Cobalt sources

Evaluation of Cobalt Sources ia Westinghouse-Designed Three- and Eour Loop Plants," Report NP-2681, Electric Power Research Institute, Palo Alto, Calif., Oct. 1983. 

A fermentation such as that of Pseudomonas dentrificans typicaby requires 3—6 days. A submerged culture is employed with glucose, comsteep Hquor and/or yeast extract, and a cobalt source (nitrate or chloride). Other minerals may be required for optimal growth. pH control at 6—7 is usuaby required and is achieved by ammonium or calcium salts. Under most conditions, adequate 5,6-dimethylben2imida2ole is produced in the fermentation. However, in some circumstances, supplementation maybe required. 

A cobalt source was used to provide gamma radiation for a powdered polymer sample under a nitrogen atmosphere. A total dose of 20 Mrad was applied. Solutions with 1.0 dl/g were made of the initial and exposed polymer in THF at 30 °C. In the usual fashion, the reduced viscosity, risp/c was calculated for each. From an original value of 1.81, the i)sp/c fell to 0.14 after irradiation. 

Body-doped pigments contain 1-5% cobalt that is uniformly distributed throughout the bulk of the pigment particles. It is either incorporated during production of the FeOOH precursor or precipitated as the hydroxide onto one of the intermediate products [5.11] using cobalt(II) salts as the cobalt source. 

The conveyor used with the cobalt source was originally designed to be used with no lubrication. However, because of rust buildup on the wearing surfaces it was found to function better if lubricated (Atomic Energy of Canada, Ltd., SKF-M-3 ball grease base). 

The cobalt source is raised into the irradiation cell from the bottom of its storage pool for irradiation by the source elevator. The drive for the elevator is located in the modulator room. The motor for lifting the source is mounted on the main drive shaft by a torque-sensitive drive mechanism. This mechanism provides a safety feature by which, if the source jams, the elevator motor will hit limit switches and stop. 

To calibrate the cobalt source, three systems are most often used ferrous sulfate, ferrous sulfate-cupric sulfate, and ceric sulfate. Dosimeters of these solutions are prepared by filling 5-ml. chemical-resistant glass ampoules with approximately 5 ml. of solution and flame-sealing the ampoules. The ampoules are then arranged in phantoms of Masonite or similar materials (Figure 13) to simulate the food items. These phantoms are placed in containers similar to those used for food products, and arranged in the conveyor carrier in which they are transported into the irradiation cell. Because of the upper dose limit of the ferrous sulfate and ferrous sulfate-cupric sulfate dosimeters (40,000 and 800,000 rads, respectively), these systems can be used only to establish the dose rate in the facility and not to monitor the total dose during food irradiation. The ceric dosimeter which... 

However, on a process scale isotopes suffer the disadvantages of low dose rates, which limit process flow. A large cobalt source, for example, delivers about 10 kGy hr-1, while rates as high as 1 kGy s 1 are common with accelerators. A further problem of isotopes is that the common 60Co source has a 5.27-year half-life. It thus loses 12.5% of its activity annually. Economic analyses have shown that when cobalt replacement costs are accounted for, e-beams are more cost-effective sources for generating the absorbed doses usually necessary for treatment [51]. 

Confluent cultures containing (2 X 106 cells/90 mm dish are irradiated with 4000-6000 rads of y-radiation from a cobalt source. Irradiation should last for less than 1 min and a variety of cell lines (e.g. HeLa, BHK21/C13 or 3T3) are suitable (Puck et al., 1956). These cells may be used directly or may be trypsinised into smaller vessels. They may appear healthy for up to 4 weeks but do not divide. 

Several non-carbonyl cobalt sources used recently show high efficiency in the catalysis of the PKR. Chung has reported different reusable catalysts like cobalt supported on mesoporous silica or on charcoal that work under high CO pressures [ 127]. Most recently they have described milder conditions with the use of colloidal cobalt nanoparticles, which react at lower CO pressures and can be used in aqueous media [128]. 

Figure 3. Sensitivity to gamma radiation (Cobalt source) CO, G(s) 5.1 O PMMA, G(S) 0.8.

Roberts 127) have noted some cases of a significantly greater amount of methanol formation during the synthesis at 1 atm. over zinc oxide which was being irradiated in situ by 7-rays from a 350-curie cobalt source. 

Cobalt containing ZSM5 zeolite was synthesized hydrothermally in a stirred autoclave in 48 h at 743 K according to refs. (4, 5) using C0CI2.6H2O as cobalt source. After synthesis the sample was calcined to remove the template. 

Synonym Carbonyl(r7 -cyclopentadienyl) [tris(4-trimethylsilylphenyl)phosphine] cobalt Source Montilla, R Galindo, A. Rosa,... 

DM digestibility (sheep) timothy 45.5% and alfalfa 48.5%. b 2.7 X 108 rads from a cobalt source. 

Mine. T. I rbanski and falscki [96] examined Ihc action ofioni/inc radiation fioni Cobalt source ((iamm.i Cell 220) upon u-hexane dissolved in N Oj in sealed Kibes. The re.iclion was carried out for 200 hr at room temperatures, and the yield of I-tiiirohexane was Ia. The expeninents were discontinued when a. iolent explosion occurred in one of the lubes. 

Initially, the aqueous impregnation routes were beset with problems due to cobalt hydrolysis reactions that were amplified by the presence of the support material. The rate and extent of these reactions was highly dependent on, for instance, cobalt source, metal concentration, temperature and time. However, after much work, the chemistry was understood well enough to allow aqueous solutions to be used for impregnation. The ultimate performance of catalysts in the FT reaction (activity, selectivity and stability) could be directly related to the structure of the catalyst precursors. Detailed recipes were required to ensure that the correct precursors were made during the impregnation and subsequent calcination steps. 

Cobalt oxide (ous) cobalt source, water-soluble Cobalt sulfate (ous) cobalt steel mfg. 

The mobile irradiator incorporates a compact cobalt source of 20,000 curies in a small irradiation chamber shielded by lead. The method of feeding the plant and handling the boxes during irradiation is shown in Fig. 6. The boxes travel two circuits around the source to obtain an equalized dose. 

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