Martin Peehs

Survey of binary oxide fuel manufacturing and quality control

Quality assurance of the binary oxides UO2-Gd2O3, UO2-PuO2 and ThO2-UO2 is based on the implementation of adequate production procedures and on the application of appropriate testing procedures. The oxides are manufactured by cold pressing of the powders and sintering to pellets. This survey shows as examples the use of physical mixing (UO2-Gd2O3 and UO2-PuO2), the application of co-precipitation (UO2-PuO2) and the realization of the gelation process (ThO2-UO2). Gd2O3 powder is mixed with flowable UO2 powder ex AUC. A master-mix of UO2-PuO2 produced by either co-precipitation or co-milling is blended with UO2. (Th, U)O2 microspheres are manufactured as press-feed material.

Spent LWR fuel dry storage in large transport and storage casks after extended burnup

Abstract Dry spent LWR fuel storage is licensed for single fuel assemblies with rod burnup to 65 GWd/tHM. This allows dry spent fuel storage of reloads with a batch average up to 55 GWd/tHM. The leading defect mechanism for spent fuel rods in dry storage is hoop strain. Fuel rod degradation can be prevented by limiting creep. Post-pile creep of fuel rod cladding can be described conservatively by the creep of unirradiated cladding. In order to extend the database, internally pressurized creep samples were investigated for time intervals up to 10 000 h. Test temperatures were between 250 and 400°C, and the hoop stresses applied ranged from 80 to 150 N/mm 2 . The resulting data were described mathematically by an interpolation formula. Based on the fuel assemblies end-of-life data the maximum CASTOR V cask storage temperature was calculated to be between 348°C and 358°C at the beginning.

Zur wärmeleitfähigkeit und plastizität von UO2 mit Gd-zusätzen

The thermal diffusivity and the thermal conductivity were measured for UO2-Gd2O3 with Gd2O3 ⩽ 10 W/O in the temperature range 25 °C ⩽ ⩽ 500 °C. An evaluation of the experimental data has shown, that the thermal conductivity is mainly influenced by microstructural changes in the mixed oxide structure due to Gd2O3-content. This result was also confirmed by detailed investigations of the structure of UO2-Gd2O3. Measurements of the stationary creep rate at Δ = 1500 °C and 100 N/mm2 from UO2 and UO2-6,5 W/O Gd2O3, showed, that the plasticity of such fuel is scarcely influenced by the Gd2O3, content.

Einstellung und charakterisierung der strukturgrössen von lwr-brennstoff

Zusammenfassung LWR fuel for high-burn up has initiated some efforts at the accommodation of the microstructural fuel properties. The adaption of the pore size can easily be performed by the addition of U 3 O 8 in well defined powder fractions. The adjustment of a coarse grain structure without the addition of oxidic dopants can be reached by using an oxidative sintering process. This process utilizes the diffusion enhancing effect of interstitial oxygen in UO 2 . Both measures do not only guarantee a reliable adjustment of the fuel properties, but also meet the conditions for a well controlled manufacturing procedure.

Sauerstoff-diffusionssperren zwischen U02 und ZrCu-Legierungen

Zusammenfassung Versuche haben gezeigt, dass ZrCu-Legierungen uber 600 °C mit UO 2 nicht vertraglich sind. Insbesondere wandert Sauerstoff aus dem UO 2 in das ZrCu. Zur Unterdruckung dieser Reaktionen wurden daher PyC-und C-, Cu- und Ni-Schichten sowie Kombinationen aus diesen Metallen und mit Cr auf ihre Eignung als Diffusionssperren gepruft. Kohlenstoff erwies sich als wirksame Sperre. Die Metallschichten — Ni ausgenommen — hemmen die Diffusion ebenfalls. PyC wurde auf dem UO 2 , alle ubrigen Schichten auf dem ZrCu abgeschieden. Die Abscheidungstechnik fur C und Cu konnte auch auf das Hullrohrinnere ubertragen werden. Mehrere Testbrennstabe fur Reaktortests im C0 2 -Loop des BR 2-Reaktors in Mol wurden mit diesen Sperren versehen.