Determination of plutonium in soil

A procedure for the determination of plutonium isotopes in soil is described. The method involves conversion of plutonium to acid-soluble form, dissolution, purification, electrodeposition and alpha-spectrometric determination. Final recovery is in the range from 27 to 51%. In this work increased attention was paid to the problem of equilibration of the chemical yield monitor with plutonium present in the soil sample.     

Potentiometric determination of plutonium by sodium bismuthate oxidation

A potentiometric method for the determination of plutonium is described, in which the plutonium is quantitatively oxidized to plutonium(VI) with sodium bismuthate in nitric acid medium, the excess of oxidant is destroyed chemically and plutonium(VI) is reduced to plutonium(IV) with a measured excess of iron(II), the surplus of which is back-titrated with dichromate. For 3–5 mg of plutonium the error is less than 0.2%. For submilligram quantities of plutonium in presence of macro-amounts of uranium the error is below 2.0%.     

Determination of uranium and plutonium in plutonium based fuels by sequential amperometric titration

A method is described for the sequential determination of uranium and plutonium in plutonium bearing fuel materials. Uranium and plutonium are reduced to U(IV) and Pu(III) with titanous chloride and then titrated with dichromate to two end points which are detected amperometrically using two polarized platinum electrodes. Uranium-plutonium solutions of known concentrations containing plutonium in the proportions of 4, 30, 50, and 70% were analyzed with precisions better than 0.3%, maintaining the amounts of plutonium per aliquot in the range of 2–10 mg. No significant bias could be detected. Several samples of (U, Pu)O₂ and (U, Pu)C were analyzed by this procedure. The effects of iron, fluoride, oxalic acid and mellitic acid on the method were also studied.     

Determination of plutonium by secondary coulometric titration with internally generated iron(II)

The method for plutonium determination based on secondary controlled-potential coulometry, as described by SHULTS, is applied for analysis in the range of 0.1–5 mg plutonium. The method involves the oxidation of plutonium to Pu(VI) with perchloric acid followed by its reduction by an internally generated ferrous mediator. This is a two step procedure, involving the reduction of Pu(VI) and Fe(III) to a mixture of Pu(III) and Fe(II), followed by the oxidation of Pu(III) and Fe(II) to Pu(IV) and Fe(III), respectively. The net results is the reduction of Pu(VI) to Pu(IV), measured as the difference between the currents consumed during the reduction and oxidation steps. The original method of SHULTS involves 10–25 mg plutonium for each determination. Since the present method is intended for the analysis of smaller amounts of plutonium, the oxidation procedure described in the original version had to be modified. The method is found to work satisfactorily with a precision better than 0.1% at 5 mg level and 1.2% for 0.1 mg plutonium.     

A modified radiometric method for plutonium determination in irradiated fuel

A modified radiometric method for the determination of plutonium in irradiated nuclear fuel is described. The analysis consists of total plutonium alpha-activity, activity ratio²³⁸Pu:(²³⁹Pu+²⁴⁰Pu) and burnup determination. The error of plutonium determination is practically identical with that of a classical radiometric method. The method suggested is suitable for large sample series of the same type of irradiated nuclear fuel.     

Age determination of plutonium material in nuclear forensics by thermal ionisation mass spectrometry

Age is a key parameter when deducing the history of plutonium material, i.e. the plutonium produced in the nuclear reactors. This is of vital importance, when a smuggled plutonium sample has been seized and the origin has to be determined. A methodology is described which allows accurately to determine the age of plutonium material by thermal ionisation mass spectrometry using independent parent/daughter relations. This has been demonstrated for Reference Materials of known ages as well as for real samples. The already established method using gamma spectrometry is compared to this.     

Age determination of plutonium material in nuclear forensics by thermal ionisation mass spectrometry

Age is a key parameter when deducing the history of plutonium material, i.e. the plutonium produced in the nuclear reactors. This is of vital importance, when a smuggled plutonium sample has been seized and the origin has to be determined. A methodology is described which allows accurately to determine the age of plutonium material by thermal ionisation mass spectrometry using independent parent/daughter relations. This has been demonstrated for Reference Materials of known ages as well as for real samples. The already established method using gamma spectrometry is compared to this.     

A spectrophotometric method for the determination of plutonium in fuel solutions

A spectrophotometric method is described in which microgram amounts of plutonium can be determined in the presence of uranium, thorium, fission products and cladding materials. Plutonium is extracted with TTA in xylene and reextracted into a solution of Arsenazo III. Zirconium is masked by a Fe(III)-EDTA mixture, fluoride ions by Al(III). 2 to 40 μg of plutonium are required for one analysis. The standard deviation is 1.3% at 15 μg plutonium.     

Determination of plutonium oxidation states in dilute nitric acid by complementary tristimulus colorimetry

The preparation of reference standards for use in complementary tristimulus colorimetry for plutonium is described. Plutonium(III) and (VI) are prepared by hydrazine reduction and silver(II) oxidation, respectively, of plutonium(IV). Plutonium(V) is prepared by reduction of plutonium(VI) with ascorbic or sulphurous acid. A method for computerizing tristimulus colorimetry is presented, and the technique is extended to three dimensions ("quadristimulus colorimetry").     

Airborne plutonium monitoring

Methods of monitoring low plutonium concentration in the inner and outer atmosphere are analyzed and compared. It is shown that monitors based on the gross alpha counting of air filters are not sensitive enough to measure reliably plutonium activities below 1 MPC. A spectrometric discontinuously operating monitor using a gridded ionization chamber and a membrane filter having 70 cm² active area is described. Plutonium activities of the order of 0.01 MPC /1 mBq.m^–3/ can be measured by the spectrometer at 1 h sampling and 1 h counting time.     

A rapid and specific determination of traces of plutonium with a recording spectrophotometer

A spectrophotometric method for the determination of plutonium in the range of 0.2–140 mg/1 is described. The method is based on the measurement of the absorption of plutonium (VI) at 831 nm. A recording spectrophotometer with variable slit width, 10-cm cells and scale expansion facilities, is necessary. Uranium up to 20 g/1 does not interfere.     

Improved method for the constant-current potentiometric determination of plutonium

A highly precise method is described for the determination of plutonium by constant-current potentiometric titration with primary standard potassium dichromate. The relative standard deviation is 0.04% or better.     

The determination of plutonium by mass spectrometry using a [242]-plutonium tracer

An isotopic dilution method is described for the determination ot plutonium in samples of irradiated uranium using a ²⁴²Pu tracer. An aliquot of tracer is added to the sample and the mixture treated to ensure isotopic exchange; plutonium is then separated by an ion exchange procedure and an isotopic analysis made using an M.S.5. mass spectrometer. The precision (3 σ) for an aliquot containing 0.1 μg plutonium is 0.6%. A possible application of the method would be its use for control analyses of the feed solution in a chemical plant processing natural uranium fuel elements as, for example, the Windscale primary separation plant.     

On the concentration and determination of plutonium in natural waters by adsorption on MnO2 filters

A new method of analysis of the efficiency of four filters of MnO₂ in series which takes into account the reactions induced in plutonium by the sorbent is described. The system of differential equations describing the behaviour of plutonium in water as it passes through the filters is solved and the parameters of the filters are determined for a best fitting of the solutions corresponding to the experimental uncertainties. The method is checked by numerical simulation and then applied to water solutions with a known plutonium concentration and to some experimental results given by other authors. In all occassions the results are consistent with the possibility of determining the contents of plutonium in sea and continental waters with uncertainties of the order of 10%.     

A spectrophotometric method for the determination of neptunium and plutonium in process solutions

A method is described for the determination of neptunium and plutonium in process solutions. This involves the separation of these elements followed by their spectrophotometric determination as Arsenazo III complexes. Neptunium(IV) and plutonium(IV) are separated using TTA extraction method and the separated Np(IV) and Pu(IV) are then determined as their Arzenazo III complexes in 5M HNO₃. A few solutions obtained by dissolving irradiated fuels were analysed for plutonium and neptunium using this method and the results were compared with those obtained by other methods. An attempt was made to use Arsenazo III to determine uranium in the plant solutions.     

New fecal method for plutonium and americium

A new fecal analysis method that dissolves plutonium oxide was developedat the Westinghouse Savannah River Site. Diphonix Resin . (Eichrom Technologies),is used to pre-concentrate the actinides from digested fecal samples. A rapidmicrowave digestion technique is used to remove the actinides from the DiphonixResin ., which effectively extracts plutonium and americium from acidic solutionscontaining hydrofluoric acid. After resin digestion, the plutonium and americiumare recovered in a small volume of nitric acid that is loaded onto small extractionchromatography columns, TEVA Resin and TRU Resin (Eichrom Technologies). Themethod enables complete dissolution of plutonium oxide and provides high recoveryof plutonium and americium with good removal of thorium isotopes such as ²²⁸Th.     

Determination of plutonium by isotopic dilution mass spectrometry following TTA-extraction

Isotopic dilution mass spectrometry has been applied to assess the plutonium concentration in samples such as those obtained from the dissolution of irradiated uranium fuels in a reprocessing plant. Prior to the analysis, plutonium is taken through a redox cycle and is separated from uranium and fission products by extraction into TTA-xylene. The extraction procedure, the standardization of the spike solution and the mass assay of the plutonium are described; typical results under plant conditions are given. The overall precision of a single measurement of the plutonium concentration is 0.6%, expressed as relative standard deviation, including the plant sampling error, dilution error and analytical error.     

Determination of sulphate and nitrate in plutonium compounds by infrared spectroscopy

An infrared spectrophotometric method is described for the determination of sulphate and nitrate in plutonium peroxide and plutonium tetrafluoride. Spectra of the samples in potassium bromide pellets are obtained over the 4000-4680 cm(-1) wavelength region; sulphate is determined from the absorbance of the 1103 cm(-1) absorption band and nitrate from the 1370 cm(-1) band. Data are given on the precision and accuracy for analyses of peroxide and tetrafluoride samples.     

Determination of plutonium in the presence of uranium by alpha-spectrometry

The plutonium determination by alpha-particle spectrometry with semiconductor detectors in the presence of uranium has been described. It has been found that plutonium as well as uranium can be electrodeposited quantitatively on nickel or stainless steel discs from solutions in isopropanol. The time of deposition does not exceed 35–40 min. The determination of plutonium is possible within the uranium to plutonium weight ratio of 4000 with the accuracy better than 2%.     

Empirical method for preparing a plutonium predominance-region diagram

An empirical method for preparing a plutonium predominance-region diagram is illustrated by an example. The method estimates the boundaries of the forbidden, unique, and ambiguous regions as defined by the equilibrium fraction of hexavalent plutonium and the plutonium oxidation number.