Linear No-Threshold Model


  • The U.S. Nuclear Regulatory Commission (NRC) decisively upheld the Linear No-Threshold Model to prescribe radiation safety standards, ending the protracted controversy on the topic.

Key Details

  • Over six years ago, during February 2015, petitions were filed requesting the NRC, “to amend its regulations based on their evidence that contradicts the linear no-threshold (LNT) dose-effect model.
  • The petitioners support “radiation hormesis,” a concept that proposes that low doses of ionising radiation protect against the deleterious effects of high doses of radiation and result in beneficial effects to humans. This was denied by the NRC.
  • Petitioners’ proposed:
    • substantial increase in dose limits to workers;
    • raise the public dose limits to be the same as the worker doses;
    • end differential doses to pregnant women, embryos and fetuses, and children less than 18 years of age;
    • remove the As Low As Is Reasonably Achievable (ALARA) principle entirely from the regulations because they claim that ‘‘it makes no sense to decrease radiation doses that are not only harmless but may be hormetic’’.

About Linear No-Threshold (LNT) Model 

  • The LNT Model is a dose-response model used in radiation protection to estimate probable health effects such as radiation-induced cancer, genetic mutations on the human body due to exposure to ionizing radiation.

    Linear No-Threshold Model
    Credit: Wikipedia
  • The LNT model helps the agencies to regulate radiation exposures to diverse categories of licensees, from commercial nuclear power plants to individual industrial radiographers and nuclear medical practices.
  • The LNT model states that biological effects such as cancer and hereditary effects due to exposure to ionising radiation increase as a linear function of dose, without threshold.
  • The NRC noted that although there are studies and other scholarly papers that support the petitioners’ assertions, there are also studies and findings that support the continued use of the LNT model, including those by national and international authoritative scientific advisory bodies.

Back to basics

About Nuclear Regulatory Commission (NRC)

  • The Nuclear Regulatory Commission (NRC) is an independent agency of the United States government tasked with protecting public health and safety related to nuclear energy.
  • Established by the Energy Reorganization Act of 1974, the NRC began operations on January 19, 1975, as one of two successor agencies to the United States Atomic Energy Commission.
  • Its functions include overseeing reactor safety and security, administering reactor licensing and renewal, licensing radioactive materials, radionuclide safety, and managing the storage, security, recycling, and disposal of spent fuel.

Source: TH

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