Monitoring arrangement for vented nuclear fuel elements

In a core assembly for a nuclear reactor having a plurality of fuel-rod containing fuel elements compactly arranged in a hexagonal array and supported closely adjacent each other during operation of the core, each of the fuel elements including means for admitting coolant gas to an interior portion thereof in order to equalize static pressure across cladding of the fuel rods and permit concomitant venting of fission gases, each of the fuel elements having diametrically opposed vents to facilitate selective rotation of the fuel elements to compensate for bowing due to irradiation, an improved arrangement of interconnecting means for communicating vents on the individual fuel elements with respective monitoring means comprising a grid plate surrounding and engaging each of the fuel elements adjacent the diametrically opposed outlet vents therein, monitoring passages being formed in said grid plate for respective communication with the outlet vents in the individual fuel elements, combinations of said monitoring passages being interconnected with a common monitor passage, means connecting each common monitor passage with a single monitor line, the combination of monitor passages being interconnected with each common monitor passage being selected to permit a uniformly repeating geometric arrangement of monitoring passages throughout the hexagonal array of fuel elements and with the opposed vents of each fuel element being interconnected with different common monitor passages.