Routine PIXE at the University of Aarhus

The setup currently in use at the Aarhus PIXE facility is described, with the emphasis on features necessary for fast and reliable routine operation.     

The results of 5% small-break LOCA tests and natural circulation tests at the ROSA-IV LSTF

Five 5% small-break loss-of-coolant accident (SBLOCA) experiments and two natural circulation experiments were conducted at the ROSA-IV Large Scale Test Facility (LSTF). The liquid holdup in the upflow side of steam generator (SG) U-tubes temporarily depressed the core collapsed liquid level below the bottom of core during the loop seal clearing in the cold-leg break SBLOCA tests. This phenomena was affected by the core power and core bypass but was affected little by the actuation of the high pressure injection system. Overall thermal-hydraulic phenomena in a loop seal line break test was similar to that of cold-leg break tests, however, the liquid holdup phenomena played a little role. In a hot-leg break test a temporary but rapid depression of the core liquid level was observed immediately after the initiation of accumulator injection which caused condensation and depressurization in the cold leg. The change of natural circulation flow rate with the decrease of primary system mass inventory was qualitatively the same as observed in Semiscale, LOBI and PKL. The SG effective overall heat transfer coefficient below the secondary-side collapsed liquid level was weakly dependent on the secondary side liquid level and the core power. The measured minimum heat transfer coefficient was 1.7 kW/m²K for the full secondary side mass inventory.     

Accelerator mass spectrometry at the University of Pennsylvania

Since 1979 over 1000 measurements have been made on ¹⁰Be and about 50 on ²⁶Al. Although the experimental program is diverse, emphasis has been placed on the study of ¹⁰Be in the environment, particularly its rate of influx in precipitation, its retention by soil and transport by ground water. The global flux for 1982–1983 is estimated to be 0.33 at. cm^?2 s^?1. The application of ¹⁰Be as a tracer is discussed and the results of 46 measurements on lavas from island-arc volcanoes and 47 Australasian tektites are presented. ²⁶Al has also been measured in 6 tektites and the observed ²⁶Al:¹⁰Be ratio is consistent with a terrestrial origin. Exploratory measurements have been made on a wide range of terrestrial and extraterrestrial samples including several organic materials such as peat, oil, coal, teeth, shells and trees.     

The nuclear microprobe at the University of Arizona

A nuclear microprobe has been operational at the University of Arizona since early 1994. It utilizes a magnetic quadrupole doublet (model QL-300 from Microscope Associates, Inc.) with an 11 mm diameter aperture and lens lengths of 6 cm each. The magnetic pole tips are electrically insulated to enable electric rotational alignment and beam rastering by application of varying voltages to the pole tips. Ion beams are obtained from a 5.5 MV model CN, High Voltage Engineering Corp. Van de Graaff accelerator with a Penning type ion source. Present mininum beam spot size is about 2 μm obtained with a 4 MeV H₂⁺ beam with a current of about 40 pA. To date, the instrument has been successfully used to map concentrations of Hg, Cr, and As in rabbit renal slices using PIXE.     

Results of CMM standalone tests at DTP2

A full scale physical test facility, DTP2 (Divertor Test Platform 2) has been established in Finland for demonstrating and refining the Remote Handling (RH) equipment designs for ITER. The first prototype RH equipment at DTP2 is the Cassette Multifunctional Mover (CMM) equipped with the Second Cassette End Effector (SCEE) delivered to DTP2 in October 2008. The purpose is to prove that CMM/SCEE prototype can be used successfully for the 2nd cassette RH operations. At the end of F4E grant “DTP2 test facility operation and upgrade preparation”, the RH operations of the 2nd cassette were successfully demonstrated to the representatives of Fusion for Energy (F4E).During the grant the High Level Control (HLC) software developed at DTP2 was integrated with the CMM/SCEE hardware. The performance criteria of the CMM/SCEE equipment were defined based on the ‘EN ISO 9283 Manipulating industrial robots – Performance criteria and related test methods’ standard. Considerable improvement to the performance was achieved with the aid of compensation functions, which took into account the deflections and the compliance effects caused by the Divertor Cassette weighting 9000 kg. According to measurements the positioning error at the furthest point of the cassette was reduced from 80 mm to 5 mm.So far the 2nd cassette mock-up has been installed and removed already some tens of times. The reliability of the HLC software is sufficient to operate the CMM/SCEE all day without interruptions. Also the execution of the automatic RH processes with the overall RH system is reliable and repeatable in terms of accuracy and cycle time.These experiments provide a solid basis for investigating the RH system ability to perform fail-safe operations in various failure scenarios and to recover from them. The target of the continuing R&D is to find out a more complete set of functional and non-functional requirements for the RH system for Divertor Cassette maintenance to ensure an adequate level of requirements and procedures for ITER.     

Status of the AMS facility at the University of Georgia

Since 2001, the Center for Applied Isotope Studies at the University of Georgia has analyzed more than 10,000 samples using a compact AMS system for carbon isotope measurement. The system, manufactured by National Electrostatics Corporation, utilizes a Model 1.5SDH-1 Pelletron accelerator with a maximum terminal voltage of 0.5 MV. The source has recently been modified, doubling the count rate and improving efficiency more than 50%. Background values have reached 0.12 pMC and the precision is below 0.4 pMC for modern samples. The control and data acquisition system has also been upgraded.     

Fast flux irradiation tests performed at high temperature

The first gas-cooled fast breeder reactor (GCFR) fast flux irradiation experiment [F-1(X094)] consists of seven fuel rods clad in 20% cold-worked 316 stainless steel. The rods are individually encapsuled, with sodium filling the gaps within the capsule walls. The rods are fueled with (15% Pu, 85% U)O₂ and have depleted UO₂ lower and upper axial blankets and charcoal to trap volatile fission products. The cladding i.d. temperature range covered by these rods is 570–760°C (1055–1400°F).The in-reactor performance of the fuel rods in the F-1 high-temperature experiment, which achieved a burnup of 121 MWd/kg (13.0 at.%) on the lead rod, is described. All rods in the experiment have remained intact. The results of interim examinations [at 25 and 50 MWd/kg (2.7 and 5.4 at.%)] of fuel and fission product behavior and transport and comparisons of observed results with LIFE-III code predictions are described.The F-3 experiment, which consists of ten encapsulated GCFR fuel rods with surface-roughened (ribbed) cladding, shares a nineteen capsule subassembly with Argonne National Laboratory. Temperatures are controlled over the range 675°C (1250°F) to 750°C (1380°F). Irradiation is in the core region of the EBR-II and thus permits achievement of a higher fluence-to-burnup ratio than that obtained in the F-1 experiment.Preliminary results of a planned interim examination at an exposure of 46 MWd/kg (4.9 at.%) burnup and a fluence of 5.2 × 10²² n/cm² show that cladding failures occurred in nine of the ten rods. Preliminary indications are that the failures are due to defects in the sodium bond between the fuel rod and the capsule.The tests completed and currently under way have been scoping in nature, and irradiation in EBR-II of GCFR prototypical fuel (pressure equalized) rods with ribbed cladding is required to provide the information needed for reactor design on effects of exposure to high fluence and burnup and on design reliability for a statistically significant number of rods. The design and the operating conditions for the F-5 experiment being prepared for this purpose are described.     

Simulation of hydrogen deflagration and detonation in a BWR reactor building

A systematic study was carried out to investigate the hydrogen behaviour in a BWR reactor building during a severe accident. BWR core contains a large amount of Zircaloy and the containment is relatively small. Because containment leakage cannot be totally excluded, hydrogen can build up in the reactor building, where the atmosphere is normal air. The objective of the work was to investigate, whether hydrogen can form flammable and detonable mixtures in the reactor building, evaluate the possibility of onset of detonation and assess the pressure loads under detonation conditions. The safety concern is, whether the hydrogen in the reactor building can detonate and whether the external detonation can jeopardize the containment integrity. The analysis indicated that the possibility of flame acceleration and deflagration-to-detonation transition (DDT) in the reactor building could not be ruled out in case of a 20 mm² leakage from the containment. The detonation analyses indicated that maximum pressure spike of about 7 MPa was observed in the reactor building room selected for the analysis.     

Hydrogen distribution tests under severe accident conditions at the large-scale HDR-facility

The E11 tests series covered a combination of important issues dominating the physical phenomena controlling the hydrogen distribution mechanisms, namely: large-scale, multi-compartment, geometry with large-sized dome volume, high gas release rates, multiple steam and gas injection phases at different axial positions and examinations of the efficiencies of mitigative system features including the impact of external sprays at the top of the dome.The test series consisted of a total of eight different experiments covering all aspects of the H₂-distribution and potential mitigation features.A total of 700 sensors were applied during these experiments.The paper outlines experimental and computational results of tests E11.2 and E11.4 which were chosen for two computational PHDR-Benchmark Exercises in the context of blind posttest predictions with broad international participation applying the majority of known computer codes. In addition test E11.2 was selected as an open post-test, OECD International Standard Problem No. 29 (H. Karwat, Distribution of hydrogen within the HDR-containment under severe accident conditions — Task specifications (July 1990)) which is presently in progress.     

Transient tests on blower trip and rod removal at the HTR-10

Safety demonstration tests on the 10 MW high temperature gas-cooled reactor test module (HTR-10) were conducted to verify the inherent safety features of MHTGRs and to obtain the core and primary cooling system transient data for validation of safety analysis codes.Two simulated anticipated transients without scram (ATWS) tests, lose of forced cooling by trip of the helium blower and reactivity insertion via control rod withdrawal were performed. This paper describes the tests with detailed test method, condition and results.Calculated results show that the strongly negative temperature coefficient causes reactor power to closely follow heat removal levels. Maximum fuel temperature changes are limited by the large core heat capacity to below 1230 °C during two tests.The test of tripping the helium circulator ATWS test was conducted on October 15, 2003. Although none of 10 control rods was moved, the reactor power immediately decreased due to the negative temperature coefficient. After about 50 min, the reactor became criticality again. Finally, the reactor power went to a stable level with about 200 kW.The test of reactivity insertion ATWS test was conducted two times. Following the control rod withdrawal, the reactor power increased rapidly, the maximum power level reached to 5037 and 7230 kW from the initial power of 3000 kW in accordance with reactivity insertion of $ 0.136 and 0.689, respectively. After the reactivity introduced was compensated by means of the strong negative reactivity feedback effect, the reactor went to subcritical and the power decreased.     

复旦大学单粒子微束研制进展

建设了一基于复旦大学2×3 MV串列加速器的单粒子微束装置。离子束经分析磁铁30°水平偏转传输后再经90°偏转磁铁竖直上行至辐照终端,以内径1.5 μm的毛细玻璃管微准直器获取离子微束。采用薄膜闪烁体结合光电倍增管的探测结构对微束离子进行精确探测和计数,并以高压静电偏转开关快速关断束流以实现对离子数目的精确控制。目前实验已获得在质子能量为3 MeV时,能散（能量分布曲线中半高宽FWHM）<60 keV、束分辨<2.2 μm、定量照射精度>95%的质子微束。本文对复旦大学单粒子微束的束流管道设计、微束获取、束开关及单粒子探测等核心环节的研制进展进行介绍。     

The verification tests of the melting conditions for homogenization of metallic LLW at the JAEA

To clarify the operating conditions for the homogenization of metallic low-level radioactive wastes (LLW), melting tests were conducted in the metal melting system of the Advanced Volume Reduction Facilities at the Japan Atomic Energy Agency (JAEA). Simulated metallic LLW with a non-radioactive tracer were melted in the induction furnace of the metal melting system. Regardless of the chemical composition or amounts of the simulated wastes, the tracer distribution in the solidified products was nearly homogeneous when the simulated wastes were completely melted in the range from 1550 °C to 1638 °C.     

High-temperature triaxial torsional creep tests of concrete at various hygral conditions

Results of an initial series of six-day creep tests under a program aimed at establishing fundamental deformation properties of concrete at high temperatures under triaxial loading with shear and various hygral conditions, both constant and transient, are reported. The tests are conducted in a novel large triaxial torsional testing machine with hygrothermal control. Tested are cylinders of six inch diameter, sealed or unsealed, loaded by compressive axial force, chamber pressure and torque. Some specimens are sealed wet, some are sealed after drying in an oven, and some are let to dry during the test. Significant differences in creep at various hygro-thermal conditions are observed. Particularly interesting is the fact that hygro-thermal changes affect not only normal creep strains but also shear creep strains. The results are of interest for the formulation of constitutive relations needed for the analysis of nuclear reactor accidents, radioactive waste disposal, and fire resistance.     

北京大学RFQ加速器研究进展

北京大学在20世纪90年代末成功研制了1台整体分离环重离子射频四极场(RFQ)加速器ISR-1000,近年来经升级后它可提供1 MeV/2 mA氧离子束流.为提高RFQ加速器在较高能量下的加速效率,北京大学提出并正在研制1种新型分离作用RFQ加速结构(SFRFQ),所建造的加速腔实验样机可与ISR-1000构成组合加速系统,将mA级氧离子加速到1.6 MeV.北京大学参与了"973"项目350 MHz四翼型强流质子RFQ加速器的研究,并研制了1台全尺寸无氧铜工艺腔.北京大学还计划在近年内建造1台中子源用201.5 MHz、2 MeV/50 mA微翼四杆型氘离子RFQ加速器.     

Strain analysis on ductile cast iron containers at drop tests

Ductile cast iron (DCI) containers for transportation and deposition of radioactive waste have to be designed carefully in order to avoid unacceptable damages and leakages in case of an accident. Therefore various calculations and experimental methods are used during development and licensing of the containers. Besides others the container has to suffer severe impacts (e.g. falling from a height of several meters onto a concrete base). The level of strains must not exceed a value which would adversely affect the package in such a way that it would fail to meet the applicable requirements. In practice complex events such as drop tests are very difficult to calculate. Both the position of maximum stress and the time of its occurrence are not easily predicted with the method of FEM. The uncertainty of the material modelling for plastic deformation by dynamic loading rates is the limiting factor. Therefore holography as an integral measuring technique in combination with strain gauge techniques were used to fit the FEM. By using the FEM calculations in the case of licensing, the FE and the material model have to be verified. The verification of the FE model has to be done by comparison of the local maxima measured by strain gauges and by comparison of the vibration modes. These vibration modes we take from holographic measurements. In this paper we explain container vibrations after impact analysed with holographic measurements, FEM calculations and the comparison of the results. The comparison of the local maxima (strain gauges/FEM) is reported elsewhere (Schreiber, D. et al., 1993. Trans. 12th Int. Conf. J04, 5, pp. 101–108; Völzer, W. et al., 1997. Technical Semin. on Brittle Fracture. Krefeld 27–28.10.94, RAMTRANS (in press)).     

Hydrogen analysis of mineral samples at University of Tsukuba

This study reports the present status of our work on the hydrogen analysis of mineral and rock samples. The preparation of a standard material by means of ion implantation, a method of its calibration and the application of the method are described. The number of hydrogen atoms per unit volume in the standard material can be determined from the simultaneous observation of -particles, γ rays and –γ coincidence events for the ¹H(¹⁹F,γ) reaction at the 16.44 MeV resonance energy. The hydrogen content in a natural obsidian determined with the method mentioned above is in agreement with that obtained by FTIR. A heavy-ion microbeam system under construction, which consists of a Russian-type quadrupole magnet for beam focusing, a beam defining slit system and a γ-ray detector, is also described.     

Proof pressure tests of the first reactor vessels at Hartlepool and Heysham nuclear power stations

The nuclear stations currently nearing completion at Hartlepool and Heysham are the world's first design of Advanced Gas Cooled Reactor to use podded boiler construction. The proof pressure tests on the first reactor pressure vessels at both stations were carried out during the early part of 1980. The object of the proof pressure test is to satisfy statutory and contractual requirements by demonstrating the integrity of the completed concrete pressure vessel, liners and pressurised penetrations when subjected to a pneumatic test pressure of 740 lbf/in² g, equivalent to 1.15 times the design pressure of 644 lbf/in² g. Testing was carried out in the latter period of the construction phase of each station with the majority of the plant and buildings in an advanced state of construction and the reactor internals essentially complete. This paper examines the results of both reactor 1 vessel tests and compares the behaviour of the vessels with one another and with analytical predictions. Possible sources of instrumentation error are identified and discussed. The conclusions are drawn from correlation of the test results with theoretical predictions.The vessel pressure was raised and lowered in six stages to and from the test pressure with a hold period between each stage to read instruments, examine the vessel surfaces and leak check the penetrations and closures. To obtain the relevant information at each pressure hold, the vessels' permanent instrumentation, consisting of vibrating wire strain gauges and their associated electrical resistance thermometers, and the liner and reactor internal thermocouples were monitored. In addition, strain gauges fixed to the concrete face of the liner during construction were monitored and liner strains measured during the test were compared with predictions. Vessel deflections were monitored by special equipment mounted on the reactor building to enable vessel dilation to be measured. The vessel top and bottom caps were instrumented by manometric systems in order that the cap profiles and deflections could also be determined.The measurements and observations made during the proof pressure tests adequately demonstrated that the vessels behaved in accordance with predictions. The concrete strains and vessel external deflections confirmed that the vessels behaved in a linear and elastic manner throughout the tests, with no cracking being observed in the concrete during the tests. Liner strains compared favourably with predicted values, exhibiting a linear behaviour under increasing pressure. The strain levels recorded gave complete confidence in the liner design.The tests confirmed the integrity of the vessels, thus enabling them to go forward to the engineering run stage in the commissioning programme leading ultimately to the raising of power.