Radioactive materials fissile material

This brief discussion of the Purex process is expanded in Chap. 10, which discusses other processes for treating irradiated fuel and which deals with novel aspects of processing highly radioactive and fissile materials. 

The approval of the shipments for important amounts of radioactive and fissile materials ... 

Radioactive and Fissile Material Limits Worker Safety/Defense in Depth AC... 

Limits on radioactive and fissile material inventories are established by administrative controls. These limits, as described in Section 5.5.6.3, are in effect for all modes. 

As indicated in Section 5.3, there are no SLs, LCSs, or LCOs associated with maintaining radioactive and fissile material limits. 

Safety Standards for the Packaging of Radioactive and Fissile Materials," U.SJ Atomic Energy Commission, AEC Manual, Chap. 0529 (August 1968). 

There are nine classes of dangerous goods, with divisions of some classes. The classes are explosive flammable and non-flammable non-toxic gases flammable liquids flammable solids and spontaneously combustible materials oxidizing substances and organic peroxides toxic and infectious substances radioactive and fissile materials corrosive substances and miscellaneous. 

Nuclear processes provide humankind with a double-edged sword. On one hand, there are many useful applications of radioactive substances in science and medicine. Nuclear power is, and will continue to be, an important soiuce of energy. On the other hand, there is always the danger of radioactive or fissile materials being used to threaten people s lives. No one can make radioactive or fissile materials just go away. Hopefully, wisdom will prevail, and peaceful applications of nuclear materials will dominate their use. 

A D—T fusion reactor is expected to have a tritium inventory of a few kilograms. Tritium is a relatively short-Hved (12.36 year half-life) and benign (beta emitter) radioactive material, and represents a radiological ha2ard many orders of magnitude less than does the fuel inventory in a fission reactor. Clearly, however, fusion reactors must be designed to preclude the accidental release of tritium or any other volatile radioactive material. There is no need to have fissile materials present in a fusion reactor, and relatively simple inspection techniques should suffice to prevent any clandestine breeding of fissile materials, eg, for potential weapons diversion. 

Since the amount of fissile material in the fuel assemblies is only about 3 percent of the uranium present, it is obvious that there cannot be a large amount of radioactive material in the SNF after fission. The neutron flux produces some newly radioactive material in the form of uranium and plutonium isotopes. The amount of this other newly radioactive material is small compared to the volume of the fuel assembly. These facts prompt some to argue that SNF should be chemically processed and the various components separated into nonradioac-tive material, material that will be radioactive for a long time, and material that could be refabricated into new reactor fuel. Reprocessing the fuel to isolate the plutonium is seen as a reason not to proceed with this technology in the United States. 

Maximum difficulty to recover radioactive constituents from waste form (especially fissile materials, such as Pu). 

Radioactive Material From 49 CFR 173.403, a radioactive material is any material having a specific activity greater than 0.002 microcuries per gram (uCi/g). Specifications and descriptions can be found in the regulations. The reader may also refer to the term fissile material in this glossary. 

Most radioactive particles and vapours, once deposited, are held rather firmly on surfaces, but resuspension does occur. A radioactive particle may be blown off the surface, or, more probably, the fragment of soil or vegetation to which it is attached may become airborne. This occurs most readily where soils and vegetation are dry and friable. Most nuclear bomb tests and experimental dispersions of fissile material have taken place in arid regions, but there is also the possibility of resuspension from agricultural and urban land, as an aftermath of accidental dispersion. This is particularly relevant to plutonium and other actinide elements, which are very toxic, and are absorbed slowly from the lung, but are poorly absorbed from the digestive tract. Inhalation of resuspended activity may be the most important route of human uptake for actinide elements, whereas entry into food chains is critical for fission products such as strontium and caesium. 

However, as pointed out by Bamaby (1990), there is a real risk that sub-national groups will in the future acquire fissile material— particularly plutonium—and construct a nuclear explosive. Equally disturbing, and perhaps more likely, is the possibility that plutonium may be acquired by a group who will threaten to disperse it, by an explosion, and radioactively contaminate a large urban area. 

Diversion of spent or extensively irradiated fuel for clandestine chemical extraction of fissile material in a reprocessing facility this scenario is technically more demanding and time-consuming than the one mentioned above because of the high level of radioactivity from the fuel which is involved. However, it is of particular concern at about 15 research reactors under IAEA safeguards due to large accumulated quantities of spent fuel, and it is of importance at more than 100 others. 

Aqueous reprocessing methods have been developed to effect an efficient and thorough separation of fissile elements from the contaminating fission products in spent fuel( l). While these processes may be altered to yield a proliferations-resistant product by coprocessing or by the addition of radioactive material that will contaminate the clean fissile material, it still is necessary to safeguard some of the process steps to ensure that material useful in nuclear weapons will not be diverted (3). The safeguard requirements and the ease of subversion of such provisions make many versions of the conventional processes subject to unacceptable proliferation risks. 

Although the retention of selective fission products in fissile materials may not adversely affect the performance of fuel in a reactor, the intensity of the gamma radiation is such that the fissile material must be handled, transferred, and fabricated remotely. As a result, it is both technically difficult to divert the fissile material and fabricate a weapon, and nearly impossible to do so without detection. The levels of residual radioactivity in the product of some of the pyrochemical or dry processing methods is close to that found in spent unreprocessed fuel and hence the reprocessed product presents a risk to proliferation only trivially less than that of spent fuel. Pyrochemical and dry processing methods can be used that will... 

Spent fuel is generally regarded as proliferation-resistant due to the high level of radioactivity and the low concentration of fissile material in the fuel removed from a reactor. High levels of radioactivity promote proliferation resistance because special, easily monitored facilities are required to process the fuel and the high level of radioactivity makes removal of fuel without detection extremely difficult. Spent fuel is also proliferation-resistant because the concentration of fissile material is below that required to achieve a nuclear detonation. 

A RADIOACTIVE WHITE-I label must be affixed to each package measuring 0.5 miUirem or less per hour at each point on the external surface of the package, provided the package is not a Fissile Class II or EH, or does not contain a large quantity of radioactive material, as defined in Section 173.389 of the regulations... 

---