[1] ENEA-Nuclear Fission Division, Via Martiri di Monte Sole 4, 40129 Bologna, Italy
[2] ENEA-INN/NUMA, Faenza Research Center, 48018 Faenza, Italy
[3] ENEA-INN-NUMA, Casaccia Research Center, 00060 Rome, Italy
[4] FN-New Technol. and Adv. Services, 15062 Bosco Marengo, AL, Italy
[5] Polytechnic of Milan, Department of Nuclear Engineering, Via Ponzio 34/3, 20133 Milan, Italy