EXPOSURE LIMIT-For recovery planning purposes, the maximum exposure that Command decides recovery personnel can be exposed to during the recovery operations. In using this manual, one of the following values may be selected: 25 r, 50 r, 100 r, or 200 r. Also, the maximum exposure that Command decides mission personnel can be exposed to during a specified interval from the time of burst to the MET. For conservative planning using this manual, the exposure limit (lower limit) for mission personnel is 110 r in any one month or longer period (during the mission duration.) For the upper limit, the corresponding values are 190 r/day, 250 r/wk, or 500 r/month or longer period.

EXPOSURE MULTIPLIER-A constant number associated with a given time after attack that, when multiplied by the standard exposure rate, gives an estimate of the exposure to unprotected personnel in the open from the time of attack to that time.

EXPOSURE PERIOD-See STAYTIME.

EXPOSURE RATE-The time rate of gamma-radiation-produced ionization, as measured in air in units of roentgens/hr; the exposure rate is a measure of the strength of a gamma-ray field at a given time. Exposure rate multiplied by staytime in the radiation field is the exposure.

EXTERNAL HAZARD-Hazard caused by radiation coming from a source outside the body. The only important external hazard is gamma radiation. Beta radiation is a limited external hazard causing burns only on unprotected, or lightly protected, skin resulting essentially only from skin or clothing contamination. Alpha radiation is not an external hazard.

FALLOUT-The radioactive contamination produced by a nuclear-weapon explosion and deposited on the earth's surface after falling from the nuclear cloud.

FALLOUT ARRIVAL-The time after burst when radioactive fallout starts depositing on a surface.

FALLOUT CESSATION-The time after burst when radioactive fallout stops depositing on a surface.

FALLOUT CONTOURS-The distribution of fallout depicted in terms of standard-exposurerate contours or exposure contours.

FALLOUT PERIOD-The time interval from fallout arrival to fallout cessation.

FILLING-A reclamation method in which uncontaminated dirt fill is used to cover a contaminated area, thus reducing exposure rate above the surface.

FILM BADGE-A photographic dosimeter worn on the body to indicate gamma exposure. Badges may also be designed to indicate beta does.

FINAL RECOVERY PHASE-The third and last phase of radiological defense, starting at the MET and covering the time period after gamma radiation ceases to be a significant hazard and extending up to the time period when normal operations are resumed. Contamination control is the primary countermeasure.

FIREBALL-The luminous, intensely hot mass of gas and fission products formed at the time of a nuclear explosion. It emits initial nuclear radiation, thermal radiation, and brilliant light.

FIREHOSING-A decontamination method by which a strong stream of water is applied to a contaminated surface with a firehose and nozzle to remove the contaminant.

FISSION PRODUCTS-Radioactive elements resulting from nuclear fission at the instant of a nuclear explosion.

GAMMA RADIATION-High-energy electromagnetic radiation similar to X-rays. Gamma rays can penetrate hundreds of feet of air, and can never be completely absorbed by a barrier. However, they can be reduced to harmless exposure-rate level by a sufficient thickness of material.

GRADING-A reclamation method that removes an upper layer of contaminated soil.

GROUND ZERO (GZ)-The point on the ground surface that is vertically beneath or above the point at which a nuclear explosion occurs.

HALF LIFE-Time required for half of an original number of radioactive atoms to undergo decay. (See DECAY, RADIOACTIVE.)

HIGH-ALTITUDE BURST-The bomb explodes above 100,000 feet.

HOTSPOT-A local area where the exposure rate of the radiation field is above the average exposure rate of the surrounding area. Hotspots may result from variations in fallout deposition, variations in the wind pattern around structures, piling up of contamination in natural collecting locations, poor drainage, spillage during reclamation, high surface containability, etc.

INITIAL NUCLEAR RADIATION-Nuclear radiation (essentially neutrons and gamma rays) emitted from the fireball and the cloud column during the first minute after a nuclear explosion. The time limit of 1 minute is set, somewhat arbitrarily, as that required for the source of part of the radiations (fission products, etc., in the radioactive cloud) to attain such a height that only insignificant amounts reach the Earth's surface. (See RESIDUAL NUCLEAR RADIATION.)

INSTALLATION-A fixed military facility, together with its buildings, equipment, subsidiary facilities.

ISOTOPE-Atoms of an element having the same atomic number but different mass numbers are called isotopes.

KILOTON (KT)-A unit of measurement of nuclear-weapon yield, roughly equivalent to the explosive energy released by 1,000 tons of TNT.

LATE EFFECTS-Biological effects noticeable months to years after receiving radiation exposure: for example, leukemia, cancer, anemia, and general shortening of the life span. Late effects are dependent on the total exposure received and are probably independent of the time period over which the exposure if received. Biological recovery does not apply to late effects.

MEGATON (MT)-A unit of measurement of nuclear-weapon yield equivalent of 1,000 kilotons.

MET-See MISSION ENTRY TIME.

MICRO-ORGANISM-Minute living organisms capable of carrying on all functions of life, including growth and reproduction.

MISSION-An installation's mission consists of all essential operations and functions. The mission does not include the special recovery efforts required after contaminating nuclear attack.

MISSION DURATION-The length of time that the installation's mission must be performed after radiological recovery. Taken in this manual to be two years.

MISSION ENTRY TIME (MET)-The time, measured from the time of burst, at which mission personnel can enter the vital area of the installation to resume the essential functions without receiving excessive radiation exposure.

MISSION PERSONNEL-Personnel who are to perform the essential functions of the installation after recovery has been achieved.

MOLECULE-The smallest particle of any substance which can exist free and still exhibit all properties of the substance.

MONITOR-A person trained to measure radiation-field exposure rates and the amount of contamination on personnel and equipment by using suitable radiac instruments.

MONITORING-Locating radioactive contamination and measuring its radiation exposure rate by means of radiac instruments.

MPE-Maximum permissible exposure. Amount of radiation or contamination established as the maximum to which personnel may be exposed under wartime conditions.

NUCLEAR CLOUD-The characteristic cloud of a nuclear explosion formed upon cooling of the fireball. It contains the fission products of the explosion and is highly radioactive.

NUCLEAR RADIATIONS-The radiations emitted from the nuclei of the radioactive atoms in the contaminant or during fission. These may include alpha, beta, gamma, and neutron radiations. Gamma radiation is nuclear radiation of primary significance to this manual (beta radiation is a hazard only if skin or clothes become contaminated).