After the closure of the Ringhals 1 BWR on the westcoast of Sweden, it is planned to ship partly burnt fuelassemblies to the Forsmark plant on the east coast ofSweden for further operation to their target end-of-lifedischarge burnup. The fuel will be transported in ahorizontal position in dry spent fuel casks normally usedfor shipment of spent fuel from the Swedish nuclear powerplants to the CLAB central interim storage facility.In the framework of the transport qualification and thequalification of the fuel for re-use after the transport theplenum spring of a 1-cycle irradiated fuel rod wasinvestigated. The compressed length of the spring in theplenum, its free length after removal, and its springconstant have been determined by hot cell post-irradiationmeasurements. Together these data can be used todetermine the restraining force of the spring on the fuelcolumn. The results demonstrate adequate transportmargins, and enable an evaluation of unplanned transportevents.In addition, cold pellet-clad gap measurements indicatethat already after one annual cycle only a small part of thepellets in the fuel column still behave as intact solidcylinders without cracking and radial relocation. Crackedand relocated pellets require less restraint from the plenumspring to prevent pellet stack movement under horizontalacceleration during transportation.
展开▼
