A maintenance management suitable to nuclear power plants (NPP) at R&D stage was discussed. Objectives of
maintenance management of NPP at R&D stage was first clarified. Next, applicability of codes for maintenance
management of commercial NPP to NPP at R&D stage was discussed. Then, requirements and consideration for
maintenance management of NPP at R&D stage was proposed. Finally, an example that the proposal was
applied to setting maintenance program of sodium-cooled fast reactor was presented.
Filter vent model for THALES-2 code was developed and the effect of the filter vent system was evaluated with
the code. In Japan, the installation of filter venting system to the BWRs was considered after the accident of
Fukushima-daiichi, where the total blackout caused by tsunami resulted in the large amount of fission product
(FP) release to the environment. In this study, the effect of filter vent system in such a total blackout sequence
was evaluated. The amount of fission product release was smaller with the filter venting compared to the case in
which the reactor containment failed without depressurization.