Patent Number: 061730289
Section: claims

1. A structure for promoting intermixing of heated fluid streams in a nuclear reactor, said structure being disposed within a upper plenum (40) defined within a nuclear reactor vessel (10) of said nuclear reactor above a core having a low temperature region (a) and a high temperature region (d) where a heated fluid flows at a low temperature and a high temperature, respectively, said upper plenum (40) being hydraulically communicated to an outlet nozzle (12) installed at a side wall of said nuclear reactor vessel (10), said intermixing promoting structure comprising: heated fluid guide members each formed in a short length and installed within said upper plenum (40) for guiding said heated fluid (b') flowing out from said low temperature region (a) of said reactor core to the vicinity of said outlet nozzle (12).  wherein the length of said short-length heated fluid guide member is selected such that a top end thereof is positioned at a height lower than that of a bottom of a bore of said outlet nozzle (12) and higher than a middle position between the bottom of said bore of said outlet nozzle (12) and an upper surface of an upper core plate (21).  wherein said heated fluid guide members of short length are disposed at available positions, respectively, in an outer peripheral portion of said upper plenum (40) where neither upper core support columns (23) nor control rod cluster guide tubes (22) are disposed.  wherein said heated fluid guide members of short length are disposed at positions in an outer peripheral portion of said upper plenum (40) which corresponds to an outer peripheral portion of said reactor core.  wherein said heated fluid guide members of short length are disposed at available positions, respectively, in an outer peripheral portion of said upper plenum (40) where neither upper core support columns (23) nor control rod cluster guide tubes (22) are disposed.  wherein said heated fluid guide members of short length are disposed at positions in an outer peripheral portion of said upper plenum (40) which corresponds to an outer peripheral portion of said reactor core. 2. A structure for promoting intermixing of heated fluid streams in a nuclear reactor as set forth in claim 1, 3. A structure for promoting intermixing of heated fluid streams in a nuclear reactor as set forth in claim 1, 4. A structure for promoting intermixing of heated fluid streams in a nuclear reactor as set forth in claim 1, 5. A structure for promoting intermixing of heated fluid streams in a nuclear reactor as set forth in claim 2, 6. A structure for promoting intermixing of heated fluid streams in a nuclear reactor as set forth in claim 2,