0000000000020013
AUTHOR
Aigars Vītiņš
Tritium release behavior of beryllium pebbles after neutron irradiation between 523 and 823K
Abstract Post-irradiation tritium release from the Pebble Bed Assembly (PBA) neutron-irradiated beryllium (Be) pebbles (∅ ≈ 1 mm; the total tritium inventory 2–4 GBq/g) was investigated on annealing in He + 0.1% H 2 . Temperature ramps of 2.3 K/min followed by annealing for 1 h at 1310–1320 K resulted in complete detritiation of the PBA Be pebbles. The tritium burst release occurred after a time lag of 1–6.5 h during constant temperature anneals at 1089–1180 K, with the release time measured after reaching the annealing temperature. Tritium burst release was also observed to occur during cool down. Anneals at 1089 K for 8 h and at 1045 K for 23 h caused detritiation of the PBA Be pebbles by…
Structural and conductivity studies in LiFeP 2 O 7 , LiScP 2 O 7 , and NaScP 2 O 7
Structural studies of LiScP2O7 by Rietveld refinement confirm that this material is isostructural with LiFeP2O7 studied previously. However, NaScP2O7 shows a structure different from the structural types of the basic group of NaIMIIIP2O7 known thus far. Systematic ranges for the six structural types of AIMIIIP2O7 are presented in terms of ion radii sums and ratios. The framework of LiMP2O7 (M=Sc, Fe) has rather wide tunnels running along the crystallographic c-axis. This feature has determined our interest to check the ion conductivity in AIMIIIP2O7 (A=Li, Na; M=Sc, Fe). The bulk conductivity, however, is low in these compounds, 10−6–10−7 S/cm at 300 °C, as determined by impedance spectrosc…
Effects of external energetic factors on tritium release from the EXOTIC 8-3/13 neutron-irradiated beryllium pebbles
Abstract Tritium release from samples of 9–13 mg of the EXOTIC 8-3/13 neutron-irradiated beryllium pebbles under the separate and simultaneous action of temperature 490–770 K, 5 MeV fast-electron radiation 14 MGy h−1 for 3 h and magnetic field (MF) of 1.7 T was investigated. The pebbles were found to be very dissimilar with respect to their total tritium content—2.5–9 MBq g−1. The batch contained also some coarse agglomerates of the pebbles containing 10–19 MBq g−1 of tritium having also a high tritium release. For the pebbles having the total tritium 2.5–5.3 MBq g−1, the electron radiation for 3 h caused the fractional tritium release 17–26% (B = 0) and 21–29% (B = 1.7 T), the temperature …
Conductivities and silver electrode polarization resistance of solid electrolyte ceramics from ZrO 2 -Y 2 O 3 powder synthesized in air plasma
Ceramic specimens have been obtained from the powder of ZrO2-7.5 mol% Y2O3 having a specific surface area of 30 m2/g synthesized in air plasma. The novelty of this research lies in the fact that the plasma process makes it possible to prepare so-called nanopowders with a particle size less than 100 nm, possessing specific physical, chemical and technological properties. The sintered density of the specimens was 94–96% of the theoretical value, 6.001 g/cm3. The X-ray diffraction pattern of the specimens corresponded to a face-centered cubic lattice. Impedance in the frequency range of 100 Hz–15 MHz and d.c. polarization curves in a potential range of −10 to 10 mV were measured in the tempera…
TRITIUM RELEASE CHARACTERISTICS OF NEUTRON-IRRADIATED REFERENCE BERYLLIUM PEBBLES FOR THE HELIUM COOLED PEBBLE BED (HCPB) BLANKET
In this paper, we present results on tritium release from the beryllium pebbles irradiated for 294 full power days from 17 April 2003 to November 2004 to the neutron fluence of 1.5-2 × 1025 m-2 (E>...
Magnetic field effects on tritium release from neutron-irradiated beryllium pebbles
The effects of temperature, magnetic field (MF), and ionizing radiation on the release of tritium from the Be pebbles irradiated in the BERYLLIUM experiment in 1994 in Petten, The Netherlands (irradiation neutron fluence 1.24×10 25 m -2 , irradiation temperature 780 K, and 3 H content 7 appm) were investigated in this study. Simultaneous action of these factors corresponds to the real operating conditions of the blanket of a fusion reactor. The total amount of tritium in a separate pebble, the chemical forms of localized tritium (T 0 , T 2 , and T + ), and the tritium distribution in the pebble volume were determined by a lyomethod (dissolution). Thermoannealing experiments were performed a…
Tritium sorption and desorption from JET beryllium tiles under temperature, electron radiation and magnetic field
Abstract Tritium release at annealing of samples cut from beryllium tiles exposed to D + D, D + T plasma in the Joint European Torus (JET) was investigated under 5 MeV fast-electron radiation at the dose rate 14 MGy h −1 and in a magnetic field of 1.7 T separately and simultaneously in order to evaluate possible effects of these factors. Abundances of chemical forms of tritium—molecular T 2 (44%), atomic T 0 (42%), and ionic T + (14%) and their distribution were determined in the plasma-exposed beryllium samples with lyomethods. Fast-electron radiation considerably increased the fractional tritium release at annealing by a factor of approximately 5. The magnetic field increased the fraction…