Mitsubishi Heavy Industries Limited

Takehiko Tsutsui

Hajime Izumi

Chikara Kurimura

Toshio Ichikawa

Makoto Nakajima

Noboru Kubo

Mikio Kurihara

Yoko Matsushima

Within an upper plenum of a nuclear reactor, a portion of a heated coolant flows radially outward from a central portion of a core barrel ( ) towards outlet nozzles ( ) in a region of an upper core plate ( ) extending outside of an outer periphery of the core along an inner wall of a core barrel ( ). Portions of the coolant flows beneath the outlet nozzles ( ). Thus, streams of heated coolant flowing in opposite directions may collide with each other. After collision, the flow directions of the heated coolant are changed to flow upward. Due to the collision, the coolant flow behavior becomes complicated and unstable, making it difficult to measure the temperature of the heated coolant with an outlet pipe ( ) connected to the outlet nozzle ( ). Within an upper plenum ( ) defined above a fuel region through which a coolant flows and which is hydraulically communicated with a plurality of outlet nozzles ( ) mounted on a side wall of a nuclear reactor vessel ( ), short flow stabilizing members ( ) each being lower than the outlet nozzle ( ) are disposed in the vicinity of a core barrel ( ) in an region outside of the fuel region.

Internal structure of nuclear reactor with coolant flow stabilizing facility

An apparatus for promoting intermixing of heated fluid streams within a nuclear reactor vessel is implemented in such structural configuration and disposition as to be capable of not only promoting uniform temperature distribution of a heated fluid stream flowing into an outlet nozzle but also reducing flow resistance which the heated fluid encounters within a upper plenum of the reactor vessel. The apparatus is disposed within a upper plenum (,) defined within a nuclear reactor vessel (,) of a 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. The upper plenum (,) is hydraulically communicated to outlet nozzles (,) installed at a side wall of the nuclear reactor vessel (,). The apparatus includes heated fluid guide members each having a predetermined short length and installed within the upper plenum (,) for guiding a heated fluid (b&prime;) flowing out from the low temperature region of the reactor core to the vicinity of the outlet nozzle (,).

Apparatus for promoting intermixing of heated coolant streams in nuclear reactor

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Hyogo-ken, Japan

Takehiko Tsutsui