Das Gesamtziel ist die Methodenentwicklung zur Beschreibung des thermo-mechanischen Brennstabverhaltens bei Reaktivitäts- und Kühlmittelverluststörfällen (RIA und LOCA) und dem Lastfolgebetrieb (LFB). Die Methoden dienen der Brennstabintegritäts-Bewertung während des Betriebs und bei Störfällen. Die derzeit verfügbaren Methoden berücksichtigen die aktuellen, an die Brennstäbe gestellten, Anforderungen nicht im ausreichenden Maße. Hierzu zählen erhöhte Brennstoffabbrände, neue Beladeschemen, der verstärke Einsatz von Mischoxid-Brennstoff (MOX) und häufigere Leistungsänderungen. Sie dienen zur Erweiterung des GRS-Brennstab-Codes TESPA-ROD, der dann auch unter den neuen Bedingungen zur Beurteilung genutzt werden kann. Dieses Vorhaben baut auf den Erkenntnissen des Vorhabens RS1518 auf.
Objective: To study mechanisms and properties determining fuel and fission product behaviour during both, base and off-normal conditions. This activity involves unirradiated and irradiated 'classical' and 'improved' fuel samples of various composition and over a wide range of temperatures, up to very high burn-up, and makes use of appropriate computer models. The final aim of the activity is the improvement of the safety of fuel operation in a reactor. General Information: Progress to end 1990. The Laboratory continued its cooperation with the International Fission Gas Release Project Riso III (Dk) by incorporating the extensive experimental data resulting from the programme into the OFT data bank and evaluating them with existing TU fuel performance codes. - The OECD-coordinated activity for analysing fuel and fuel debris of the Three Mile Island (TMI) damaged reactor has been concluded. An apparatus for thermal diffusivity measurements on active specimens with the laser flash technique has been constructed. - Nitride fuels with a 'tailored' structure and heterogeneous fuels (U, Pu)O2 and UN) were fabricated for short-term irradiations in the HFR-reactor. Irradiations of fuels for future reactors to test their behaviour at the beginning of life (BOL) and at the end of life (EOL), NILOC (HFR) and NIMPHE (PHENIX), respectively, have been continued. Out-of-pile tests were performed to study changes in structure and composition of mixed nitride fuel pins in an axial temperature gradient. - Measurements of the heat capacity of UO2 up to 8000K were concluded and the results are being analysed. Radiative properties of oxides (thoria, urania, zirconia) were measured in the solid and the liquid range. A model for the total emissivity of urania was developed. - The code MITRA has been adapted to perform source term calculations. A computer code for the calculation of the thermo chemical equilibrium of fission products was written and a database for fission product compounds has been implemented with interface to the SOLGASMIX/MITRA codes. A shielded Knudsen cell for irradiated UO2 fuel has been assembled. - Work in 1990 on the safety of nuclear fuels has resulted in 33 (status September '90) contributions to conferences, articles in scientific journals, reports and chapters in books; two patents were granted. Detailed description of work foreseen in 1991 (expected results). Riso III results will undergo final evaluation and fuel work will concentrate on MOX fuel and on the structural and chemical changes at local burn-ups of up to 15 per cent . Laboratory work will principally deal with SIMFUEL with 6 and 8 per cent burn-up. Modelling work will continue. Annealing tests will be performed under oxidizing and reducing atmosphere on U02 samples irradiated up to 55 GWd/t, in order to determine fission gas release as a function of O/M . A remotely controlled thermal diffusivity apparatus will be mounted in a hot cell. BOL and EOL irradiations NILOC and ...
Am 3. August 2011 gab die Nuclear Decommissioning Authority, abgekürzt NDA, die Behörde für die Stilllegung kerntechnischer Anlagen im Vereinigten Königreich, ihre Pläne bekannt, die kerntechnische Anlage für Mischoxid-Brennelemente in der englischen Atomanlage Sellafield stillzulegen. Indirekt ist dies die Folge der Atomkatastrophe von Fukushima im März 2011. Japanische Kernkraftwerke sind die einzigen Abnehmer für die MOX-Brennelemente.