Central Bureau For Nuclear Measurements Research Articles

Fissile mass estimation using β-delayed γ-rays and neutrons from fast and epithermal induced fissions

A potential method for mass estimation of shielded special nuclear materials (SNM) is proposed. The method uses fast and epithermal neutrons, generated by an external pulsed neutron source, to induce fission in SNM. The subsequent β-delayed γ-rays and neutrons, emitted by the fission products, are measured simultaneously by two 3He slab detectors and a coaxial high purity germanium (HPGe) detector, located around the tested material. Measuring simultaneously both, β-delayed γ-rays and neutrons measurement, offers improved sensitivity for fissile materials detecting.Laboratory examination of the method was performed in the Pulsed Neutron Interrogation Test Assembly (PUNITA), using CBNM (Central Bureau for Nuclear Measurements) samples of Uranium.

In Memoriam—Paul De Bièvre

AbstractPaul De Bièvre was born in Blankenberge (Belgium) on 7 July 1933. He obtained his PhD from Gent University in 1959 where he continued to work as a lecturer until 1961. In 1961 he joined the Central Bureau for Nuclear Measurements of the European Commission (renamed Institute for Reference Materials and Measurements in 1994) where he was Head of the Isotope Measurement Unit until 1998 and Advisor to the Director until 2002.

Targets for accelerator-based research

This special issue of the Journal of Radioanalytical and Nuclear Chemistry is dedicated to the 26th World Conference of the International Nuclear Target Development Society (INTDS 2012) held from August 19th to 24th, 2012 at the conference center Erbacher Hof in Mainz, Germany with special emphasis on targets for acceleratorbased research. The INTDS 2012 was co-organized by the Johannes Gutenberg-Universitat Mainz and the GSI Helmholtzzentrum fur Schwerionenforschung, Darmstadt. The 4th Target Fabrication Workshop (TFW), dedicated to targets for laser application and hosted by the Technical University Darmstadt, was held in parallel to the INTDS 2012 at the Erbacher Hof with common plenary sessions giving the participants of both events the opportunity of exchanging experiences and know-how. Accordingly, these proceedings contain some contributions presented at the 4th Target Fabrication Workshop. The series of INTDS conferences dates back to 1963 when the ‘‘First Symposium on Research Materials for Nuclear Measurements’’ was held sponsored by the Central Bureau for Nuclear Measurements (CBNM, recently IRMM—Institute for Reference Materials and Measurements) in Belgium. Since then researchers involved in target preparation share experience and discuss related problems during biennial conferences hosted alternatively in Europe, North America and Asia (www.intds.org). It dates back to 1978 and 1988 when the 7th and the 14th INTDS conference were held at Garching, organized by Ludwig-Maximilians-Universitat together with Technische Universitat Munchen and at Darmstadt, organized by GSI, respectively. Thus, it was delightful to meet again in Germany on the occasion of the 26th International INTDS conference. More than 70 participating scientists from 15 countries (Belgium, Canada, France, Germany, India, Italy, Japan, Korea, Poland, Romania, Russia, South Africa, Switzerland, UK, USA), met in Mainz presenting over 50 scientific contributions covering the wide field of ‘‘Targets for Accelerator-bases Research’’. Two complementary visits to GSI and the TRIGA Mainz research reactor operated by the Johannes Gutenberg-Universitat were included in the scientific program to introduce the institutions and laboratories. The conference comprised seven different sessions titled ‘‘Classical Accelerator Targets’’, ‘‘Laser& Accelerator Based Research’’, ‘‘RIB Targets’’, ‘‘Isotope Enrichment and Medical Radioisotopes’’, ‘‘Stripper’’, K. Eberhardt (&) Johannes Gutenberg-Universitat Mainz, 55128 Mainz, Germany e-mail: klaus.eberhardt@uni-mainz.de

Reference materials: from CBNM to IRMM

In 2010, IRMM celebrated its 50th anniversary. The institute, created as Central Bureau for Nuclear Measurements, has developed during these 50 years from a nuclear institute producing so-called reference samples to support nuclear activities worldwide to a major producer of certified reference materials covering a broad range of application sectors both in the nuclear and especially in the non-nuclear field. A short historical overview on related IRMM developments is provided here.

An isotope dilution mass spectrometric measurement procedure has the potential of being a very good reference measurement procedure, but is not a “definitive” one

The term ‘‘definitive methods’’ to describe isotope dilution mass spectrometry (IDMS) as a powerful measurement procedure [1], started to be recognized in the seventies [2– 9]. It was inspired by the at that time impressive achievements in analytical measurement in chemistry at the isotope mass spectrometry laboratories of the National Bureau of Standards (NBS) in Gaithersburg (US) and the Central Bureau for Nuclear Measurements (CBNM) in Geel (EC). Applying the measurement principle of isotope dilution and combining it with isotope mass spectrometry, enabled to certify ‘‘reference values’’ with drastically reduced measurement uncertainties. Described in the simplest form, the measurement of a number N(E) of atoms of an isotope E of an element E, can be performed by adding a known number of atoms N(E) of another isotope E (= a ‘‘spike’’) of the same element, and measuring the number-ratio N(E)/N(E). [A similar approach had long been used by analysts in classical chemistry. It is called the ‘‘standard addition method’’. An unknown number N(iE) of atoms of an element iE is measured by adding a known number of atoms N(jE) of atoms of another element jE and measuring the number-ratio N(iE)/N(jE).] This number-ratio measurement is independent of chemical effects since isotopes of the same element have the same chemical properties. The approach consists of selecting a major abundant isotope E of the element E in a sample and selecting another—but also major abundant— isotope E of E in the ‘‘spike’’. Since in most cases, the aim of IDMS is not to measure an isotope amount (which can be done) but an element amount, the minor-abundant isotopes must be taken into account in the unknown sample as well as in the spike. In the spike this is done by measuring them through a number-ratio measurement relative to the major-abundant isotope E. Similarly, in the sample, this is done by measuring the minor-abundant isotopes through a number-ratio measurement relative to the major-abundant isotope E [10–12]. Thus the traditional measurement of a number-ratio of specified atomic entities (in the ‘‘standard addition method’’) is replaced by the measurement of a numberratio of specified isotopic entities (in IDMS). Since chemical, i.e. element-dependent effects, play their full role in any element-to-element ratio measurement, this ratio is far more dependent on chemical systematic effects (which are different for different elements) than an isotope-toisotope number-ratio where the chemical effects play the same role, and hence are cancelled out in the measurement of the number-ratio of isotopic atoms: the same systematic effects which will influence proportionally the nominator of the number-ratio, will also influence the corresponding denominator of that number-ratio. The effects in nominator and denominator will cancel because they are identical (they relate to the same element). [The small systematic effect due to mass discrimination is not discussed here because it is small relative to chemical affects.] The result is that both precision and accuracy of the measured ratio value is very much improved. In GUM language, it reduces the overall measurement uncertainty of that measurement result. This drastic improvement of the quality of measurement gave rise to the creation of the concept ‘‘definitive method’’: suddenly a very good reference measurement procedure became available yielding results with much P. De Bievre (&) Kasterlee, Belgium e-mail: paul.de.bievre@skynet.be

Actinide target preparation at IRMM—then and now

Since the beginning of its activity IRMM (originally CBNM, Central Bureau for Nuclear Measurements) was engaged in measurements of parameters relevant to nuclear energy. High-purity samples and targets of radioactive materials required for measurements of cross-sections and studies of fission fragments or fuel elements were prepared by the IRMM's target group by means of various techniques reviewed in this presentation. Applying these techniques the target group had been preparing targets of U, Pu, Np, Am, Th for in-house physicists and for external customers. Recently, after a long process of decontamination and refurbishment of the old equipment, custom-made 233U and 235U targets were prepared by electro-deposition and by high-vacuum evaporation. Other actinide targets (U, Th) have been prepared using mechanical reshaping techniques.

Mass assay and uniformity tests of boron targets by neutron beam methods

The areal densities (g/cm 2) of enriched boron and lithium fluoride targets were compared to those of reference deposits from the Central Bureau for Nuclear Measurements (CBNM, Geel, Belgium) by charged-particle counting at the NIST Research Reactor. The uniformity of the target thickness was also investigated by scans with a small-diameter, intense neutron beam. The neutron uniformity measurements agree satisfactorily with previously reported interferometric results and no pattern of uniformity variation except the expected, small radial dependence was found. In a separate series of measurements, the boron areal density ratios of a number of the deposits were determined using a new double ionization chamber. The new double ionization chamber permits a comparison of two targets directly without a beam monitor and without sensitivity to the exact placement of the samples. The new device needs only a very simple data acquisition system and requires less neutron beam intensity than the previously employed systems with arrays of surface barrier detectors. The ionization chamber counting losses from the combined effects of self-absorption and sub-threshold pulse-height formation were determined by comparison with ratio measurements made by the conventional surface barrier detector technique.

Reference materials by isotope ratio mass spectrometry

Mass Spectrometry ReviewsVolume 12, Issue 3 p. 143-172 Article Reference materials by isotope ratio mass spectrometry Paul De Bièvre, Corresponding Author Paul De Bièvre Institute for Reference Materials and Measurements (formerly Central Bureau for Nuclear Measurements), Commission of the European Communities - Joint Research Centre, B 2440 Geel, BelgiumInstitute for Reference Materials and Measurements (formerly Central Bureau for Nuclear Measurements), Commission of the European Communities - Joint Research Centre, B 2440 Geel, BelgiumSearch for more papers by this authorJohn R. De Laeter, John R. De Laeter Department of Applied Physics, Curtin University of Technology, Perth, Western Australia 6001, AustraliaSearch for more papers by this authorH. Steffen Peiser, H. Steffen Peiser 638 Blossom Drive, Rockville, Maryland 20850Search for more papers by this authorWilliam P. Reed, William P. Reed National Institute of Standards and Technology, Gaithersburg, Maryland 20899Search for more papers by this author Paul De Bièvre, Corresponding Author Paul De Bièvre Institute for Reference Materials and Measurements (formerly Central Bureau for Nuclear Measurements), Commission of the European Communities - Joint Research Centre, B 2440 Geel, BelgiumInstitute for Reference Materials and Measurements (formerly Central Bureau for Nuclear Measurements), Commission of the European Communities - Joint Research Centre, B 2440 Geel, BelgiumSearch for more papers by this authorJohn R. De Laeter, John R. De Laeter Department of Applied Physics, Curtin University of Technology, Perth, Western Australia 6001, AustraliaSearch for more papers by this authorH. Steffen Peiser, H. Steffen Peiser 638 Blossom Drive, Rockville, Maryland 20850Search for more papers by this authorWilliam P. Reed, William P. Reed National Institute of Standards and Technology, Gaithersburg, Maryland 20899Search for more papers by this author First published: May 1993 https://doi.org/10.1002/mas.1280120302Citations: 35AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume12, Issue3May 1993Pages 143-172 RelatedInformation

A Three-Ratio Scheme for the Measurement of Isotopic Ratios of Silicon.

This paper proposes a scheme of measurement sequences that has been used for the redetermination of the molar mass (atomic weight) of silicon at the Central Bureau for Nuclear Measurements (now Institute for Reference Materials and Measurements). This scheme avoids correlations among the measured ratios caused by normalizing all ion current measurements to that of the largest ion current. It also provides additional information for checking on the consistency of these ratios within a cycle of scans. Measurements of isotope abundance ratios of silicon are used as an illustration.

The CBNM scanning nuclear microprobe analytical facility

The new scanning nuclear microprobe setup of the Central Bureau for Nuclear Measurements (CBNM) in Geel, Belgium, is described. A 2.5 × 2.5 μm 2 proton beam is routinely achieved with 100 pA beam current by means of a special focusing procedure. Elemental analysis using both particle induced X-ray emission (PIXE) and Rutherford backscattering spectrometry (RBS), as well as the detection of secondary electrons for imaging are implemented. A comprehensive, user-friendly computer system facilities flexible real-time elemental mapping and analysis of incoming data in a menu style fashion. In addition the complete data stream can be collected in a list-mode fashion or as spectra pixel by pixel for later off-line and detailed analysis.

Evaporated and implanted reference layers for calibration in surface analysis

AbstractThe potential of thin reference layers prepared by the Central Bureau for Nuclear Measurements, especially for calibration puposes in surface analysis, is presented. Our special preparation procedure is outlined, making use of an ultrahigh vacuum microbalance with the substitution principle of weighing applied. Our procedure of chracterizing the areal density of the evaporated layers is unique in that it provides for an optimal traceability to the SI unit of mass. Besides thin metal layers evaporated onto vitreous carbon substrates, which can serve for yield calibration in surface analysis, we are making use of thin layers as internal standards on implanted samples in order to perform high‐accuracy determinations of the retained dose through Rutherford backscattering spectroscopy. After sensitive tests of the thickness uniformity, evaporated and implanted thin layers are made available as reference samples.

The CBNM scanning nuclear muprobe for materials analysis

This paper gives a brief description of the scanning nuclear muprobe instrument at the Central Bureau for Nuclear Measurements (CBNM) in Geel, emphasizing the facilities for materials analysis. A 2.5 × 2.5 μm 2 proton beam is routinely achieved using a new focusing procedure utilizing the grid shadow method. Both particle-induced X-ray emission (PIXE) and Rutherford backscattering spectroscopy (RBS) as well as the detection of secondary electrons are implemented. An “easy-to-use” computer system and a comprehensive software package has been developed to facilitate user-friendly and rapid on-line as well as off-line analysis. Among other applications, the CBNM muprobe is used for materials analysis. A custom-built, large solid angle, implanted silicon detector has been included for high-efficiency RBS analysis. Examples of the usefulness of the muprobe facility for materials research are given.

A quality control exercise of radionuclide calibrators among Belgian hospitals

On the initiative of the Belgian Association of Hospital Physicists, eleven Belgian hospitals participated in a quality control of radionuclide calibrators conducted in collaboration with the Central Bureau for Nuclear Measurements of the Commission of the European Communities. For practical reasons the nuclide 57Co was chosen. The results from 20 different radionuclide calibrators show a fair agreement with a similar comparison carried out in 1980 in the UK.

Nuclear analytical application of thermionic mass spectrometry

The relative uncertainty on the isotope abundance ratio measurements of uranium and plutonium samples by means of thermionic mass spectrometry at the Central Bureau for Nuclear Measurements (CBNM) in Geel, Belgium, has decreased to a level of about 2 · 10−4.

The Assay of Uranium and Plutonium in Reprocessing Input Solutions by Isotope Dilution Mass Spectrometry: Results of the Isotope Dilution Analysis Measurement Evaluation Programs

For analytical methods to be applied to international safeguards, precision and accuracy must be well established. With this objective an interlaboratory measurement evaluation program— “IDA-80,” which determined the elemental and isotopic content of the input solutions to reprocessing plants—was carried out with the participation of 33 laboratories from 15 countries or international organizations. It was guided jointly by the Central Bureau for Nuclear Measurements (CBNM) and the Kernforschungszentrum Karlsruhe (KfK) under the auspices of the European Safeguards Research and Development Association and with the support of the International Atomic Energy Agency. The element concentrations and isotopic compositions of all test materials were characterized by CBNM and the U.S. National Bureau of Standards to a high accuracy. The evaluation of more than 60000 analytical data reported by the participating laboratories yielded detailed estimates of the isotopic measurement capability of the laboratories for uranium and plutonium isotopes as well as for uranium and plutonium element assay by isotope dilution mass spectrometry. It also identified a number of sources of error. Compared to the results obtained in the “IDA-72” interlaboratory experiment—a similar program organized earlier by KfK with the participation of 22 laboratories from 13 countries or international organizations—considerable improvement of isotope dilution analysis over the last decade is shown.

The feasibility of electromagnetic actinide isotope separation in the European community

The production of actinide reference materials in the European Community depends in those cases in which electromagnetically enriched material is required on the supply from the USA Department of Energy/Oak Ridge National Laboratory (DOE/ORNL). A study carried out by the Central Bureau for Nuclear Measurements (CBNM) is based on the needs for actinide reference materials in the European Community (EC) as determined by a separate inquiry in 1977 and examines the conditions for the installation of an electromagnetic separation facility of appropriate size in the EC. From a compilation of all the information about the production, chemical purification and isotopic enrichment of all actinide nuclides needed in the EC those cases have been assessed for which the application of electromagnetic isotope separation is at present unavoided (but feasible with the glovebox technique). Base materials for this separation process are readily available within the EC with the exception of 244Pu. The production of 244Pu was experimentally studied and extrapolated to production scale. The use of this isotope as a spike material in mass spectrometric plutonium determination is shown to be uneconomic. An electromagnetic separator adapted in capacity to EC needs was designed. Special containments and facilities for handling the radioactive actinide elements are proposed. From the cost price of this facility and operational experience of a few EC laboratories the total running costs and the specific product costs for the EC needs are calculated.

A European community source of reference materials for neutron metrology requirements

Recognizing the importance of an assured supply of reference materials of high purity for use as neutron dosimeters, the Monitor Materials subgroup of the European Working Group on Reactor Dosimetry collaborated with the Central Bureau for Nuclear Measurements, Geel, Belgium to establish a list of requirements. CBNM is organizing the availability and characterization of these materials in collaboration with specialist laboratories within the European Community. At present 12 activation and 6 fission dosimetry materials are being examined prior to certification and issue. This source of materials is expected to be of great use for reactor surveillance, interlaboratory comparisons, and other neutron metrology requirements.

Neutron-Induced Fission Cross Section of Plutonium-240 in the Energy Range from 10 keV to 10 MeV

The neutron-induced fission cross section of 240Pu was measured in the neutron energy range from 10 keV to 10 MeV using the 7-MV Van de Graaff and the electron linear accelerator of the Central Bureau for Nuclear Measurements as pulsed neutron sources, which delivered monoenergetic and continuous neutron spectra, respectively. The neutron-induced fission events were detected with a parallel plate ionization chamber that provided a fast and narrow output signal allowing nanosecond timing, but where the time integral of the pulse contained, at the same time, the energy information of the ionizing particle. This detector permitted a high discrimination between alpha particles and fission fragments at an alpha emission rate of some 107 s−1. The fission cross-section data below 400 keV are especially remarkable since they were taken with an energy resolution almost one order of magnitude better than any other published data set. In this region, large structures in the fission cross section due to Class II states in the second well of the double-humped fission barrier were found. The spontaneous fission half-life of 240Pu was measured to be (1.15 ± 0.03)·1011 yr.

Measurement of (n, α) Cross Sections of Chromium, Iron, and Nickel in the 5- to 10-MeV Neutron Energy Range

A measuring program has been carried out at the Van de Graaff accelerator facility of the Central Bureau for Nuclear Measurements for the determination of (n, α) cross sections on the main constituents of fast reactor structural materials, namely the elements chromium, iron, and nickel. The alpha particles are detected in a reaction chamber by telescope counter arrangements at five observation angles between 14 and 141 deg. Results obtained in the energy range from 5 to 10 MeV are presented in terms of laboratory angle-differential cross sections, relative Legendre polynomial coefficients of angular distributions, angle-integrated cross sections, and average alpha energies.

Modernization at Geel

The Central Bureau for Nuclear Measurements in Geel, Belgium, one of the four laboratories of the Joint Research Centre of the European Commission, is to modernize its major research equipment. The existing equipment, which is over 10 years old, comprises an 80 MeV electron linear accelerator (LINAC) operated almost exclusively as a neutron source for neutron data measurements.