Abstract
The JAERI/USDOE collaborative program is going on using the FNS facility at JAERI. The phase-III is a new series on tritium breeding measurements with a totally different experimental arrangement from the previous ones that used a point neutron source geometry. The new series basically consists of an annular test blanket and a pseudo-line source to investigate the effect source spread on the neutronic performance. A concise description is made on the features of the simulated line source, the test blanket systems for phase-IIIA and -IIIB, measured items, experimental results, and their analysis. Within the same program, nuclear heating rate, gamma-ray activities and resultant energy releases have been measured to provide experimental data for safety related issues. A comparative study was also performed among the phase-I, phase-II and phase-III.