The Euratom Safeguards On-site Laboratories at the Reprocessing Plants of La Hague and Sellafield

In the European Union, nuclear material is reprocessed from irradiated power reactor fuel at two sites ¿ La Hague in France and Sellafield in the United Kingdom. These are the largest nuclear sites within the EU, processing many hundreds of tons of nuclear material in a year. Under the Euratom Treaty, the European Commission has the duty to assure that the nuclear material is only used for declared purposes. The Directorate General for Energy (DG ENER), acting for the Commission, assures itself that the terms of Article 77 of Chapter VII of the Treaty have been complied with. In contrast to the Non Proliferation Treaty, the Euratom Treaty requires to safeguard all civil nuclear material in all EU member states ¿ including the nuclear weapons states. The considerable amount of fissile material separated per year (several tonnes) calls for a stringent system of safeguards measures. The aim of safeguards is to deter diversion of nuclear material from peaceful use by maximizing the chance of early detection. At a broader level, it provides assurance to the public that the European nuclear industry, the EU member states and the European Union honour their legal duties under the Euratom Treaty and their commitments to the Non-Proliferation Treaty. Efficient and effective safeguards measures are essential for the public acceptance of nuclear activities.JRC.E.7-Nuclear Safeguards and Forensic

New recommendation for the thermal conductivity of irradiated (U, Pu)O2 fuels under Fast Reactor conditions. Comparison with recent experimental data.

New experimental results obtained at the Joint Research Centre in Karlsruhe (JRC-Karlsruhe) within the European Sustainable Nuclear Industrial Initiative Plus project (ESNII + ) were used to develop an updated recommendation for the thermal conductivity of (U, Pu)O 2 fuels irradiated in fast reactor (FR) conditions. Fresh and irradiated FR fuels were characterised, and their thermal diffusivity and heat capacity were measured by the laser flash technique. The thermal conductivity of those fuels was calculated, using hydrostatic density measurements when available or using calculated density. The thermal conductivity model, developed in this work, describes different effects induced by irra- diation on the degradation of thermal conductivity: soluble fission products (FPs), precipitated FPs, ra- diation damage, and porosity. Those effects are considered in separate corrective factors, which depend on the chemical composition of the irradiated fuel, its microstructure, and the temperature. To estimate these parameters, thermomechanical calculations (PLEIADES-GERMINAL V2) and thermochemical calcula- tions (Thermo-Calc V4.1 with the TAF-ID V11 database) were carried out in conjunction. This paper discusses the uncertainties related to the irradiation conditions and the data provided by the GERMINAL-Thermo- Calc calculation.JRC.G.I.2 - Nuclear Material Researc

Examining the thermal properties of unirradiated nuclear grade graphite between 750 and 2500 K

This study presents the first high temperature measurements (between 750 K and 2500 K) of thermal conductivity, thermal diffusivity, specific heat and spectral emissivity of virgin graphite samples (type IM1-24) from advanced gas-cooled reactor (AGR) fuel assembly bricks. Scanning electron microscope (SEM) and X-ray computed tomography (XRT) techniques were used to verify the presence of Gilsocarbon filler particles (a characteristic microstructural feature of IM1-24 graphite). All thermal properties were investigated in two orthogonal directions, which showed the effective macroscopic thermal conductivity to be the same (to within experimental error). This can be linked to the morphology of the filler particles that consist of concentrically aligned graphitic platelets. The resulting spherical symmetry allows for heat to flow in the same manner in both macroscopic directions. The current thermal conductivity results were compared to other isotropic grade graphite materials. The significant discrepancies between the thermal conductivities of the individual grades are likely the result of different manufacturing processes yielding variations in the microstructure of the final product. Differences were identified in the filler particle size and structure, and possibly the degree of graphitization compared to other reported nuclear graphites.JRC.G.I.3 - Nuclear Fuel Safet

Structural and physical investigation of ordered BaO-deficient Ba3PuO6

Abstract Ternary actinide compounds allow for a range of oxidation states and a rich but often not well-known chemistry. Here, a BaO-deficient plutonium-containing perovskite with a composition close to Ba3PuO6 has been obtained via solid state synthesis. The compound was characterised using X-Ray Diffraction from room temperature up to 1473 K, revealing two phase transitions and ordered Ba-deficiency. X-ray Absorption Spectroscopy was performed at the Pu L 3- and M 5-edges. The XANES spectrum at the Pu L 3-edge and the XANES in high-energy resolution mode at the Pu M 5-edge both indicate a Pu(VI) oxidation state. Despite the rather complex crystallographic unit cell, Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy at the Pu L 3-edge yields Pu-O distances of 2.01(1) and 2.4(3) Å. The low-temperature heat capacity of Ba2.875PuO5.875 was measured between 5 and 270 K. The heat capacity and standard entropy at 298.15 K were found to be C p = (251 ± 8) J⋅K−1⋅mol−1 and $${S}_{m}^{0}=(318\pm 8)\,{{\rm{J}}} \! \cdot \! {{{\rm{K}}}}^{-1} \cdot {{{\rm{mol}}}}^{-1}$$ S m 0 = ( 318 ± 8 ) J ⋅ K − 1 ⋅ mol − 1 , respectively. The magnetic susceptibility was measured from 2 to 320 K and shows a temperature-independent paramagnetism, consistent with the hexavalent oxidation state of Pu. This article reports the first extended low-temperature heat capacity curve and a temperature-dependent magnetic susceptibility measurement in a [Rn]5f 2 Pu-based system

Comparative assessment of the Pu content of MOX samples by different techniques

The isotopic composition and concentration of Pu in eight "high-burn-up" mixed-oxide (MOX) fuel samples has been determined by destructive and non-destructive techniques. In addition, the U concentration and U isotopic composition was also available from the destructive techniques. The applied non-destructive techniques were gamma spectrometry, calorimetry and neutron coincidence counting, while the destructive techniques were titration, alpha spectrometry and thermal ionization mass spectrometry combined with isotope dilution. The current study describes the measurements and compares the results obtained by the mentioned techniques. Some lessons learned for the improvement of the non-destructive assay are also discussed.JRC.E.7 - Nuclear Safeguards and Forensic

Comparative assessment of the Pu content of MOX samples by different techniques

The isotopic composition and concentration of Pu in eight "high-burn-up" mixed-oxide (MOX) fuel samples has been determined by destructive and non-destructive techniques. In addition, the U concentration and U isotopic composition was also available from the destructive techniques. The applied non-destructive techniques were gamma spectrometry, calorimetry and neutron coincidence counting, while the destructive techniques were titration, alpha spectrometry and thermal ionization mass spectrometry combined with isotope dilution. The current study describes the measurements and compares the results obtained by the mentioned techniques. Some lessons learned for the improvement of the non-destructive assay are also discussed.JRC.E.7-Nuclear Safeguards and Forensic

In-field Timely and Accurate Measurements - Fundamental to Minimising Safeguards Issues in Reprocessing Facilities

The two large reprocessing plants in Europe, located in Sellafield (UK) and La Hague (F) have a throughput of 800 t and 1600 t of spent fuel per year. In order to meet the safeguards criteria of quantity, timeliness and probability (QTP), these facilities deserve particular attention and appropriate safeguards measures have to be implemented. At either plant Euratom installed an on-site laboratory where the verification measurements are performed with minimal time delays and at highest possible accuracy.JRC.E-Institute for Transuranium Elements (Karlsruhe