Nuclear agents
Primary reference(s)
IAEA, 2004. Radiation, People and the Environment. International Atomic Energy Agency (IAEA). Accessed 1 December 2019.
Additional scientific description
Dispersal of neutron radiation through nuclear weapons, including improvised nuclear devices (IND) results in a nuclear yield unlike radiation dispersal devices (RDD). This nuclear yield is measured in kilotons (kT) and one unit has the explosive energy equivalent to a thousand tons of TNT. Nuclear detonations are capable of producing impacts far surpassing that of any conventional explosive (IAEA, 2004).
A significant effect of a nuclear explosion is the blast generated. The blast originates from the rapidly expanding fireball of the explosion, which generates a pressure wave moving rapidly away from the point of detonation. Initially, near the point of detonation (also referred to as ‘ground zero’) for a surface nuclear burst, the overpressure is extremely high. With increasing distance from ground zero, the overpressure and speed of the blast wave dissipate to a point at which they cease to be destructive. In the case of a nuclear terrorism incident, the thermal pulse can cause skin burns on those people within a few miles of the incident who have a line-of-sight view of the fireball (IAEA, 2004).
There will be many hazards after a nuclear terrorism incident, including widespread fires and the presence of toxic materials, but one of the most significant in terms of human health for a ground level or near ground level nuclear incident, will be the residual radiation from radioactive fallout and neutron activation of materials. Although the radiation levels are most hazardous in the first few hours, some areas within a few miles downwind may still be hazardous days after the incident. Rapid identification of these fallout areas for implementation of protective measures is one of the highest priorities for emergency management and public health authorities (IAEA, 2004).
Metrics and numeric limits
Identifying the dangerous-radiation zone (exposure rate ≥10 R h–1 , ∼0.1 Gy h–1 air-kerma rate) will have critical implications on response activities in or near fallout areas. The dangerous-radiation zone is an area where large doses could be delivered to emergency responders in a short period of time. The relation of dose and health effect is mainly established via the survivors of the bombs of Hiroshima and Nagasaki, assessed in 1950 and continued by the US Atomic Bomb Causality Commission (ABCC) and its successor, the USA–Japan binational Radiation Effects Research Foundation (RERF) (NCRP, 2010).
After a ground-level nuclear terrorism incident, the dangerous-radiation zone will be created by fallout that is deposited in the first few hours and will have boundaries that may extend for 20 miles (~32 km), depending on the yield and weather. The dangerous-radiation zone will rapidly shrink as the fallout decays and may only be a mile or two long after a few days. As an example, an emergency responder working in an area with an initial 10 R h–1 exposure rate (~0.1 Gy h–1 air-kerma rate) 4 hours after the nuclear terrorism incident will receive ~25 R (~0.25 Gy air kerma) in a 4-hour work period (NCRP, 2010).
Key relevant UN convention / multilateral treaty
Effective national and global response arrangements and capabilities are essential to minimise the impacts from nuclear and radiological incidents and emergencies. The International Atomic Energy Agency (IAEA) maintains the international Emergency Preparedness and Response (EPR) framework, which is based on international legal instruments (IAEA, 2019).
As part of these activities, the IAEA develops safety standards, guidelines and technical tools; assists Member States in building the capacity for emergency response; and maintains the IAEA Incident and Emergency System to efficiently implement its role in response to nuclear or radiological incidents and emergencies, regardless of whether they arise from accident, negligence or deliberate act.
The IAEA Preventive Measures for Nuclear and Other Radioactive Material out of Regulatory Control elaborates upon the recommendations given in IAEA Nuclear Security Series No. 15, Nuclear Security Recommendations on Nuclear and Other Radioactive Material out of Regulatory Control, in relation to preventative measures (IAEA, 2019). It serves as a guidance document for Member States interested in strengthening their nuclear security regime as it relates to nuclear and other radioactive material out of regulatory control and in improving their capabilities.
Examples of drivers, outcomes and risk management
A life-span study to investigate the health consequences on a large population after the bombs of Hiroshima and Nagasaki, showed that the survivors within 1500 m of the epicentre (shielded whole body kerma >1 Gy) on average had a reduction of 2.6 years of life expectancy due to radiation-induced cancer (Smith, 2007).
References
IAEA, 2004. Radiation, People and the Environment. International Atomic Energy Agency (IAEA). Accessed 1 December 2019.
IAEA, 2019. Preventive measures for nuclear and other radioactive material out of regulatory control: Implementing guide. Nuclear Security Series No. 36-G. International Atomic Energy Agency (IAEA). Accessed 1 December 2019.
NCRP, 2010. Responding to a Radiological or Nuclear Terrorism Incident: A guide for decision makers. NCRP Report no. 165. National Council on Radiation Protection and Measurements (NCRP). Accessed 1 December 2019.
Smith, J.T., 2007. Are passive smoking, air pollution and obesity a greater mortality risk than major radiation incidents? BMC Public Health, 7:49doi.org/10.1186/1471-2458-7-49. Accessed 1 December 2019.