The 240Pu oxide, enriched to 98.5% in 240Pu, used for the half-life measurements was prepared by ion-exchange purification in nitric acid solution, followed by heating at 1250°C to the oxide. Four laboratories provided characterizations of plutonium chemical assay, mass-spectrometric isotopic abundances, and measurements of radioactive and nonradioactive impurities. The 95% confidence interval associated with the computed number of atoms of 240Pu per gram of oxide is ±0.03%.

The half-life of 241Pu has been measured by mass-spectrometric determinations of the decreasing ratio of a mixture of nearly equal numbers of atoms of 241Pu and 242Pu over decay periods of up to 3.6 yr. The measured half-life is 14.38 yr with an associated standard deviation of the mean of 0.013 yr and 95% confidence limits of 14.32 and 14.43 yr. All experimental uncertainties and their statistical treatment are presented in detail.

Uranium(VI) is selectively determined by a compleximetric titration with pyridine-2,6-dicarboxylic acid, using arsenazo-I indicator and hexamethylenetetramine buffer at pH 4.9. Cyclohexanediaminetetraacetic acid and diethylenetriaminepentaacetic acid provide masking of interfering metal ions. A probe colorimeter apparatus is recommended for end-point detection. The relative standard deviation is 0.6% for 0.17–0.76 μmol of uranium.

Total plutonium is selectively determined by a controlled-potential coulometric method in which plutonium is reduced to Pu(III) at 0.25 V (vs. SCE) in a 5.5 M hydrochloric acid—0.015 M sulfamic acid electrolyte, diverse ions are oxidized at 0.57 V, phosphate is added to reduce the Pu(III)—Pu(IV) potential, and Pu(III) is oxidized to Pu(IV) at 0.68 V. None of more than 50 metal ions present in nuclear fuel-cycle material interferes. Many anions are without effect and most interfering ones are removed by preliminary fuming with perchloric acid. The apparatus described consists mainly of commercial components. The relative standard deviation is <0.1% at the 5-mg plutonium level.

Procedures are presented for preparing mixed oxide with assigned values of plutonium and uranium contents and isotopic distributions. This material is used to calibrate and maintain quality control surveillance of chemical methods for the analysis of nuclear, fuel-cycle mixed oxide. Detailed statistical treatments are included that give a reliability measure of the prepared material for application to nuclear material accountability and safeguards.

The LASL automated spectrophotometer for the determination of both uranium and plutonium is described. Data are given showing its extension to the determination of submilligram amounts of uranium. A microgram-sensitive method for uranium has been developed and its adaptation to the instrument is underway.

An effective quality assurance program for the chemical analysis of nuclear fuel is essential to assure that the fuel will meet the strict chemical specifications required for optimum reactor performance. Such a program has been in operation since 1972 for the fuels manufactured for the Fast Flux Test Facility. This program, through the use of common quality control and calibration standards, has consistently provided high levels of agreement among laboratories in all areas of analysis. The paper presented gives a summary of the chemical specifications for the fuel and source material, an outline of the requirements for laboratory qualifications and the preparation of calibration and quality control materials, general administration details of the plan, and examples where the program has been useful in solving laboratory problems.

A chemical burnup procedure incorporates the ion-exchange separation of uranium, plutonium, and total rare earth fission products (as the fission monitor) followed by the spectrophotometric determination of each. The separation involves retaining uranyl and plutonyl chloride complexes on a macroporous anion exchange column from 12 M HCl, whereas the rare earths and most fission products pass through. Subsequently, plutonium is eluted with 0.1 M HI-12 M HCl and uranium with 0.1 M HCl. From the initial effluent of the first column, the rare earth group is separated on a second column of either (1) macroporous anion exchange resin from HNO/sub 3/-CH/sub 3/OH, or (2) pellicular cation exchange particles from HCl-C/sub 2/H/sub 5/OH. The HNO/sub 3/--CH/sub 3/OH system normally is used to separate the rare earth group from fuel cladding elements and other fission products. The HCl--C/sub 2/H/sub 5/OH system additionally separates the rare earth group from americium. Arsenazo III is the chromogenic agent for the spectrophotometric determination of the separated uranium, plutonium, and rare earth fractions.

Also, a preliminary three-dimensional model has been completed. These results are discussed in this report along with future work.

The automated spectrophotometer described is the first in a planned series of automated instruments for determining plutonium and uranium in nuclear fuel cycle materials. It has a throughput rate of 5 min per sample and uses a highly specific method of analysis for these elements. The range of plutonium and uranium measured is 0.5 to 14 mg and 1 to 14 mg, respectively, in 0.5 ml or less of solution with an option to pre-evaporate larger volumes. The precision of the measurements is about 0.02 mg standard deviation over the range corresponding to about 2 rel percent at the 1-mg level and 0.2 rel percent at the 10-mg level. The method of analysis involves the extraction of tetrapropylammonium plutonyl and uranyl trinitrate complexes into 2-nitropropane and the measurement of the optical absorbances in the organic phase at unique peak wavelengths. Various aspects of the chemistry associated with the method are presented. The automated spectrophotometer features a turntable that rotates as many as 24 samples in tubes to a series of stations for the sequential chemical operations of reagent addition and phase mixing to effect extraction, and then to a station for the absorbance measurement. With this system, the complications of sample transfers and flow-through cells are avoided. The absorbance measurement system features highly stable interference filters and a microcomputer that controls the timing sequence and operation of the system components. Output is a paper tape printout of three numbers: a four-digit number proportional to the quantity of plutonium or uranium, a two-digit number that designates the position of the tube in the turntable, and a one-digit number that designates whether plutonium or uranium was determined. Details of the mechanical and electrical components of the instrument and of the hardware and software aspects of the computerized control system are provided.

and tributylphosphate has shown separation factors of up to 800 for americium over europium in a single extraction stage. Such systems could find application in advanced partitioning schemes for nuclear waste.