Certified Reference Materials for Radiometric Safeguards Analyticak Measurements. A Demanding Issue.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

Fitting of Germanium X-Ray Escape Peaks in Hybrid Densitometer X-Ray Fluorescence Spectra

A hybrid K-edge/X-ray fluorescence densitometer (HKED) combines information from two highpurity germanium detector systems to determine the actinide content of a liquid sample. In this study, only spectra from the X-ray fluorescence subsystem of a hybrid densitometer are considered. A method for fitting germanium X-ray escape peaks (GXEPs) in hybrid X-ray fluorescence spectra is described. The relative prominence of the GXEPs that correspond to 103-, 122-, and 136-keV gamma rays was measured in the laboratory. Each gamma-ray peak was found to be accompanied by a germanium K-alpha-1 escape peak approximately one one-thousandth the area of the fullenergy peak. This may seem like a small effect, but the GXEPs for uranium K-beta X-rays appear in the vicinity of neptunium K-alpha X-rays. For samples with high concentrations of uranium and high uranium/neptunium ratios, GXEPs in the vicinity of neptunium K-alpha X-rays would artificially increase the reported neptunium concentration. Failure to account for the presence of GXEPs would cause the neptunium concentration to be overestimated by 10 percent or more in samples with uranium/neptunium ratios greater than 100. A feature that compensates for the effect of GXEPs on the neptunium concentration was included in the Los Alamos National Laboratory (LANL) HKED analytical code. The effectiveness of this feature was evaluated during the analysis of several uranium-neptunium samples, and the results are discussed.JRC.E.8-Nuclear safeguards and Securit

Combined Calorimetry-Neutron-Coincidence Counting-Gamma Spectrometry (CANEGA) Measurement for Plutonium Mass and Isotopic Assay

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

International Workshop on Gamma Evaluation Codes for Plutonium and Uranium Isotope Abundance Measurements by High-Resolution Gamma Spectrometry

An international workshop on Gamma Evaluation Codes for Plutonium and Uranium Isotope Abundance Measurements was held at ITU, Karlsruhe in November 2005, as a kind of follow-up of a 1st workshop of this kind held in 1994 at IRMM, Geel, Belgium. 44 participants from 12 countries attended the present workshop, with representatives from national, European and International safeguards authorities as well as from national and international research and development facilities among them. Two firms specialised in nuclear instrumentation and distribution of the main analysis codes MGA and FRAM were also present. The workshop extended over two and a half days, with two days mainly dedicated to 25 presentations from the participants. A half day was reserved for general discussions, for drawing conclusions and for agreeing on future actions. Among the two days of presentations many salient points were underlined by the speakers and again deeply discussed in the half-day discussion session. Many recommendations and actions have been decided by the participants. Some of the agreed actions will be driven by the ESARDA-NDA working group. This paper will summarise the outputs of this workshop.JRC.G.8-Nuclear safeguard

Streamlined Reprocessing Input Verification Measurements in the Euratom On-Site Laboratory at La Hague.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

Analysis of 237Np in Spent Fuel Solutions.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

New Measurement of the Emission Probability of the 63.290 keV 234Th gamma Ray from 238U alpha Decay.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

MCNP Modelling of a combindes Neutron/Gamma Counter.

A series of Monte Carlo neutron calculations for a combined gamma/passive neutron coincidence counter has been performed. This type of detector, part of a suite of non-destructive assay instruments utilised for the enforcement of the Euratom nuclear safeguards within the European Union, is to be used for high accuracy measurements of the plutonium content of nuclear materials. The multi-purpose Monte Carlo N-Particle (MCNP) code version 4B has been used to model in detail the neutron coincidence detector and to investigate the leakage self-multiplication of PuO2 and Mixed U-Pu Oxide (MOX) reference samples used to calibrate the instrument. The MCNP calculations have been used together with a neutron coincidence counting interpretative model to determine characteristic parameters of the detector. A comparative study to both experimental and previous numerical results has been performed. Sensitivity curves of the variation of the detector's efficiency, epsilon, to the (alpha,n), to spontaneous fission neutron emission rate ratio, alpha, and to the reals coincidence gate utilisation factor, fr, are presented. Once bias-corrected, the trends of the real coincidence counts rate as a function of sample mass for three types of sample could be matched within 0.33% of experimental results. This result confirms the possible use of MCNP to calculate response trends accurately for a wide variety of source materials, given a limited experimental calibration set. Sources of the inaccuracy in the calculations have not yet been fully investigated, because of the vast parameter space to be investigated, but values of the coincidence gate utilisation factor derived directly from the MCNP data have been found to be overestimated by about 8.2%.JRC.E-Institute for Transuranium Elements (Karlsruhe

240Pu Effective Mass of 238Pu in Relation to Passive Neutron Coincidence and Multiplicity Counting.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe