Search

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 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...

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.