Nuclear detonation detection system facts for kids

A nuclear detonation detection system (NDDS) is a group of tools and devices. They can find out if a nuclear explosion has happened. They can also tell where it happened and from what direction. The main goal of these systems is to check if countries are following treaties they signed. Examples include the Partial Test Ban Treaty of 1963 (PTBT) and the Treaty of Tlatelolco. These treaties aim to limit nuclear testing.

There are many ways to detect a nuclear explosion. These include seismic (ground vibrations), hydroacoustic (underwater sound), and infrasound (low-frequency air sound). Other methods are air sampling and using satellites. Each method has its own strengths and weaknesses. They also have different uses. While each can be used alone, the best results come from using data from all of them together. This is because the energy from an explosion spreads through different materials.

Detecting Nuclear Explosions

How Seismic Sensors Work

Seismic networks are one way to detect nuclear explosions. When a nuclear explosion happens above ground, it creates a large mushroom cloud. But it also sends vibrations through the ground. These vibrations can travel very far. In the 1980s, nuclear weapons tests moved underground. Even then, these tests are hard to detect, especially if the explosion is small. With a seismic network, detecting these underground nuclear tests becomes possible.

The Partial Test Ban Treaty (PTBT) stopped nuclear testing in the atmosphere, underwater, and in outer space. The U.S. created many devices to make sure the Soviet Union followed this treaty. The PTBT also wanted to ban underground testing. However, at that time, the technology could not detect small underground explosions very well. It was also hard to tell them apart from earthquakes. Larger explosions could be identified, but smaller ones could not. Even big explosions could be made harder to detect by creating a large empty space underground. Because of the chance of the Soviet Union doing underground tests, the U.S. invested a lot in seismology research.

The main system for finding underground explosions needed many monitoring stations. Because it was hard to create the technology and so many stations were needed, the PTBT allowed some underground testing.

Listening in the Ocean: Hydroacoustics

There are 11 hydroacoustic stations placed in the oceans. They are set up to watch for any activity underwater. These stations were made to ensure the ban on underwater testing. Because water can carry sound very well, these stations are very good at their job. They collect data all the time, 24 hours a day, every day of the year.

However, hydroacoustic systems sometimes have trouble finding the exact spot of an explosion. So, they often need to be used with another detection method. Other challenges for hydroacoustics include the shape of the sea floor and islands. These can block sound waves. Sound travels best in deep ocean. This means events near shallow water might not be detected as well. Besides detection, hydroacoustic devices are also used for studying ocean events.

Hearing Air Waves: Infrasound

Infrasound detection uses many stations with microbarometers. These devices listen for very low-frequency sound waves. These waves can be caused by explosions, volcanoes, or other natural events. Like other detection methods, infrasound was developed during the Cold War. These stations were made to detect explosions as small as 1 kiloton (a measure of explosive power). After the PTBT, satellites took over detecting atmospheric explosions.

Even though infrasound waves can travel around the Earth many times, they are easily affected by wind and temperature changes. It can also be hard to tell the difference between long-range infrasound waves from different sources. For example, it's hard to tell if it's from a chemical explosion or a nuclear one.

Collecting Air Samples

Another way to find a nuclear explosion is by taking air samples. After a nuclear explosion, radioactive isotopes are released into the air. These can be collected by planes. These radioactive materials, called radionuclides, include substances like americium-241, iodine-131, caesium-137, krypton-85, strontium-90, plutonium-239, tritium, and xenon.

Sending planes over or near an area can show if a nuclear explosion happened recently. Most air samples are taken at special radionuclide stations around the world. Even underground explosions will eventually release radioactive gases, especially xenon. These gases can also be detected this way. Challenges with air sampling tools include how sensitive they are, how easy they are to use, and how much power they need.

One problem with air sampling is that air currents can move the gases or radionuclides in unexpected ways. This depends on where the explosion was and the weather at the time. The detection process involves taking air samples with a filter paper. This paper collects the radioactive material. Then, a computer can count and analyze it. Other "noise" like radiation from factories or nuclear plants can affect the results. Another challenge is that special materials are needed for certain radionuclides. For example, radioactive iodine comes in many forms. It can combine with different gases, making it hard to detect directly.

How Radioactive Particles Spread

The Chernobyl disaster shows how easily radioactive particles can spread. When the reactor failed, a lot of radionuclides were released into the air. Air currents carried this radiation far away. It was detected in Sweden and other countries hundreds of miles away within a few days. The same thing happened during the Fukushima Daiichi disaster. Radioactive xenon gas, iodine-131, and caesium-137 were detected on different continents many miles away.

Watching from Space: Satellites

Satellites use sensors to watch for radiation from nuclear explosions. Nuclear explosions always produce gamma rays, x-rays, and neutrons. They release a huge burst of x-rays very quickly. Satellites can pick up these signals. Groups of satellites can then figure out the exact location of the explosion. Satellites were first used in 1963 and throughout the Cold War. Their job was to make sure no nuclear testing was happening. A small problem with satellite detection is that some cosmic rays also release neutrons. These can sometimes give false signals to the sensors.

Vela Satellites: Early Space Detectors

Starting on October 17, 1963, in the USA, special Vela Satellites were first used. The Air Force and the Atomic Energy Commission (now part of the Department of Energy) operated them. The Vela satellite was created after the PTBT (Partial Test Ban Treaty) was signed in August 1963. Vela's goal was to act as a nuclear explosion detector for the PTBT. The project included 12 satellites. Each had x-ray, neutron, and gamma ray detectors. They could also measure light and radio waves.

Today, satellites also have cameras that can see the full visible light spectrum. These cameras can capture images of explosions above ground. With Global Position System (GPS) satellites now carrying nuclear detection systems, satellites have become a very important way to detect explosions.

Newer satellites launched after 2018 have improved Space and Atmospheric Burst Reporting System (SABRS) equipment. This equipment makes detection more reliable, smaller, and better at finding nuclear explosions.

The Comprehensive Test Ban Treaty

The Comprehensive Nuclear Test Ban Treaty (CTBT) banned all types of nuclear testing. Its aim was to reduce and move away from nuclear weapons. But this brought back old challenges, like how to make sure countries would not secretly test. To solve this, the International Monitoring System (IMS) was created. It has 321 stations that use all the sensor types described earlier.

The IMS uses data from hydroacoustic, infrasound, and seismic wave detection systems. It also uses air samplers for radionuclides. All this information is collected by the Preparatory Commission for the Comprehensive Test-Ban Treaty Organization (CTBTO). The CTBTO is located in Vienna, Austria.

How Well Do These Systems Work?

One of the first times the CTBTO and its detection systems proved effective was in May 1998. They were able to identify nuclear testing by India and Pakistan.

Another important example is the detection of North Korean testing. Most countries have stopped nuclear tests. However, North Korea has tried to create powerful nuclear devices. Because North Korea is very secretive, the IMS provides researchers with information to understand North Korea's actions. Even their first attempt at a nuclear device in 2006, which was a small explosion (0.6 kiloton), was detected and identified.