Preparation and Certification of IRMM 1027n, Large-Sized Dried (LSD) Spike

Abstract

Large-sized dried spikes (LSD) have become a fundamental part of the fissile material control of irradiated nuclear fuel. Within the programme at IRMM to provide these spikes to the nuclear industry and the safeguards¿ inspectorate, a new set of LSD Spikes for the determination of uranium and plutonium by isotope dilution mass spectrometry (IDMS) 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. An automated system was used to dispense and weigh the vials. The new batch of large size dried spikes contains ca. 50 mg of uranium with a 235U amount fraction of 19.5% and ca. 1.8 mg of plutonium with a 239Pu amount fraction of 97.8% in each individual vial, covered with a light layer of organic material (cellulose acetate butyrate) as stabilizer. The U amount content was certified based on values from mass metrology of the validated automated system. Verification of the U amount contents of the spike was done by IDMS at IRMM. The values measured for the dried covered spikes agreed well with those calculated from the masses of starting materials dissolved and the masses of the final solution. The Pu amount content was certified by using IDMS.