238Pu determination

The radiation resistance of zirconolite has been tested with 238Pu- and 244Cm-doped and ion-irradiated samples (Weber et aL 1998 Weber Ewing 2002). Amorphization of zirconolite occurred at doses corresponding to 0.3-0.5 dpa at room temperature. Dose-age relationships have been determined by analytical transmission electron microscopy for the onset dose and critical amorphization dose of a suite of natural zirconolites (Lumpkin etal. 1994,1998b). 

Am with a half-life of ti = 432 a has to be determined in waste and environmental samples by mass spectrometry. The determination of 238Pu (ti 88 a) at the trace level is difficult in the presence of uranium due to isobaric interference with 238 U+ in mass spectra measured by ICP-MS or LA-ICP-MS. Therefore the application of a sensitive and selective technique such as RIMS or AMS is advantageous. The determination of 238Pu for plutonium isotope analysis in irradiated... 

The isotope plutonium-238 [13981 -16-3]y 238>Pu, is of technical importance because of the high heat that accompanies its radioactive decay. This isotope has been and is being used as fuel in small terrestrial and space nuclear-powered sources (3,4). 238Pu-based radioisotope thermal generator systems delivered 7 W/kg and cost 120,000/W in 1991 (3). For some time, 238>Pu was considered to be the most promising power source for the radioisotope-powered artificial heart and for cardiovascular pacemakers. Usage of plutonium was discontinued, however, after it was determined that adequate elimination of penetrating radiation was uncertain (5) (see Prosthetic and biomedical devices). 

It has been estimated that 1.3 x 1016 Bq of 239+240 pu has been released to the environment from atmospheric detonation of nuclear weapons that 7.9 x 1014 Bq of 238Pu has been released, mosdy from bum-up of the nuclear powered satellite SNAP-9a and that 3.7 x 1013 Bq of 239+240 Pu was released by the Chernobyl accident (167,168). Many studies have been done to determine the cumulative fallout on soils, plants, bodies of water, animals, and humans. For example, the cumulative 239+240 pu fallout in forest and grasslands and in the liver of eldedy humans in Bavaria, Germany are approximately 50 Bq/m2 and 0.02 Bq/kg wet mass, respectively (167). 

Hydrolysis reactions of Am(in) and Pu(VI) ions in CO2-free solutions of 0.1 M NaC104 were studied by means of solubility experiments using the oxide or hydroxide of 241 Am and 238Pu. The pH of solutions was varied from 3 to 13.5. All experiments were carried out under an argon atmosphere. The speciation of dissolved species was determined as far as possible by spectrophotometry. Various ultrafiltration membranes were applied to examine the proper phase separation. Stability constants of all possible hydrolysis products are presented and compared with literature data. 

On the other hand, Np and Pu are very radiotoxic elements and the long-term hazard potential (fig. 1) of a final HTGR-waste deposit is especially determined hy 237Np and 238pu (2.) while the other actinides, apart from the non-recovered U, are of minor importance. Hence, alternative solutions for their disposal are now discussed and investigated (j ). 

Several liters of the wastewater to be used as feed to the columns were spiked with 238pu to a concentration of about 4 pCi/L. The pH was re-adjusted to the original 8.3 using dilute NaOH. This solution was pumped with an Eldex Model E-120-S precision metering pump through a 1.0 pm pore size Teflon Millipore filter and then to the bottom of a column prepared as in the previous paragraph. The effluent from the top of the column was collected in plastic tubes with an HBI Model LC 200 fraction collector. Each tube collected one pore volume of effluent. Six flow rates were used to determine the rates of adsorption 0.5, 1, 2, 3, 4, and 5 ml/min. At least five consecutive pore volumes were collected for each flow rate to ensure steady state concentrations of plutonium in the effluent. The effluent concentration, C, was compared with the influent concentration, Co. 

The spectrometer used permitted the simultaneous determination of americium and plutonium 1n the sample and canceled out any corrections due to geometry. Similarly an x-ray spectrometer was employed to detect the attenuation of 238Pu L x-rays as the Pu migrated Into the body of a piece of rock. By measuring the changes in the La/Lg or LY/Lg ratios the penetration of Pu into the solid could be calculated after calibration with stone absorbers. 

The concentrations of the 238Pu in the salt solutions shown in Figs. 15 and 16 were determined by alpha counting the concentrations of americium 1n the salt solutions shown in Fig. 17 were determined by gamma counting. Since the alphacounting techniques are much more susceptible to sample thickness, the abrupt bends in the curves in Fig. 16 at high salt concentrations may be in part caused by this effect. 

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