The concept of directly spiking samples of the solution with dissolved irradiated nuclear fuel for later dilution and measurement of the isotopic contents of uranium and plutonium has been developed successfully. Large sized dried spikes (LSD) have become a fundamental part of the fissile material control of irradiated nuclear fuel. In the frame of providing these spikes to the nuclear industry, a new set of LSD Spikes for the determination of uranium and plutonium by isotope dilution mass spectrometry in solutions of spent fuel from reprocessing plants has been prepared and certified for uranium and plutonium isotopic contents. The methodology followed was comparable to that of previous batches. The solution, made by dissolution of the starting materials in nitric acid, was dispensed directly into individual penicillin vials. However in this campaign an automated system was introduced to dispense and weigh the majority of vials. At the same time the system was validated by comparing the results with those of the traditional syringe dispensing and substitution weighing.
This new batch of large size dried spikes contains ca. 50 mg of uranium (235U abundance = 19.1%) and ca. 1.8 mg of plutonium (239Pu abundance = 97.8%) in each individual vial, covered with a light layer of organic material (cellulose acetate butyrate) as stabilizer.
The U and Pu amount content was certified based on values from mass metrology of the validated automated system or from the manual weighings. Verification of the amount contents of the spike was done by IDMS at IRMM. The values measured for the batch solution and of the dried covered spikes agreed well with those calculated from the weights of starting materials dissolved and the weights of the final solution.JRC.D.4-Isotope measurement
