and calibration requirements, see American National Standards Institute [ANSI],* NCRP Commentary #19 [2005],49 and Federal Planning Guidance for Response to Radiological and Nuclear Threats [2010].5) To overcome anticipated staffing deficits, at-risk jurisdictions should develop mutual aid agreements with neighboring urban centers and states for sharing radiation health personnel; develop just-in-time training for formal and volunteer responders; have protocols ready for incorporating federal personnel; and recruit and register radiological health professionals into existing volunteer programs (also see Task 1.3).

Task 5.3—Develop plans for synthesizing diverse data scattered across the region to render an accurate picture of fallout distribution.

As noted above, key decisions such as if, when, and who to evacuate will rest on good understanding of the fallout footprint. Various inputs could help construct this broad operating picture: plume projections from federal or other sources; visual observations of the fallout cloud and its downwind drift; discernible fallout particulates that look like fine, sandy material near the detonation; and, most important, actual radiation measurements from the field.5 At-risk jurisdictions and neighboring communities should jointly plan to incorporate diverse data points into a fuller understanding of the dangerous fallout zone and to distribute information, maps, and displays to emergency operations centers throughout the region.22 A region could establish a network of “plume tracking groups”—that is, people who are practiced and exercised in compiling diverse plume data and in knowing where to seek information while working their way up to the best quality materials, likely to be available last. Information must be updated sequentially as more radiation readings are obtained and because of the rapid drop-off in levels of radioactivity over time. Planning should also address how fallout data will be combined with infrastructure damage data to guide staged evacuations.

Task 5.4—Plan for the prompt release of plume maps via broadcast media and social media to reassure the public and support decisions to seek adequate shelter.

Because images are powerful communicators, plume maps should be released without delay, to alert people to the presence—and, equally important, the absence—of a risk; to prevent possible exposure to fallout; and to avoid self-evacuation when it is unnecessary and when it may be harmful. Indeed, as part of pre-incident public education, it will be useful to show what a plume map looks like so people will be familiar with their meaning in an actual incident. Planners should also note that Doppler weather radar may be able to follow the fallout cloud; thus, it will be important for officials to work with television stations in advance to tap this resource as part of the region’s plume mapping endeavor and to train producers, meteorologists, and broadcast announcers in how to put out statements in the interest of the public’s health.

Task 5.5—Pre-position a network of automated radiation monitors to limit human exposure as well as human errors in readings.

Because responders charged with mapping fallout may be exposed to significant levels of radiation, the fewer personnel deployed the better. It would thus be prudent—when economically and technically feasible—to pre-position a broadly distributed network of detection and monitoring equipment that could provide radiation readings automatically to supplement input from roving personnel. Owners of private buildings will be key allies to approach for hosting equipment in technically strategic locations. At this time, there are both technical and financial limits to a “pre-positioned” monitoring system. Such equipment is expensive, and the high levels of radiation anticipated with a nuclear detonation may saturate devices (ie, render them useless).

Nonetheless, some forms of automation are obtainable in the short term. For example, Los Angeles County uses a telemetry system, coupled with a GPS, to automate collection and display of readings on a map of the county to gather situational awareness. Previous nuclear response exercises revealed that responders would be unable to use radios to call in dose readings, as the radio system would be quickly overwhelmed, and that miscommunication was possible between a person giving a field reading and a person recording it on a map at the command center. Following a nuclear terrorism incident, Los Angeles County staff from public health, law enforcement, the fire department, and other cities within the county plan to drive around the county with meters and send measurements over cellular data bandwidth for central plotting and display.50 A rough cost estimate for a telemetry system comprised of10 instruments and supporting software is $140,000.


*The American National Standards Institute is developing performance criteria for Personal Emergency Radiation Detectors (PERDs). There are two standards:(1) Alarming Electronic Personal Emergency Radiation Detectors (PERDs) for Exposure Control (ANSI N42.49A) are alarming electronic radiation measurement instruments used to manage exposure by alerting the emergency responders when they are exposed to photon radiation; (2) Nonalarming Personal Emergency Radiation Detectors (PERDs) for Exposure Control (ANSI N42.49B) are ionizing photon radiation–measuring detectors that provide a visual indication of the exposure to the user and are designed to be worn or carried on the body of the user.