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The first irradiation testing of TRISO-coated particle fuel to demonstrate and qualify its use in a VHTR was finished at the beginning of 2014 in HANARO, Korea. A PIE (post-irradiation examination) of the irradiated TRISO-coated particle fuel was then performed. The irradiation device contained two kinds of test rods: one containing nine fuel compacts, and the other five compacts and eight graphite specimens between the fuel compacts. The irradiation testing was carried out under the condition of filled with an inert gas atmosphere and being sealed (no sweep gas). After irradiation testing, the maximum power of the fuel compact was estimated to be around 56 W at 25 EFPD, and the maximum power of the particle was calculated to be 215.4 mW. And, the maximum discharged burn-up was evaluated to be about 37,344 MWD/MTU (3.99% FIMA). The estimated maximum fast fluence of the graphite specimen was 2.99 × 1020 n/cm2 (E > 0.18 MeV). In this paper, the characteristics of TRISO-coated particle fuels, the estimated thermal power, fuel temperature, burnup, fluence, and some PIE results were described.

An instrumented creep testing capability is being developed for specimens irradiated in Pressurized Water Reactor (PWR) coolant conditions at the Advanced Test Reactor (ATR). The test rig has been developed such that samples will be subjected to stresses ranging from 92 to 350 MPa at temperatures between 290 and 370 °C up to at least 2 dpa (displacement per atom). The status of Idaho National Laboratory (INL) efforts to develop the test rig in-situ creep testing capability for the ATR is described. In addition to providing an overview of in-pile creep test capabilities available at other test reactors, this paper reports efforts by INL to evaluate a prototype test rig in an autoclave at INL’s High Temperature Test Laboratory (HTTL). Initial data from autoclave tests with 304 stainless steel (304 SS) specimens are reported.

Over 50 years of nuclear fuels and materials irradiation testing has led to many countries developing significant improvements in instrumentation to monitor physical parameters and to control the test conditions in material test reactors (MTRs). Recently, there is increased interest to irradiate new materials and reactor fuels for advanced pressurized water reactors and Gen-IV reactor systems, such as sodium-cooled fast reactors, very high temperature reactors, supercritical water-cooled reactors, and gas-cooled fast reactors. This review paper documents the current state of instrumentation technologies in MTRs in the world and summarizes ongoing research efforts to deploy new sensors. As described in this paper, a wide range of sensors is available to measure key parameters of interest during fuels and materials irradiations in MTRs. Ongoing development efforts focus on providing MTR users a wider range of parameter measurements with smaller, higher accuracy sensors.

The “analytical” PYCASSO (PYrocarbon irradiation for Creep and Swelling/Shrinkage of Objects) irradiations focus on determining the effects of neutron irradiation in the temperature range of 900–1100 °C, excluding effects due to the presence of fuel, such as pressurization or chemical attack by fission products. These irradiations can therefore be considered separate effect tests, where only the influence of neutron fluence and temperature on coatings and coating combinations is investigated. For this purpose dedicated particles have been manufactured consisting of surrogate kernels (ZrO 2 and Al 2 O 3 ) with different types of PyC/SiC/ZrC coatings and coating combinations. All specimens delivered have been extensively characterized, such that even potentially small changes due to the irradiation in dimensions, microstructure and density can be determined accurately after irradiation. Partners involved in this irradiation are CEA (France), JAEA (Japan) and KAERI (South Korea). The PYCASSO irradiations take place in the High Flux Reactor (HFR) in Petten, and are coordinated by NRG (The Netherlands). The partnership for PYCASSO was initiated by the RAPHAEL (V)HTR European 6th Framework Program and is integrated in the Generation IV International Forum VHTR Fuel and Fuel Cycle project.

The High flux Advanced Neutron Application ReactOr (HANARO), an open-tank-in-pool type reactor, is one of the multi-purpose research reactors in the world. Since the commencement of HANARO’s operations in 1995, a significant number of experimental facilities have been developed and installed at HANARO, and continued efforts to develop more facilities are in progress. Owing to the stable operation of the reactor and its frequent utilization, more experimental facilities are being continuously added to satisfy various fields of study and diverse applications. The irradiation testing equipment for nuclear fuels and materials at HANARO can be classified into capsules and the Fuel Test Loop (FTL). Capsules for irradiation tests of nuclear fuels in HANARO have been developed for use under the dry conditions of the coolant and materials at HANARO and are now successfully utilized to perform irradiation tests. The FTL can be used to conduct irradiation testing of a nuclear fuel under the operating conditions of commercial nuclear power plants. During irradiation tests conducted using these capsules in HANARO, instruments such as the thermocouple, Linear Variable Differential Transformer (LVDT), small heater, Fluence Monitor (F/M) and Self-Powered Neutron Detector (SPND) are used to measure various characteristics of the nuclear fuel and irradiated material. This paper describes not only the status of HANARO and the status and perspective of irradiation devices and instrumentation for carrying out nuclear fuel and material tests in HANARO but also some results from instrumentation during irradiation tests.

The status of R&D works being carried out for the development of the technology for the coated fuel particles and the achievements in the first phase in Korea is described. Emphasis is given to the development of the laboratory equipment and apparatus and the first results of the experiments carried out for the kernel preparation and coating of PyC and SiC as well as their respective characterizations and relevant quality control (QC) methods. The current status of the in-reactor performance model and the analytical code development are included as well as some preliminary results from the feasibility study on the irradiation test of the fuel specimens in the HANARO research reactor in Korea. Also discussed are the essential involvements in the GIF collaboration and with the IAEA as well as other international collaboration schemes during the development.

An in-pile test program for the development of a high burn-up fuel is planned for the HANARO reactor. The source term originates from a leakage of fission products from the anticipated failed fuels into the gas flow tubes and around the instrumentation and control system. In order to quantify the fuel composition in the event of a fuel failure, the isotope generation and depletion code ORIGEN 2.0 was used. The computer program Microshield 6.2 was used to calculate the doses from specific locations, where a high radioactivity is expected during an irradiation. The results indicate that the equivalent dose in the investigated working areas is less than the permitted dose rate of 6.25 μSv/hr. However, access to the area of a decay vessel may need to be limited, and the installation of a Pb wall with a 20.5 cm thickness is recommended. From the analysis of a radioactive decay with time, most of the concerned gaseous nuclides with short half-lives after 3 months, were decayed, with one exception which was Kr-8...

A material capsule system including a main capsule, a fixing, a control, a cutting, and a transport system was developed for an irradiation test of non-fissile materials in HANARO. This capsule system has been actively utilized for the various material irradiation tests requested by users from research institutes, universities, and the industries. Based on the accumulated irradiation experience and the user’s sophisticated requirements, the instrumented capsule technologies for a more precise control of the irradiation temperature and fluence of a specimen were developed in HANARO. 6,000 specimens from domestic research institutes, nuclear industry companies and universities, were irradiated in HANARO for 54,000 hours by using the developed capsule irradiation system. Recently, development of new instrumented capsule technologies for an IP/OR irradiation test and a high temperature irradiation test has been performed in HANARO for relevant ongoing R&D for the international Gen IV Program. New irradiation technologies are also under development for the production of new functional materials including superconductor and optical/electrical materials.

A fatigue capsule is one of the special capsules to investigate the fatigue characteristics of the nuclear materials during an irradiation test in a research reactor, HANARO. In this study, the performance test and the preliminary fatigue test results by using a cyclic load device newly developed for a fatigue capsule are described. In order to obtain the characteristics such as a realization and a controllability of the periodic wave shape and the relationship between the pressure and the load, a spring and rigid bar specimens are used. The fatigue test for the 316L stainless steel specimen with 1.8mm in diameter and 12.5mm in gage length is also performed under the same conditions as the temperature() of the specimen during irradiation tests. As a result of the test, the fracture of the specimen occurs at a total of 70,120 cycles(about 12 days), and the displacement in this case is 2.02 mm. It is expected that these results will be used for determining test conditions and a comparison of the in-pile fatigue test results.

Small specimen with simple geometry has advantage for irradiation tests because the tests have limits for experiments and nuclear wastes after irradiation tests. In this study, a kinetic indentation technique is applied to evaluate mechanical properties of coated layers of a particle fuel of a high temperature gas cooled reactor. Hardness of buffer, IPyC and OPyC are 0.55, 0.874 and 2.726 GPa, respectively. The density, strength and friction coefficient estimated by kinetic indentation method are 1.08, 1.15 and 1.81 g/cm3, and 174, 291 and 606 MPa, and 0.51, 0.45 and 0.4, respectively.

Post irradiation annealing tests were performed to obtain the Xe-133 diffusion coefficients in a SIMFUEL which was a simulated irradiated UO2 fuel with a burnup of 27,300 MWd/t U. Specimens were fabricated as cubic polycrystals with the same composition for a given burnup. Each 300 mg specimen was irradiated in the HANARO research reactor for up to a 0.1 MWd/t U burnup. Post irradiation annealing tests were carried out at 1400 °C, 1500 °C and 1600 °C. The xenon diffusion coefficients for the SIMFUEL were lower than those for UO2 in near stoichiometric UO2 due to a relatively higher concentration of the tri-valent additives, which is related to the concentration of a cation vacancy. The activation energy in the SIMFUEL was also lower than that in UO2 due to the lower formation energy of a cation vacancy and the migration energy. The xenon diffusion coefficient for the SIMFUEL increased with an increasing oxygen potential of the ambient gas.

The neutron irradiation effect of polycrystalline Si 1− x Mn x semiconductor thin films has been studied. The Si 1− x Mn x semiconductor thin films were grown on SiO 2 /(1 0 0)Si substrate at 400 °C by using a MBE. The as-grown specimens are irradiated by the fast neutrons of 0.82 MeV in a neutron research reactor at KAERI. After neutron irradiation, the electrical resistivities of neutron-irradiated specimens increase with the irradiation amount, while the saturation magnetizations decrease. Hall analysis reveals that the mobility of neutron-irradiated specimen decreases remarkably. The XRD and TEM analyses show that the phase transformation is not induced by the neutron irradiation.

Polycrystalline Ge 1− x Mn x thin films were irradiated with neutrons, and their electrical and magnetic properties have been investigated. As-grown specimens have p-type carriers and electrical resistivities are in the range of 1.3 × 10 −4 –5.2 × 10 −4 ohm cm at room temperature. After the irradiation of neutrons the carrier type is not changed, but the electrical resistivities increase with the amount of neutron irradiation. In addition, some of neutron-irradiated Ge 1− x Mn x thin films transform from the semiconductor characteristics into the metallic characteristics at low temperature. The saturation magnetizations of neutron-irradiated Ge 1− x Mn x thin films decrease, but the coercive forces increase with the irradiation amounts. The XRD analysis suggests that the defects generated by the neutron-irradiation cause the change of electrical and magnetic properties of Ge 1− x Mn x thin films exposed to neutron irradiation.

Postirradiation annealing tests were performed to obtain the {sup 133}Xe diffusion coefficients in uranium dioxide (UO{sub 2}) and mixed thorium-uranium dioxide [(Th-U)O{sub 2}] fuels. Specimens were a single-grained UO{sub 2}, a polycrystalline UO{sub 2}, and a polycrystalline (Th-U)O{sub 2}. The (Th-U)O{sub 2} specimen was a mixture of 35% ThO{sub 2} and 65% UO{sub 2}. Each 300-mg specimen was irradiated to a burnup of 0.1 MWd/t U. Postirradiation annealing tests were performed at 1400, 1500, and 1600 deg. C, continuously. The xenon diffusion coefficients for the nearly stoichiometric single-grained UO{sub 2} agree well with the data of others. The xenon diffusion coefficients in the polycrystalline (Th-U)O{sub 2} are approximately one order lower than those in the polycrystalline UO{sub 2}. The xenon diffusion coefficient in the (Th-U)O{sub 2} increases with the increasing oxygen potential of the ambient gas.

The diffusion coefficient of Xe-133 was obtained from an annealing test. The specimen was made from U02 single crystal powder with natural enrichment and a grain size of 25 μm. Gamma scanning was performed before and after the annealing test to obtain total fission gas release fractions. The annealing test was performed for 10 hours with three temperature changes. Gamma ray peaks from the trap system were measured every 20 minutes during the annealing test. Activation energy and the pre-exponential factor of the diffusion coefficient equation were calculated using the release fraction data and a diffusion equation. The values were determined to be 360(±0.5%) kJ/mol and 2.0xl0-7(±10%), respectively.

Silicon carbide was deposited by a self-propagating high temperature synthesis reaction between graphite and silicon layers on an oxide substrate. Chemical analyses by Auger electron microscopy and X-ray diffractometry revealed that the final product was beta-SiC without an inter-diffusional layer at the interface between the carbide and graphite layers. Transmission electron microscope observation showed that the silicon carbide layer has fine crystalline structure. Numerical analysis showed that the combustion limit decreases with initial reaction temperature, which means that additional heat is required for the complete reaction. Activation energies between liquid silicon and carbon fiber or carbon black were 2875 and 1782 kJ/mol, respectively. The silicon carbide prepared by the combustion reaction between silicon and carbon was formed by the carbon diffusion at the interface between liquid silicon and silicon carbide. The reaction rate significantly depended on the specific surface area of carbon.

Oxidation behaviour of TiAl intermetallic compounds with the additions of Cr, V, Si, Mo, or Nb was investigated at 900~1100 °C under the atmospheric environment. The reaction products were examined by XRD and SEM equipped with WDX. The weight gain by continuous oxidation increased with the addition of Cr or V, but there was less weight gain when Mo, Si or Nb was added individually. Thus, it is concluded that the addition of Cr or V did not improve the oxidation resistance, whereas the addition of Si, Mo or Nb improved it. Nb strengthened the tendency to form Al2O3 in the early stage of oxidation, due to the formation of the continuous Al2O3 and dense TiO2 + Al2O3 layers. According to the Pt-marker test of TiAl-5wt%Nb, oxides were formed mainly by inward diffusion of oxygen. Upon thermal cyclic oxidation at 900 °C, it was shown that the addition of Cr or Nb improved the adherence of oxide scale to the substrate.

Within the Raphael (V)HTR 6th framework EU-program, the PYCASSO experiments have been devised to investigate coating behaviour under irradiation. Samples have been included from CEA (France), JAEA (Japan) and KAERI (Republic of Korea), which makes this irradiation a real Generation IV effort. The experiment is a separate effect test, where the influence of fuel (coating corrosion or micro structural change due to fission products), thermal gradients, and variation in coating microstructure and dimensions have been minimized by the use of dummy kernels (Al2O3 and ZrO2), high conductivity particle holder material combined with low energy production of the kernels, and strict (fabrication) quality control and selection procedures respectively. The purpose of the experiment is threefold for the partners involved: - for CEA to determine the behaviour of pyrocarbon under irradiation, especially the interaction of pyrocarbon swelling and creep with SiC coating layers. The results will be used to validate and improve HTR fuel performance modelling. - for JAEA to investigate the behaviour of ZrC coatings, which have been successfully manufactured, but require post-irradiation investigation and characterization. - for KAERI to determine the influence of fabrication of pyrocarbon layers with different densities on the behaviour under irradiation. The paper will go into more detail on the goals to be achieved by the different partners. The PYCASSO-I irradiation is performed in the High Flux Reactor (HFR) in Petten, The Netherlands. The experiment accommodates temperature regions of 900, 1000 and 1100°C, and contains 76 separate particle sample holders. The PYCASSO-I irradiation is a completely new design and will be described in detail, including the route from the concept definition via feasibility studies, fabrication and assembly, up to the irradiation, which took only 1, 5 year. At the time of the conference, the PYCASSO-I irradiation will be finished and a full evaluation of the irradiation will be presented. Additionally, the future post irradiation examination planned for the PYCASSO-I samples and the details of the PYCASSO-II irradiation will be outlined.Copyright © 2008 by ASME