Cesium-137 Radioactive Bomb

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Lore & Background

Dirty bombs have never been used, only tested. They are designed to disperse radioactive material over a certain area. They act through the effects of radioactive contamination on the environment and related health effects of radiation poisoning in the affected populations. The containment and decontamination of victims, as well as decontamination of the affected area require considerable time and expenses, rendering areas partly unusable and causing economic damage. Dirty bombs might be used to create mass panic as a weapon of terror.

In Their Own Story

The first attempt of radiological terror was reportedly carried out in November 1995 by a group of Chechen separatists, who buried a caesium-137 source wrapped in explosives at the Izmaylovsky Park in Moscow. A Chechen rebel leader alerted the media, the bomb was never activated, and the incident amounted to a mere publicity stunt. In December 1998, a second attempt was announced by the Chechen Security Service, who discovered a container filled with radioactive materials attached to an explosive mine. The bomb was hidden near a railway line in the suburban area Argun, ten miles east of the Chechen capital of Grozny. The same Chechen separatist group was suspected to be involved. On 8 May 2002, José Padilla (a.k.a. Abdulla al-Muhajir) was arrested on suspicion that he was an al-Qaeda terrorist planning to detonate a dirty bomb.

Reader's Guide

When dealing with the implications of a dirty bomb attack, there are two main areas to be addressed: the civilian impact, not only dealing with immediate casualties and long term health issues, but also the psychological effect; and the economic impact. With no prior event of a dirty bomb detonation, it is considered difficult to predict the impact. Several analyses have predicted that radiological dispersal devices will neither sicken nor kill many people. The effects of uncontrolled radioactive contamination have been reported several times. One example is the radiological accident occurring in Goiânia, Brazil, between September 1987 and March 1988: Two metal scavengers broke into an abandoned radiotherapy clinic and removed a teletherapy source capsule containing powdered caesium-137 with an activity of 50 TBq. They brought it back to the home of one of the men to take it apart and sell as scrap metal. Later that day both men were showing acute signs of radiation illness with vomiting and one of them had a swollen hand and diarrhea. A few days later one of the men punctured the 1-millimetre-thick (0.039 in) thick window of the capsule, allowing the caesium chloride powder to leak out and when realizing the powder glowed blue in the dark, brought it back home to his family and friends to show it off. After two weeks of spread by contact contamination causing an increasing number of adverse health effects, the correct diagnosis of acute radiation sickness was made at a hospital and proper precautions could be put into procedure. By this time 249 people were contaminated, 151 exhibited both external and internal contamination, of whom 20 people were seriously ill and five people died.

Did You Know?

• Dirty bombs have never been used, only tested.
• The Goiânia incident in Brazil (1987-1988) involved a caesium-137 source that contaminated 249 people, with 20 seriously ill and five deaths.
• In December 2001, three Georgian woodcutters found a strontium-90 radioisotope thermoelectric generator and suffered acute radiation sickness within hours.
• The U.S. Nuclear Regulatory Commission estimates that approximately one radioactive source is lost, abandoned or stolen every day in the U.S.
• The first reported attempt of radiological terror was in November 1995 by Chechen separatists, who buried a caesium-137 source wrapped in explosives in Moscow's Izmaylovsky Park.

Formation and Decay Dynamics

Nuclear fission occurs when a massive atomic nucleus, such as uranium, splits into two smaller fragments known as fission products. This process releases neutrons, heat energy, and gamma rays. A rare occurrence called ternary fission happens in about 0.2% to 0.4% of events, producing a third light nucleus like helium-4 or tritium. The resulting fragments are typically unstable because they possess an excess of neutrons relative to their atomic number compared to stable nuclei. To achieve stability, these neutron-rich products undergo beta decay, converting neutrons into protons while emitting beta particles, antineutrinos, and additional gamma rays. This secondary radiation begins immediately after the initial split. While most fission products decay via beta emission rather than alpha decay, some short-lived variants release delayed neutrons during their decay chain. These delayed neutrons are critical for controlling nuclear reactors. The mass of the resulting cooled fragments is always less than the original atom due to energy loss as heat and free neutrons.

Radioactivity Evolution Over Time

The radioactivity of fission products varies significantly based on the half-lives of the specific radionuclides created. Short-lived isotopes, such as strontium-89 with a half-life of roughly 50 days, decay rapidly and emit high levels of radiation initially. In contrast, longer-lived isotopes like strontium-90 persist for decades, contributing to long-term hazards. Because hundreds of different radionuclides are produced, the initial intense radioactivity fades quickly as the short-lived components vanish; approximately 87% decay into stable forms within the first month after removal from a reactor core. However, radiation never ceases completely due to longer-lived isotopes. Pure fission products generally see their total radioactivity drop rapidly over several hundred years before stabilizing at a low level for hundreds of thousands of years. This contrasts with fuel containing actinides, which remain highly radioactive in the intermediate timeframe. Consequently, advanced reactor designs aim to consume all actinides so that waste becomes less radioactive than natural uranium ore within 200 years.

Statistical Yield and Distribution

Although individual fission events are unpredictable regarding specific outcomes, the production of fission products follows statistically predictable patterns known as yields. These yields represent the percentage of a specific isotope produced per parent fission event, totaling approximately 200% because each split creates two main fragments. While fission can produce elements ranging from zinc to the lanthanides, the distribution is not uniform. The exact yield of these isotopes depends on the specific parent atom undergoing fission and the energy level of the initiating neutron. Generally, higher energy states during fission influence the likelihood of certain products forming. This statistical predictability allows scientists to anticipate the composition of nuclear waste and understand the radiation profile generated by spent fuel.

Thermal Hazards and Waste Management

The decay of unstable fission products generates significant heat alongside radiation, posing immediate challenges for storing spent nuclear fuel. The most intense heat and radiation come from short-lived radionuclides that are predominant immediately after a reactor is shut down. As these isotopes decay rapidly, the thermal output decreases, but the initial period requires careful cooling management to prevent overheating. Less stable fission products often decay into other radioactive nuclides rather than directly reaching stability, creating complex decay chains that extend radiation emission over time. While short-lived products dominate the immediate hazard profile, longer-lived radionuclides ensure that radioactivity persists for millennia. The primary emissions from these products are beta particles and gamma rays, distinct from the alpha radiation primarily emitted by actinides found in unprocessed fuel. Understanding this thermal and radiological behavior is essential for designing safe storage solutions and developing nuclear fuel cycles that minimize long-term environmental impact.