Decontamination first steps

However, due to the chemical similarities of the trivalent actinide and lanthanide elements, historically, it has been easier to develop step-by-step processes first, An(III) + Ln(III) coextraction processes, which also address the problem of waste alpha decontamination, and second, An(III)/Ln(III) separation processes, which can only be implemented on the solutions produced by the first-step processes. Today, however, a few processes are available that allow recovery of the trivalent actinides in a single step from highly active liquid waste. 

The extraction of Zr increased with the absorbed y-dose (factor of 20 up to 0.7-0.8 MGy for linear amides in n-dodecane (191) and factors of 4-6 up to 0.3-0.6 MGy for shorter amides in benzene) (192). Beyond this threshold, the extraction decreased slightly. This effect is more noticeable with N-methyl amides (192). As for Pu(TV), the first step has been explained by authors by a synergistic extraction due to the presence of carboxylic acids as degradation products (191). Nevertheless, the degradation had a stronger effect on the decontamination factors of U and Pu with respect to Zr(IV) than with TBP (191). Typically, decontamination factors were DEM/Zr = 7 and 12 for, respectively, U(VI) and Pu(IV) with TBP and 5 with the monoamide DHOA at an irradiation dose of 300 MGy (193). 

Mound Facility Low-Risk Waste. Approximately 3 x 105 l of low-level waste are generated weekly at the Mound Facility. This particular waste stream is essentially local hard water which has been demineralized and then used in various chemical processes involving the radionuclides 238Pu and 233U. The first step in decontaminating the low-risk wastes entails addition of small amounts of calcium and iron salts followed by addition of NaOH to pH 11.5 to precipitate iron and calcium hydroxides and carbonates. The clarified effluent from the precipitation step is then passed through a 200 micrometer sand filter to yield a solution containing, typically, 0.1+ d/min/m alpha activity. 

When caring for victims, rapid decontamination is an essential first step in reducing exposure. The basic purpose of decontamination is to reduce external contamination, contain the contamination present, and prevent the spread of the hazardous material. In the words of the Agency for Toxic Substances and Disease Registry (ATSDR) (9), remove what you can and contain what you can t. ... 

Contaminated feed poses a serious source of infection for livestock. Animals rarely show symptoms of salmonellosis and there is always the risk of undetected carriers entering the food production chain. Safe feed is the first step in a farm-to-fork food safety concept to guarantee safe food. All raw feed components should be considered as a potential source of Salmonella, and, therefore, decontamination steps are of utmost importance to avoid contaminated feed spreading to herds (Sauli, Danuser, and Geeraerd, 2005). 

If excessive, this contamination must be removed by aqueous-acid decontamination prior to equipment maintenance. Neutralizing the chemical activity of the sodium is the first step in such decontamination. 

The removal of solid or liquid chemical agent from exposed individuals is the first step in preventing severe injury or death. Civilian Hazmat teams generally have basic decontamination plans in place, though proficiency may vary widely. Very few teams are staffed, equipped, or trained for mass decontamination. Hospitals need to be prepared to decontaminate patients, despite plans that call for field decontamination of all patients before transport to hospitals. However, few hospitals have formal decontamination facilities even fewer have dedicated outdoor facilities or an easy way of expanding their decontamination operations in an event involving mass casualties. 

As noted above, among the first steps in the decontamination process is the removal and disposal of clothing. Cox (1994) estimates that 70 to 80 percent of contaminant will be removed with the patient s clothes. Little scientific data exist to support this assertion, however. The ideal skin decontaminant would remove and neutralize a wide range of hazardous... 

Before entering such a scene you should take appropriate self-protection steps, ensuring that you have respiratory protection and are wearing at least Level C PPE. It is best if someone (usually a HazMat team) enters the scene and identifies the chemical agent using a chemical agent detector (See Chapter 2 and Practical Skills 5). While this is going on, your first step is to immediately remove the ambulatory patients from tbe decontaminated area, have the patients remove their contaminated clothes, decontaminate the patients, perform a brief medical... 

In the reverse TALSPEAK process, the An(III) + Ln(III) fraction is first coextracted from a feed, the acidity of which has to be reduced to 0.1 M by denitration or nitric acid extraction. An(III) are then selectively stripped using DTPA in citric acid (1 M) at pH 3 (hence the name reverse TALSPEAK process), and the Ln(III) are finally stripped by 6 M HN03. Attempts to apply this TALSPEAK variant to the treatment of actual UREX + raffinates are reported in the literature, but they involve several steps. The problematic Zr and Mo elements are first removed by direct extraction with HDEHP (0.8 M in di-iso-propylbenzene) from the high-acidity raffinate stream arising from the UREX + co-decontamination process (238). The remaining fission products and actinides can then be concentrated by acid evaporation and denitration processes. This concentrate is further diluted to a lower acidity (e.g., [HN03] = 0.03 M) to allow the coextraction of An(III) and Ln(III) by the TALSPEAK solvent. 

The bismuth phosphate process consisted of a number of steps in which plutonium is made alternatively soluble and insoluble. Fuel elements containing plutonium, uranium, and fission products were first dissolved in nitric acid. Plutonium was reduced to the tetravalent state by addition of sodium nitrite. Plutonium phosphate Pu3 (P04)4 was coprecipitated with bismuth phosphate BiP04, by addition of bismuth nitrate and sodium phosphate. Coprecipitation of uranium was prevented by the presence of sufficient sulfate ion to form anionic UO2(804)2. The BiP04 precipitate was redissolved in nitric acid and subjected to two decontamination cycles to purify the plutonium. In each cycle the plutonium was oxidized to the soluble hexavalent state by NaBiOs or other strong oxidant. Next bismuth phosphate was again precipitated, to remove fission products while hexavalent plutonium remained in solution. Then plutonium was reduced to the tetravalent state and again coprecipitated with bismuth phosphate. 

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