RESULTS OF A NEW PRODUCTION OF NUCLEAR-GRADE 1.4970 '15-15TI' STAINLESS STEEL FUEL CLADDING TUBES FOR GEN IV REACTORS

Titanium stabilized 1.4970 '15-15Ti' stainless steel cladding is the primary choice for fuel cladding of several current fast spectrum research reactor projects. The choice of cladding material is based on past experiences and the availability of material databases from similar steel grades that have proven their reliability in past sodium-cooled fast reactors programs. However the last production in Europe of nuclear-grade 15-15Ti was more than 20 years ago and it remained to be seen if the know-how to produce such steel with the strict specifications for nuclear fuel cladding was still available. Results of a new production of nuclear-grade 15-15Ti cladding tubes at Sandvik for SCK.CEN is presented in this paper. It is shown that materials properties are within the strict specifications similar to the ones used during past sodium-cooled fast reactors programs. Special attention is given to microstructural analysis of the newly produced steel which contains a large number of stabilizing Ti(C-N) precipitates known for their beneficial effect on in-pile material properties and thermal creep. Results from metallography, SEM and TEM investigations are presented.