Educational Resources on Pilgrim Nuclear Power Station

This section contains words used frequently in our industry when referring to radiation and emergency planning.

Radiation Measurements

Dose: The amount of energy absorbed by matter received from ionizing radiation per unit mass of matter; expressed in rads.

Exposure: A measure of the ionization produced in air by x- or gamma radiation; expressed in roentgens (R). Although - dose - and - exposure - often are used interchangeably, a dose in a measurement of energy absorbed in body tissue, while exposure is a measurement of ionizations in the air due to the presence of radiation.

Rad: Unit of radiation dose.

Roentgen (R): Unit of exposure, applicable only to X- and gamma radiations.

o: A unit used to express all types of ionizing radiation on a common scale to indicate relative biological effects.

For beta and gamma radiation: exposure to 1 roentgen delivers a dose of 1 rad, which is equivalent to 1 rem.

Curie (Ci): Amount of radioactive material in which 37 billion atoms decay per second. The rate at which radioactive material is released into the environment may be expressed in unites of curies per second (Ci/sec.).

Milli-(m): One-thousandth of a unit (10-3), i.e., millirem (mRem) or milliroentgen (mR).

Micro-(u): One-millionth of a unit (10-6).

Pico: One-trillionth of a unit (10-12).

Radiological Definitions

Airborne Radioactive Material: Any radioactive material dispersed in the air in the form of dust, fumes, mist, vapor or gas.

Background Radiation: Cosmic rays and natural radioactivity are always present in the environment. In addition, man-made sources also contribute to the background radiation level. The average New Yorker receives approximately 360 millirem per year from background radiation.

Decontamination: The reduction or removal of contaminating radioactive material from a structure, area, object or person.

Dosimeter: A personal monitoring instrument that measures the radiation dose received by an individual using the device.

Exposure Pathways: The ways in which the presence of radioactive materials in the environment lead to potential exposure to humans - i.e., inhalation of airborne radioactive material, ingestion of contaminated food or drink and whole body exposure to a passing plume or ground contamination.

Exposure Rate: Amount of exposure received per unit of time - i.e., roentgens per second or roentgens per hour. A radiation detection instrument such as a Geiger counter or an ionization chamber measures the exposure rate.

Film Badge: Film encased in a badge-like holder that records radiation exposure for personnel monitoring purposes. The film usually is processed monthly for calculation of the absorbed dose. Results are reported in millirems (mRem).

Half-life: The time required for radioactive material to lose 50% of its activity by radioactive decay.

KI-Potassium Iodide: A substance taken as a protective measure to reduce the uptake by the thyroid of radioiodine - i.e., potassium iodide (KI). KI is not an alternative to evacuation. It protects one organ (the thyroid) from one form of radiation (radioiodine). A 130mg tablet is the recommended dose. Children under one year of age should be given a 65mg dose, or one half of the adult tablet. KI is available from the counties emergency management offices or as an over the counter medicine at many drug stores.

Monitoring: Periodic or continuous measuring of radiation by means of survey instruments that can detect and measure ionizing radiation. Area monitoring measures radiation level or contamination present in a specific area, building, room, etc.

Personal Monitoring: Measurement of radiation levels that may have been received by an individual to the whole body or specific organs or body parts. The most common devices used for measuring exposures from external sources are film badges, thermoluminescent dosimeters (TLDs) and pocket dosimeters. Whole body counting or bioassay measurements of breath or excretions may be taken to determine intake of radioactive materials. [Note: bioassays, or biological assays, are a means of testing and measuring the effects of a substance on a living organism.]

Nuclear Reactor: A containment structure in which a fission chain reaction can be initiated, maintained and controlled. Its essential component is a core with fissionable fuel.

Radiation: The emission of energy through a material medium in the form of electromagnetic waves or particles that may impart their energy to the medium through the creation of electrically charged ion pairs. X- and gamma rays and alpha and beta particles are examples of ionizing radiation.

Radioactive Decay: The process by which an unstable nucleus of an atom spontaneously releases energy through the emission of radiation.

Radioactive Release: Introduction of radioactive materials into an uncontrolled environment.

Thyroid Exposure: Exposure of the thyroid gland to radiation from radioactive isotopes of iodine which have been inhaled, absorbed or ingested. Accumulation of iodine is rapid in the thyroid gland.

Thermoluminescent Dosimeter (TLD): A dosimeter made of material that, when heated, emits light in an amount proportional to the amount of radiation dose it received. Placed on a badge-type holder, it can be worn by an individual to measure possible exposure to ionizing radiation.

Whole Body Exposure: Exposure of a major portion of the body to an external radiation field or radioactive material distributed throughout the body. Exposure of blood forming organs, reproductive organs, head, trunk and lenses of the eyes is also considered exposure of the whole body.

Emergency Planning

Congregate Care Center: Facility where shelter and food is provided to evacuees.

Disaster Preparedness Plan: A plan that details comprehensive emergency procedures for all types of disaster emergencies in the state - i.e., floods, hurricanes, etc. A portion of this plan is the Radiological Emergency Preparedness Plan (REPP).

Emergency Classification: The Nuclear Regulatory Commission's classification of four levels of radiological emergencies - notification of unusual event, alert, site area emergency and general emergency.

Emergency Operations Center (EOC): A designated location at county and/or state headquarters from which a chief executive and staff can direct the action of state and local agencies and emergency services.

Emergency Operations Facility (EOF): A facility operated by the power plant licensee for evaluating and controlling emergency situations and coordinating responses with local and state representatives. Its location is normally outside of the plant exclusion area.

Emergency Planning Zone (EPZ): The area surrounding a nuclear power plant site designated for emergency planning purposes. The EPZ encompasses a radius of about 10 miles for the plume exposure pathway and about 50 miles for the ingestion exposure pathway.

Emergency Response Planning Area (ERPA): A subdivision of the plume exposure emergency planning zone. An emergency planning zone is made up of several ERPAs.

Exclusion Area: The area surrounding a nuclear power plant facility in which the facility operator has the authority to determine and control all activities. No residences exist within a nuclear power plant exclusion area.

Ingestion Emergency Planning Zone: For planning purposes, the area surrounding a site within an approximate 50-mile radius where the principal source of exposure from an accident would be the ingestion of contaminated food or water.

Nuclear Facility Operator (NFO): The organization licensed by the Nuclear Regulatory Commission to operate a nuclear facility.

Plume: A - cloud - of radioactive material made up of gases or particles.

Plume Exposure Pathway: The area surrounding a nuclear facility site (usually a radius of approximately 10 miles) where the principal exposure would be from: (a) whole body exposure to gamma radiation from the plume and deposited material, and (b) inhalation exposure from the assign plume.

Prevention/Mitigation: The first of three designated phases of activity in the state and county plans for radiological emergencies (response and recovery phases follow). Actions during this phase aim to eliminate or reduce the probability of an emergency situation occurring, and minimize the impact of an emergency on public health and property.

Protective Action: Any action taken to protect the public's health in response to a radiological emergency - i.e., recommending sheltering or evacuation/ingesting KI.

Reception Center: A pre-designated location outside the plume exposure pathway EPZ through which evacuees will pass to receive initial assistance, including personal monitoring, receipt of additional KI-potassium iodide, first aid or direction to a congregate care center or medical facility.

Recovery: The last phase of activity in the state and county plans for radiological emergencies; efforts during this phase are to return to pre-emergency conditions.

Response: The phase of activity in a radiological emergency when protective actions are taken to protect public health and mitigate effects of a radioactive release.