Chapter 69: Security of Radioactive Material

Radioactive material is used throughout the world for a wide variety of beneficial purposes, for example in industry, medicine, research, agriculture and education.  Security measures are needed to prevent the acquisition of such material for a malicious act causing a radiological hazard, and thus the measures should protect individuals, society and the environment from such harmful effects.

Radioactivity is a part of nature.  Everything is made of atoms.  Radioactive atoms are unstable; that is, they have too much energy.  When radioactive atoms spontaneously release their extra energy, they are said to decay.  All radioactive atoms decay eventually, though they do not all decay at the same rate.  After releasing all their excess energy, the atoms become stable and are no longer radioactive.  The time required for decay depends upon the type of atom.

The nucleus of a radionuclide spontaneously gives up its extra energy, that energy is called ionizing radiation.  Ionizing radiation may take the form of alpha particles, beta particles, or gamma rays. The process of emitting the radiation is called radioactive decay.

When the nucleus of a radioactive atom decays, giving up its excess energy, the nucleus is altered. It is transformed into another atom which in many cases is a different element.  This new atom may be stable or unstable.  If it is stable, the new atom is not radioactive.  If it is unstable, it also will decay, transforming its nucleus and emitting more ionizing radiation.  Several decays may be required before a stable atom is produced.

This sequence is known as a decay chain.

1.      RADIOACTIVE HAZARDS:

Radioactive materials are things that contain unstable elements such as Plutonium, Uranium, Tritium, Thorium, and others. They emit ionizing radiation and are thus called radioactive.
1.1        Plutonium (Pu):

Plutonium is a heavy metal with a shiny appearance (similar to stainless steel) when freshly machined.  After exposure to the atmosphere for a short period of time, it will oxidize to a dark brown or black appearance.

Plutonium is considered the most significant radiological hazard associated with an accident involving nuclear weapons containing plutonium.  The primary hazard of plutonium, an alpha emitter, results from-entry into the body by inhalation and subsequent deposition in the lungs.  Most of the plutonium that eventually enters the blood stream is deposited in the bone and liver.  Bone deposition may produce bone diseases (including cancer) many years later.  Because both the physical and biological half-lives of plutonium are extremely long, it will essentially be held within the body for a lifetime.  The hazards from americium taken inside the body are comparable to those of plutonium.

1.2       Uranium (U):

Uranium is a heavy element which occurs in nature in significant quantities.  When first machined, it has the appearance of stainless steel. When exposed to the atmosphere for a short period, it will oxidize to a golden-yellow color and from that to black.  Three forms of uranium have been used in nuclear weapons—natural uranium, depleted uranium, and enriched uranium.

The radiological hazards associated with any of the isotopes of uranium are less severe generally than those of plutonium.  If uranium is taken internally, a type of heavy metal poisoning may occur, and lung contamination due to inhalation can cause a long term hazard. In general, when involved in a fire, uranium will melt and form a slag with only a portion of it oxidizing. However, the possibility of hazardous airborne contamination exists and protective measures must be taken to protect against inhalation or ingestion.  An M 17 protective mask and standard anti-contamination clothing will protect personnel adequately against uranium hazards.

1.3        Tritium (T):

Tritium is a radioactive isotope of hydrogen and diffuses very rapidly in the air with a measurable diffusion rate even through very dense material such as steel.  Tritium combines chemically with a number of elements liberating heat in the process, and like normal hydrogen, can combine combustively with air forming water and release great amounts of heat.

Metals react with tritium in two ways by plating (the process by which a thin film of tritium is deposited on the surface of the metal) and by hydriding (the chemical combination of tritium with the metal).  In either reaction, the surface of the metal will become contaminated with radioactive material.

Tritium constitutes a health hazard when personnel are engaged in specific weapon render-safe procedures, when responding to an accident that has occurred in an enclosed space, and during accidents which have occurred in rain, snow, or in a body of water.  In its gaseous state, tritium is not absorbed by the skin to any significant degree. The hazardous nature of tritium is due to its ability to combine with other material.

Tritium water vapor (TO or HTO) is readily absorbed by the body, both through inhalation and absorption through the skin.  The radioactive water that enters the body is chemically identical to ordinary water and is distributed throughout the body tissue.  Although it takes a relatively large amount of tritium to be a significant radiation hazard, caution should be taken.  Tritium which has plated out on a surface or combined chemically with solid material is a contact hazard.  The human body normally eliminates and renews 50 percent of its water in about 8-12 days.  This turnover time or biological half-life varies with the fluid intake.  Since tritium oxide is water, its residence time in the body may be significantly reduced by increasing the fluid intake.

Under medical supervision, the biological half-life may be reduced to about three days. If forced-fluid treatment is deemed necessary and medical supervision is unavailable, a recommended procedure is to have the patient drink one quart of water within one-half hour after exposure. Thereafter, maintain the body’s water content by imbibing the same amount as that excreted until medical assistance can be obtained.  Medical assistance should be obtained as soon as possible.

Although the biological half-life of tritium is short, personal hazard results because of the ease with which tritium water vapor is absorbed and its rapid distribution throughout the body tissue.  A self-contained breathing apparatus and protective clothing will protect personnel against tritium absorption for short periods of time.  A filter mask such as M 17 has no protective value for tritium.

1.4       Thorium (Th):

Thorium is a heavy, dense gray metal which is about three times as abundant as uranium.  Thirteen isotopes are known, with atomic masses ranging from 223 through 235.

Thorium-232 is the principal isotope.  It decays by a series of alpha emissions to radium-225, whose radiological half-life of 14.1 billion years. Thorium-232 is not fissionable, but it is used in reactors to produce fissionable uranium-233 by neutron bombardment.  A non-nuclear property of thorium is that when heated in air, it glows with a dazzling white light, Because of this property; one of the major uses of thorium has been in the Welbach lantern mantel used in portable gas lights.  An unburned mantle will provide an alpha indication of approximately 15,000 CPM on standard alpha survey instruments. Mantle ash from a single mantle will provide even higher readings.

Thorium presents both a toxic and radiological hazard. Toxicologically, it causes heavy metal poisoning similar to lead or the uranium isotopes. Biologically, thorium accumulates in the skeletal system where it has a biological half-life of 200 years, the same as plutonium.  An M 17 protective mask and standard anti-contamination clothing will adequately protect against thorium.

1.5       Other – Fission Products:

The material considered thus far are used in weapons in pure forms and in combinations with other elements.

Due to weapon design, the probability of a nuclear detonation as a result of an accident is unlikely.  If fission occurs, the products of the reaction may pose a severe hazard. In general, fission products are beta and gamma emitters and are hazardous, even when external to the body.  To predict and estimate the quantity of fission products is difficult since the amount of fission is unknown, and to further complicate the situation, the relative isotopic abundances will change with time as the shorter lived radioisotopes decay.  An estimate of the hazard may be obtained by beta and gamma monitoring.

2.     NUCLEAR SECURITY MEASURES FOR RADIOACTIVE MATERIAL:

In addition to those States that need a nuclear security infrastructure to deal with radioactive material, other than nuclear material, and associated facilities and associated activities, States embarking on or expanding a nuclear power programme need measures for protection against unauthorized removal and sabotage of radioactive material.  Establishment of appropriate nuclear security infrastructure and implementation of systems and measures to address radioactive material, associated facilities and associated activities should be addressed at this earliest stage of the nuclear power programme.

Furthermore, a large inventory of radioactive material will accumulate during the life of the nuclear power plant and will need protection from unauthorized removal and against sabotage.  Therefore, a State should have adequate nuclear security measures in place for the radioactive material, its associated facilities and associated activities, including for the transport of radioactive material within the context of its nuclear power programme.

Implementation of nuclear security systems and measures for radioactive material, associated facilities and associated activities falls within the overall nuclear security infrastructure of any State where radioactive material are used.

The nuclear security measures should be designed to:

  • Deter, detect and delay unauthorized access to or unauthorized removal of radioactive material;
  • Allow rapid assessment of any nuclear security events to enable initiation of appropriate response and to allow recovery of radioactive material and mitigation of the event to start as soon as possible; and
  • Provide for rapid response to any attempted or actual unauthorized access to radioactive material.

2.1               General Measures:

The following actions for nuclear security measures for radioactive material and associated facilities and activities should be developed and implemented whether or not the State has a nuclear power programme.  In the case of States wishing to embark on a nuclear power programme, it would be beneficial to the State’s overall security programme to have the actions fully in place as early as possible and prior to the introduction of radioactive material for the construction of the first nuclear power plant. Slide1Slide2

1.1                Security of Radioactive Material in Use and Storage:

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2.3       Security of Radioactive Material in Transport:

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 Resources:

  1. What is Radioactive Materials – Facts Sheet;
  2. Radioactive Materials, Characteristics, Hazards and Health Considerations; and
  3. Establishing the Nuclear Security Infrastructure for a Nuclear Power Programme.

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