Historical Radiological Event Monitoring
Since the 1940s, U.S. and foreign nuclear weapons tests, reactor accidents and other radiological events have released radioactive material into the environment. One of EPA's roles during and after these events is to monitor the environment for radiation.
- History of RadNet timeline - shows how the RadNet system has changed over time and some of its important uses.
- Historical Uses of RadNet Data (PDF) (36 pp, 564.16 K, About PDF) - shows historical information about how RadNet data have been used.
On March 11, 2011, a 9.0-magnitude earthquake struck off the coast of northern Japan. The epicenter of the powerful earthquake was under the Pacific Ocean, approximately 80 miles east of Sendai, where the Fukushima Daiichi nuclear power plant is located. The plant’s automatic earthquake detectors successfully inserted all the control rods into the three reactors that were operating at the time. However, less than an hour later, a massive tsunami inundated the Fukushima power plant, causing widespread destruction and knocking out the reactors' emergency cooling systems. The reactors overheated, damaging the nuclear fuel and producing hydrogen explosions that breached the reactor buildings and allowed radioactive elements to escape into the environment.
- How did EPA respond?
EPA’s RadNet system detected nothing unusual in the first week after the Fukushima accident. During this time, EPA deployed additional portable air monitors in Alaska, Hawaii, Idaho and two U.S. Pacific Territories. The RadNet system went on an emergency schedule, with accelerated sampling and analysis of precipitation, drinking water and milk. After a thorough data review showing declining radiation levels in these samples, EPA returned to the routine RadNet sampling and analysis schedule for precipitation, drinking water and milk on May 3, 2011. The last time that EPA detected radioactive elements associated with Fukushima was July 28, 2011 in Hawaii.
On March 18, 2011, the RadNet air monitor in Hawaii detected very low levels of iodine-131 in real-time. Iodine-131 is a radionuclide that would be expected from the Fukushima nuclear incident. During the rest of March and April, laboratory analyses of RadNet samples collected throughout the U.S. detected very low amounts of iodine-131 and other radionuclides expected following a nuclear incident. All of the radionuclides detected in the U.S. from Japan were far below levels of public health concern. No protective actions were needed in the U.S. or its Pacific Territories. After a thorough review of all the sampling and monitoring results showed declining levels of radiation from Japan, RadNet returned to a routine sampling schedule on May 3, 2011.
- Sharing Data with the Public
To keep the public informed, EPA launched a Japan 2011 website which displayed near real-time air monitoring results and associated laboratory analysis data from RadNet. Search the EPA Archives for the EPA Japan 2011 website.
More information and data about EPA's RadNet monitoring of the Fukushima accident can be viewed on the 2011 Japanese Nuclear Incident page
On Saturday, April 26, 1986, a nuclear accident at reactor number four at the former Soviet Union's Chernobyl nuclear power station exploded and burned. The accident, which occurred during unauthorized testing, emitted large quantities of radioactive material. The heat from the fire was so intense that the glowing reactor could be seen even from space, as shown in the satellite photo below.
- How did EPA respond?
In the days following the accident, the Soviets released little data on the severity of the accident. Almost no data were available on the extent of radioactive (falloutfalloutRadioactive particles that fall to the ground after a nuclear explosion.) in Europe and the rest of the world. In response to Americans' concern about potential health effects in the United States, the White House assigned the responsibility for leading the U.S. response to EPA. The Agency immediately took several steps:
- Increased the Environmental Radiation Ambient Monitoring System (abbreviated ERAMS, now RadNet) sampling and analysis frequency.
- Established a group to provide advice on preventing contamination of the food supply and protecting public health.
- Established an information center to gather and distribute facts and data about the accident.
- Arranged daily press conferences to keep the public up-to-date and to give EPA an opportunity to answer the public's concerns.
- How did EPA monitor the plume as it crossed the U.S.?
RadNet's predecessor, the Environmental Radiation Ambient Monitoring System (ERAMS), first detected radiation from the accident at ground level on the West Coast one week after the accident. Although radioactivity levels were somewhat elevated, they were well below levels requiring protective actions. The slideshow below shows the fluctuations in air beta levels across the contiguous U.S. between March and July, 1986.
- How did EPA protect U.S. citizens in Europe?
EPA sent experts to Europe to monitor and assess levels of radioactivity around U.S. embassies. For sometime after the accident, EPA scientists measured radioactivity in the Black Sea and Kiev Reservoir in cooperation with the former Soviet Union.
- Chernobyl Disaster: An Inside Tour
Ten years after the 1986 explosion of Unit 4 of the Chernobyl Nuclear Power Plant near Pripyat, Ukraine, EPA staff member Gregg Dempsey was given a rare tour inside the Sarcophagus that surrounds Unit 4. His slideshow from that visit offers a unique historical snapshot of the conditions and challenges inside the plant. It provides views of the interior of Unit 4 not seen elsewhere in Chernobyl photo collections. In addition, it offers the personal perspectives of workers who were present at the time of the accident. One of these workers returns to his flat in the nearby city of Pripyat for the first time since leaving it 10 years earlier.
- Backgrounder on Chernobyl Nuclear Power Plant Accident
U.S. Nuclear Regulatory Commission
This page describes the accident and provides links to reports on its aftermath.
- Researchers Determine Chernobyl Liquidators' Exposure
Lawrence Livermore Laboratory
This article describes how researchers use special techniques to monitor genetic damage in people exposed to ionizing radiation.
- Maps and additional photographs of Pripyat, Ukraine and Chernobyl Exit
This site provides an interactive map with links to pictures.
- Backgrounder on Chernobyl Nuclear Power Plant Accident
On September 30, 1999, three workers at the Japan Nuclear Fuel Conversion Company transferred several times the allowable limit of enriched uranium into a precipitation tank, bypassing criticality controls. The transfer caused an uncontrolled, self-sustained nuclear reaction. Though the accident released radioactive noble gases and gaseous radioiodine, most of these substances were confined to the building.
EPA used the Environmental Radiation Ambient Monitoring System (ERAMS), now RadNet, to monitor the radioactivity in air, precipitation and pasteurized milk. As expected, no increase in radioactivity above typical background levels was measured in any of the samples analyzed, so protective actions were not needed.
The People’s Republic of China conducted two test detonations of nuclear weapons on September 26 and November 17, 1976. Both detonations were conducted above ground, injecting radioactive material into the atmosphere.
EPA used the Environmental Radiation Ambient Monitoring System (ERAMS), now RadNet, to monitor the radioactivity in air, precipitation and pasteurized milk. EPA’s monitoring system identified low, but measurable, quantities of radioactive material throughout the United States from the September 26 test. No additional material from the November 17 test was detected. As a result of the findings, state agencies in Connecticut and Massachusetts ordered farmers to switch dairy herds to stored feed only, minimizing the potential impact on milk supplies. EPA continued to monitor radioactivity levels until they returned to normal background levels in November 1976.
ERAMS monitored each atmospheric nuclear test, as the system is continuously in operation. EPA also responded to the last recorded atmospheric test on October 16, 1980 (which occurred in China) with increased milk collection.