[en] Reports from the meetings at Petten (Nov. - Dec. 1978), Portland (April-May 1979) and Arles (May 1979) have been reviewed together with various reports related to the Three-Mile Island accident. The reports were selected to cover transients in normal operation (power ramps, load-following) as well as off-normal transients. (author)

No abstract available

No abstract available

[en] Three UO₂-Zr test fuel pins were irradiated together to 2330 GJ/kg U (23,800 MWD/te UO₂)at heat loads decreasing from 50 to 24 kW/m (500 to 240 W/cm) (test average levels), the latest being 31 kW/m (310 W/cm). One pin was then power ramped to 45 kW/m (450 W/cm) at 35 W/m.s (21 W/cm.min.) and kept there for 2 Ms (550 hrs.) without failure indication. The other two pins were further irradiated to 2450 GJ/kg U (25,000 MWD/te UO₂) at approximately 23 kW/m (230 W/cm). Ramp testing to 43 kW/m (430 W/cm) did not produce failure during 2.4 Ms (670 hrs.). The fission gas release in the three pins was 30-40%. A limited metallographic examination revealed extensive fuel-clad reaction. Design and irradiation details are included for use as input in the validation of fuel performance codes. (author)

[en] Test 022 comprised three UO₂-Zr test fuel pins which were irradiated in the DR 3 reactor at Risoe at 7.2 MPa (70 ato) system pressure. A burnup of approximately 3530 GJ/kg U (36,000 MWD/te UO₂) was accumulated at heat loads in the range 35 to 53 kW/m (350 to 530 W/cm) (test avg. values). Fission gas analysis for two of the pins showed that the releases were 48 and 36%. The experimental data are presented in sufficient detail for use in the validation of fuel performance codes. (author)

No abstract available

[en] The Risoe Fission Gas Project has provided experimental data on fission gas release from high-burnup water reactor fuel. The data are well-characterized with respect to pre-irradiation measurement, irradiation and post-irradiation examination. The experimental data were obtained with 12 Zircaloy-clad UO₂ pellet fuel pins, irradiated in a test assembly to an average of 32,000 MWd (tU)^-1. Most of the fuel pins were submitted to short-term re-irradiation at increased power levels ('bump testing') in a test reactor in order to simulate postulated power increases late in life. The bump tests covered a range of bump terminal levels of 320 to 462 W cm^-1 (peak pellet), mostly with a hold time of 24 h. Extensive hot-cell examinations were performed of base-irradiated and bump-tested fuel pins. The fission gas release resulting from the bump testing was in the range 0 to 16%, increasing with peak pellet levels above 400 W cm^-1. Local fission gas releases were determined from retained-gas measurements on pellet size samples. Release of the fission product cesium as a function of local bump terminal level resembled the local fission gas release. The gas release measurements were corroborated by extensive ceramographic examinations and pore size analysis. (author)

[en] This note was prepared as one of the introductory contributions at the IAEA Specialists' Meeting on ''High Burnup in Power Reactor Fuel'' at Mol, 24-27 March 1981. Consequently, emphasis was placed on investigations where high burnups, here defined as approximately 30,000 MWD/tU or above, have been achieved. It should also be borne in mind that the reporting on national programs at the meetings of the International Working Group on Water Reactor Fuel Performance and Technology (IWG-FPT) of the IAEA is informal; it was not attempted to take detailed notes during the meeting, the present overview is, therefore, mainly based on those contributions where hand-outs were available. The various undertakings are mentioned alphabetically countrywise, according to IAEA practice

[en] The Risoe Fission Gas Project has provided experimental data on fission gas release from high-burnup water reactor fuel. The data are well-characterized with respect to pre-irradiation measurement, irradiation and post-irradiation examination, thus enabling their use in fuel performance code validation. The experimental data were obtained with 12 Zircaloy clad UO₂ pellet fuel pins, irradiated in a test assembly to an average of 32,000 Mwd/tU. Most of the fuel pins were submitted to short-term reirradiation at increased power levels ('bump testing') in a test reactor, in order to simulate postulated power increases late in life. The bump tests covered a range of bump terminal levels of 320-462 U/cm (peak pellet), mostly with a hold time of 24 h. Extensive hot-cell examinations were performed of base-irradiated and bump-tested fuel pins. The fission gas release resulting from the bump testing was in the range 0-16%, increasing with peak pellet levels above 400 U/cm. Local fission gas releases were determined from retained gas measurements on pellet size samples. Release of fission product cesium as a function of local bump terminal level resembled the local fission gas release. The gas release measurements were corroborated by extensive ceramographic examinations and pore size analysis. (author)

[en] The Risoe neutron radiography (NR) facility utilizes a homogeneous solution-type reactor (L-55, Atomics International) as the neutron source. Two horizontal, parallel neutron beams, each having a cross section of 10 x 10 cm and a thermal neutron flux of 10⁶ n/cm²s are available. The collimators are so arranged that the L/D-ratio vertically and horizontally is 110 and 30, respectively. The principal application of the Risoe facility is the nondestructive examination of water reactor fuel, i.e. Zircaloy clad uranium dioxide. This has included 3 m long power reactor fuel rods and 15-200 cm fuel rods from test reactor irradiations. Pin lengths up to 9/2 m can be examined. The burnup of some of this fuel exceeds 50,000 MWD/tU. The NR technique is useful for the characterisation of features which would otherwise normally require destructive examination. Examples are: pellet cracks and center voids, local hydriding of the cladding, and presence of water in defect fuel rods. The usefulness of the technique is very much increased by detailed correlation with other methods such as visual inspection, eddy-current testing, axial gamma scanning, and profilometry. Consequently, it is possible to limit the costly destructive examinations, such as metallography, to sample locations of real importance. (Auth.)