[en] A solid U-Si-Al element clad in cold-worked Zr-2.5 wt% Nb and containing four internal thermocouples was irradiated to a burnup of about 50 MWh/kg U at a linear power of 55 kW/m (182 MeV/fission). The central fuel temperature at full power decreases continuously from 817 K just after the initial startup to 782 K after a burnup of 50 MWh/kg U. The thermal conductivity determined from data obtained from the initial reactor startup fit the relation lambda(T) = 0.0108 + 2.52 x 10^-5 (T-273) kWm^-1K^-1. This agrees to within 5% of data obtained independently from out-reactor tests. Irradiation caused a small decrease in conductivity at temperatures below 675 K and a corresponding slight increase in the temperature sensitivity. At a burnup of 40 MWh/kg U the in-reactor data fit the relation lambda(T) = 0.00776 + 3.32 x 10^-5 (T-273) kWm^-1K^-1. Both of these relations result in a thermal conductivity 10%-20% lower than that for U₃Si. The observed decrease in operating fuel temperature is consistent with an increase in fuel/sheath heat transfer coefficients with burnup, which has been postulated for uranium silicide fuel elements. Heat transfer coefficients calculated from data obtained in this experiment ranged from 25 kWm^-2K^-1 for fresh fuel to 160 kWm^-2K^-1 after a burnup of 40 MWh/kg U. (author)

No abstract available

[en] Peripheral voidage in the form of longitudinal slots on the surface of the fuel is effective in accommodating the irradiation induced swelling of U-Si-Al rods clad in cold-worked Zr-2.5 wt% Nb. Diametral increases in elements operated at steady powers between 50 and 80 kW/m to a burnup of 240 MW.h/kg U were less than 1.25%. Similar to U₃Si elements, lower sheath strength or higher temperatures resulted in greater diametral increases. An oxide or graphite interlayer between the fuel and sheath was shown to be effective in preventing the development of a fuel/sheath bond. The ability of U-Si-Al elements to successfully survive a power increase from 35 to 70 kW/m after appreciable burnup at the lower power has also been demonstrated. (author)

[en] A 500 mm long Zircaloy-clad element of U₃Si (4.3 wt% Si) containing a 13% central void was irradiated to an average burnup of 3600 MWd/tonne U at an average linear power output of 790 W/cm, in boiling water coolant at 55 bars pressure. A larger diameter increase (1.5%) at the mid-plane of the element than elsewhere was attributed to the reduced restraint imposed on the fuel in this area as a consequence of β annealing a section of the cold worked sheath. Diameter increases in the cold worked portions of the sheath (average 0.7%) were greater than in similar elements irradiated in pressurized water at 96 bars pressure the difference is attributed to higher linear power output of the element in this test. External swelling of the element before filling of the central void was complete is attributed to the higher silicon content of the fuel compared with previous tests. No reaction between U₃Si and Zircaloy was observed at a fuel sheath interface temperature near 400^oC. (author)

[en] A new facility based on the MAPLE research reactor concept is being planned for the Chalk River Nuclear Laboratories in Canada. The reactor with be used primarily for the production of short lived radioisotopes and will also serve as a prototype of a MAPLE research reactor

[en] U₃Si fuel elements clad in zirconium alloy sheaths have been irradiated to burnups close to 15,000 MWd/tonne U in pressurized water at 220^oC, 98 bars. The results show that the external swelling can be controlled by incorporating free volume in the element. The dimensional stability of such elements is adequate to permit their use in power reactor fuel bundles. A diameter increase of 1.2% had occurred in an element initially containing 12.8% total free volume, after a burnup of 14,700 MWd/tonne U. There was no change in diameter between burnups of 5200 and 14,700 MWd/tonne U. Elements containing 3% total free volume had increased in diameter about 2.5% at 2000 MWd/tonne U compared to 0.2% at 9500 MWd/tonne U for elements containing 22% total free volume. The observed swelling in the U₃Si is discussed in terms of possible mechanisms. (author)

[en] Enriched uranium-silicon alloy specimens close to the U₃Si composition (U-3.9 wt% Si) and clad in Zircaloy-2 are being irradiated in the X-5 pressurized-water loop at powers of 600 - 800 W/cm length. Extrapolation, of the swelling curve indicates a total volume increase in U₃Si of 13% after a burnup of 10,000 MWd/tonne U. Destructive examination. of selected specimens showed that the U₃Si was plastic enough to flow into a 7 vol% central void provided in the fuel, suggesting that the total volume increase could be accommodated without excessive sheath strain. (author)

No abstract available

[en] The MAPLE-X10 Reactor is a 10 MW light-water-cooled and moderated pool-type reactor which is being planned for the Chalk River Nuclear Laboratories (CRNL) of Atomic Energy of Canada Limited. The main use of the reactor at CRNL will be for the production of short-lived radioisotopes. MAPLE-X10 will also serve as a demonstration of the generic MAPLE concept

[en] Short communication