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Nuclear reactors

Nuclear Power Plant / Nuclear Reactor Incidents

General Information

  • The core of a nuclear reactor (including those found in nuclear power plants), contains large amounts of highly radioactive material.
  • There are various kinds (designs) of nuclear reactors.
  • Site safety is enhanced by many factors including
    • Stainless steel core around the radioactive material
    • Very thick concrete walls of the containment building
    • Highly trained staff
    • Detailed security precautions and procedures
    • Adherence to formal, detailed incident response plans
    • Requirements to practice these response plans regularly

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Emergency Planning and Response

  • The Emergency Planning Zone (EPZ)
    • Definition: the area surrounding a nuclear power plant for which plans required by the NRC have been made in advance to ensure that prompt and effective actions are taken to protect the health and safety of the public in case of an incident
    • The Nuclear Regulatory Commission (NRC) has described 2 EPZs
      • Plume Exposure Pathway EPZ: within a 10 mile (16.1 km) radius of the nuclear power plant
      • Ingestion Exposure Pathway EPZ: within a 50 mile (80.5 km) radius of the nuclear power plant
  • If a release of radioactivity occurs, response managers will recommend public health protective actions. Depending on the circumstances, these actions could include
    • Evacuation from areas at risk of being significantly contaminated by the plume
    • Sheltering-in-place (intake ventilation off, windows closed) to avoid the radioactive plume
    • Interdiction of contaminated or potentially contaminated food
    • Use of medical countermeasures
  • If a serious release of radioactivity occurs, there is likely to be a window of time before it starts, so that the response plan can be implemented.
  • Radioisotopes released into the air after an incident could contain alpha, beta and gamma radiation
  • Workers close to the reactor could be affected by
    • External exposure to highly radioactive materials within the reactor
    • External contamination by radioactivity released and dispersed locally in the plume
    • Internal contamination by radioactivity released, dispersed locally, and then ingested, inhaled, and/or incorporated
  • The general public could be affected by
  • Communicating During and After a Nuclear Power Plant Incident (US Government Interagency Nuclear Detonation Response Communications Working Group, June 2013)

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Radioisotopes in the Plume

  • Radioiodines
    • Can travel over long distances in air after release and settle to the ground
    • Can be inhaled or ingested from the water supply or food chain except for foodstuffs that were encapsulated/sealed/canned prior to the event
    • Primary health threat from a release is likely to be from radioiodines and I-131 particularly, although other radioiodine isotopes are possible.
    • Heath effects
      • No short term acute health effects
      • Potential longer term health effects could develop if there is sufficient internal contamination and incorporation of radioiodine by the thyroid gland. These late effects could include
        • Hypothyroidism, with special consequences in infants and children
        • Thyroid cancer, particularly in younger individuals
      • Radioiodine is not concentrated in organs other than the thyroid.
    • Prophylaxis (before the exposure) and treatment (after the exposure) to radioactive iodine
      • Administration of non-radioactive potassium iodide (KI) or other iodine substances blocks the thyroid from accumulating radioactive iodine, thereby minimizing/avoiding subsequent risks.
      • KI is most effective if given a few hours before exposure, but it is also effective if given within several hours after exposure.
      • The need for prophylaxis and/or treatment with KI will be determined by officials managing the event, and instructions to the general public will be given based on the assessment of risk.
      • KI should be taken only on the advice of emergency management officials, public health officials, or a personal physician.
  • Other radioisotopes might be released, with possible health effects only if an individual receives a high enough dose
  • Monitoring radionuclides in drinking water and food: routinely and after a release

Figure 1. Internal Exposure to Iodine-131 Through Ingestion

Internal Exposure to Iodine-131 Through Ingestion

Adapted from Radioactive Iodine (I-131) and Thyroid Cancer — An Education Resource (PDF - 791 KB) (HHS/National Cancer Institute/Division of Cancer Epidemiology and Genetics)

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General information

  1. Christodouleas JP, Forrest RD, Ainsley CG, Tochner Z, Hahn SM, Glatstein E. Short-Term and Long-Term Health Risks of Nuclear-Power-Plant Accidents. N Engl J Med. 2011 Jun 16;364(24):2334-41. [PubMed Citation]
  2. Coleman CN, Blumenthal DJ, Casto CA, Alfant M, Simon SL, Remick AL, Gepford HJ, Bowman T, Telfer JL, Blumenthal PM, Noska MA, Recovery and Resilience After a Nuclear Power Plant Disaster: A Medical Decision Model for Managing an Effective, Timely, and Balanced Response, Dis Med Pub Health Prep 2013;7(2),2013. [PubMed Citation]
  3. Zwolinski LR, Stanbury M, Manente S. Nuclear power plant emergency preparedness: results from an evaluation of Michigan's potassium iodide distribution program. Disaster Med Public Health Prep. 2012 Oct;6(3):263-9. [PubMed Citation]

Guidance documents about nuclear power plants

  1. Actions to Protect the Public in an Emergency due to Severe Conditions at a Light Water Reactor (IAEA, 2013)
  2. Radiological Emergency Preparedness, Program Manual (Draft), Released for Public Comment, May 18, 2009 (PDF - 1.53 MB) (FEMA). This document is about creating a response plan for a nuclear reactor accident and is currently under review.
  3. Planning Guidance for Protection and Recovery Following Radiological Dispersal Device (RDD) and Improvised Nuclear Device (IND) Incidents (PDF - 519 KB) (DHS/FEMA, published in Federal Register, August 1, 2008, Z-RIN 1660-ZA02)
  4. Contamination Monitoring Guidance for Portable Instruments Used for Radiological Emergency Response to Nuclear Power Plant Accidents (PDF - 233 KB)(FEMA, October 2002)

Guidance documents about managing internal contamination

  1. Management of Persons Contaminated with Radionuclides: Scientific and Technical Bases (NCRP Report No. 161, Volume II), National Council on Radiation Protection and Measurements, Bethesda, MD, 2010.
  2. Management of Persons Contaminated With Radionuclides: Handbook (NCRP Report No. 161, Volume I), National Council on Radiation Protection and Measurements, Bethesda, MD, 2008.
  3. Management of Persons Accidentally Contaminated with Radionuclides (NCRP Report No. 65), National Council on Radiation Protection and Measurements, Bethesda, MD, 1980. [This document has been superseded by NCRP 161.]
  4. Dose assessment of inhaled radionuclides in emergency situations (Health Protection Agency/United Kingdom and Treatment Initiatives After Radiological Accidents (TIARA) project/European Commission, August 2007)

History of radiation incidents


  1. Report of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), General Assembly Official Records, 68th session, Supplement No. 46 (See year 2013, select Report A/68/46)
    • See chapter III (page 7- 16) for excellent UNSCEAR summary report on the levels and effects of radiation exposure due to the nuclear accident after the 2011 great east-Japan earthquake and tsunami.
  2. UNSCEAR Press Briefing on Fukushima, May 31, 2013, YouTube video. Scientific discussion begins at 4 min 45 secs. Watch video
  3. International Academic Conference on Radiation Health Risk Management in Fukushima, February 2013, Summaries of presentations. Fukushima Radiation and Health, Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University.
  4. Health Physics News, The Boice Report #11, Aprils 2013: Summary of the NCRP February 2013 Fukushima Conference (PDF - 155 KB)
  5. Gonzalez A, Akashi M, Boice JD, et al. Radiological protection issues arising during and after the Fukushima nuclear reactor accident. J Radiol Prot. 2013 Jun 27;33(3):497-571. [PubMed Citation]
  6. Wilson T, Chang F, Berro A, et al. US screening of international travelers for radioactive contamination after the Japanese nuclear plant disaster in March 2011. Disaster Med Public Health Prep. 2012 Oct;6(3):291-6. [PubMed Citation]
  7. Akiba S. Epidemiological studies of Fukushima residents exposed to ionising radiation from the Fukushima Daiichi Nuclear Power Plant prefecture--a preliminary review of current plans. J Radiol Prot. 2012 Mar;32(1):1-10. [PubMed Citation]
  8. Fukushima Nuclear Reactor Radiation Crisis: A National Review of the U.S. Domestic Public Health and Medical Response (PDF - 1.01 MB) (Association of State and Territorial Heath Officials, May 2012)
  9. The Journal of Radiological Protection published a special subsection of the March 2012 issue with 22 excellent articles on the Japanese Fukushima nuclear power plant incident (based on the September 2011 International Expert Symposium in Fukushima: Radiation and Health Risks) J Radiol Prot. 2012 Jun;32(1) (special section)


  1. The International Chernobyl Project (IAEA), This resource presents international findings about the incident. Also on the page are many other resources.
  2. Balonov MI. On protecting the inexperienced reader from Chernobyl myths. J Radiol Prot. 2012 Jun;32(2):181-9. Epub 2012 May 8. [PubMed Citation]
  3. Thomas GA (ed.), The Radiobiological Consequences of the Chernobyl Accident 25 Years On - April 2011, Clin Oncol (R Coll Radiol). 2011 May;23(4):229-308. (Note: All 11 articles in this issue are on this topic.)
  4. Fukushima Daiichi nuclear disaster (Wikipedia)
  5. Chernobyl disaster (Wikipedia)
  6. See also: History of Radiation Incidents


  1. Potassium Iodide (CDC, March 17, 2011)
  2. Radiation and Potassium Iodide (CDC, March 18, 2011)
  3. Case Studies in Environmental Medicine (CSEM): Radiation Exposure from Iodine 131, Course SS3117. (HHS/ATSDR, November 2002)


  1. Frequently Asked Questions on Potassium Iodide (KI) (March 18, 2011, HHS/FDA)
  2. Guidance: Potassium Iodide as a Thyroid Blocking Agent in Radiation Emergencies (PDF - 40 KB) (HHS/FDA, December 2001)
  3. Other KI resources including information for infants and small children (HHS/FDA)

Nuclear Regulatory Commission

  1. Consideration of Potassium Iodide in Emergency Planning (March 14, 2011)
  2. Fact sheet on Emergency Preparedness at Nuclear Power Plants (July, 2010)
  3. Criteria for Preparation and Evaluation of Radiological Emergency Response Plans and Preparedness in Support of Nuclear Power Plants (NUREG-0654/FEMA-REP-1)
  4. Student's Corner - Nuclear Reactors
  5. Operating Nuclear Power Reactors (by Location or Name)

Other Agencies

  1. Medical Effectiveness of Iodine Prophylaxis in a Nuclear Reactor Emergency Situation and Overview of European Practices (PDF - 717 KB) (European Commission, Directorate-General for Energy Directorate D - Nuclear Energy Unit D4, Radiation Protection No. 165, 2010)
  2. Distribution and Administration of Potassium Iodide in the Event of a Nuclear Incident (Committee to Assess the Distribution and Administration of Potassium Iodide in the Event of a Nuclear Incident, National Research Council, 2004)
  3. Federal Policy on Use of Potassium Iodide (KI) (PDF - 43 KB) (DHS/FEMA document, published in Federal Register January 10, 2002)
  4. Guidelines for Iodine Prophylaxis following Nuclear Accidents (PDF - 96 KB) (WHO, 1999)

Pediatric issues

  1. Pediatric Counter-terrorism Measures (HHS/FDA, 2/2010) See KI information.
  2. American Academy of Pediatrics Committee on Environmental Health. Radiation disasters and children. Pediatrics. 2003 Jun;111(6 Pt 1):1455-66. [PubMed Citation]

National Council on Radiation Protection and Measurements (NCRP)

  1. Population Monitoring and Radionuclide Decorporation Following a Radiological or Nuclear Incident (NCRP Report No. 166), National Council on Radiation Protection and Measurements, Bethesda, MD, 2011.
  2. Responding to a Radiological or Nuclear Terrorism Incident: A Guide for Decision Makers (NCRP Report No. 165), Bethesda, MD, 2010.
  3. Management of Persons Contaminated with Radionuclides: Scientific and Technical Bases (NCRP Report No. 161, Volume II), Bethesda, MD, 2010.
  4. Management of Persons Contaminated With Radionuclides: Handbook (NCRP Report No. 161, Volume I), Bethesda, MD, 2008.
  5. Management of Persons Accidentally Contaminated with Radionuclides (NCRP Report No. 65), Bethesda, MD, 1980. [NCRP 65 has been superseded by NCRP 161.]
  6. Cesium-137 in the Environment: Radioecology and Approaches to Assessment and Management (NCRP Report No. 154), Bethesda, MD, 2006.
  7. Risk to the Thyroid from Ionizing Radiation (NCRP Report No. 159), Bethesda, MD, 2008.

US Department of Health & Human Services     
U.S. Department of Health & Human Services Office of the Assistant Secretary for Preparedness and Response National Library of Medicine