Spallation Neutron Source SINQ Research Articles

Radiation softening and hardening of PDMS in combined neutron and γ rays

We report on the irradiation of a modified silica-filled room temperature vulcanized (RTV) PDMS. The irradiation experiments were conducted in air with combined neutron (approx. 6·1012 n·cm−2·s−1 at energies 1 meV to 1 MeV with an approximated maximum of 3% tail towards higher energy neutrons from 1 MeV up to 100 MeV) and γ rays (739–28,900 Gy at energies 0.01 MeV to 50 MeV) in the NAA position in the Swiss Spallation Neutron Source SINQ. Softening of the gel prevailed for the shorter exposures, hardening for the longer exposures within the explored range of exposure time (1.5 to 47 min). The material changes were sensed using dynamic mechanical analysis (DMA), analysis of the swelling in good solvents (o-, m-, p- xylene), Raman and FTIR spectroscopy, and water contact angle measurement. While the irradiation of PDMS influenced the swelling in the xylenes, melting temperature and elastic modulus, it did not discernibly influence the Raman and FTIR spectra, sol content, and water contact angle. Irradiation can be used as a post treatment of PDMS items enabling the optimization of elastic modulus and swelling characteristics.

The SINQ gas-jet facility as a source for radionuclides from neutron-induced fission of 235U

The Swiss Spallation Neutron Source SINQ of the Paul Scherrer Institute provides neutrons via proton-induced spallation reactions in a lead target. Produced neutrons are thermalized and impinge on 235U-targets, enclosed in a three-part chamber assembly, which is located in the inner wall of the SINQ shielding. The thermal-neutron-induced fission products can be readily transported from this chamber assembly to a radiochemical laboratory using the gas-jet technique either with a pure carrier gas or with an aerosol-particle-loaded carrier gas. In the past, mainly radioisotopes of the elements Se, Br, Rb, and Kr were retrieved and used for gas-phase chemistry experiments. Here, we present first experiments after the commissioning of the SINQ gas-jet facility as a source of recoverable, non-volatile and volatile, carrier-free fission products for general radiochemical studies and other applications.

SINQ—Performance of the New Neutron Delivery System

The Swiss spallation neutron source SINQ at Paul Scherrer Institute (PSI) has been in operation since 1996 using an optical guide system to transport low-energy neutrons from the source to the neutron beam lines. Clear signs of degradation in the guide system motivated us to redesign all neutron guides, which were then replaced in 2019–2020. All instruments received new tailored guides and SINQ operation was resumed in July 2020. Neutron flux measurements before and after the upgrade show that the expected instrument-dependent flux gain of a factor 2–10 was achieved. Furthermore, the fast-neutron background in the guide hall could be suppressed with an improved shielding in the guide bunker. The upgrade was completed with a slight delay due to the corona pandemic and in full compliance with the financial budget.

Operando Neutron Imaging for Next-Generation Solid State Batteries: A Direct Visualization of Li-Ion Transport in Sulfide Materials

Li-ion all-solid-state batteries promise to enhance safety and performance compared to conventional liquid based batteries. Nevertheless, only few investigations have been carried out on the effect of the solid electrolyte’s ionic conductivity on the electrochemical performance of batteries in order to visualize non-uniform fields of transport. Neutron Imaging (NI) is a non-intrusive technique that offers the possibility of tracking light elements such as the 6Li isotope during all phases of battery operation. Because it helps visualizing lithium’s concentration profiles, NI allows quantifying Li-ion transport and enables us to model solid state batteries. We therefore expect NI to help us explain solid state batteries’ poor rate capabilities. A reliable electrochemical cell was successfully designed and utilized for an operando test of an all-solid-state battery using PSI's high-resolution neutron imaging detector ('Neutron Microscope') at the POLDI beamline of Swiss Spallation Neutron Source SINQ (Paul Scherrer Institut). A solid state battery with a composite electrode TiS2:6Li3PS4(6LPS) and a 6Li-In alloy counter electrode have been investigated (Figure 1) and the results will be discussed. Figure 1

In situ Polarized Neutron Reflectometry: Epitaxial Thin-Film Growth of Fe on Cu(001) by dc Magnetron Sputtering

The step-wise growth of epitaxial Fe on Cu(001)/Si(001), investigated by in-situ polarized neutron reflectometry is presented. A sputter deposition system was integrated into the neutron reflectometer AMOR at the Swiss neutron spallation source SINQ, which enables the analysis of the microstructure and magnetic moments during all deposition steps of the Fe layer. We report on the progressive evolution of the accessible parameters describing the microstructure and the magnetic properties of the Fe film, which reproduce known features and extend our knowledge on the behavior of ultrathin iron films.

News from the Swiss Spallation Neutron Source SINQ: diffraction at non-ambient conditions

News from the Swiss Spallation Neutron Source SINQ: diffraction at non-ambient conditions

A Drabkin-type spin resonator as tunable neutron beam monochromator

A Drabkin-type spin resonator was designed and successfully implemented at the multi-purpose beam line BOA at the spallation neutron source SINQ at the Paul Scherrer Institute. The device selectively acts on the magnetic moment of neutrons within an adjustable velocity band and hence can be utilized as a tunable neutron beam monochromator. Several neutron time-of-flight (TOF) spectra have been recorded employing various settings in order to characterize its performance. In a first test application the velocity dependent transmission of a beryllium filter was determined. In addition, we demonstrate that using an exponential current distribution in the spin resonator coil the side-maxima in the TOF spectra usually associated with a Drabkin setup can be strongly suppressed.

The meson target stations and the high power spallation neutron source SINQ at PSI

The Paul Scherrer Institut operates two meson graphite targets, Target M and Target E, for creating the world’s most intense pion and muon beams by using 590 MeV protons and c.w. beam currents of up to 2.4 mA (=1.4 MW). The energy deposit on Target E is 20 kW mA−1. The proton beam feeds also the spallation neutron source SINQ, which operates in DC mode and produces thermal and cold neutrons. The SINQ target consists of a bundle of lead filled Zircaloy tubes. In this report the continuous developments of both target facilities and their operation are presented.

Development status of CLAM steel for fusion application

The China low activation martensitic (CLAM) steel is being developed at the Institute of Nuclear Energy Safety Technology (INEST) under wide collaboration within China. Significant R&D work on CLAM steel was carried out to help make it suitable for industrial applications. The effect of refining processes and thermal aging on composition, microstructures and mechanical properties were investigated. Material properties before irradiation including impact, fracture toughness, thermal aging, creep and fatigue properties etc. were assessed. A series of irradiation tests in the fission reactor HFETR in Chengdu up to 2dpa and in the spallation neutron source SINQ in Paul Scherrer Institute up to 20dpa were performed. PbLi corrosion tests for more than 10,000h were done in the DRAGON-I and PICOLO loops. Fabrication techniques for a test blanket module (TBM) are being developed and a 1/3 scale TBM prototype is being fabricated with CLAM steel. Recent progresses on the development status of this steel are presented here. The code qualification of CLAM steel is under plan for its final application in ITER-TBM and DEMO in the future.

Determination of the ¹⁴C content in activated steel components from a neutron spallation source and a nuclear power plant.

The (14)C content in activated steel components from the Swiss Nuclear Power Plant (NPP) Gösgen and the Spallation Neutron Source SINQ at the Paul Scherrer Institute is determined using a wet chemistry digestion technique and liquid scintillation counting for (14)C activity measurements. The (14)C activity of an activated fuel assembly steel nut from the NPP is further compared with theoretical predictions made on the basis of a Monte Carlo reactor model for this NPP. Knowledge of the (14)C inventory in these activated steel materials is important in conjunction with future corrosion studies on these materials aimed at identifying the (14)C containing organic compounds possibly formed in the cement-based near field of a repository for radioactive waste.

Neutron imaging options at the BOA beamline at Paul Scherrer Institut

The BOA beamline at the Swiss spallation neutron source SINQ at Paul Scherrer Institut is a flexible instrument used mainly for testing novel techniques and devices for neutron scattering and optics, but, due to the large and relatively homogeneous field of view, it can be successfully used for experiments in the field of neutron imaging. The beamline allows also for the exploitation of advanced imaging concepts such as polarized neutron imaging and diffractive neutron imaging. In this paper we present the characterization of the BOA beamline in the light of its neutron imaging capabilities. We show also the different techniques that can be employed there as user-friendly plugins for non-standard neutron imaging experiments.

Radiochemical separation of 7Be from the cooling water of the neutron spallation source SINQ at PSI

Summary 7Be is a key radionuclide for investigation of several astrophysical processes and phenomena. In addition, it is used as a tracer in wear measurements. It is produced in considerable amounts in the cooling water (D2O) of the Spallation Induced Neutron Source (SINQ) facility at PSI by spallation reactions on 16O with the generated fast neutrons. A shielded ion-exchange filter containing 100 mL of the mixed-bed ion exchanger LEWATIT was installed as a bypass for the cooling water into the cooling loop of SINQ for three months. The collected activity of 7Be was in the range of several hundred GBq. Further, the 7Be was separated and purified in a hot-cell remotely-controlled using a separation system installed. With the exception of 10Be, radioactive byproducts can be neglected, so that this cooling water could serve as an ideal source for highly active 7Be-samples. The facility is capable of producing 7Be with activities up to 1 TBq per year. The 7Be sample preparation is described in detail and the possible uses are discussed. In particular some preliminary results of 7Be ion beam production are presented.

Quantitative characterization of Japanese ancient swords through energy-resolved neutron imaging

Japanese blades are culturally interesting objects both from the stylistic point of view and because of their fantastic performance. In this work, we present new results, using a non-invasive approach, concerning these peculiar artefacts. Five Japanese swords pertaining to Koto (987–1596) and Shinto (1596–1781) periods have been analysed through white beam and energy resolved neutron-imaging techniques. The experiments have been performed at the ICON beam line, operating at the spallation neutron source SINQ, Paul Scherrer Institut in Switzerland. The reconstruction of projection data into neutron tomographic slices or volumes allowed us to identify some peculiar characteristics, related to the forging methods that were used by the different schools and traditions in Japan.

Materials issues of the SINQ high-power spallation target

Abstract The Swiss spallation neutron source SINQ operated at the Paul Scherrer Institut is driven by PSI's 590 MeV proton accelerator at a beam power of 0.8 MW, as such being the most powerful (CW) spallation source worldwide. The core element of such a facility is the neutron production target. Since the commissioning in 1997, PSI has always fostered combined efforts in the development of the spallation target, including dedicated materials research for high dose radiation environments. The overall goal was to achieve optimized neutron production, combined with sufficient robustness, thermo-mechanical stability and radiation resistance to withstand the severe loads of high-dose irradiation and frequent thermal cycling over an acceptable lifetime. The target itself has been improved in several steps by searching for the optimal materials and geometries. In parallel, numerous experiments have been conducted in the targets of SINQ for studying radiation damage effects induced by high energy protons and spallation neutrons.

Cold-neutron tomography of annular flow and functional spacer performance in a model of a boiling water reactor fuel rod bundle

Dryout of the coolant liquid film at the upper part of the fuel pins of a boiling water reactor (BWR) core constitutes the type of heat transfer crisis relevant for the conditions of high void fractions. It is both a safety concern and a limiting factor in the thermal power and thus for the economy of BWRs. We have investigated adiabatic, air–water annular flows in a scaled-up model of two neighboring subchannels as found in BWR fuel assemblies using cold-neutron tomography. The imaging of the double suchannel has been performed at the ICON beamline at the neutron spallation source SINQ at the Paul Scherrer Institute, Switzerland. Cold-neutron tomography is shown here to be an excellent tool for investigating air–water annular flows and the influence of functional spacers of different geometries on such flows. The high-resolution, high-contrast measurements provide the spatial distributions of the coolant liquid film thickness on the fuel pin surfaces as well as on the surfaces of the spacer vanes. The axial variations of the cross-section averaged liquid hold-up and its fraction in the gas core shows the effect of the spacers on the redistribution of the two phases.

EFFECTS OF RADIATION AND He ON MICROSTRUC- TURES OF LOW ACTIVE FERRITIC/MARTENSITIC STEEL F82H

Low active ferritic/martensitic steel,F82H,has been developed as a candidate material for structural applications of fusion reactors because it has relatively low shifts in ductile-to-brittle transition temperature(DBTT) and excellent irradiation swell resistance.More works have been done in recent years on the microstructure and mechanical properties of F82H steel before and after irradiation,but most of the tested samples were irradiated at low temperature(400℃).In this work,the microstructure of F82H steel irradiated in the Swiss spallation neutron source SINQ in a temperature range of 150—450℃and a dose range of 6.1—20.2 dpa was studied.Defect clusters and He bubble were observed by TEM in the irradiated specimens.The results showed that there existed high density He bubbles with size of 1.6 nm under irradiation temperature higher than 208℃, irradiation dose higher than 9.5 dpa and He concentration 680×10~(-6).The effects of irradiation dose, irradiation temperature and He concentration on microstructure of F82H steel were discussed.

Cold neutron tomography of annular coolant flow in a double subchannel model of a boiling water reactor

Dryout of the liquid coolant film on fuel pins at the top of boiling water reactor (BWR) cores constitutes the type of heat transfer crisis relevant for the conditions of high void fractions. It is a limiting factor in the thermal power, and therefore the economy, of BWRs. Ongoing research on multiphase annular flow, specifically the liquid film thickness, is fundamental not only to nuclear reactor safety and operation but also to that of evaporators, condensers, and pipelines in a general industrial context. We have performed cold neutron tomography of adiabatic air water annular flow in a scaled up model of the subchannel geometry found in BWR fuel assemblies today. All imaging has been performed at the ICON beamline at the neutron spallation source SINQ at the Paul Scherrer Institut in Switzerland. Neutron tomography is shown to excel in investigating the interactions of air water two phase flows with spacer vanes of different geometry. The high resolution, high contrast measurements provide spatial distributions of the coolant on top of the surfaces of the spacer, including the vanes, and in the subchannel downstream of the spacers.

How to organize a neutron imaging user lab? 13 years of experience at PSI, CH

PSI has a relatively long tradition in neutron imaging since the first trials were done at its formerly existing research reactor SAPHIR with film methods. This reactor source was replaced after its shutdown in 1994 by the spallation neutron source SINQ in 1996, driven by the 590 MeV cyclotron for protons with presently up to 2.3 mA beam current. One of the first experimental devices at SINQ was the thermal neutron imaging facility NEUTRA, which was designed from scratch and has been the first device of its kind at a spallation source. Until now, NEUTRA has been successfully in use for many investigations in a wide range of studies covering fuel cell research, environmental behavior of plants, nuclear fuel inspection and the research on cultural heritage objects. It has been the host of PhD projects for students from all over Europe for years. In a previous meeting it has been offered as a European reference facility. Some of its features were really adapted to the layout of new installations. In 2004, it was possible to initiate the project of a second beam line at SINQ for imaging with cold neutrons. Previous studies have shown the potential of this option in order to broaden the user profile and to extend the scientific basis for neutron imaging. It was inaugurated with a workshop at PSI in 2005. The user service was started at the facility ICON in 2006. Beside the setup, installation and optimization of the facilities, the organization of the user program plays an important role. The two neutron imaging beam lines are equal installations at SINQ among the 14 scientific devices. Therefore, the user approach is organized via “calls for proposals”, which are sent out each half year via the “Digital User Office (DUO)” (see http://duo.web.psi.ch). The evaluation of the proposals is done by the “Advisory Committee for Neutron Imaging (ACNI)” consisting of 6 external and PSI internal members. Further requests are given by industrial collaborations. This beam time allocation is handled more directly and in time in order to fulfill the companies’ demands. Here, the confidentiality plays a more important role than in scientific studies that are done with the aim of a free publication. It has been possible to earn money regularly from the industrial projects in order to cover the salary cost of some positions within the NIAG group. The permanent improvement of the methodology and performance in neutron imaging is a third major activity of the NIAG team. Running projects in this direction are the permanent insert of a grating interferometry device, improved energy selection with the help of single graphite crystals and utilization of the beam line BOA at SINQ for the energy range between 4 and 15 Å.

Advanced on-target beam monitoring for spallation sources

The correct distribution of the incident proton beam density is crucial for the safe operation of high-power spallation targets. In all installations the proton beam footprint has to be monitored and any deviation from tight reference values must invariably lead to the prompt interruption of the irradiation. Based on several years’ experience with the dedicated optical system VIMOS at the Paul Scherrer Institute (PSI) neutron spallation source SINQ, issues, which turned out important and difficult, are highlighted.

PSI status 2008—Developments at the 590 MeV proton accelerator facility

The PSI accelerator, a 590 MeV/51 MHz ring cyclotron, routinely delivers 2.0 mA of proton current, which makes it the most powerful machine of this kind worldwide. An upgrade program will boost the current to 2.6 mA and ultimately to 3 mA, in a time frame of 4–5 years from now. Priority applications nowadays are muon spectroscopy (μSR) and neutron scattering. Six μSR-instruments are in operation, and the Swiss spallation neutron source SINQ hosts 15 instruments serving neutron scattering and imaging. PSI always seeks for options to improve the performance of the spallation target to optimized neutron production and reliability at high-power levels. In this context, MEGAPIE (MEGAwatt PIlot Experiment), a liquid metal target for SINQ, is the most recent outstanding project. In the near future, batches of 1% duty cycle of the full proton beam will be deflected to a new Ultracold Neutron source which is currently under construction and will be a key tool for particle physics at PSI.