Plutonium, handling

L. G. Eaust, Health Physics Manual of Good Practicesfor Plutonium Handling, PNL-6534, Pacific Northwest Laboratory, Richland, Wash., 1988. 

B. A. J. Lister, Health Physics Aspects of Plutonium Handling, AERE-L151, A ERE, HarweU, U.K., 1964. 

Proceedings of the Roc Flats Symposium on Safety in Plutonium Handling Facilities, U.S. Atomic Energy Commission, Washington, D.C., 1971. 

Polzer, W.L. Proc. Rocky Flats Symp. on Safety in Plutonium Handling Facilities, USAEC CONF-710401, 1971. 

White, P. A. F., and S. E. Smith, 1962 Inert Atmospheres, Butterworth, London. This book presents an excellent discussion of inert-gas purification, with emphasis on the purification of glovebox atmospheres for large plutonium-handling facilities. Since the appearance of this book better methods of supporting MnO have been developed and various other advances discussed in the present chapter have been made. Nevertheless, this book provides useful general information. 

Trauwaert, E and Demonie, M. (1995) Plutonium handling and vitrification main process steps and their cost evaluation, NATO Advanced Research Workshop, May 14-17,1995, St. Petersburg, Russia. 

See Appendix I for a more detailed set of requirements. Specific issues include mission requirements, potential burnup criteria, heat rejection, economic resources, environmental impact, safety, technology development risk, completion schedule, repository issues, social and political acceptance, and diversion and proliferation. In addition to these issues, others that need to be considered include plutonium handling, waste disposal, environmental regulations, safety regulations and analysis, safeguards and security, technology development, economic analysis, and government and public policies. A variety of reactor concepts exists, and each concept has unique and specific concerns. The intent is not to present a complete set of requirements, but to briefly discuss a few selected issues. 

In a routine work incident in a plutonium-handling facility (276), a worker was exposed to a small amount of plutonium dioxide while performing a routine pressing, sintering, and density measurement of plutonium dioxide pellets in a glovebox. Because of a fatigue crack in a glove, a small amount of plutonium dioxide powder was released to the room when the worker removed his arm from... 

Because of the high rate of emission of alpha particles and the element being specifically absorbed on bone the surface and collected in the liver, plutonium, as well as all of the other transuranium elements except neptunium, are radiological poisons and must be handled with very special equipment and precautions. Plutonium is a very dangerous radiological hazard. Precautions must also be taken to prevent the unintentional formulation of a critical mass. Plutonium in liquid solution is more likely to become critical than solid plutonium. The shape of the mass must also be considered where criticality is concerned. 

Most chemical iavestigations with plutonium to date have been performed with Pu, but the isotopes Pu and Pu (produced by iatensive neutron irradiation of plutonium) are more suitable for such work because of their longer half-Hves and consequendy lower specific activities. Much work on the chemical properties of americium has been carried out with Am, which is also difficult to handle because of its relatively high specific alpha radioactivity, about 7 x 10 alpha particles/(mg-min). The isotope Am has a specific alpha activity about twenty times less than Am and is thus a more attractive isotope for chemical iavestigations. Much of the earher work with curium used the isotopes and Cm, but the heavier isotopes... 

The simple box-type mixer—settler (113) has been used extensively in the UK for the separation and purification of uranium and plutonium (114). In this type of extractor, interstage flow is handled through a partitioned box constmction. Interstage pumping is not needed because the driving force is provided by the density difference between solutions in successive stages (see Plutoniumand plutonium compounds Uraniumand uranium compounds). 

Storage and Handling. Plutonium can be stored safely in dry air. Because of self-heating, storage accompanied by heat removal is advisable. The metal can be machined in moisture-free air containing at least 70 vol % Ar or He. Casting and foundry operations that requite melting of the metal must be carried out in vacuum or inert atmospheres and special containers. 

The principal ha2ards of plutonium ate those posed by its radioactivity, nuclear critical potential, and chemical reactivity ia the metallic state. Pu is primarily an a-emitter. Thus, protection of a worker from its radiation is simple and usually no shielding is requited unless very large (kilogram) quantities are handled or unless other isotopes are present. 

Plutonium solutions that have a low activity (<3.7 x 10 Bq (1 mCi) or 10 mg of Pu) and that do not produce aerosols can be handled safely by a trained radiochemist in a laboratory fume hood with face velocity 125—150 linear feet per minute (38—45 m/min). Larger amounts of solutions, solutions that may produce aerosols, and plutonium compounds that are not air-sensitive are handled in glove boxes that ate maintained at a slight negative pressure, ca 0.1 kPa (0.001 atm, more precisely measured as 1.0—1.2 cm (0.35—0.50 in.) differential pressure on a water column) with respect to the surrounding laboratory pressure (176,179—181). This air is exhausted through high efficiency particulate (HEPA) filters. 

Safe Handling of Plutonium, A Panel Report, Safety Series No. 38, IAEA, Vienna, Austria, 1974. 

Air monitoring will be required, e.g., when volatiles are handled in quantity, where use of radioaetive isotopes has led to unaeeeptable workplaee eontaiuination, when proeessing plutonium or other transuranie elements, when handling unsealed sourees in hospitals in therapeutie amounts, and in the use of hot eells/reaetors and eritieal faeilities. Routine monitoring of skin, notably the hands, may be required. 

Plutonium has a much shorter half-life than uranium (24.000 years for Pu-239 6,500 years for Pu-240). Plutonium is most toxic if it is inhaled. The radioactive decay that plutonium undergoes (alpha decay) is of little external consequence, since the alpha particles are blocked by human skin and travel only a few inches. If inhaled, however, the soft tissue of the lungs will suffer an internal dose of radiation. Particles may also enter the blood stream and irradiate other parts of the body. The safest way to handle plutonium is in its plutonium dioxide (PuOj) form because PuOj is virtually insoluble inside the human body, gi eatly reducing the risk of internal contamination. 

Figure 4. Plutonium oxide (2.77 micrograms) weighed on September 10, 1942. It is shown on a platinum weighing boat magnified approximately 40-fold. The Pu oxide appears as a crusty deposit (indicated by the arrow) near the end of the platinum weighing boat, which is held with forceps that grip a small handle.

All plutonium produced must be prevented from spreading into the environment. It is presently believed that the safest way is to store plutonium waste in deep underground facilities, and several such are now being constructed (8, 9, 12, 13). In the future, however, releases of various sizes must be anticipated, considering the large amounts of plutonium being handled. The hazards associated with such releases must be reliably assessed. 

Waste Handling for Unirradiated Plutonium Processing. Higher capacity, better-performing, and more radiation-resistant separation materials such as new ion exchange resins(21) and solvent extractants, similar to dihexyl-N,N-di ethyl carbamoyl methylphosphonate,(22) are needed to selectively recover actinides from acidic wastes. The application of membranes and other new techniques should be explored. 

Though both hydrofluorination and reduction were accomplished with relative ease, three significant problems were apparent. First, PuFt is a neutron emitter, requiring considerable protective shielding and creating difficulty in handling. Secondly, the use of HF requires costly equipment which must be resistant to corrosion. Finally, the salt from the reduction, CaF2, is not discardable, and must be processed to recover residual plutonium. 

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