Minimizing plutonium measurement uncertainty is essential to nuclear material control and international safeguards. In 2005,
the International Organization for Standardization (ISO) published ISO 12183 “Controlled-potential coulometric assay of plutonium,”
2nd edition. ISO 12183:2005 recommends a target of ±0.01% for the mass of original sample in the aliquot because it is a critical
assay variable. Mass measurements in radiological containment were evaluated and uncertainties estimated. The uncertainty
estimate for the mass measurement also includes uncertainty in correcting for buoyancy effects from air acting as a fluid
and from decreased pressure of heated air from the specific heat of the plutonium isotopes.
Authors:R. Dybczyński, M. Wasek, and H. Maleszewska
A highly accurate and precise procedure deserving the name of definitive method has been devised for the determination of copper in biological materials. The method is based on combination of neutron activation and very selective and quantitative post-irradiation separation of copper from other radionuclides by extraction chromatography, using columns with LIX 70 on Bio-Beads SM-1, followed by gamma-ray spectrometric measurement. All potential sources of errors were carefully examined and eliminated or appropriate corrections were introduced into the procedure. The method contains several warning mechanisms safeguarding against making gross errors. Limit of detection for rather short irradiation time (tir
1 h) (which enables radiochemical work without sophisticated shielding) amounts to 15 g/kg. Results for copper concentration in several NBS, IAEA and other certified reference materials are presented and a new recommended value for IAEA's Milk Powder (A-11) is proposed.
The use of environmental monitoring as a technique to identify activities related to the nuclear fuel cycle has been proposed by international organizations as an additional measure to the safeguards agreements currently in force. The specific element for each kind of nuclear activity, or nuclear signature, inserted into the ecosystem by several transfer paths, can be intercepted to a greater or lesser degree by different living organisms. This work demonstrates the technical viability of using pine needles as bioindicators for some nuclear signatures (Co, Ni, La, Ce, Sm, Th, and U) associated with uranium enrichment activities using high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). The concentrations of the elements whose signatures were sought and were determined in pine needle samples collected at five specific sampling locations inside the area investigated demonstrate the potential of the instrument and of the method used to identify and quantify the sought signatures present in low quantities (traces) in the evaluated matrix.
Authors:F. Macášek, P. Kováč, P. Rajec, and R. Lepej
Except the nuclear fuel reprocessing and nuclear materials safeguards, at present there are two areas of an increased responsibility
of nuclear scientists for their results: radioecology and human medicaments. At both of them, quality and trustfulness of
results is of great importance for their end-users and may have serious economical and legal consequences. The trends of implementation
of good laboratory and manufacturing practices under umbrella of international quality management standards like ISO 17025:2005
and ISO 9001:2000 in radiochemical and radiopharmaceutical laboratories are discussed as expanding to “good scientific practice”.
The case studies of the Comenius University laboratory LARCHA authorized for radiochemical analysis, and the company BIONT
producing medical radionuclides and PET radiopharmaceuticals are used as the examples.
Assays of alpha- and beta-emitting radionuclides in swipe samples are often required to monitor the presence of removable
surface contamination for radiological protection and control in nuclear facilities. Swipe analysis has also proven to be
a very sensitive analytical technique to detect nuclear signatures for safeguard verification purposes. A new sequential method
for the determination of actinide isotopes and radiostrontium in swipe samples, which utilizes a streamlined column separation
with stacked anion and extraction chromatography resins, has been developed. To validate the separation procedure, spike and
blank samples were prepared and analyzed by inductively coupled mass spectrometry (ICP-MS), alpha spectrometry and liquid
scintillation (LS) counting. Low detection limits have been achieved for isotopic analysis of Pu (238Pu, 239Pu, 240Pu, 241Pu), U (234U, 235U, 238U), Am (241Am), Cm (242Cm, 243/244Cm) and Sr (90Sr) at ultra-trace concentration levels in swipe samples.
Authors:Lav Tandon, Kevin Kuhn, Patrick Martinez, Joseph Banar, Laurie Walker, Terry Hahn, David Beddingfield, Donivan Porterfield, Steven Myers, Stephen LaMont, Daniel Schwartz, David Gallimore, Scott Garner, Khalil Spencer, Lisa Townsend, Heather Volz, Russ Gritzo, Rodney McCabe, Ramiro Pereyra, Dominic Peterson, Mark Scott, Christy Ruggiero, Diana Decker, and Amy Wong
This paper presents results from the examination of a number of archived neutron-irradiated uranium targets used for past
plutonium production testing. Three of these targets were destructively characterized using Los Alamos National Laboratory
actinide analytical chemistry capabilities. A validated conduct-of-operations protocol was followed for this characterization
effort. Chemical analyses included measurements for radionuclides, uranium assay, uranium isotopic abundances, trace actinides,
trace metals, and non-metals. Material scientists also examined materials for morphological and microstructural properties
and individual particles were examined for trace impurities. After characterization of the targets was completed, a reactor
modeling effort was undertaken to corroborate target details in historical records. Time since irradiation calculations utilized
both activation and fission products. The described examination of uranium targets has a tremendous impact from a safeguards
verification and nuclear forensics perspective.
Authors:Weihua Zhang, Kurt Ungar, Ian Hoffman, and Ryan Lawrie
To support interpretation of observed atmospheric krypton radioisotopes, a database of krypton radioisotope in the primary
coolant of CANDU reactors has been established. This database is comprised of 40,000 records of high-quality 89Kr, 87Kr, 88Kr and 85mKr analyses. Records from the database were retrieved by a specifically designed data-mining module and subjected to further
analysis. Results from the analysis were subsequently used to study isotopic ratios of observed krypton radioisotopes in the
CANDU reactor primary coolant. These studies provided practical information on the characterization of CANDU reactor krypton
radioisotope, which can potentially be used to discriminate between reactor effluent and fuel reprocessing for nuclear safeguard
85Kr monitoring applications (Kalinowski et al., J Environ Radioact 73:203, 2004). The study also has some potential application
to Fissile material cut-off treaty.
Authors:Yan Chen, Zhi-yuan Chang, Yong-gang Zhao, Ji-long Zhang, Jing-huai Li, and Fu-jun Shu
An isotope dilution multicollector inductive coupled plasma mass spectrometry (ID-MC-ICP-MS) method for determining age of
trace Pu through measuring 241Pu/241Am, 240Pu/236U ratio was established. At the same time, other two methods-α-spectrometry combined with MC-ICP-MS and liquid scintillator
combined with α-spectrometry through measuring 241Pu/241Am ratio to determine the age of trace Pu were also studied. The techniques were explored for the age determination of nanogram
grade Pu sample on the basis of Pu/Am, Pu/U separation. The ages of two Pu samples—one with known and the other with unknown
age—were determined by the three methods. The determined ages by the three methods were all in agreement with the reference
value. The established methods for determining the age of trace Pu could be adopted in the verification activities of nuclear
safeguards and nuclear arms control.
High precision gamma spectrometry measurements have been made on five sets of uranium isotope abundance reference materials for nondestructive assay (NDA). These sets are intended for international safeguards use as primary reference materials for the determination of the235U abundance in homogeneous uranium bulk material by gamma spectrometry. The measurements were made to determine the count rate uniformity of the235U 185.7 keV gamma-ray as well as the235U isotope abundance for each sample. Since the samples were packaged such that the U3O8 is infinitely thick for the 185.7 keV gamma-ray, the measured count rate was not dependent on the material density. In addition, the activity observed by the detector was collimated to simulate calibration conditions used to measure bulk material in the field. The sample-to-sample variations observed within the 5 sets of samples ranged between 0.005–0.11% (1s) with standard deviations of the mean ranging from 0.01–0.02%. This observed variation appears to be due predominantly to counting statistics and not to material inhomogeneity and/or packaging. The results of this study indicate that accuracy of235U determinations via gamma spectrometry, in the range of few hundredths of a percent (2), is achievable. The main requirement for achieving this level of accuracy is a set of standards whose235U isotope abundances are known to within 0.01% (2).