Measurement of non-separated U/Pu samples: optimization of TIMS procedures for safeguards purposes at Rokkasho on-site laboratory

Optimized Chemical Separation and Measurement by TE TIMS Using Carburized Filaments for Uranium Isotope Ratio Measurements Applied to Plutonium Chronometry

“…This can be explained by the differences in the ionization yields of uranium and plutonium: during a simultaneous measurement of uranium and plutonium, the yield of Pu + ions is 5–10 times greater than that of U + ions . Therefore, more Pu + ions are formed compared to U + ions, although other authors observed a certain quenching effect on the Pu + ion formation when uranium and plutonium are measured simultaneously …”

“…As a consequence, finding an answer to dealing with the isobaric interference of 238 Pu when measuring 238 U isotope is of vital importance. Several studies on the characterization of mixed uranium–plutonium oxides (MOX) and of unseparated safeguards samples containing plutonium and uranium emphasize the topicality of the measurement of 238 Pu in the presence of 238 U and vice versa by mass spectrometry. ,− These articles deal with materials that contain 3 to 300 times more uranium than plutonium, ,, materials that have a 1:1 ratio of plutonium and uranium, , and with materials that contain up to 5 to 10 times , more plutonium than uranium. U/Pu ratios between 1:10 and 100:1 for direct safeguards measurements of 235 U/ 238 U and 240 Pu/ 239 Pu in unseparated samples have also been investigated .…”

“…Several studies on the characterization of mixed uranium–plutonium oxides (MOX) and of unseparated safeguards samples containing plutonium and uranium emphasize the topicality of the measurement of 238 Pu in the presence of 238 U and vice versa by mass spectrometry. ,− These articles deal with materials that contain 3 to 300 times more uranium than plutonium, ,, materials that have a 1:1 ratio of plutonium and uranium, , and with materials that contain up to 5 to 10 times , more plutonium than uranium. U/Pu ratios between 1:10 and 100:1 for direct safeguards measurements of 235 U/ 238 U and 240 Pu/ 239 Pu in unseparated samples have also been investigated . As far as the age determination of plutonium is concerned, NBS 946 contains, for example, about 450 times more plutonium than uranium (g·g –1 ) since only a small fraction of plutonium has decayed to uranium in the 41 years elapsed since the last purification of the plutonium from its uranium daughter nuclides .…”

Thermal Ionisation Mass Spectrometry

“…177,178 Multicollector TIMS is one of the main analytical techniques that are traditionally being employed at safeguards laboratories 71,74,169,177,179 for uranium and plutonium analysis of nuclear materials originating from various parts of the industrial nuclear fuel cycle. These instruments are also installed at on-site laboratories at reprocessing facilities such as Rokkasho, Japan 180 and Sellafield, UK 181 to ensure timely analytical response. The results of nuclear safeguards analyses need to meet strict criteria as driven by the so-called International Target Values (ITVs).…”

Direct isotope ratio analysis of individual uranium–plutonium mixed particles with various U/Pu ratios by thermal ionization mass spectrometry

“…However, no measurements of U-Pu mixed particles over a wide range of U/Pu ratios were performed. Raptis et al (2013) measured U-Pu mixed solutions with U/Pu ratios ranging from 0.1 to 100 by TIMS without prior chemical separation and accurately determined the 240 Pu/ 239 Pu and 242 Pu/ 239 Pu isotope ratios. However, the isobaric interferences of 241 Am to 241 Pu peaks made it impossible to accurately determine the 241 Pu/ 239 Pu isotope ratios.…”