Episodic speleothem deposition tracks the terrestrial impact of millennial-scale last glacial climate variability in SW Ireland

Eighty four new U-Th ages are presented for twenty randomly selected broken, displaced and reworked calcite speleothems retrieved from clastic sedimentary fill and from isolated bedding-plane shelves in Crag cave (SW Ireland). The dated pre-Holocene samples span much of the last glacial, ranging in age from 85.15 ± 0.60 to 23.45 ± 0.17 ka. Speleothem deposition requires the presence of liquid water, and because Crag cave is a shallow system, deposition is considered likely only when mean annual air temperatures (MAAT) exceed the freezing point of water. Deposition at this mid-latitude ocean-marginal site occurred episodically during MIS5a through to MIS2, synchronously within dating uncertainties, with the timing of Greenland Interstadials (GI). In the latter part of Marine Isotope Stage 3 (MIS3), deposition was particularly intense, consistent with regional scale climate amelioration inferred previously from radiocarbon ages for sparse MIS3 organic and freshwater surficial deposits in N. Ireland. A brief episode of speleothem deposition at c.23.40 ± 0.22 ka coincides with GI-2, demonstrating the sensitivity of the site to brief climate amelioration episodes in Greenland during MIS2. Conditions favourable for speleothem deposition occurred periodically during the last glacial, indicating temperature changes of at least 10oC between stadials and interstadials at this mid-latitude site. Deposition ceased during Greenland Stadials (GS), including during periods of ice-rafting in the adjacent N. Atlantic Ocean (Heinrich events). Oxygen and carbon isotope ratios of the last glacial speleothems are generally elevated, reflecting non-equilibrium isotope fractionation effects. However, establishment of low 13C values often occurred within a few decades of climate amelioration, indicating that biogenic CO2 production resumed rapidly at this site, particularly during MIS3. Speleothem 18O variability was driven largely by long-term changes in the 18O value of the adjacent North Atlantic surface water, in turn largely reflecting changes in global ice volume. In common with published speleothem datasets, warming episodes in Ireland associated with GI events typically pre-date their timing in the GICC05 and GICC05modelext time scales, but lie comfortably within the maximum counting uncertainties of these ice core age models

Preparation and certification of 243Am spike reference material: IRMM-0243 : Certified reference material for the amount content of 243Am and n(241Am)7n(243Am) isotope amount ratio

This report describes the preparation and certification of IRMM-0243, a 243Am spike reference material. It is certified for the amount content of 243Am and the isotope amount ratios of n(241Am)/n(243Am) and n(242mAm)/n(243Am). Furthermore, the material is certified for the amount contents of 241Am and total Am, the mass fractions of 243Am, 241Am and total Am, the isotope amount and mass fractions (e.g. isotopic composition) and the molar mass of Am. The material was produced in compliance with ISO/IEC 17034:2016 and certified in accordance with ISO Guide 35:2006. The material was prepared by dilution of an americium starting solution in nitric acid and dispensing of the solution into glass ampoules. In total 587 units were produced. Between-unit homogeneity was quantified and stability during dispatch and storage were assessed in accordance with ISO Guide 35:2006. The characterisation of the amount content of 243Am was performed by Isotope Dilution Mass Spectrometry (IDMS) using a 241Am spike, produced from highly enriched 241Pu material. The isotope amount ratios of n(241Am)/n(243Am) and n(242mAm)/n(243Am) were measured by Thermal Ionisation Mass Spectrometry (TIMS). The certified values were verified by alpha particle spectrometry, alpha particle counting at a defined solid angle (DSA) and high-resolution gamma-ray spectrometry as independent verification methods. The uncertainties of the certified values were estimated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) [ ] and include uncertainties related to possible inhomogeneity, instability and characterisation. The main purpose of this material is for use as a spike isotopic reference material for the quantification of americium by IDMS in unknown samples. A unit of IRMM-0243 consists of a glass ampoule with a screw cap containing about 3.5 mL nitric acid solution (c = 1 mol/L) with an americium mass fraction of about 1.5 μg/g solution. The material is a true solution; therefore there is no recommended minimum sample intake to be taken into account.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Separation and recovery of exotic radiolanthanides from irradiated tantalum targets for half-life measurements.

The current knowledge of the half-lives (T1/2) of several radiolanthanides is either affected by a high uncertainty or is still awaiting confirmation. The scientific information deriving from this imprecise T1/2 data has a significant impact on a variety of research fields, e.g., astrophysics, fundamental nuclear sciences, and nuclear energy and safety. The main reason for these shortcomings in the nuclear databases is the limited availability of suitable sample material together with the difficulties in performing accurate activity measurements with low uncertainties. In reaction to the urgent need to improve the current nuclear databases, the long-term project "ERAWAST" (Exotic Radionuclides from Accelerator Waste for Science and Technology) was launched at Paul Scherrer Institute (PSI). In this context, we present a wet radiochemical separation procedure for the extraction and purification of dysprosium (Dy), terbium (Tb), gadolinium (Gd), and samarium (Sm) fractions from highly radioactive tantalum specimens, in order to obtain 154Dy, 157-158Tb, 148,150Gd, and 146Sm samples, needed for T1/2 determination studies. Ion-exchange chromatography was successfully applied for the separation of individual lanthanides. All separations were conducted in aqueous phase. The separation process was monitored via γ-spectrometry using suitable radioactive tracers. Both the purity and the quantification of the desired radiolanthanides were assessed by inductively coupled plasma mass spectrometry. Test experiments revealed that, prior to the Dy, Tb, Gd, and Sm separation, the removal of hafnium, lutetium, and barium from the irradiated tantalum material was necessary to minimize the overall dose rate exposure (in the mSv/h range), as well to obtain pure lanthanide fractions. With the herein proposed separation method, exotic 154Dy, 157-158Tb, 148,150Gd, and 146Sm radionuclides were obtained in sufficient amounts and purity for the preparation of samples for envisaged half-life measurements. During the separation process, fractions containing holmium, europium, and promethium radionuclides were collected and stored for further use

Contribution of an interlaboratory comparison to the certification of the STAM/IRMM‑0243 243Am reference material

Following the expression of the need for an americium (Am) standard and particularly for one with a certified americium 243 (243Am) content in 2009 and thereafter by the International Atomic Energy Agency, the Commissariat à l’Energie Atomique (CEA) et aux Energies Alternatives/ Direction de l’Energie Nucléaire of Marcoule and the Joint Research Center in Geel carried out a collaborative project for the production of a certified reference material enriched in 243Am. CEA’s Commission d’ETAblissement des Méthodes d’Analyse organized an interlaboratory comparison on this material prior to the issuing of its certificate. The usefulness of an interlaboratory comparison to assess the measurement capabilities in the field and to confirm the provisional certified values for the amount contents of 243Am, 241Am, total Am, the isotopic composition and the molar mass of Am has been demonstrated. Further this interlaboratory comparison enabled to derive an indicative value for the n(242mAm)/n(243Am) isotope amount ratio.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

News about certified nuclear isotope reference materials at Joint Research Centre – Unit G.2 - METRO group in Geel

At the Joint Research Centre (JRC), Directorate G (Nuclear Safety and Security), Unit G.2 (Standards for Nuclear Safety, Security and Safeguards, SN3S), in Geel (Belgium), formerly called IRMM (Institute for Reference Materials and Measurements), the so-called METRO (metrological tools for nuclear safeguards) group is engaged in the preparation and certification of nuclear isotopic reference materials. Within the several recent and the current year, the focus was on renewals of two Pu spike reference materials, namely IRMM-042a (244Pu spike) and IRMM-049e (242Pu spike), and in particular on the certification of the first Am spike isotope reference material, certified for the 241Am/243Am isotope ratio using TIMS (total evaporation) and the 241Am and 243Am amount concentrations. The certification of the 243Am amount concentration was performed by reverse IDMS due to the use of a highly enriched 241Pu material, which served to create a special in-house spike of 241Am grown in from the decay of the 241Pu. The new Am spike isotope reference material is very useful for age dating using the 241Pu/241Am clock in nuclear forensics. In terms of uranium, the re-certification of the IRMM-019-029 series of UF6 reference materials will be used for the preparation of new uranium solution reference materials suitable for TIMS and MC-ICPMS instruments, the IRMM-2019-2029 series, and furthermore for the preparation of micrometer size uranium particles certified for the isotopic composition and the uranium amount per particle. The certified isotopic composition of the uranium solutions as well as for the uranium particle reference materials will be identical to the certified ratios of the UF6 reference materials IRMM-019-029. These were (previously) determined using state-of-the art TIMS methods such as MTE (modified total evaporation) and DS (Double Spike) and using gravimetrically prepared isotope mixtures for instrument calibration, and were confirmed by a second method, in this case UF6-gas source mass spectrometry, as required by the ISO 17034. Using various types of "process control measurements" it will be ensured that the isotopic composition is not changed during the preparation of the solutions (e.g. by diluting and dispensing), and due to the preparation of the particles using the particle generator.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Quality control tools for age dating in nuclear safeguards and forensics

Nuclear safeguards conclusions are based to a large extent on comparison of measurement results between operator and safeguards laboratories. Nuclear forensics deals with consistency of information, coherence between materials or samples, conformity of findings with declared processes and comparison of external and internal data. Representative samples are measured by respective networks of laboratories. For nuclear safeguards these are the Euratom safeguards and the IAEA Network of Analytical laboratories (IAEA-NWAL). For nuclear forensics, the laboratories are mainly members of the Nuclear Forensics International Technical Working Group (ITWG). Metrological quality control tools are a means to establish accurate, traceable and comparable measurement results. The European Commission-Joint Research Centre (EC-JRC) has therefore put effort into the development of certified reference materials and the provision of conformity assessment tools, particularly for "age-dating" of uranium and plutonium samples, which is of importance to both communities. In this context the new IRMM-1000a and IRMM-1000b, certified for the production date based on the 230Th/234U radiochronometer, will be presented, and the results from the Regular European Inter-laboratory Measurement Evaluation Programme (REIMEP-22) on 'U Age Dating' will be discussed. Furthermore the status of the on-going development of a 243Am spike reference material in the frame of the recently signed collaboration agreement between the EC-JRC and the CEA/DEN will be presented. This spike is intended for use in the determination of the last separation date of plutonium samples by Isotope Dilution Mass Spectrometry (IDMS) using the 241Pu/241Am radiochronometer.JRC.G.2-Standards for Nuclear Safety, Security and Safeguar

243Am certified reference material for nuclear safeguards and security

The Joint Research Centre (EC-JRC, Geel, Belgium) and the Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA/DEN, Marcoule, France) jointly prepared and certified a 243Am spike reference material in compliance with ISO 17034. This reference material is needed for accurate mass spectrometry measurements of 241Am in nuclear forensics, security and safeguards applications but also for the characterisation of radioactive waste. Nearly 600 units of this material were produced, each containing about 3.5 mL of dilute nitric acid solution with an Am mass fraction of 1.5 µg·g-1. The reference material is certified for the 243Am amount content by Isotope Dilution Mass Spectrometry (IDMS) using an in-house 241Am spike, produced by beta-decay from highly enriched 241Pu (99.3 %) material. The americium isotope amount ratios were certified by Thermal Ionisation Mass spectrometry (TIMS). Independent verification measurements were performed by alpha-particle spectrometry, high-resolution gamma-ray spectrometry for activity ratios, and alpha counting for the total massic activity of 241,243Am.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard